Scientific Understanding of Consciousness
Long-Term Memory Social Conformity
Science 1 July 2011: Vol. 333 no. 6038 pp. 108-111
Following the Crowd: Brain Substrates of Long-Term Memory Conformity
Micah Edelson1, Tali Sharot2, Raymond J. Dolan2, Yadin Dudai1
1Department of Neurobiology, Weizmann Institute of Science, Israel.
2Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London, UK.
Human memory is strikingly susceptible to social influences, yet we know little about the underlying mechanisms. We examined how socially induced memory errors are generated in the brain by studying the memory of individuals exposed to recollections of others. Participants exhibited a strong tendency to conform to erroneous recollections of the group, producing both long-lasting and temporary errors, even when their initial memory was strong and accurate. Functional brain imaging revealed that social influence modified the neuronal representation of memory. Specifically, a particular brain signature of enhanced amygdala activity and enhanced amygdala-hippocampus connectivity predicted long-lasting but not temporary memory alterations. Our findings reveal how social manipulation can alter memory and extend the known functions of the amygdala to encompass socially mediated memory distortions.
Our memories are often inaccurate. Ubiquitous sources of false recollection are social pressure and interpersonal influence. This phenomenon, dubbed “memory conformity”, is encountered in a variety of contexts, including social interactions, mass media exposure, and eyewitness testimony. In such settings an individual may change veridical recollections of past events to match a false account provided by others. Although these social influences on memory have been extensively demonstrated, the underlying neurobiology of this process is unknown.
Conformity may present in two forms, which initially convey similar explicit behavior but are fundamentally different. In one type, known as private conformity, an individual’s recollection may genuinely be altered by social influence, resulting in long-lasting, persistent memory errors. In such circumstances, even when social influence is removed, the individuals will persist in claiming an erroneous memory as part of their own experience. Private conformity could hence be considered a bona fide memory change. In the second type, known as public conformity, individuals may choose to outwardly comply, providing an account that fits that of others, but inwardly maintain certitude in their own original memory. Public conformity can be dispelled when the veracity of the socially transferred information abates. Thus, errors induced by public conformity are transient and appear to represent a change in behavior in the absence of lasting alterations to a memory engram.
Enhanced activation in the bilateral amygdala and heightened functional connectivity with the anterior hippocampus were a signature of long-term memory change induced by the social environment. This indicates that the incorporation of external social information into memory may involve the amygdala’s intercedence, in accordance with its special position at the crossroads of social cognition and memory.
Multiple formal models have proposed trace attributes that might contribute to memory distortion in different false memory protocols. These postulated attributes refer, for example, to potential heterogeneity in episodic content and the persistence of memory trace elements. Our laboratory analog to socially induced memory distortion was not intended to distinguish between specific models. However, further exploitation of our protocol, combined with cross-fertilization of behavioral and brain data, might contribute to the refinement of current models and better understanding of the biological and cognitive mechanisms of memory conformity.
Altering memory in response to group influence may produce untoward effects. For example, social influence such as false propaganda can deleteriously affect individuals’ memory in political campaigns and commercial advertising and impede justice by influencing eyewitness testimony. However, memory conformity may also serve an adaptive purpose, because social learning is often more efficient and accurate than individual learning. For this reason, humans may be predisposed to trust the judgment of the group, even when it stands in opposition to their own original beliefs. Such influences and their long-term effects, the neurobiological basis of which we describe here, may contribute to the extraordinary levels of persistent conformity seen in authoritarian cults and societies.
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