Social Influence and Perceptual Decision Making

Abstract

Classic studies on social influence used simple perceptual decision-making tasks to examine how the opinions of others change individuals' judgments. Since then, one of the most fundamental questions in social psychology has been whether social influence can alter basic perceptual processes. To address this issue, we used a diffusion model analysis. Diffusion models provide a stochastic approach for separating the cognitive processes underlying speeded binary decisions. Following this approach, our study is the first to disentangle whether social influence on decision making is due to altering the uptake of available sensory information or due to shifting the decision criteria. In two experiments, we found consistent evidence for the idea that social influence alters the uptake of available sensory evidence. By contrast, participants did not adjust their decision criteria.

Social conformity is due to biased stimulus processing: electrophysiological and diffusion analyses

“…On the basis of a pretest (Germar et al, 2014), we chose two types of stimuli for this study: In one-half of the trials, stimuli were presented whose dominant color had been identified well above chance level (i.e. 80% correct responses on average) in the pretest.…”

“…Since the majority response was presented before stimulus onset, effects on stimulus processing could be due to both social influence and priming. In order to disentangle these processes, participants were randomly assigned to one of two betweensubjects conditions (Germar et al, 2014): Participants in the experimental condition were told that their fellow group members would consecutively respond to the same stimulus per trial; therefore, the majority response would be relevant for the participants' own responses. In contrast, participants in the control condition were instructed that their fellow group members' responses were not relevant to them because all participants would respond to different stimuli on each trial.…”

“…Additionally, as only the effects of correct vs incorrect group judgments were compared, it remains unclear how social influence per se (irrespective of its validity) alters perceptual decision-making. Germar et al (2014) employed a control condition to address these critical points. In each experimental session, four participants were asked to complete a perceptual decision-making task on separate computers.…”

“…To address this issue, we employed three complementary methods: stimulus evoked potentials (SEPs), lateralized readiness potentials (LRPs) and a diffusion model analysis of reaction time data. Moreover, we adapted the paradigm described above (Germar et al, 2014), which allowed us to investigate the effects of social influence per se.…”

“…In our study, zr values above 0.5 would indicate a shift in decision criteria toward the majority response. Based on Germar et al (2014), we predicted that social influence would lead to biased (i.e. higher values of ) and more careful (i.e.…”