Mirror neuron, by Wikipedia

Mirror neuron, by Wikipedia

Postby admin » Wed Feb 20, 2019 2:06 am

Part 1 of 2

Mirror neuron
by Wikipedia
Accessed: 2/19/19

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A mirror neuron is a neuron that fires both when an animal acts and when the animal observes the same action performed by another.[1][2][3] Thus, the neuron "mirrors" the behavior of the other, as though the observer were itself acting. Such neurons have been directly observed in primate species.[4] Birds have been shown to have imitative resonance behaviors and neurological evidence suggests the presence of some form of mirroring system.[4][5] In humans, brain activity consistent with that of mirror neurons has been found in the premotor cortex, the supplementary motor area, the primary somatosensory cortex and the inferior parietal cortex.[6]

The function of the mirror system in humans is a subject of much speculation. Some researchers in cognitive neuroscience and cognitive psychology consider that this system provides the physiological mechanism for the perception/action coupling (see the common coding theory).[3] They argue that mirror neurons may be important for understanding the actions of other people, and for learning new skills by imitation. Some researchers speculate that mirror systems may simulate observed actions, and thus contribute to theory of mind skills,[7][8] while others relate mirror neurons to language abilities.[9] Neuroscientists such as Marco Iacoboni (UCLA) have argued that mirror neuron systems in the human brain help us understand the actions and intentions of other people. In a study published in March 2005 Iacoboni and his colleagues reported that mirror neurons could discern whether another person who was picking up a cup of tea planned to drink from it or clear it from the table.[10] In addition, Iacoboni has argued that mirror neurons are the neural basis of the human capacity for emotions such as empathy.[11]

However, there are scientists who express skepticism about the theories being advanced to explain the function of mirror neurons. In a 2013 article for Wired, Christian Jarrett cautioned that:

...mirror neurons are an exciting, intriguing discovery – but when you see them mentioned in the media, remember that most of the research on these cells has been conducted in monkeys. Remember too that there are many different types of mirror neuron. And that we're still trying to establish for sure whether they exist in humans, and how they compare with the monkey versions. As for understanding the functional significance of these cells … don't be fooled: that journey has only just begun.[12]


To date, no widely accepted neural or computational models have been put forward to describe how mirror neuron activity supports cognitive functions.[13][14][15] The subject of mirror neurons continues to generate intense debate. In 2014, Philosophical Transactions of the Royal Society B published a special issue entirely devoted to mirror neuron research.[16]

Discovery

In the 1980s and 1990s, neurophysiologists Giacomo Rizzolatti, Giuseppe Di Pellegrino, Luciano Fadiga, Leonardo Fogassi, and Vittorio Gallese at the University of Parma placed electrodes in the ventral premotor cortex of the macaque monkey to study neurons specialized in the control of hand and mouth actions; for example, taking hold of an object and manipulating it. During each experiment, the researchers allowed the monkey to reach for pieces of food, and recorded from single neurons in the monkey's brain, thus measuring the neuron's response to certain movements.[17][18] They found that some neurons responded when the monkey observed a person picking up a piece of food, and also when the monkey itself picked up the food. The discovery was initially sent to Nature, but was rejected for its "lack of general interest" before being published in a less competitive journal.[19]

A few years later, the same group published another empirical paper, discussing the role of the mirror-neuron system in action recognition, and proposing that the human Broca's region was the homologue region of the monkey ventral premotor cortex.[20] While these papers reported the presence of mirror neurons responding to hand actions, a subsequent study by Pier Francesco Ferrari and colleagues[21] described the presence of mirror neurons responding to mouth actions and facial gestures.

Further experiments confirmed that about 10% of neurons in the monkey inferior frontal and inferior parietal cortex have "mirror" properties and give similar responses to performed hand actions and observed actions. In 2002 Christian Keysers and colleagues reported that, in both humans and monkeys, the mirror system also responds to the sound of actions.[3][22][23]

Reports on mirror neurons have been widely published[24] and confirmed[25] with mirror neurons found in both inferior frontal and inferior parietal regions of the brain. Recently, evidence from functional neuroimaging strongly suggests that humans have similar mirror neurons systems: researchers have identified brain regions which respond during both action and observation of action. Not surprisingly, these brain regions include those found in the macaque monkey[1] However, functional magnetic resonance imaging (fMRI) can examine the entire brain at once and suggests that a much wider network of brain areas shows mirror properties in humans than previously thought. These additional areas include the somatosensory cortex and are thought to make the observer feel what it feels like to move in the observed way.[26][27]

Origin

The most common theory behind the origin of mirror neuron is the genetic account which suggests that the mirrorness of mirror neurons is due primarily to heritable genetic factors and that the genetic predisposition to develop Mirror neuron evolved because they facilitate action understanding. The other theories as to the origin of mirror neurons include Associative Learning, Canalization and Exaptation.[28]

In monkeys

Image
Neonatal (newborn) macaque imitating facial expressions

The first animal in which researchers have studied mirror neurons individually is the macaque monkey. In these monkeys, mirror neurons are found in the inferior frontal gyrus (region F5) and the inferior parietal lobule.[1]

Mirror neurons are believed to mediate the understanding of other animals' behaviour. For example, a mirror neuron which fires when the monkey rips a piece of paper would also fire when the monkey sees a person rip paper, or hears paper ripping (without visual cues). These properties have led researchers to believe that mirror neurons encode abstract concepts of actions like 'ripping paper', whether the action is performed by the monkey or another animal.[1]

The function of mirror neurons in macaques remains unknown. Adult macaques do not seem to learn by imitation. Recent experiments by Ferrari and colleagues suggest that infant macaques can imitate a human's face movements, though only as neonates and during a limited temporal window.[29] Even if it has not yet been empirically demonstrated, it has been proposed that mirror neurons underlie this behaviour and other imitative phenomena.[30] Indeed, there is limited understanding of the degree to which monkeys show imitative behaviour.[13]

In adult monkeys, mirror neurons may enable the monkey to understand what another monkey is doing, or to recognize the other monkey's action.[31]

In humans

It is not normally possible to study single neurons in the human brain, so most evidence for mirror neurons in humans is indirect. Brain imaging experiments using functional magnetic resonance imaging (fMRI) have shown that the human inferior frontal cortex and superior parietal lobe are active when the person performs an action and also when the person sees another individual performing an action. It has been suggested that these brain regions contain mirror neurons, and they have been defined as the human mirror neuron system.[32] More recent experiments have shown that even at the level of single participants, scanned using fMRI, large areas containing multiple fMRI voxels increase their activity both during the observation and execution of actions.[26]

Neuropsychological studies looking at lesion areas that cause action knowledge, pantomime interpretation, and biological motion perception deficits have pointed to a causal link between the integrity of the inferior frontal gyrus and these behaviours.[33][34][35] Transcranial magnetic stimulation studies have confirmed this as well.[36][37] These results indicate the activation in mirror neuron related areas are unlikely to be just epiphenomenal.

A study published in April 2010 reports recordings from single neurons with mirror properties in the human brain.[38] Mukamel et al. (Current Biology, 2010) recorded from the brains of 21 patients who were being treated at Ronald Reagan UCLA Medical Center for intractable epilepsy. The patients had been implanted with intracranial depth electrodes to identify seizure foci for potential surgical treatment. Electrode location was based solely on clinical criteria; the researchers, with the patients' consent, used the same electrodes to "piggyback" their research. The researchers found a small number of neurons that fired or showed their greatest activity both when the individual performed a task and when they observed a task. Other neurons had anti-mirror properties, that is, they responded when the participant performed an action but were inhibited when the participant saw that action.

