Is the Bump Just for Autobiographical Memory

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The studies reviewed so far are all about autobiographical memory. But once one starts to look, one finds plots similar to the bump in autobiographical memory in other domains as well. A full explanation of the bump needs to take such plots into account and decide whether they are relevant to processes occurring in autobiographical memory. The oldest such plot I know about appears in Ribot (1882). He claims that for most people, imagination rises and drops in a fashion similar to the plots shown for autobiographical memory. For a select few, such as Ribot, I assume, it continues at a high level though old age. Like the bump, it has components. Early in the lifespan, imagination is used for play, then for sexual fantasy, and finally for more mature use.

Other classic theories also have peaks that correspond to those in the bump. Identity formation in personality theories is the most obvious (Erickson, 1950). Ideas similar to the bump are common, especially when the effects of narrative on autobiographical memory are considered (Holmes & Conway, 1999; Fitzgerald, 1988; Gergen & Gergen, 1983; Robinson, 1996). However, even evolutionary theory would predict a

Age of 1000 Wives

Figure 6

Births per 1,000 wives in traditional societies as a function of the age of the wife. (Data from Menken, Trussell & Larsen, 1986.) The data up to age 20 are hypothetical values based on the percentage of women reaching menarche. (Data from Komura, Miyake, Chen, Tanizawa & Yoshikawa, 1992.)

Age of 1000 Wives

Figure 6

Births per 1,000 wives in traditional societies as a function of the age of the wife. (Data from Menken, Trussell & Larsen, 1986.) The data up to age 20 are hypothetical values based on the percentage of women reaching menarche. (Data from Komura, Miyake, Chen, Tanizawa & Yoshikawa, 1992.)

bump if the increase in memories is due to increases in cognitive abilities that happen to occur when we are most likely to be making decisions about childbearing and child raising. Figure 6 is a plot of when in the lifespan births occur in traditional societies without modern birth control. Such evolutionary ideas are not without behavioral support. We are faster during the period in which the bump occurs, as shown in figure 7. We also do better on standardized memory tests, such as the Wechsler Memory Scale, and so need more items correct during this period to obtain any percentile score, as shown in figure 8. A more recent theoretical plot was presented by Fredrickson and Carstensen (1990) to account for social contact and for the observation that it is most varied in early adulthood. In the course of a normative life in our culture, two motives for social contact peak near the peak of the bump: self-concept development and information seeking.

In summary, many empirically observed abilities, and the many theoretical constructs needed to explain them, peak at about the same time as the bump (for others see, Rubin, Rahhal & Poon, 1998). But so do many

Figure 7

The reciprocal of the reaction times of people of different ages in a simple task. (Data from Noble, Baker & Jones 1964.)

Figure 7

The reciprocal of the reaction times of people of different ages in a simple task. (Data from Noble, Baker & Jones 1964.)

Ribot 1882

Figure 8

The raw scores needed on the Wechsler Memory Scale to score as average for a given age. Included without a line are the raw scores needed to be 2.7 and 1 standard deviation above the mean and 1 and 3 standard deviations below the

Figure 8

The raw scores needed on the Wechsler Memory Scale to score as average for a given age. Included without a line are the raw scores needed to be 2.7 and 1 standard deviation above the mean and 1 and 3 standard deviations below the mean.

other forms of memory or preference. People are more accurate in recalling public events (Rubin et al., 1998) and music (Schulkind, Hennis & Rubin, 1999) that occurred when they were between 10 and 30 years old. They prefer or are personally most affected by music (Holbrook & Schindler, 1989; Schulkind et al., 1999), films (Sehulster, 1996), and books (Larsen, 1996) from this period. They judge public events that occurred when they were in this period of life to be more important (Schuman, Belli & Bischoping, 1997). They concentrate on this period when choosing important events in their lives in psychology experiments (Fitzgerald, 1996; Fromholt & Larsen, 1991, 1992; Rubin & Schulkind, 1997a) and in written autobiographies (Mackavey, Malley & Stewart, 1991). Some of these findings are more directly related to the bump in autobiographical memory than others, but they all point to an increase in memory and preference for events from the bump period.

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