Search

Depression is one of the leading mental health problems experienced worldwide. Whilst treatments are available for depression, individual treatment response is varied. The intersection between self, emotion, and reward, referred to in combination as self-referential affective processing, may be a key cognitive vulnerability in depression and a sensitive target for intervention. I aimed to: (1) evaluate whether depression is associated with differences in processing of self-related information, and whether this varies depending on the emotional valence or rewarding nature of information; (2) understand whether antidepressants are associated with change in self-referential affective processing. In chapter 1, I addressed my first aim by conducting a cross-sectional study where adults experiencing varying depression (n = 144) completed cognitive tasks measuring self, emotion, and reward processing, occurring independently and in combination. Depression was most reliably associated with self-referential processing occurring in interaction with reward and emotion. Participants with greater depression were worse at learning positive versus negative social evaluations about the self in a reinforcement learning task (β = 0.13, 95% CI: 0.06, 0.20, p < .001). In chapter 2, I validated these findings using an individual participant dataset collated from studies previously conducted within this research group (n = 552) and a second independent dataset of participants recruited online (n = 807). Replicating chapter 1, participants with greater depression were again worse at learning positive versus negative social evaluations about the self (dataset 1: β = 0.27, 95% CI: 0.20, 0.35, p < .001; dataset 2: β = 0.10, 95% CI: 0.02, 0.17, p = 0.009). Treatments that increase learning of positive social evaluations about the self may therefore be helpful in addressing depressive symptoms. In the second half of my thesis, I subsequently investigated the effect of antidepressants on self-referential affective processing. In chapter 3 I conducted a systematic review, narrative synthesis (k = 82), and meta-analysis (k = 28) of behavioural evidence for change in emotional processing following antidepressant administration. I did not find reliable evidence that current behavioural measures of emotional processing were altered following antidepressant administration (positive: SMD = 0.08, 95% CI = -0.05, 0.22, p = 0.230; negative: SMD = -0.04, 95% CI = -0.12, 0.04, p = 0.341). In chapters 4 and 5, I therefore investigated whether change in self-referential affective processing may be a more sensitive measure of early antidepressant action. I did not find evidence that learning social evaluations about the self differed in healthy volunteers randomised to acute citalopram versus placebo (chapter 4: b = 1.95, -2.25, 6.16), or that this was associated with change in depression over the first eight weeks of antidepressant treatment in a prospective observational cohort of primary care patients (chapter 5: β = 0.15, 95% CI: -0.10, 0.39, p = 0.239). However, acute administration of an antidepressant increased positive social behaviours (chapter 4; b = 20%, 95% CI: 2%, 37%, p = 0.030). Additionally, exploratory analyses also indicated that antidepressants increased positive affective biases towards familiar others (chapter 4: b = 4.06, 95% CI: 0.88, 7.24), which weakly predicted a reduction in a secondary measure of depression, the BDI-II, in primary care patients (chapter 5: β = 0.24, 95% CI: -0.01, 0.49, p = 0.069). Exploratory analyses in chapter 5 also indicated stronger evidence that increased learning of positive versus negative evaluations about both the self (β = 0.34, 95% CI: 0.14, 0.55, p = 0.002) and a friend (β = 0.36, 95% CI: 0.16, 0.56, p = 0.001) were associated with a reduction in anxiety. Due to weak evidence for the role of self-referential affective processing in antidepressant treatment found in chapters 4-5, as well as chapter 3 highlighting the need for novel psychological measures of antidepressant effects, in chapter 6 I evaluated a different area of cognition: optimistic belief updating. Whereas healthy participants updated their beliefs regarding negative life events more following good versus bad news, individuals experiencing depression lacked this bias (β = 0.71, β 95% CI: 0.24, 1.18, p = 0.004). In line with my previous findings of reduced learning of positive social evaluations, treatments attempting to increase the accommodation of positive information may be beneficial in remediating negative beliefs associated with depression. Overall, whilst depression was reliably associated with reduced self-referential affective biases, this did not appear to be important in early antidepressant treatment. However, I identified potential areas of interest for future research on psychopharmacological antidepressant effects. Firstly, I found evidence that antidepressants may operate by increasing sensitivity to positive information about familiar others and increasing positive social behaviours. This may treat depression by increasing enjoyment and engagement in social interactions. Secondly, exploratory analyses suggested that change in affective biases may be important in remediating anxiety rather than depression. It is therefore possible that antidepressants operate in part by remediating threat-related biases that maintain anxiety symptoms.

The self bias effect refers to the prioritised processing of self-related information (i.e. faster RTs and higher accuracy) over information about others. This phenomenon has been widely observed across many areas of cognition such as memory, attention and perception. However, current knowledge of the self bias effect is still insufficient. This thesis utilises the perceptual matching paradigm as an experimental instrument to study the self bias effect in three main aspects. First, the impact of social experiences on self bias is examined. This thesis presents data that demonstrate the modulation of self bias as a result of three factors - cultural background, situational cues and major life developments. Comparisons of the self bias between independent and interdependent cultures reveal a difference in the self bias relative to strangers. Priming of interdependent frames of mind reduces the self bias relative to friend in people with low bias, which suggests individual differences in the magnitude of the self bias effect. The transition into motherhood, as a major life development, demonstrates a loss of the self bias effect due to maternal behaviour. Second, in the attempt to explain the robustness of the self bias effect, this thesis investigates the underlying mechanisms of self bias through parallel comparisons of self-related and reward-related stimuli using the perceptual matching task. To further explain the relationship between self and reward processes, electrophysiological responses are also examined with electroencephalogram (EEG) methods. The data demonstrate partial distinctions in the neural pathway that underlie self and reward processes. Third, social psychology methods, in addition to methods from experimental psychology, are used to study the self bias effect from another perspective. However, the data are unable to link the self bias effect with trait characteristics at this stage. This thesis contributes to current understanding of self-related processing by identifying the factors that modulate self bias and exploring the underlying mechanisms of self bias.

The notion of the self as distinct from other people is fundamental to the study of human psychology. Closely tied to this sense of self is the profound importance of belonging to social groups. The cognitive prioritisation of self- and ingroup-related information, known as self-bias and ingroup-bias, occurs across a multitude of cognitive domains. Although adaptively beneficial, biases arising from social categorisation are the source of prejudiced attitudes, discriminatory behaviours and intergroup conflict. Several studies have demonstrated enhanced response times and accuracy performance in perceptual matching for self and ingroup stimuli compared to others and outgroups. However, the cognitive and neural mechanisms underlying these effects are relatively unexplored. The present thesis examines five core outstanding research questions: 1. What is the relationship between perceptual prioritisation for the self and social ingroups? 2. How does social context modulate ingroup-bias? 3. How quickly does group affiliation affect early perceptual processing? 4. Do trait differences underlie the strength of perceptual prioritisation for the self and social groups? 5. What are the commonalities and distinctions in the neural regions that underpin biases for the self and social ingroups? Broadly, the findings of this thesis suggest that: 1. There is an overlap in the representation of stimuli associated with the self and ingroups but the performance advantages are likely to be driven by partly distinct processes. 2. Perceptual biases for ingroups are robust across differing social contexts. 3. Social categorisation quickly enhances low-level perceptual processing even when this categorisation is novel and random. 4. There is no evidence to suggest that individual trait differences in group identification or self-concept underpin the perceptual biases. 5. Cognitive prioritisation for the self and ingroups are supported at least in part by distinct neural mechanisms. Together, these findings provide a novel perspective on the relations between self and ingroup representation in brain and behaviour.