The mirror neurons found were located in the supplementary motor area and medial temporal cortex (other brain regions were not sampled). For purely practical reasons, these regions are not the same as those in which mirror neurons had been recorded from in the monkey: researchers in Parma were studying the ventral premotor cortex and the associated inferior parietal lobe, two regions in which epilepsy rarely occurs, and hence, single cell recordings in these regions are not usually done in humans. On the other hand, no one has to date looked for mirror neurons in the supplementary motor area or the medial temporal lobe in the monkey. Together, this therefore does not suggest that humans and monkeys have mirror neurons in different locations, but rather that they may have mirror neurons both in the ventral premotor cortex and inferior parietal lobe, where they have been recorded in the monkey, and in the supplementary motor areas and medial temporal lobe, where they have been recorded from in human – especially because detailed human fMRI analyses suggest activity compatible with the presence of mirror neurons in all these regions.[26]

Another study has suggested that human beings don't necessarily have more mirror neurons than monkeys, but instead that there is a core set of mirror neurons used in action observation and execution. However, for other proposed functions of mirror neurons the mirror system may have the ability to recruit other areas of the brain when doing its auditory, somatosensory, and affective components.[39]

Doubts concerning mirror neurons

Although many in the scientific community have expressed excitement about the discovery of mirror neurons, there are scientists who have expressed doubts about both the existence and role of mirror neurons in humans. According to scientists such as Hickok, Pascolo, and Dinstein, it is not clear whether mirror neurons really form a distinct class of cells (as opposed to an occasional phenomenon seen in cells that have other functions),[40] and whether mirror activity is a distinct type of response or simply an artifact of an overall facilitation of the motor system.[14]

In 2008, Ilan Dinstein et al. argued that the original analyses were unconvincing because they were based on qualitative descriptions of individual cell properties, and did not take into account the small number of strongly mirror-selective neurons in motor areas.[13] Other scientists have argued that the measurements of neuron fire delay seem not to be compatible with standard reaction times,[40] and pointed out that nobody has reported that an interruption of the motor areas in F5 would produce a decrease in action recognition.[14] (Critics of this argument have replied that these authors have missed human neuropsychological and TMS studies reporting disruption of these areas do indeed cause action deficits[34][36] without affecting other kinds of perception.)[35]

In 2009, Lingnau et al. carried out an experiment in which they compared motor acts that were first observed and then executed to motor acts that were first executed and then observed. They concluded that there was a significant asymmetry between the two processes that indicated that mirror neurons do not exist in humans. They stated "Crucially, we found no signs of adaptation for motor acts that were first executed and then observed. Failure to find cross-modal adaptation for executed and observed motor acts is not compatible with the core assumption of mirror neuron theory, which holds that action recognition and understanding are based on motor simulation."[41] However, in the same year, Kilner et al. showed that if goal directed actions are used as stimuli, both IPL and premotor regions show the repetition suppression between observation and execution that is predicted by mirror neurons.[42]

In 2009, Greg Hickok published an extensive argument against the claim that mirror neurons are involved in action-understanding: "Eight Problems for the Mirror Neuron Theory of Action Understanding in Monkeys and Humans." He concluded that "The early hypothesis that these cells underlie action understanding is likewise an interesting and prima facie reasonable idea. However, despite its widespread acceptance, the proposal has never been adequately tested in monkeys, and in humans there is strong empirical evidence, in the form of physiological and neuropsychological (double-) dissociations, against the claim."[14]

Image
The mirror neurons can be activated only after the goal of the observed action has been attributed by other brain structures.

Vladimir Kosonogov sees another contradiction. The proponents of mirror neuron theory of action understanding postulate that the mirror neurons code the goals of others actions because they are activated if the observed action is goal-directed. However, the mirror neurons are activated only when the observed action is goal-directed (object-directed action or a communicative gesture, which certainly has a goal too). How do they "know" that the definite action is goal-directed? At what stage of their activation do they detect a goal of the movement or its absence? In his opinion, the mirror neuron system can be activated only after the goal of the observed action is attributed by some other brain structures.[43]

Neurophilosophers such as Patricia Churchland have expressed both scientific and philosophical objections to the theory that mirror neurons are responsible for understanding the intentions of others. In chapter 5 of her 2011 book, Braintrust, Churchland points out that the claim that mirror neurons are involved in understanding intentions (through simulating observed actions) is based on assumptions that are clouded by unresolved philosophical issues. She makes the argument that intentions are understood (coded) at a more complex level of neural activity than that of individual neurons. Churchland states that "A neuron, though computationally complex, is just a neuron. It is not an intelligent homunculus. If a neural network represents something complex, such as an intention [to insult], it must have the right input and be in the right place in the neural circuitry to do that".[44]

Recently, Cecilia Heyes (Professor of Experimental Psychology, Oxford) has advanced the theory that mirror neurons are the byproduct of associative learning as opposed to evolutionary adaptation. She argues that mirror neurons in humans are the product of social interaction and not an evolutionary adaptation for action-understanding. In particular, Heyes rejects the theory advanced by V.S. Ramachandran that mirror neurons have been "the driving force behind the great leap forward in human evolution."[15][45]


Development

Human infant data using eye-tracking measures suggest that the mirror neuron system develops before 12 months of age, and that this system may help human infants understand other people's actions.[46] A critical question concerns how mirror neurons acquire mirror properties. Two closely related models postulate that mirror neurons are trained through Hebbian[47] or Associative learning[48][49][50] (see Associative Sequence Learning). However, if premotor neurons need to be trained by action in order to acquire mirror properties, it is unclear how newborn babies are able to mimic the facial gestures of another person (imitation of unseen actions), as suggested by the work of Meltzoff and Moore. One possibility is that the sight of tongue protrusion recruits an innate releasing mechanism in neonates. Careful analysis suggests that 'imitation' of this single gesture may account for almost all reports of facial mimicry by new-born infants.[51]

Possible functions

Understanding intentions


Many studies link mirror neurons to understanding goals and intentions. Fogassi et al. (2005)[52] recorded the activity of 41 mirror neurons in the inferior parietal lobe (IPL) of two rhesus macaques. The IPL has long been recognized as an association cortex that integrates sensory information. The monkeys watched an experimenter either grasp an apple and bring it to his mouth or grasp an object and place it in a cup.

In total, 15 mirror neurons fired vigorously when the monkey observed the "grasp-to-eat" motion, but registered no activity while exposed to the "grasp-to-place" condition.

For 4 other mirror neurons, the reverse held true: they activated in response to the experimenter eventually placing the apple in the cup but not to eating it.


Only the type of action, and not the kinematic force with which models manipulated objects, determined neuron activity. It was also significant that neurons fired before the monkey observed the human model starting the second motor act (bringing the object to the mouth or placing it in a cup). Therefore, IPL neurons "code the same act (grasping) in a different way according to the final goal of the action in which the act is embedded".[52] They may furnish a neural basis for predicting another individual's subsequent actions and inferring intention.[52]

Learning facilitation

Another possible function of mirror neurons would be facilitation of learning. The mirror neurons code the concrete representation of the action, i.e., the representation that would be activated if the observer acted. This would allow us to simulate (to repeat internally) the observed action implicitly (in the brain) to collect our own motor programs of observed actions and to get ready to reproduce the actions later. It is implicit training. Due to this, the observer will produce the action explicitly (in his/her behavior) with agility and finesse. This happens due to associative learning processes. The more frequently a synaptic connection is activated, the stronger it becomes.[43]

Empathy

Stephanie Preston and Frans de Waal,[53] Jean Decety,[54][55] and Vittorio Gallese[56][57] and Christian Keysers[3] have independently argued that the mirror neuron system is involved in empathy. A large number of experiments using fMRI, electroencephalography (EEG) and magnetoencephalography (MEG) have shown that certain brain regions (in particular the anterior insula, anterior cingulate cortex, and inferior frontal cortex) are active when people experience an emotion (disgust, happiness, pain, etc.) and when they see another person experiencing an emotion.[58][59][60][61][62][63][64] David Freedberg and Vittorio Gallese have also put forward the idea that this function of the mirror neuron system is crucial for aesthetic experiences.[65] However, these brain regions are not quite the same as the ones which mirror hand actions, and mirror neurons for emotional states or empathy have not yet been described in monkeys.

