題目： Impact of mood and arousal on attention and memory
担当教官： Mark H.B. Radford
Depressed or anxious mood impacts cognition, and cognition, in turn can impact depressed or anxious mood (cf. Teasdale, 1988). From an evolutionary perspective (e.g. Nesse, 2000), depression and anxiety evolved to solve different types of adaptive problems. Depression ‘slows’ people, helping them save resources for socially unpropitious situations. Anxiety should ’arouse’ people to being vigilant about possible danger. If both depression and anxiety are adaptations, at least within the normal range, it is possible that different cognitive biases associated with these ‘moods’ are acquired through evolutionary history. Further, each should be related to social environment. Although there is growing interest in an evolutionary perspective in psychiatry, most work to date has been theoretical. There are few empirical studies that examine depression or anxiety from an evolutionary perspective. Three experiments were conducted to examine the relationship between depression and anxiety and cognitive functioning, and to see if the results can be interpreted from an evolutionary perspective.
In experiment 1 (Chapter 2), we used an “emotion task” to look at the influence of context vs. content attention. Using facial emotions, we found that anxious people are more likely to attend to background information than depressed people, and this tendency tends to be stronger when the background contains emotional information (i.e. happy and sad faces). In particular, the results suggest that high trait anxious people are more likely to be affected by the emotions of the background figures, and therefore possibly by their environment. This result is consistent with the prediction from an evolutionary perspective. Anxious people need to attend to threats from some where, therefore they have to attend to the context.
In experiment 2 (Chapter 3), we used a “face-name memory task” and looked at social memory (memory for identifying others) using facial emotions. It was shown that high trait-anxious female participants recalled names of the face expressing fear less than low trait-anxious female participants. This result is not consistent with the prediction that anxious people can recall threat-related stimuli (i.e. fear and angry face). A possible reason for this could be related to the relationship between anxiety and fear. Anxiety and fear are similar moods (or emotions), which are distinguished by whether the specific object of the mood actually exists (fear) or is just thought to exist (anxiety). People have to make quick decisions about what to do next, not attend to ‘who’ expresses fear. Trait anxious people should have sensitivity for the expressed fear.
In experiment 3 (Chapter 4), we used a “prospective memory task” and looked at both prospective memory (memory for the future) and retrospective memory using emotional (negative) and neutral words. It was shown that high depressed people recall words of prospective memory less than low depressed people. For the negative retrospective memory task, high depressed people recall more than low depressed people. One possibility from an evolutionary perspective is that depression makes people allocate their cognitive resources not to the future but to the past. By doing so, depressed people may avoid the possible danger in the future. It is also shown that cortisol may have an impact on retrospective memory, not on prospective memory. Some studies have shown that the prefrontal cortex is associated with prospective memory performance. Other types of memory have been found to be hippocampus-dependent, and it is known that there is a relationship between the hippocampus and cortisol (e.g., Takahashi et al., 2004). The result that there was no correlation between cortisol and prospective memory may support the idea that prospective memory is not hippocampus-dependent, and therefore prospective memory is a different type of memory to retrospective memory. This result, which showed no correlation between prospective memory and retrospective memory also supports this possibility.
In summary, the data in this study generally supported our predictions. In particular, the results provide support for an evolutionary perspective on depression and anxiety. However, there were sex differences and stimuli-specific effects. We believe empirical studies are necessary to understand evolutionary functions of depression and anxiety. Examining cognitive biases such as this study is one approach for understanding the role of evolution in human behavior and thinking. Such data may also give a new perspective for depression and anxiety, which could have important clinical applications.