Nesse's formulation should stimulate productive debate. I explore the topic from two perspectives. Firstly that mood variation plays a crucial role in the regulation of aggressive behaviors and, secondly, that it helps the individual find the most appropriate level in the social hierarchy. Each perspective generates conclusions that are compatible with Nesse's.
2. I believe that Nesse's elegant formulation of the role of mood function should stimulate productive debate. I plan to explore the topic from two perspectives, each of which generates conclusions that are compatible with Nesse's.
3. I first propose that mood variation plays a crucial role in the regulation of aggressive behaviors that are necessary for survival. Low mood could be said to serve a double function; one within the individual and the other as communication to others. The feelings of inadequacy, discouragement, hopelessness, etc. that characterize low mood are designed to turn off aggression within the individual as well as to inhibit aggression directed by others towards that individual.
4. For example, the low mood response enables the infant to pass from Bowlby's state of protest at separation to depression - withdrawal (Bowlby, 1982). Through the communicative function the infant elicits sympathy from others, including some who may have been turned off by the child's angry protests. By causing the individual to internalize the badness that was previously perceived in the other individual, the low mood affective response tends to reduce and supplant the earlier aggressive response. It also serves the function of ending an agonistic conflict by causing individuals who are losing to submit to their opponents. This enables them to elicit sympathy, perhaps from the same individuals they were previously challenging.
5. When the mechanism that regulates low mood is functioning efficiently, it assists the individual to turn off the bad mood by obtaining nurturing, ending the conflict, submitting, getting out of the situation, or ending frustration by giving up unrealistic goals (Sloman, Gardner & Price, 1989). This allows the individual to engage in activities that may be more productive and therefore mood elevating.
6. One can differentiate a possible sequence of affective states (behavioral subroutines), with each state being followed by another that is specifically programmed to switch off and terminate the previous one (Sloman & Price, 1987). For example, one might observe aggression, followed by low mood, followed by submission, followed by activities in another domain. These termination mechanisms facilitate moving from frustrating failure to creativity; they also form a major interface with affiliative behavior.
7. High mood also plays a role in the regulation of aggression by terminating aggression and facilitating the acceptance of the opponent's act of submission, which brings the conflict to an end. It also contributes to an increase in self-confidence which encourages the individual to tackle new challenges and may promote that individual's chances of being successful in future conflicts.
8. Another view of mood function is that it helps the individual find the most appropriate level in the social hierarchy, bearing in mind that humans belong to several status hierarchies. If people who have good skills fail to have their skills recognized and are consequently struck in a low position in a hierarchy, this may create frustration for them because they cannot express their talents in a productive fashion. If they are too high in the hierarchy they are likely to experience frustration and failure, because they lack the necessary competence to maintain their position. Mood variation assists individuals to attain an appropriate position in the hierarchy which assists them in developing realistic goals, enabling them to be more productive.
9. The results of competitive struggles provide information about the competitor's talents or skills. Success leads to high mood, which encourages further efforts in that arena, which in turn contributes to the development of skills and to rising in that hierarchy. When individuals have a high position in a particular hierarchy and their skills in that arena are recognized by the group, they should have a good opportunity to utilize and develop their talents for the benefit of the group.
10. For example, in hunter-gatherer society the group will benefit by being able to recognize those who are potentially the best trackers, warriors or weapon makers and to encourage them to develop their skills. In this way the talents of the individual are best utilized in promoting the survival of his kin. If, on the other hand, the individual tries his hand at an activity for which he is unsuited, his consequent low mood would discourage him from further efforts in that direction and encourage him to try to succeed in another arena where he could more productive. This hypothesis is in line with Nesse's, but it adds that an important aspect of the role of mood variation in humans occurs in the context of one of a range of status hierarchies.
11. With regard to Nesse's statement that some low-status people are happy and many high-status people are unhappy, one should remember that our behavioral subroutines were programmed to respond to conditions that were very different from those of present day society. One could also note that the reluctance of most people to give up power or status seems to be associated with the fact that the loss of one's position in a hierarchy usually generates low mood.
12. To conclude, I agree with Nesse's major hypothesis about the function of mood. I have put forward additional hypotheses, suggested by other perspectives. Although my arguments were highly condensed, I hope they were sufficiently clear to stimulate further discussion of this interesting topic.
Bowlby J (1982). Attachment and Loss, Vol I: Attachment, 2nd ed. New York, Basic Books, 1982.
Sloman L, Gardner R & Price J (1989). Biology of family systems and mood disorders. Family Process 28:387-398.
Sloman L & Price J (1987). Losing behavior (yielding subroutine) and human depression: Proximate and selective mechanisms. Ethology and Sociobiology 8 (Suppl.) 99-109.
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