More recently, Christian Keysers at the Social Brain Lab and colleagues have shown that people who are more empathic according to self-report questionnaires have stronger activations both in the mirror system for hand actions[66] and the mirror system for emotions,[63] providing more direct support for the idea that the mirror system is linked to empathy. Some researchers observed that the human mirror system does not passively respond to the observation of actions but is influenced by the mindset of the observer.[67] Researchers observed the link of the mirror neurons during empathetic engagement in patient care.[68]

Human self awareness

V. S. Ramachandran has speculated that mirror neurons may provide the neurological basis of human self-awareness.[69] In an essay written for the Edge Foundation in 2009 Ramachandran gave the following explanation of his theory: "... I also speculated that these neurons can not only help simulate other people's behavior but can be turned 'inward'—as it were—to create second-order representations or meta-representations of your own earlier brain processes. This could be the neural basis of introspection, and of the reciprocity of self awareness and other awareness. There is obviously a chicken-or-egg question here as to which evolved first, but... The main point is that the two co-evolved, mutually enriching each other to create the mature representation of self that characterizes modern humans".[70]

Language

In humans, functional MRI studies have reported finding areas homologous to the monkey mirror neuron system in the inferior frontal cortex, close to Broca's area, one of the hypothesized language regions of the brain. This has led to suggestions that human language evolved from a gesture performance/understanding system implemented in mirror neurons. Mirror neurons have been said to have the potential to provide a mechanism for action-understanding, imitation-learning, and the simulation of other people's behaviour.[71] This hypothesis is supported by some cytoarchitectonic homologies between monkey premotor area F5 and human Broca's area.[72] Rates of vocabulary expansion link to the ability of children to vocally mirror non-words and so to acquire the new word pronunciations. Such speech repetition occurs automatically, fast[73] and separately in the brain to speech perception.[74][75] Moreover, such vocal imitation can occur without comprehension such as in speech shadowing[76] and echolalia.[77]

Further evidence for this link comes from a recent study in which the brain activity of two participants was measured using fMRI while they were gesturing words to each other using hand gestures with a game of charades – a modality that some have suggested might represent the evolutionary precursor of human language. Analysis of the data using Granger Causality revealed that the mirror-neuron system of the observer indeed reflects the pattern of activity in the motor system of the sender, supporting the idea that the motor concept associated with the words is indeed transmitted from one brain to another using the mirror system[78]

The mirror neuron system seems to be inherently inadequate to play any role in syntax, given that this definitory property of human languages which is implemented in hierarchical recursive structure is flattened into linear sequences of phonemes making the recursive structure not accessible to sensory detection[79]

Automatic imitation

The term is commonly used to refer to cases in which an individual, having observed a body movement, unintentionally performs a similar body movement or alters the way that a body movement is performed. Automatic imitation rarely involves overt execution of matching responses. Instead the effects typically consist of reaction time, rather than accuracy, differences between compatible and incompatible trials. Research reveals that the existence of automatic imitation, which is a covert form of imitation, is distinct from spatial compatibility. It also indicates that, although automatic imitation is subject to input modulation by attentional processes, and output modulation by inhibitory processes, it is mediated by learned, long-term sensorimotor associations that cannot be altered directly by intentional processes. Many researchers believe that automatic imitation is mediated by the mirror neuron system.[80] Additionally, there are data that demonstrate that our postural control is impaired when people listen to sentences about other actions. For example, if the task is to maintain posture, people do it worse when they listen to sentences like this: "I get up, put on my slippers, go to the bathroom". This phenomenon may be due to the fact that during action perception there is similar motor cortex activation as if a human being performed the same action (mirror neurons system).[81]

Motor mimicry

In contrast with automatic imitation, motor mimicry is observed in (1) naturalistic social situations and (2) via measures of action frequency within a session rather than measures of speed and/or accuracy within trials.[82]

The integration of research on motor mimicry and automatic imitation could reveal plausible indications that these phenomena depend on the same psychological and neural processes. Preliminary evidence however comes from studies showing that social priming has similar effects on motor mimicry.[83][84]

Nevertheless, the similarities between automatic imitation, mirror effects, and motor mimicry have led some researchers to propose that automatic imitation is mediated by the mirror neuron system and that it is a tightly controlled laboratory equivalent of the motor mimicry observed in naturalistic social contexts. If true, then automatic imitation can be used as a tool to investigate how the mirror neuron system contributes to cognitive functioning and how motor mimicry promotes prosocial attitudes and behavior.[85][86]

Meta-analysis of imitation studies in humans suggest that there is enough evidence of mirror system activation during imitation that mirror neuron involvement is likely, even though no published studies have recorded the activities of singular neurons. However, it is likely insufficient for motor imitation. Studies show that regions of the frontal and parietal lobes that extend beyond the classical mirror system are equally activated during imitation. This suggests that other areas, along with the mirror system are crucial to imitation behaviors.[6]

Autism

It has also been proposed that problems with the mirror neuron system may underlie cognitive disorders, particularly autism.[87][88] However the connection between mirror neuron dysfunction and autism is tentative and it remains to be demonstrated how mirror neurons are related to many of the important characteristics of autism.[13]

Some researchers claim there is a link between mirror neuron deficiency and autism. EEG recordings from motor areas are suppressed when someone watches another person move, a signal that may relate to mirror neuron system. This suppression was less in children with autism.[87] Although these findings have been replicated by several groups,[89][90] other studies have not found evidence of a dysfunctional mirror neuron system in autism.[13] In 2008, Oberman et al. published a research paper that presented conflicting EEG evidence. Oberman and Ramachandran found typical mu-suppression for familiar stimuli, but not for unfamiliar stimuli, leading them to conclude that the mirror neuron system of children with ASD (Autism Spectrum Disorder) was functional, but less sensitive than that of typical children.[91] Based on the conflicting evidence presented by mu-wave suppression experiments, Patricia Churchland has cautioned that mu-wave suppression results cannot be used as a valid index for measuring the performance of mirror neuron systems.[92] Recent research indicates that mirror neurons do not play a role in autism:

...no clear cut evidence emerges for a fundamental mirror system deficit in autism. Behavioural studies have shown that people with autism have a good understanding of action goals.Furthermore, two independent neuroimaging studies have reported that the parietal component of the mirror system is functioning typically in individuals with autism.[93]


Some anatomical differences have been found in the mirror neuron related brain areas in adults with autism spectrum disorders, compared to non-autistic adults. All these cortical areas were thinner and the degree of thinning was correlated with autism symptom severity, a correlation nearly restricted to these brain regions.[94] Based on these results, some researchers claim that autism is caused by impairments in the mirror neuron system, leading to disabilities in social skills, imitation, empathy and theory of mind.[who?]

