It is easy to assume that humans have full control over how they react to different societal encounters. However, this is not the case. Individuals can exhibit certain reactions without being aware of their own motives or even the actions themselves. Anthony Greenwald and Mahzarin Banaji explained such a phenomenon using the concept of implicit social cognition. Despite being a recently introduced topic, it has drawn the attention of many researchers who came up with neuroscientific explanations as well as different types of measurements. This article discusses three regions of the temporal lobe - the amygdala, hippocampus, and perirhinal cortex- that are intertwined with implicit social cognition and the recent techniques that are used to study where and how different types of implicit mechanisms are being promoted.
Implicit social cognition (ISC) refers to any type of cognitive response that is unintentional, unconscious, and therefore, uncontrollable. It can be applied to areas such as attitude, bias, or even self-perception . ISC may differ from what the person expresses outwardly, either because they are not aware of their honest feelings or opinions or are intentionally hiding it from others to secure a positive social reputation. Hence, the elements of ISC cannot be captured through explicit measures such as self-introspection or direct responses from people. Studying how ISC develops neurologically and further characterizing its trends are crucial for uncovering certain cognitive associations that are left without being noticed and understanding issues stemming from microaggression .
Different Regions of the Brain That Contribute to ISC
There is a strong correlation between the role of the amygdala and ISC. The amygdala is located in the frontal portion of the temporal lobe and contains three major subnuclei—central (CeA), basal (BA), and lateral (LA) nuclei— to detect external cues that are potentially harmful to the body . The activation of the amygdala enables nearby regions of the brain to release cortisol (a stress hormone) that stimulates fear and physical responses for self-protection. Fear itself is categorized as an unconscious mechanism that is built through past experiences . Therefore, regardless of people’s awareness, when they encounter a stimulus similar to the ones that they have identified as threatening or unfamiliar before, their amygdala evokes negative emotions including fear . When the amygdala is repeatedly associated with a certain social group or environmental cues, it can lead to the development of implicit bias. Many experiments have used the relationship between the IAT scores and fMRI results to demonstrate that the amygdala is especially involved in provoking ISC responses to race. Those with negative implicit attitudes towards a certain racial group exhibited a greater amygdala activation when they were presented with the faces of people in that group .
The hippocampus, which is located on the edge of the temporal lobe, systematically maps the information acquired from the environment into long term memories and uses them to guide future decisions and responses . Neurologists often refer to implicit memories, which build the ISC, as ‘hippocampus -independent memories,’ assuming that they do not rely on one another. Previous studies have supported this hypothesis as patients with hippocampus damage experienced few difficulties with implicit memory, while their explicit memories were damaged . However, recent studies have questioned this hypothesis. They propose that certain implicit learning mechanisms require the support of the hippocampus . In 1998, Chung and Phelps suggested that the hippocampus is responsible for the performance of contextual (visual) cueing tasks, which is an implicit learning skill that allows people to spend less time searching for a certain target when they are repeatedly exposed to the same image or scene. In their experiment, two groups of participants - one with normal memory (control group) and another with amnesic impairment due to hippocampal damage (experimental group)- were shown twelve different sets of a T-shaped target randomly placed among L-shaped targets. Both groups were asked to identify the direction of a T-shaped target but none of them was informed that some sets were being repeatedly shown while going through thirty different trials. People with normal memory took advantage of visual cueing tasks and spent less time responding when they were given the image that they were previously exposed to. The amnesic patients did so too; however, they still took longer than when they were shown with the images for the first time . The validity of the statement made by Chun and Phelps is still under controversy, not only because the statistical difference in reduction of time between the control group and experimental group was insignificant, but also because there is not enough evidence to prove that contextual cueing tasks are solely dependent on the hippocampus. There is also a possibility that explicit memory, which the hippocampus also plays a role in, may have influenced people’s performance as well . The relationship between hippocampus and ISC is still under active study and therefore is worthwhile to pay attention to.
Perirhinal Cortex (PRC)
Unlike the hippocampus, the PRC has been shown to play an important role in conceptual implicit memory, which refers to the use of conceptual information that has been unconsciously acquired from the past . The PRC is a region of the medial temporal lobe that is placed on the back of the hippocampus and the amygdala. The PRC usually works with the hippocampus to carry out skills such as the learning of faces and scenes as well as different types of memory . However, the PRC itself is also responsible for familiarity-based discrimination of societal elements, which is a cognitive practice of differentiating something as either familiar or unfamiliar . The processing of conceptual implicit memory shares a closely related, fundamentally almost the same, mechanism with familiarity-based judgements . Therefore, it is reasonable for PRC to be involved in certain conceptual implicit memory as well as tasks such as semantic decision making and exemplar generation priming, which is the ability to come up with examples that fall into a certain semantic category . The fMRI results and implicit task experiments both revealed that the patients with the damage in PRC are unable to hold proper conceptual implicit memory. Even for those who are healthy, the activity of PRC during implicit encoding of information is directly proportional to the person’s ability to connect the concept with other societal characteristics .
