Evolution Defensive Processing And The Self

There is little doubt that depression involves biases and distortions in attention, memory, and information processing (Gotlib et al., 2000). One has to ask whether these can be adaptive. To answer this, we should distinguish between adaptations and 'exaptations'. Exaptations are adaptations that are recruited for new uses for which they were not originally designed, or triggered by contexts which were not present in the ancestral environment (Buss, 1999). They can be helpful; we did not evolve our finger dexterity or memory systems to perform piano concertos, but systems already evolved can be used and developed for these extraordinary feats. However, some exaptations can be unhelpful liabilities.

There is good evidence that many 'normal' information-processing routines have built-in biases, including biases to think more positively of one's own group and kin than outgroups and non-kin, self-serving biases, and sexual-attraction biases (Tobena et al., 1999). As noted elsewhere (Gilbert, 1998b), cognitive distortions can also be linked to a basic defensive heuristics and biases in information processing; for example, better safe than sorry. Thus, if an animal hears a sound in the bushes, it may be better for it to assume a predator and run away than stay to gather the evidence. Overestimating danger may lead to the expenditure of effort by running away when one did not need to, but underestimating a danger could be fatal. Algorithms for information processing under stress are thus often based on quick, safety-first heuristics rather than logic or rationality.

For a harassed subordinate, the defeated, or an unprotected juvenile, downregulation of PA that puts powerful breaks on exploration and resource-seeking behaviour could be adaptive. These same processes may be involved in reducing access to memories of positive events or being able to anticipate positive outcomes of efforts to improve one's position. However, these mechanisms evolved long before humans evolved competencies of self-awareness and self-reflection ('I am a failure'), and capacities to ruminate on oneself and, via self-criticism, to 'harass oneself'. These higher-level possibilities for metarepresentations can both reflect and feed back onto evolved strategies that regulate affect. Such processes can create highly maladaptive feedback loops of spiralling depression and state shifts. This touches on the important new area of research into metacognition (thinking and reflecting on one's thoughts and feelings) (Wells, 2000). It is highly unlikely that metacognitive abilities evolved to worsen depression (more likely, they evolved because they gave advantages in competing for social attractiveness via working out advantageous self-presentation) (Gilbert, 1997). Nonetheless, because evolved functions can be used in ways for which they were not designed, metacognitive abilities may work to reduce thresholds for, intensify, and maintain depression by setting up maladaptive feedback cycles. Some of the therapeutic manoeuvres used when working with metacognitions (Wells, 2000) may work if they help to decouple evolved mechanisms (as for defeat or subordination) from higher self-defining competencies; for example, 'I may feel like a failure because this is the program my primate limbic system is running, but this does not mean I am a failure.' Note that in evolutionary cognitive therapy we might sometimes use notions of underlying evolved algorithms as explanations for why people feel as they do, and to underline the importance of exploring one's thinking in a more detached way.

Another aspect to this has been noted by Teasdale (1988), who suggested that as people face setbacks or become depressed, some are able to self-sooth and limit the slide, while, for others, memories of past defeats and harm, self-attacking, and more extreme types of negative thinking come to the fore. Indeed, it is not just metacognition that sets up painful spirals, but, as Reynolds and Brewin (1999) have found, depressed people can suffer from painful intrusive negative memories, especially those of loss, rejection, failure, and/or being bullied; in a way, perhaps, they are being 'reinfected' with these negative signals.

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