Many researchers have pointed out that the "broken mirrors" theory of autism is overly simplistic, and mirror neurons alone cannot explain the differences found in individuals with autism. First of all, as noted above, none of these studies were direct measures of mirror neuron activity - in other words fMRI activity or EEG rhythm suppression do not unequivocally index mirror neurons. Dinstein and colleagues found normal mirror neuron activity in people with autism using fMRI.[95] In individuals with autism, deficits in intention understanding, action understanding and biological motion perception (the key functions of mirror neurons) are not always found,[96][97] or are task dependent.[98][99] Today, very few people believe an all-or-nothing problem with the mirror system can underlie autism. Instead, "additional research needs to be done, and more caution should be used when reaching out to the media".[100]

Research from 2010[101] concluded that autistic individuals do not exhibit mirror neuron dysfunction, although the small sample size limits the extent to which these results can be generalized.
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Re: Mirror neuron, by Wikipedia

Postby admin » Wed Feb 20, 2019 2:07 am

Part 2 of 2

Theory of mind

In Philosophy of mind, mirror neurons have become the primary rallying call of simulation theorists concerning our "theory of mind". "Theory of mind" refers to our ability to infer another person's mental state (i.e., beliefs and desires) from experiences or their behaviour.

There are several competing models which attempt to account for our theory of mind; the most notable in relation to mirror neurons is simulation theory. According to simulation theory, theory of mind is available because we subconsciously empathize with the person we're observing and, accounting for relevant differences, imagine what we would desire and believe in that scenario.[102][103] Mirror neurons have been interpreted as the mechanism by which we simulate others in order to better understand them, and therefore their discovery has been taken by some as a validation of simulation theory (which appeared a decade before the discovery of mirror neurons).[56] More recently, Theory of Mind and Simulation have been seen as complementary systems, with different developmental time courses.[104][105][106]

At the neuronal-level, in a 2015 study by Keren Haroush and Ziv Williams using jointly interacting primates performing an iterated prisoner's dilemma game, the authors identified neurons in the anterior cingulate cortex that selectively predicted an opponent's yet unknown decisions or covert state of mind. These "other-predictive neurons" differentiated between self and other decisions and were uniquely sensitive to social context, but they did not encode the opponent's observed actions or receipt of reward. These cingulate cells may therefore importantly complement the function of mirror neurons by providing additional information about other social agents that is not immediately observable or known.[107]

Gender differences

A series of recent studies conducted by Yawei Cheng, using a variety of neurophysiological measures, including MEG,[108] spinal reflex excitability,[109] electroencephalography,[110][111] have documented the presence of a gender difference in the human mirror neuron system, with female participants exhibiting stronger motor resonance than male participants.

In another study, gender differences among mirror neuron mechanisms was reinforced in that the data showed enhanced empathetic ability in female identified or female raised individuals when compared to male equivalents.
During an emotional social interaction, the female identified or raised individuals show a greater ability in emotional perspective taking than do male identified or raised individuals when interacting with another person face-to-face. This ability may be due to the fact that male socialization in most cultures requires that men limit emotional expression. However, in the study, data showed that when it came to recognizing the emotions of others, all participants' abilities were very similar and there was no key difference along a gender binary.[112]

Sleep paralysis / Ghostly Bedroom Intruders

Baland Jalal and V. S. Ramachandran have hypothesized that the mirror neuron system is important in giving rise to the intruder hallucination and out-of-body experiences during sleep paralysis.[113] According to this theory, sleep paralysis leads to disinhibition of the mirror neuron system, paving the way for hallucinations of human-like shadowy beings. The deafferentation of sensory information during sleep paralysis is proposed as the mechanism for such mirror neuron disinhibition.[113] The authors suggest that their hypothesis on the role of the mirror neuron system could be tested:
"These ideas could be explored using neuroimaging, to examine the selective activation of brain regions associated with mirror neuron activity, when the individual is hallucinating an intruder or having an out-of-body experience during sleep paralysis ."[113]

Mirror neuron function, psychosis, and empathy in schizophrenia

Recent research, which measured mu-wave suppression, suggests that mirror neuron activity is positively correlated with psychotic symptoms (i.e., greater mu suppression/mirror neuron activity was highest among subjects with the greater severity of psychotic symptoms). Researchers concluded that "higher mirror neuron activity may be the underpinning of schizophrenia sensory gating deficits and may contribute to sensory misattributions particularly in response to socially relevant stimuli, and be a putative mechanism for delusions and hallucinations."[114]

See also

• Associative sequence learning
• Common coding theory
• Emotional contagion
• Empathy
• Mirror-touch synesthesia
• Mirroring (psychology)
• Motor cognition
• Motor theory of speech perception
• On Intelligence
• Positron emission tomography
• Simulation theory of empathy
• Speech repetition
• Spindle neuron

References

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Further reading

• Hickok, Greg (2014). The Myth of Mirror Neurons. ISBN 978-0-393-08961-5.
• Keysers, C. (2011). The Empathic Brain. ISBN 1-4637-6906-7.
• Iacoboni M, Mazziotta JC (2007). "Mirror neuron system: basic findings and clinical applications". Ann Neurol. 62 (3): 213–8. doi:10.1002/ana.21198. PMID 17721988.
• Keysers, C., & Gazzola, V. (2006), Towards a unifying neural theory of social cognition, Progress in Brain Research.[3]
• Morsella, E., Bargh, J.A., & Gollwitzer, P.M. (Eds.) (2009). Oxford Handbook of Human Action. New York: Oxford University Press.
• Preston, S. D.; de Waal, F.B.M. (2002). "Empathy: Its ultimate and proximate bases". Behavioral and Brain Sciences. 25: 1–72. doi:10.1017/s0140525x02000018.
• Rizzolatti G, Fabbri-Destro M, Cattaneo L (2009). "Mirror neurons and their clinical relevance". Nat Clin Pract Neurol. 5 (1): 24–34. doi:10.1038/ncpneuro0990. PMID 19129788.
• Rizzolatti, G., Sinigaglia, C. (2008). Mirrors in the Brain. How We Share our Actions and Emotions. Oxford (UK), Oxford University Press.

External links

Wikimedia Commons has media related to Mirror neurons.

• NOVA scienceNOW: Mirror Neurons (including a 14-minute broadcast segment)
• You remind me of me in the New York Times.
• 7 Minute Video on TED.com :: Neuroscientist Vilayanur Ramachandran outlines the functions of mirror neurons
• Mirror Neuron Forum, Perspectives on Psychological Science, September, 2011
• Talking Brains, Greg Hickok and David Poeppel, News And Views On the Neural Organization of Language
• Thomas, Ben: What's So Special about Mirror Neurons? Scientific American Guest Blog, 2012 (an overview of prominent research approaches based on interviews with Iacoboni, Hickok, Heyes and Gallese)
• Mirror neurons: still an open question? Paolo B. Pascolo. Progress in Neuroscience 2013; 1 (1-4): 25-82
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Re: Mirror neuron, by Wikipedia

Postby admin » Sun Jul 07, 2019 7:17 am

Where is the love? The social aspects of mimicry
by Rick van Baaren,1,* Loes Janssen,2 Tanya L. Chartrand,3 and Ap Dijksterhuis1
Copyright © 2009 The Royal Society

1Behavioral Science Institute, Radboud University Nijmegen, The Netherlands
2Department of Communication, Twente University, The Netherlands
3Fugua Business School, Duke University, Durham, NC, USA
*Author for correspondence (ln.ur.isb@neraabnav.r).

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ABSTRACT

One striking characteristic of human social interactions is unconscious mimicry; people have a tendency to take over each other's posture, mannerisms and behaviours without awareness. Our goal is to make the case that unconscious mimicry plays an important role in human social interaction and to show that mimicry is closely related to and moderated by our connectedness to others. First we will position human unconscious mimicry in relation to types of imitation used in cognitive psychology and cognitive neuroscience. Then we will provide support for social moderation of mimicry. Characteristics of both the mimicker and the mimickee influence the degree of mimicry in a social interaction. Next, we turn to the positive social consequences of this unconscious mimicry and we will present data showing how being imitated makes people more assimilative in general. In the final section, we discuss what these findings imply for theorizing on the mechanisms of imitation and point out several issues that need to be resolved before a start can be made to integrate this field in the broader context of research on imitation.

