Investigating proximate mechanisms and ultimate functions of memory for emotional events

Abstract

This thesis is an investigation of the proximate mechanisms and ultimate functions of memory for emotional events. The theoretical basis of this Thesis is that in order to reach a full understanding of a biological phenomenon, it is important that both proximate and ultimate (functional) explanations for that phenomenon are explored. Chapters 2 and 3 present an examination of the proximate mechanisms involved in memory consolidation of emotional events. In Chapter 2, three experiments are presented each testing the hypothesis that stress hormone activation immediately following viewing an emotional event enhances memory for that event. Each of the three experiments failed to find an enhancing effect of stress hormone activation on memory consolidation. Chapter 3 describes an investigation into whether the reduced feedback from the body to the brain, which occurs as a result of total spinal cord transection, diminishes the intensity of emotional experience and therefore impairs memory for emotional events. The results of this investigation revealed no differences between spinal cord transection patients and matched control participants in emotional expressivity, emotional awareness and in memory for emotional material. Chapters 4 and 5 explore how memory and emotion may interact differently for males and females and in manner that facilitates their survival and reproduction. Evolutionary theory argues that males should be more concerned than females about threats to their social status, whereas females should be more concerned about threats to their physical appearance and sexual reputation. Chapter 4 describes two experiments testing whether a) males have enhanced emotional arousal and memory for words implying they are of low social status; b) females have enhanced emotional arousal and memory for words implying they are physically unattractive and sexually untrustworthy. The results of these experiments showed that females had enhanced memory for words relating to physical appearance, and partial evidence that males have 2 enhanced memory for words relating to social status. Chapter 5 tests the evolutionary theory that males should be more emotionally aroused and thus have greater memory for cues relating to sexual infidelity (the thought of their partner having sex with another man), whereas females should be more emotionally aroused and have greater memory for cues to emotional infidelity (the thought of their partner forming a close emotional attachment with another woman). It also examines whether relationship status affects emotional arousal and memory for these cues. The results did not find any support for these hypothesised sex difference in memory. However, those ‘currently in a relationship’ did show enhanced emotional arousal to cues to sexual infidelity compared to those ‘currently not in a relationship’. Chapter 6 presents an investigation concerning the evolutionary hypothesis that individuals tend to have enhanced recognition memory for the faces of deceivers or ‘liars’. This chapter describes a study in which participants viewed a series of short video clips of individuals, half of whom were lying, half telling the truth. Participants’ memory for the individuals that appeared in the video clips was tested but there was no evidence of enhanced memory for the faces of ‘liars’. Chapter 7 provides a general discussion of the findings of this thesis. The failure to find an enhancing effect of post learning stress hormone activation on memory for emotional material, and the failure to find an impairment in memory for emotional material in people with total spinal cord transection contradict two established views on the proximate mechanisms involved in emotion, and emotions effect of the brain. How these findings relate to the established mainstream views on emotion and memory are discussed. The findings of studies concerning the functional interaction of memory and emotion presented in this thesis are also discussed in relation to previous research.