There is much evidence that depressed individuals have an overgeneral memory style, particularly in response to positive cue words (Moore, Watts, & Williams, 1988; Williams & Broadbent, 1986; Williams & Dritschel, 1988; Williams & Scott, 1988). These findings have been extended to non-clinical populations comprising dysphoric community (Ramponi, Barnard, & Nimmo-Smith, 2004) and student (Goddard, Dritschel, & Burton, 1997; Newcomb Rekart, Mineka, & Zinbarg, 2006) participants. Overgeneral classifications consist of (a) extended memories describing extended timelines (e.g., “my holiday in Italy”), and (b) categoric memories describing generic summaries of events rather than a specific occasion (e.g., “Friday nights at the pub”). Categoric memories have been found to be particularly prevalent in clinically depressed individuals (Williams, 1996; Williams & Dritschel, 1992). Williams (1996) proposed that overgeneral memory is a trait-like cognitive style that emerges during cognitive development as a way of controlling affect. Overgeneral memory may contribute to the maintenance of depression in a number of ways, including contributing to deficits in problem solving (Evans, Williams, O’Loughlin, & Howells, 1992; Goddard, Dritschel, & Burton, 1996) and impairing the ability to specifically envision the future (Williams et al., 1996).
The cognitive processes involved in the maintenance of overgeneral memory remain unresolved. Williams (1996) suggests a ruminative self-focus maintains this memory style. A ruminative style consists of repetitive cognitions that focus attention on the causes of one's low mood and the implications of these symptoms (Nolen-Hoeksema, 1991). In a process called “mnemonic interlock”, Williams (1996, p. 245) proposed that individuals become locked at a categoric level when attempting to retrieve a specific memory in an effort to avoid unwanted affect. This exercise consequently primes other negative categoric descriptors resulting in a ruminative self-focus which feeds back to maintain this cycle. Consistent with this proposal, recent evidence suggests that overgenerality may be moderated by manipulating rumination. Relative to controls, individuals recovered from depression demonstrate a reduction in overgeneral memory following a course of mindfulness-based cognitive therapy (Williams, Teasdale, Segal, & Soulsby, 2000). Lyubomirsky, Caldwell, and Nolen-Hoeksema (1998) found that relative to distraction, a ruminative response increased the accessibility of negative autobiographical memories in dysphoric students. Whereas instructions to adopt a distraction strategy have reduced overgeneral retrieval, instructions to ruminate have maintained it (Park, Goodyer, & Teasdale, 2004; Watkins & Teasdale, 2001; Watkins, Teasdale, & Williams, 2000).
The current research aimed to extend the understanding of the relationship between rumination and overgeneral retrieval. First, we aimed to replicate the effect of rumination versus distraction interventions on overgeneral retrieval. We then examined the influence of ruminative content on autobiographical memory. Watkins and Teasdale (2001) found that whereas instructions to employ analytical thinking reduced overgeneral memory, instructions to engage in self-focus did not. Moreover, subsequent studies found that experiential self-focus reduced overgeneral memory retrieval relative to analytical self-focus (Watkins & Teasdale, 2004). These findings are consistent with Nolen-Hoeksema's (1991) suggestion that it is the style of thinking, rather than its content, that distinguishes rumination. In contrast, other theorists argue that thought content, such as valence, plays a prominent role in rumination (Martin & Tesser, 1996; Segerstrom, Stanton, Alden, & Shortridge, 2003). The relevance of this issue is highlighted by the fact that although many studies of rumination focus on style rather than content, ruminative manipulations in depressed participants may evoke negative content because of dysphoric nature of the participants. Accordingly, we aimed to conduct the first study of the differential influences of positive and negative valenced rumination on overgeneral memory. We focused on non-clinical samples to examine the extent to which the effects previously noted in clinical samples can be observed in non-clinical levels of depression.