Keywords: imitation, social, humans

Imitation, by definition, is a truly social phenomenon: it takes two to imitate. Although at first glance this statement may seem somewhat trivial, the social nature of imitation in fact has not been fully appreciated by current theorizing on imitation. Whereas we know a lot about the mechanisms of imitation from a cognitive-, developmental- and neuropsychological perspective, the social moderators and consequences are less well understood. Do we imitate everybody or are we more selective? How does our relationship to the mimicker or mimickee moderate imitation and its consequences? What are the social consequences of imitation? The purpose of this paper is to present evidence for the social side of imitation and by doing so, hopefully inspire other disciplines to integrate these findings in their theorizing and empirical work. It is not the intention to provide a complete review of all the work done on mimicry (for a review, see Chartrand & Van Baaren 2009), instead, the paper is written to make a strong case for social processes in this type of imitation.

In the next sections we will provide evidence for social moderators and consequences of mimicry, whereafter we will discuss the fit and misfit with current theorizing. It is not our intention to integrate the present chapter in the theorizing done in other chapters in this special issue, simply because there is just too little research on this type of mimicry in cognitive psychology and cognitive neuroscience. What we do instead is point out which questions, in our view, should be addressed by studies in the near future. First, however, we will clarify what type of imitation is the focus of this paper.

1. TYPE OF IMITATION: UNCONSCIOUS HUMAN MIMICRY

The social psychological studies providing evidence for the social side of imitation have mostly focused on human mimicry. In this field, mimicry is defined as unconscious or automatic imitation of gestures, behaviours, facial expressions, speech and movements (for an extensive review see Chartrand & Van Baaren 2009). A prototypical example is when two people in a bar are involved in a conversation and are unaware of the fact that they take on the same posture, nod their heads, and make the same face rubbing or hair touching movements. This type of mimicry thus is different from the more conscious types of imitation that have been studied in the realm of learning, modelling and acculturation (e.g. Bandura 1962). This type of mimicry is also different from the types used in research in cognitive psychology and cognitive neuroscience that has focused on imitation (see other chapters in the special issue). The difference in this case centres around awareness; are you aware of the behaviour you see and are you intentionally trying to copy it? When it comes to unconscious mimicry, the answer to those questions is ‘no’. In most cognitive and neuropsychological studies, at least one of these questions is answered by ‘yes’.

A related key difference between the social psychological studies and most of the studies in cognitive- and cognitive neuroscience is the relative focus on ecological versus internal validity. Most studies on unconscious mimicry use an observational method and one is in a sense waiting (like an amateur bird-watcher) until the behaviour to be imitated is spontaneously produced. This is in contrast with many tasks used in cognitive- and cognitive neuroscience where often a stimulus–response compatibility task is used (e.g. Prinz 1990; Iacoboni et al. 1999; Brass et al. 2001; Massen & Prinz 2009) and the behaviour of interest is either instructed or inherent in the task or participants are consciously observing a behaviour and their spontaneous motor or neurological responses are coded.

It is important to realize that, in studies on unconscious human mimicry, mimicry is just a by-product in the interaction. The participants are focusing on something completely different (e.g. working on a picture describing task (Chartrand & Bargh 1999) or judging advertisements (Van Baaren et al. 2003)) and they are unaware of the behaviour, the mimicry and the fact that the researchers may in fact be interested in something else other than the irrelevant task the participant is working on …. In sum, the type of imitation we have researched most extensively is unconscious, peripheral mimicry.

A prototypical example of an experimental investigation of human unconscious mimicry is the ‘Chameleon effect’ (Chartrand & Bargh 1999). In this research, participants interacted with an unknown confederate in two consecutive picture-describing sessions. In one session, the confederate either rubbed her face or shook her foot while describing the pictures with the participants, while the second confederate performed the behaviour that the first confederate did not. The behaviour of the participants, ‘secretly’ recorded on videotape, showed that participants shook their foot more in the presence of the foot-shaking confederate, and rubbed their faces more in the presence of the face-rubbing confederate. Debriefing indicated that participants were unaware of their mimicry.

2. EVIDENCE FOR SOCIAL MODERATORS: MIMICKER CHARACTERISTICS

The Chameleon effect (Chartrand & Bargh 1999) did show that there is an automatic human tendency to mimic behaviour and mannerisms. However, subsequent research revealed we don't imitate everyone all the time. Our tendency to unconsciously mimic is moderated by both enduring and temporary characteristics of the mimicker and the mimickee.

First, nonconscious mimicry is increased when people are more focused on the individuals around them.
Providing initial support for this contention, Chartrand & Bargh (1999, study 3) found that people high in perspective taking (i.e. who are paying more attention to those around them) mimicked the behaviour of a confederate to a greater extent than those low in perspective taking.

Additional evidence for the moderating role of concern with others comes from research by van Baaren et al. (2003). In three studies that either temporarily primed self-construal orientation or compared participants from different cultures, an interdependent self-construal was associated with more automatic mimicry than with an independent self-construal. In essence, self-construal refers to the extent to which people perceive themselves as unique individuals, independent of others instead of connected to, and dependent on, others (see Brewer 1991). Even though, in general, some people are enduringly more dependent than independent, self-construal can be temporarily modified. For example, priming participants by presenting them or having them read words like ‘I’, ‘me’ or ‘mine’ versus ‘we’, ‘us’ or ‘our’ temporarily shifts their self-construals on the social-personal dimension. This in turn influences the degree of unconscious mimicry in a subsequent interaction with a stranger (Van Baaren et al. 2003; study 2). That is, participants with either a temporary or enduringly dominant and interdependent self were more likely to nonconsciously take on the behaviours and mannerisms of a confederate. Using a stimulus–response compatibility task (a dependent variable more common to cognitive psychology compared to spontaneous mimicry), Leighton et al. (submitted) recently conceptually replicated this effect.

Finally, enduring or temporary attention to and concern with others have been shown to moderate the extent to which individuals mimic an interaction partner. For example, an affiliation goal is associated with more mimicry than no affiliation goal, as has been shown by Lakin & Chartrand (2003). This held regardless of whether the goal was consciously held after getting explicit instructions to get along with another person, or nonconsciously held after being subliminally primed with affiliation-related words such as affiliate, friend, team, partner, and like.

Thus, when we are more concerned with others, depend more on them, feel closer to them, or want to be liked by them, we tend to take over their behaviour to greater extent. This malleability of mimicry is beautifully captured by Brewer's (1991) optimal distinctiveness theory. The theory suggests that people try to strike a balance between a desire for distinctiveness (i.e. feeling unique and different from others) and a desire for assimilation or belonging (i.e. feeling similar to others). When people feel too distinct or too similar, they are motivated to regain the balance. Thus, they have a need to assimilate activated in situations where they feel unusual or different. In a study applying the principles of this theory to mimicry behaviour, Uldall et al. (submitted) had participants complete a supposed ‘personality test’. They were given (bogus) feedback on the test that indicated they had a ‘personality type’ that was either very similar to most others at their undergrad institution or one that was extremely unusual at their university. Participants then interacted with another student (actually a confederate), and those who had earlier been told they were very different from others at their school engaged in more mimicry of the confederate than those who had been told they were similar to others at their school. This suggests that people mimic more when they are feeling too different from in-group members. Mimicry is a way that people (nonconsciously) regain their ‘optimal’ balance (Brewer 1991) by affiliating with others in an effort to belong. It is important to note the difference between priming or activating a self-construal and the manipulation used in the Uldall et al. (2008) study. Whereas independent or interdependent self-construals are self-construals that can differ between and within people, depending on context, the Uldall et al. manipulation entails an extremely dependent or independent priming. This means that it is outside the ‘normal’ boundaries of how we relate to others and we (unconsciously) feel the need to restore the balance. In the experiments on affiliation goals and self-construal, however, the priming is not extreme and people assimilate to the prime, instead of restoring a balance. Extremity is the moderating principle here (Brewer 1991).

