Neural cognitive mechanisms and modulation of the self-positivity bias

Abstract

A critical motivational factor in maintaining health and well-being is how we view ourselves. This thesis presented a series of studies on modulating two forms of positive biases: a self-positivity bias when forecasting future adverse life events (i.e., optimism bias) and a self-positivity bias when evaluating one’s own personality traits (i.e., self-evaluative memory bias).

The first study (Chapter 2) aimed at providing EEG evidence during a belief updating task to assess optimism biases. Results showed that optimistic belief-updating biases emerged immediately and became significantly larger after 24 hours, suggesting an active role of valence-dependent offline consolidation processes in the change of optimism biases. Participants also showed optimistic memory biases: they were less accurate in remembering undesirable feedback probabilities than desirable feedback probabilities, with inferior memories of undesirable feedback associated with lower belief updating in the delayed test. Examining event-related brain potentials (ERPs) revealed the desirability of feedback-biased initial encoding: desirable feedback elicited larger P300s than undesirable feedback and the amplitudes of P300 also positively predicted belief updating and memory accuracy. To uncover the causal relationship between brain activity and optimism bias, the second study (Chapter 3) used transcranial alternating current stimulation (tACS) to target the right frontal area to probe the causal relationship between frontal alpha asymmetry (FAA) and optimism bias. Although alpha tACS did not modulate FAA or optimism bias, the gamma-tACS group modulated optimism biases. The third study (Chapter 4) analyzed data from Chapter 2 and Chapter 3. Results revealed the role of dynamic changes on cognitive control and working-memory maintenance in optimism biases.

The fourth study (Chapter 5) investigated a non-reinforced behavioral-training method called cue-approach training (CAT) to modulate self-evaluation biases. Results demonstrated that CAT-trained self-evaluative trait adjectives were recalled earlier than those that were not trained. The human brain can also process meaningful information when presented with auditory words while sleeping, using targeted memory reactivation (TMR). The final study (Chapter 6) combined CAT and TMR to modulate self-evaluative memories. After CAT, participants were required to take an afternoon nap. Once sleeping, half of the positive personality traits from the Go words were presented to participants without disrupting their sleep. During the post-TMR assessments, participants showed earlier recall order for strong memories of trait adjectives (i.e., adjectives recalled twice before sleep) than for medium (i.e., adjectives recalled once before sleep) or weak memories (i.e., adjectives not recalled before sleep) of trait adjectives. There was also a greater positive association between the initial endorsement level of strong memories and sigma power than the association for weak memories. These results demonstrated the potential benefits of combining wake and sleep training to prioritize positive self-evaluative memories.

Together, self-positivity bias can be evident in the short and long term. Non-reinforced and non-invasive modulation strategies are promising in modulating self-positivity biases. The findings also bear important implications for developing novel and non-invasive methods for modulating self-bias in healthy and mental-disorder populations.