부산대학교 도서관

This thesis will establish the influence of social saliency and affect on perceptual decision-making. Although the study of the neural basis of human decision-making has inspired great attention, much of the literature has employed fMRI to explore complex decision-making in the brain which has great advantages in providing spatial information about the underlying neural activation. But, there is a lack of studies on the temporal dynamics of simple perceptual decision-making. It is important to focus on simple perceptual decision-making because people tend to make decisions rapidly based on the presented information which varies in sociality. However, despite research that has highlighted the importance of social saliency in simple perceptual decision-making tasks (Gutnik et al., 2006) the influence of social saliency on the temporal dynamics is understudied. It is crucial to examine the influence of social saliency on decision-making because humans are bombarded with various socially salient information/stimuli which impacts subsequent behaviour. Another influence on decision-making is the affective nature of information/stimuli. Emotions are the dominant driver of the most meaningful decisions in life (Keltner & Lerner 2010; Keltner et al 2014) but the impact of affect on the temporal dynamics of simple perceptual decision-making tasks, in particular, remains to be established. The current thesis addressed those gaps in the literature by examining the influence of social saliency and affect on the temporal dynamics of simple perceptual decision-making. Three conceptually similar studies were designed involving simple perceptual decision-making tasks in which social saliency (e.g. task stimuli, word primes and context) and affect (e.g. positive and negative) were manipulated to contrast differences in amplitudes in certain processing stages dependent on social saliency and affect. The first study was a systematic review which synthesised existing neurophysiological evidence from studies that manipulated social saliency across different neuroimaging paradigms and task designs. The systematic review highlighted the scarcity of temporal examination of the influence of social saliency on decision-making and the limited use of simple perceptual decision-making tasks in that literature. The second study investigated the influence of social saliency of task stimuli on behavioural performance and temporal dynamics in a preference choice task involving two conditions: 1) choosing between faces that varied in affect - social condition and 2) choosing between landscapes that varied in affect - non-social condition. In both conditions, one happy and one sad image was presented in a pair. Results demonstrated that the sensory processing and attentional focus stages had higher amplitudes for faces, whereas the affective evaluation stage was sensitive to landscapes. During the late processing stage,social saliency did not influence the decision-related stage (i.e. there was no difference in processing based on social saliency). The third study investigated the impact of social saliency on unconscious influences using a simple perceptual decision-making task involving trustworthiness ratings about neutral faces in two conditions: 1) primed with social words and 2) primed with non-social words. To examine the contributions of affect on decision-making, in both conditions word primes varied in affective nature (positive and negative). Social saliency and affect influenced behavioural performance and trustworthiness ratings of neutral faces: reaction times were faster in trials preceded by non-social primes than social word primes and faces preceded by social word primes were rated as more trustworthy compared to non-social word primes. There was no effect of social saliency on temporal dynamics, but negatively-valenced words elicited higher ERP amplitudes during the affective evaluation and decision-related stages. The fourth study moved from manipulating the social saliency and affective nature of the task stimuli and word primes to manipulating the social context. The influence of social context on the temporal dynamics of performance monitoring was investigated while participants performed a visual discrimination task in two conditions: 1) in the presence of a passive observer - social condition and 2) alone - non-social condition. The influence of affect was examined by giving participants performance feedback (i.e. via the computer) that varied in affect (i.e. neutral, negative and positive). The findings revealed an effect of social saliency at the behavioural level: reaction times were faster during the non-social condition compared to the social condition. There was no effect of social saliency on temporal dynamics, but negative and neutral feedback elicited higher ERP amplitudes during the feedback-related stage and the mid-range stage. There was an interaction between social saliency and affect with higher amplitudes for non-social trials where negative feedback was given during the mid-range stages. Overall, the current thesis contributes to the literature by providing electrophysiological evidence that both social saliency and affect of stimuli or feedback moderate the process of decision-making at different stages depending on the type of stimuli and task used. Early components (less than < 200ms after stimulus onset) are sensitive to the social saliency, but this effect is stimuli dependent: faces as a form of social stimuli demonstrated an influence on early temporal dynamics. Mid-range and late components (around 300-600ms) are sensitive to non-social information and modulated by the affect of stimuli/feedback with sensitivity towards negatively-valenced stimuli. Finally, the electrophysiological findings show that when social saliency interacts with affect, it elicits greater ERP amplitudes (i.e. activation) during the later processing stages that decision-making evaluative judgements take place.