Social processes can extend to a basic perceptual and cognitive level, and research from cultural and social psychology indicated that the mimicker characteristics, such as self-construal, are correlated with the perceptual and cognitive mimicker characteristics (Witkin et al. 1979; Witkin & Goodenough 1981; Ji et al. 2000). Field dependence, for example, which refers to the phenomenon of perceptually integrating objects in their context, goes together with socially being more attuned to others. On the other hand, field independence, which is the tendency to perceptually isolate objects from their contexts, is related to a socially independent mindset. In three experiments by Van Baaren et al. (2004a,b), the cognitive styles (field dependency versus field independence) were either measured or experimentally primed and then the degree of unconscious mimicry in a subsequent interaction was measured. As expected, the more field dependent participants were on a test of cognitive style (e.g. the Hidden Figures Test, Witkin et al. 1971) the more they mimicked their interaction partner. This attests the idea that the mimicker characteristics influencing our unconscious mimicry are deeply rooted and fundamental.

3. EVIDENCE FOR SOCIAL MODERATORS: MIMICKEE CHARACTERISTICS

Another important social moderator of mimicry is our evaluation of the characteristics of our interaction partner. When we like a person, or his/her ethnicity, or group membership or social status, we will imitate that person to a greater extent compared to when we do not positively evaluate those characteristics. Johnston and colleagues have conducted several experiments providing evidence for this effect. First, Johnston (2002) investigated the impact of a social stigma on mimicry. In two studies, participants were ostensibly working on an icecream tasting task together with another person (a confederate), who had or had not a visible social stigma (being obese, or having a facial scar). The confederate ate a lot or a little ice cream and it was assessed whether the participant mimicked the ice cream consumption. The results revealed indeed a mimicry effect of the participant's consumption; however, no mimicry occurred when the confederate had a visible social stigma. The theory is that mimicry (unconsciously) creates a bond or connection between individuals and that humans automatically and unconsciously try to prevent mimicry in cases where they do not want to bond with another person.

Taking it more broadly than social stigma, Stel et al. (submitted) have explored the relationship between evaluation or liking of a target and mimicry. In a first study where participants' a priori liking for a target was manipulated and their mimicry of that person was then measured, they found that when a target is disliked, facial mimicry is attenuated. In another study, a reaction time measure to assess implicit associations (IAT, see Greenwald et al. 1998) towards Dutch and Moroccans was administered. With this measure, the relative evaluation of Dutch versus Moroccans can be quantified. In a subsequent session, participants watched videos of both a Dutch actor and a Moroccan actor performing some clerical tasks and in addition performing some subtle behaviours, such as face/hair touching and pen-playing. Hidden videocameras registered the participants' behaviours and it was found that the implicit attitudes correlated with unconscious mimicry, that is, the more negative participants were towards Moroccans relative to Dutch, the less relatively they mimicked a Moroccan compared to a Dutch actor. Similar results were previously obtained by Yabar et al. (2006), where instead of ethnic attitudes, implicit attitudes towards Christians (versus non-Christians) were used. Finally, several other studies found main effects of ingroup–outgroup distinction on mimicry. Heider & Skowronski (submitted) conducted a study in which African-American and Caucasian participants interacted with two confederates one after the other, one African-American and one Caucasian. They found more mimicry of ethnic ingroup members than ethnic outgroup members. Similarly, Bourgeois & Hess (2008) found more facial mimicry of ingroup members than outgroup members.

In sum, there is ample evidence for social moderation of mimicry, namely, the human nonconscious tendency to imitate. We do not just imitate everybody all the time. We imitate more when: we feel connected to others, others are important, we want to affiliate with others, we are socially oriented or have an assimilative cognitive style. Furthermore, in addition to these more general mimicker characteristics, the characteristics of the mimickee also moderate mimicry. A priori evaluations of those targets predict our subsequent mimicry.

In the next section we discuss another line of evidence lending strong support for a view that mimicry is closely related to influences and is influenced by social processes in human interactions. Then, we move on to an attempt to integrate these social moderators and consequences in current theorizing on imitation.

4. SOCIAL CONSEQUENCES OF UNCONSCIOUS MIMICRY: ON THE DYAD

In many commercial books on influence and making friends, imitation is offered as one of the means to create a good impression and have a positive relation or rapport with others (e.g. Lieberman 2000). There is now experimental evidence that this indeed occurs. Positive social consequences have been observed for mimicry of body movements and speech variables. In a typical experiment, a participant and a confederate work on an irrelevant task. During that task, the confederate mimics (or not) the posture, mannerisms, and behaviours of the participant after a short delay. These can be gestures or movements such as face-rubbing, foot-shaking, playing with a pen, orientation of the body (avoiding movements that indicate power or status), or speech variables such as using the same phrases of speech. This subtle mimicking almost always is completely unnoticed by the participant. After this imitation manipulation, the dependent variable is assessed, which is often an evaluation of or behaviour towards the confederate.

Chartrand & Bargh (1999) found that participants who were subtly mimicked by a confederate liked that confederate more and had smoother interactions with that confederate. The developmental psychology literature documents evidence that infants react more favourably towards adults who imitate them than adults who do not (Meltzoff 1990; Asendorpf et al. 1996). Interestingly, similar consequences have been observed in human–computer interactions. Bailenson & Yee (2005) had a realistic interface agent (i.e. an avatar using virtual reality technology) either imitating the participant's head movements or performing different head movements. The imitating interface agents were rated as more likeable and more persuasive than the non-mimicking avatars. Similarly, Suzuki et al. (2003) found that mimicry of certain (prosodic) properties of a participant's voice by a computer agent led to more favourable evaluations of the computer agent. Thus, the evaluative consequences of imitation are not unique to human–human interactions.

Van Baaren et al. (2004a,b; experiment 1) found that being imitated not only influences evaluations such as liking or rapport, but also makes people behave in a more pro-social manner. In this study, a mimicking or non-mimicking experimenter ‘accidentally’ dropped several pens on the floor. The dependent variable was whether participants got off their chairs and started to help (a measure developed by Macrae & Johnston 1998). The results revealed that imitated participants were considerably more helpful than non-imitated participants. This effect was recently replicated with eighteen-month old children (Carpenter et al. submitted).

What was confounded in the studies, on the consequences of imitation, is that the effects of imitation were measured vis-a-vis the imitator. This is important to note, because it could theoretically be possible that the effects of imitation are not restricted to the dyad and the imitator. Perhaps the effects extend beyond the relation between the imitator and the imitated. Accordingly, it affects the imitated person in a more fundamental way. It is possible that imitation makes one more pro-socially oriented in general.