Different Techniques of Studying the Neuroscience Behind ISC
Implicit Association Test (IAT)
The Implicit Association Test (IAT) is a psychological research tool that studies people’s unconscious evaluation of societal characteristics such as skin color, religion, or disability. Participants are given two contrasting traits of a concept and are asked to categorize them with either positive or negative words. Participants show faster performance when they are dealing with highly associated groups, which plays a role in revealing their stereotypes and preference towards certain attributes . For example, a Weight IAT indicates that one has automatic preference over Thin People over Fat People if one was faster at responding when Thin People and Good were assigned to the same response key than when Fat People and Good were classified with the same key. Based on the amount of difference between the time spent, the automatic preference can be divided into “slight”, “moderate”, and “strong” as well . The IAT is especially useful in detecting stereotypes in categories in which people are relatively more concerned about how they are represented to others . However, some psychologists have pointed out the limitations of the IAT: because it is accessible to anyone in any environment, results can be inconsistent due to external factors and are not a strong predictor of real-life behaviors in areas outside certain associations of race, age, and sexual orientation . Therefore, it is suggested that the results of the IAT can be better used when they are compared with explicit results or other implicit measurements that provide neurological insight about which region of the brain influences a certain ISC .
Non-Invasive Brain Stimulation (NIBS)
Non-invasive brain stimulation (NIBS) allows neurologists to target specific parts of the brain with electrical current without dissecting the brain. By doing so, researchers can identify which parts of the brain are involved in people’s implicit association between different social concepts and evaluations. For example, one study discovered that people’s stereotypical association between “Arabs'' and “terrorists” were reduced when NIBS was done to their anterior temporal lobe region . There are four types of NIBS techniques categorized based on how the electrical current can be applied to the brain: electroconvulsive therapy (ECT), transcranial magnetic stimulation (TMS), repeated transcranial magnetic stimulation (rTMS), and transcranial direct current stimulation (tDCS). rTMS is an enhanced version of TMS, and they can directly excite neurons to cause them to fire action potentials. On the other hand, tDCS sends low and steady pulses of electrical current through anodal (positive) and cathodal (negative)
electrodes to alter the ion threshold, and therefore, the activity of neurons . NIBS techniques, especially TMS and tCDS, are widely used to enhance people’s implicit cognitive skills. For instance, the anodal tDCS of the left temporal cortex and cathodal tDCS of the right temporal cortex can improve people’s recognition of sad faces in women . Furthermore, when there is a loss of function in the damaged area of the brain, NIBS can compensate for it by activating a nearby region of the brain that serves a similar cognitive role.
III. Functional Magnetic Resonance Imaging (fMRI)
Functional Magnetic Resonance Imaging (fMRI) measures the duration of electrical signals being sent out from different areas of the brain to detect regions that are associated with a certain behavior or cognitive function. One method to do so is to observe CBF (Cerebral Blood Flow) and BOLD (Blood Oxygenation Level Dependent) effects. The active neurons require a relatively larger amount of oxygen than those in the resting state. Therefore, when a certain cerebral region is carrying out a task, the concentration and the rate of oxygenated hemoglobin flowing into surrounding capillaries increase . fMRI has made significant contributions in studying how people’s brains react differently to certain stimuli due to unconscious intergroup bias . For instance, a case study conducted by Princeton University discovered that people tend to dehumanize homeless individuals more than middle-class individuals, as fMRI suggested that the activities of medial Prefrontal Cortex (which is responsible for identifying others as “highly human”) were only fully activated while they were making judgements about middle class people .
The invention of tools such as IAT, NIBS, and fRMI exhibits real-life cases of ISC and therefore hands important clues about how certain parts of the temporal lobe and potentially other regions of the brain interact with one another to produce implicit social behaviors. To solidify the understanding of ISC, there are more complex questions that need to be answered such as : “How do implicit and explicit processes interact?” and “What innovations to measurement methods can help capitalize on key operative processes, and minimize the influence of extraneous factors of measurement?” . Once enough data is collected to be able to generalize the patterns of ISC and to resolve the defects of technological devices, implicit measurements can be used to confirm people’s self-report in psychological experiments and to deal with microaggression using neurological interpretations.
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