5. SOCIAL CONSEQUENCES OF UNCONSCIOUS MIMICRY: BEYOND THE DYAD

Initial support for this idea was obtained in studies looking at the effects of being mimicked on behaviour towards people other than the mimicker (Van Baaren et al. 2004a,b). Similar to the previously described experiment, participants were mimicked or not by an experimenter and the effects on prosocial behaviour were assessed. This time, however, the experimenter who mimicked the participant said he was finished, and that a new experimenter would come in and left the room. After a while, the new experimenter entered the room and dropped the pens on the floor. Were mimicked participants more prosocial after being mimicked, even though the person was somebody else rather than the mimicker? The results revealed indeed that also this new person benefited from the increased pro-sociality of a mimicked participant. It could be the case that these results can be explained by a transfer of the pro-social orientation towards the mimicking experimenter onto the new experimenter, because they have similar roles and operate in the same setting. To control this, the next study looked at prosocial behaviour towards an abstract, non-human entity: donation to a charity. After the imitation manipulation, participants were left alone in a room, with the money they received for participating and they were asked to fill out a questionnaire on the ‘CliniClowns’ a Dutch charity trying to alleviate the stay in hospital for seriously ill children. There was a sealed collection box in the corner of the room and participants were in the position to anonymously donate or not. Whereas non-mimicked participants on average donated a little under 40 eurocents to the CliniClowns, the donation increased up to almost 80 eurocents for those whose behaviour had been mimicked.

6. SOCIAL CONSEQUENCES OF UNCONSCIOUS MIMICRY: SELF-CONSTRUAL

How can these general consequences be explained? As was described in the section on moderators of mimicry, self-construals are intimately linked to unconscious imitation. A interdependent (or social) self-construal goes hand in hand with mimicry and prosocial behaviour, whereas an independent (or personal) self-construal is associated with less mimicry. A bi-directional link between this mindset and mimicry could explain the general social consequences described in the previous paragraph. Ashton-James et al. (2007) tested the idea that self-construal may mediate the effect of mimicry on prosocial behaviour. In one of the experiments, participants were mimicked during an initial interaction. After this mimicry manipulation, their self-construal was assessed using the ‘Twenty Statements Test’ (TST, Kuhn & McPartland 1954), in which participants had to give twenty answers to the question ‘Who am I?’. The answers to this test are then coded for interdependence (social roles, connections to others, e.g. I am Tom's brother) and independence (unique attributes, personal characteristics, e.g. I am tall). After the TST, the measure of prosocial behaviour (in general) took place. The participant was asked to help another researcher, who was unable to pay them, with another experiment. Ashton-James et al. (2007) indeed found an effect of mimicry on both self-construal and prosocial behaviour and, in line with the hypotheses, self-construal mediated the mimicry-prosocial effect. Thus, being imitated makes people feel more attuned to and connected with others.

As was previously mentioned, there is an intimate link between self-construal and cognitive style. Assimilation on a behavioral level goes hand in hand with an assimilative information processing style, implying that if being mimicked leads to a social self-construal then it should also lead to an interdependent (field-dependent) cognitive style. Van Baaren et al. (2004a,b; experiment 3) found evidence for this hypothesis. After a mimicry manipulation, participants whose behaviour had been unobtrusively copied scored better on a memory task sensitive to contextualized memory (Chalfonte & Johnson 1996). In this measure, the relative position of an object in relation to other objects is the focus of interest and an example of an interdependent processing style.

(a) Present study

However, the question remains whether being mimicked really leads to an assimilative mindset. Instead, it could be the case that, through mimicry, we tend to relate people and objects to their context and see them in relation to other people and objects, but we do not necessarily have to assimilate object and context. Contrast could also be an outcome of such a comparative process. Here, we will present a study designed to test whether mimicry indeed truly leads to an assimilative tendency. Do people actually see more similarities between objects or people after being mimicked? To test this, a measure developed by Mussweiler (2003) will be used (see appendix A). In this task, participants see two different pictures and are asked to rate how similar they find them. There are no right or wrong answers and because there is no context or comparison to other pictures, there are no anchors to perform the task. Hence, the similarity judgement is based on a general tendency to assimilate or contrast. In this experiment we will test the hypothesis that being mimicked indeed moves people to be more assimilative in general and we expect mimicked participants to perceive more similarity between the two pictures.

7. METHOD

(a) Participants and design


Twenty-one students from Radboud University Nijmegen were randomly assigned to one or two between-subjects conditions, Mimicry (yes versus no), and received 1 euro for participation in this brief experiment.

(b) Procedure

Upon arrival at the laboratory, the participant was brought to a room by the experimenter and was asked to take a seat at a table with two chairs. The experimenter seated herself on the other chair and explained they will discuss some recent advertisements. During this discussion, she unobtrusively mimicked (or not) the spontaneous behaviour of the participant (e.g. facial expressions, face/hair touching, movements by feet or arms) with a 4-second delay. The interaction lasted between 5.5 and 6 min. After this mimicry manipulation, the experimenter handed the similarity measure to the participant and left the room.

(c) Results and discussion

To test the effect of mimicry on assimilation, a t-test was performed. As predicted, mimicked participants perceived more similarity between the two random pictures (M = 6.91, s.d. = 1.14) compared to non-mimicked participants (M = 5.6, s.d. = 1.51), t(21) = 2.26, p < 0.05.

These results demonstrate that being imitated changes the way we perceive and interact with other people on a fundamental level. After being imitated, we perceive more similarity between objects, feel more similar to others and behave in a more prosocial manner. What remains a great challenge for future research is finding out how these effects occur chronologically. What exactly activates this assimilative mindset and the related self-construal? What ingredient in mimicry triggers these assimilative and social processes? In our view, at this stage of research on the social aspects of mimicry, now is the time to focus on the neural correlates of being imitated. Until we have found sound ways to measure being imitated in the brain, the magic of mimicry remains a mystery.

In all the experiments on the consequences of being mimicked that have been described so far, the interaction is always between two strangers. In all these cases, the consequences have been positive. What happens when we a priori do not like a person? Does that yield the same results or can mimicry actually backfire?

(d) Social consequences of unconscious mimicry: when it backfires

Likowski et al. (submitted) examined the boundary conditions of the positive consequences of being mimicked. Specifically, they found that being mimicked by a member of an outgroup makes an individual like the outgroup member less, not more. Thus, outgroup members who mimic are less liked than outgroup members who do not mimic. In a second study, they examined walking synchrony. A synchronized ingroup member was liked more than a non-synchronized ingroup member, but the opposite was found for outgroup members (a synchronized outgroup member was liked less than a non-synchronized outgroup member). Interestingly, the authors also found that the effect extends to liking of the ingroup or outgroup as a whole; being mimicked by an ingroup member leads to more liking of the ingroup, whereas being mimicked by an outgroup member leads to less liking of the outgroup.

Wigboldus et al. (in preparation) showed that the consequences of being imitated by an outgroup member are moderated by implicit prejudice. The head movements of white Dutch participants were unobtrusively mimicked or not by an avatar in an immersive virtual environment. For half the participants, the avatar was Dutch looking, and for the others he was Moroccan looking. The results showed that for low-prejudiced people, the ‘normal’ effect of being mimicked occurred: a mimicking avatar was evaluated more positively than a non-mimicking avatar. Importantly, this effect was reversed for high-prejudiced participants who were mimicked by an avatar with typical Moroccan features; they evaluated the mimicking avatar less favourably compared to the non-mimicking one.

A final interesting phenomenon where mimicry is not the default is complementarity, or the tendency to automatically react opposite to the observed behaviour. When behaviour is related to status, power or hierarchy, humans seem not to imitate. Instead, dominance automatically triggers submissiveness and vice versa (Wiggins 1982; Tiedens & Fragale 2003). Tiedens & Fragale (2003) for example manipulated the dominance or submissiveness of a confederate's posture (e.g. wide versus narrow) and observed how the participant's posture changes over time in response to the confederate. They found evidence for automatic complementarity; when participants were faced with a dominant confederate, their own body gradually and unconsciously took up less space, whereas they tended to extend their bodies in space when interacting with a submissive confederate.

(e) Implications for theorizing on imitation

How do these social moderators and consequences fit within the broader theories on the mechanisms of imitation presented elsewhere in this issue? At the present time, this question cannot be answered by empirical data and any theorizing is at best speculative. The field of unconscious mimicry has worked in isolation too long. What can be done, however, is to focus on the research described in this chapter and to distill and highlight those aspects of the data that need an explanation or may be of interest to theories on imitation in a broader sense.

First of all, unconscious mimicry is surprisingly flexible, in some cases it occurs more than in others and there are even circumstances where a tendency to act in a complementary instead of assimilative way is revealed. Second, given that the studies reported here on the consequences of imitation concern effects of which the mimickee is unaware, we need to be able to explain how our brains unconsciously code or ‘recognize’ we are being imitated or not and how that affects our brains in such a way that we become more prosocial (or less in cases of not liked targets).

In our view, these aspects are currently not well understood and thus any suggestion on possible integration is inherently speculative. However, regarding the flexibility of mimicry, there are two theories that provide an architecture (theoretically or neurologically) in which flexibility of sensory-motor couplings may occur: Heyes’ Associative Sequence Learning theory on sensorimotor associations (e.g. Heyes & Bird 2007) and Keysers & Perrett's Hebbian Perspective on the mirror system (Keysers & Perrett 2004). In both these theories, the mirror system acquires its properties by learned associations between sensory input and associated actions. When there is consistent co-activation between sensory and motor neurons, in time, these neurons become capable of mutual activation. When you wave your hand and you always see your hand wave, a direct link between the perception of a waving hand and waving it occurs. This in turn, due to sensitivity of both endogenous and exogenous stimuli in the mirror system, can lead to (pre)motor activity when we see somebody else move a hand. Importantly, this can also explain why we sometimes respond in a complementary way. If we learn in life that it is healthier to respond submissively to dominant people, and vice versa, the same mechanisms of associated sensory-motor couplings can explain these automatic complementary movements. Recent work by Catmur and colleagues (Catmur et al. 2007, 2008) provides evidence for this flexibility of the mirror system (Catmur et al. 2009). In their study, a training paradigm was introduced where different types of sensory-motor couplings were trained; compatible combinations (e.g. responding with a hand movement when observing a hand movement) and incompatible combinations (e.g. responding with a foot movement when observing a hand movement or vice versa). When participants were trained in incompatible combinations, a reversal of the typical compatibility effects were found on a reaction times measure; participants were actually faster on compatible compared to incompatible trials. In addition, using fMRI, the corresponding effect also occurred in the mirror system. After incompatible training, the activation of the action observation parts of the mirror system were modulated by training. Conceptually similar effects were observed on a muscular level using TMS and a hand opening–hand closing task.

Relating this to the work on human unconscious mimicry and the finding that mimicry is moderated by a priori liking of the target (or his/her group), it would suggest that this system is also sensitive to context. Training or task demands are one type of context, but the characteristic of the person whom we are about to mimic is another important context. On a sensory level, the behaviour we observe is integrated in a more complex array of stimuli: time, place, race, prior experience, expectations and the like. If the mirror system is flexible in the sensory–action couplings, then these peripheral aspects of the sensory input could be capable of influencing the type or direction of sensory–action coupling.

A possible mechanism that may help to explain how liking of a target moderates mimicry is provided by Brass et al. (2009). They describe the function of a brain circuit, comprised mainly of anterior frontomedian cortex (aFMC) and temporoparietal junction (TPJ), that plays a crucial role in distinguishing self from other. It is possible that such a system plays an important role both in mimicry and in the consequences of being mimicked. The more self–other overlap we ‘feel’, the more we will mimic the other and the more positive the consequences of being mimicked by that other will be. Future studies will be needed to test this idea and find evidence for connections between this ‘different-from-me’ mechanism and the brain mechanisms responsible for unconscious mimicry and its consequences.

Finally, regarding the consequences of being imitated, the first question that needs to be addressed is how our brain detects we are being imitated, even though we do not consciously realize it. Theoretically, the difference between being and not being imitated can be conceptualized as the presence or absence of compatible sensory and motor concepts. When we are imitated it means our sensory and motor activation resemble each other more compared to cases where we are not imitated. How the brain detects this and how that subsequently affects our prosocial orientation is still a mystery, although the suggested link between the neural bases of imitation and empathy (Preston & de Waal 2002; Decety & Jackson 2004) may be a starting point (also see Bastiaansen et al. 2009). Both (automatic) imitation and empathy seem to share at least for a large part the same neural mechanism. In addition, De Vignemont & Singer (2006) describe the contextual malleability of empathy, where our empathic response to others is modulated by, among others, individual characteristics and relational factors. Whereas an empathic response to a specific person is something else than a general assimilative mindset, the consequences of being imitated and empathy may show considerable overlap.

Before closing, however, the mere fact that unconscious mimicry is so pervasive and omnipresent in humans is in itself relevant to several chapters in this special issue. First of all, Ferrari et al. (2009) describe two possible mechanisms by which mirror neurons can influence behaviour; a ‘direct’ and ‘indirect’ way. According to these authors, direct imitation, of which unconscious mimicry seems to be an example, is only present early in human development. Coming with age, this direct translation of perception into action is less and mirror neurons influence behaviour less directly. However, this seems to be at odds with the review of studies on unconscious mimicry in this current chapter. One possible explanation is that unconscious mimicry occurs completely outside of awareness and when it does become conscious, people tend to stop or control it immediately. The type of imitation used by Ferrari et al. and the vast majority of studies on imitation in cognitive psychology and cognitive neuroscience is not unaware and is not tested in a truly ecological valid social context. In young children, this disliking of conscious imitation seems not to be apparent, although this needs more research.

In addition, Whiten et al. (2009) theorize about the mechanisms that facilitate cumulative cultural learning in humans and chimpanzees and describe how automatic imitation plays a fundamental role in this process. Whereas chimpanzees are capable of imitation, they seem to use/apply it more conservatively, while human children (and adults) seem to be ‘enthusiastic’ imitators. Our chapter corroborates this view, at least from the human perspective in showing the omnipresence of mimicry.

A final point of concern is whether unconscious mimicry is a high level or low level automatic mechanism. In this chapter, we have repeatedly stressed its unconscious, and hence automatic nature. Conversely, we have presented moderators that seem to be more high-level, such as self-construal and liking. We think it will be a major challenge to explain how such seemingly high level psychological constructs interact with this low level motoric phenomenon. One speculative possibility is that we automatically imitate (or complement) and we need inhibitory control to stop this phenomenon (see Van Leeuwen et al. in press). The higher level moderators then may work as triggers for inhibition. Alternatively, high level moderators operate before the to-be-mimicked action is perceived and exert their moderating influence at the beginning of the process.

In sum, social processes play a crucial role in mimicry and most probably in most types of imitation. It is now the time to start to integrate this view in theories explaining the mechanisms of imitation. More emphasis on the ecological circumstances and context of imitation will undoubtedly inspire other disciplines and ultimately tell us more about the architecture of social interactions, of which imitation is a prime example. In the end, mimicry is a truly social phenomenon where multiple individuals are needed and influence each other. If we only focus on the micro-level or intra-individual aspects of mimicry, we may lose sight of the affective and emotional factors related to it, hence the title of this chapter: where is the love?

APPENDIX A: Dependent variable assimilation.

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FOOTNOTES

One contribution of 13 to a Theme Issue ‘Evolution, development and intentional control of imitation’.

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