Episodic and semantic contributions to older adults' autobiographical recall.

ONE UNIQUE characteristic of human beings is episodic memory: the ability to transport themselves mentally back in time and to recollect an event or experience from their personal past (Tulving, 1985, 1993). Most important, episodic memory is intimately related to a special type of consciousness termed autonoetic awareness. Wheeler, Stuss, and Tulving (1997) have argued that autonoetic awareness, which is driven by the prefrontal cortex, allows adults mentally to represent past, present, and future experiences in a highly personal and subjective manner. William James (1890) captured that quality of episodic memory when he commented that in some instances, "remembrance is like a direct feeling; its object is suffused with a warmth and intimacy to which no object of mere conception ever attains" (p. 239).

Semantic memory, in contrast, refers to the retention of factual or proposition information that may (or may not) be personal or autobiographical. Semantic memory is accompanied by a sense of noetic awareness--the feeling that we know certain information and that the information is objective rather than subjective (Tulving, 1985, 1993). For example, semantic memory enables a man to know what the term birthday refers to and that he celebrated his last birthday by having dinner at a particular restaurant with his wife, whereas episodic memory allows that same man to reexperience from a highly personal and subjective point of view the sights, sounds, smells, and feelings that accompanied that dinner.

Results of several different lines of research point to the validity of the distinction between episodic memory and semantic memory. Within the domain of clinical neuropsychology, for example, Tulving, Hayman, and MacDonald (1991) described a patient, K. C., who displayed a severe amnesia for all of the episodic, but not the semantic, memories he had acquired during the course of his life. After his brain injury, K. C., who loved to play chess, still knew how to play chess, knew that his father had taught him to play chess, and knew that he had played chess with his father on several occasions. K. C. could not remember, however, a single instance from his personal life in which he had actually played a game of chess with someone other than his father.

In a somewhat similar study, Klein, Loftus, and Kihlstrom (1996) reported the case of W. J., who was asked to make trait judgments about herself on two occasions: first, during the period in which she had lost access to episodic memory because of a closed head injury; and second, after her amnesia had cleared. Results showed a high degree of consistency between her trait ratings across the two testing sessions. This finding suggests that W. J.'s knowledge of her personality structure was based on information retrieved directly from semantic memory rather than from specific life experiences retrieved from episodic memory, from which generic personality traits could then be inferred.

Cognitive psychology has also contributed valuable evidence concerning the independence of episodic and semantic memory. Gardiner and colleagues (Gardiner & Java, 1990, 1993; Gardiner, Richardson-Klavhen, & Ramponi, 1997) developed a paradigm in which participants are given a recognition task for a list of common words viewed earlier and classify each of the recognized items as something they remember (R response) or know (K response) was on the study list. Participants receive detailed instructions so that their R responses and K responses reflect retrieval from episodic and semantic memory, respectively. For example, participants are told to make R responses to test items that they can consciously reexperience from the study list (e.g., participants make R responses to test items because in their mind's eye, they consciously recollect seeing those words on the study list). In contrast, participants are told to make K responses to test items if they (a) are certain those were on the study list but (b) have no specific personal or contextual recollection of the items' previous presentation. The use of this technique has shown that some independent variables (e.g., dividing attention at study) affect the frequency of R, but not K, responses, whereas other variables have the exact opposite influence.

Parkin and Walter (1992) used the R-K paradigm to examine adult age differences in episodic and semantic memory. According to their research, when younger and older adults were matched on overall recognition accuracy, the younger people made more R than K responses, but older individuals displayed more K than R responses. Furthermore, the researchers reported that the incidence of older participants' R responses was positively correlated with performance on a neuropsychological test of frontal lobe function.

The data reported by Parkin and Walter support the contentions that frontal dysfunction is a hallmark of normative biological aging (Raz et al., 1998) and that older persons experience deficits in episodic memory for which they may compensate by increased reliance on semantic memory (Schacter, 1996). How could this pattern of impairment and preservation affect the everyday life of the typical older adult? Could it be that memory for events from the recent past are supported by semantic memory but that memory for events from the distant past (e.g., childhood and adolescence) are supported by episodic memory? Do older adults remember the past but know the present?

Our overarching goal in the present study was to shed light on the aforementioned questions by examining how episodic memory and semantic memory contribute to older adults' ability to retrieve autobiographical information across the different epochs of their lives. The vast preponderance of previous research on the topic of aging and autobiographical memory has used some variation of the Crovitz and Schiffman (1974) cue-word technique. In this paradigm, a participant is presented with a cue word and is asked to respond with the first personal memory that "pops into mind" and the age at which the memory occurred. Results of this research (Fitzgerald, 1988, 1996; Hyland & Ackerman, 1988; Jansari & Parkin, 1996; Rubin & Schulkind, 1997a, 1997b; Rubin, Wetzler, & Nebes, 1986) have consistently shown that the distribution of older adults' autobiographical recall conforms to a particular pattern with three unique components. The first is a retention effect that is best described by a mathematical power function: Older adults report a large number of memories from the most recent 10 years of their lives and progressively smaller numbers of memories from earlier 10-year intervals. The second is a reminiscence bump: Older adults report a substantially large number of memories from their adolescence and early adulthood. The third component is infantile amnesia, a dramatic reduction in the number of personal memories reported from early childhood.

Of particular interest to developmentalists is the basis for the reminiscence bump. Why should older adults recall a disproportionally large number of memories from their youth? Fitzgerald (1988, 1996) put forth a "self-narrative hypothesis" that suggested that adolescence and young adulthood represent periods of the life span devoted to the process of forming a personal identity and may serve as anchor points from which people begin the story of their adult lives. Thus, people may be likely to have a storehouse of vivid and important memories from these periods of life that help them define who they are. Consistent with this viewpoint, Fitzgerald found that older and middle-aged adults displayed a reminiscence bump if they were asked to perform a free recall of vivid memories, important memories, or memories that should be included in a book about their lives. In contrast, Jansari and Parkin (1996) showed that participants did not rate memories from youth as more important, vivid, or worthy of discussion than memories from midlife. Furthermore, they argued that older adults display a reminiscence bump because of an age-related attenuation in the retention component of autobiographical recall. Jansari and Parkin reasoned that older adults possess a relatively small pool of well-articulated recent memories because of an age-related inability to integrate, encode, and retrieve new information. This argument is supported by Jansari and Parkin's finding that middle-aged adults display a reminiscence bump only if recency is blocked (i.e., if they are prevented from reporting memories from the last 2.5 years when they see a list of cue words). Likewise, Rubin and colleagues (Rubin, Rahhal, & Poon, 1998; Rubin & Schulkind, 1997b) presented data that discount the idea that the reminiscence bump is fueled by an especially large number of important memories from youth that lay the basis for one's self-narrative. They argued that the reminiscence bump occurs because various (and as yet unspecified) biological, cognitive, and environmental variables ensure that compared with memories from other life periods, memories from youth (e.g., memories of personal events, as well as factual and semantic memories for films, music, sports, and politics) are much more effectively encoded, retained, and retrieved.

We believe that part of the controversy surrounding the distribution of older adults' autobiographical memories involves the instructions to participants in this line of research, along with the underlying assumption that autobiographical recall can be equated with episodic memory. In the prototypical autobiographical memory experiment, participants are asked to report (a) memories of personal experiences elicited by various cue words or (b) personal memories that are especially important or vivid. As we have already mentioned, Wheeler et al. (1997) argued that people may recall autobiographical or personal events in either an episodic or a semantic manner. (Consider the previously mentioned example in which we showed that a man may either know semantic memory or remember episodic memory how he celebrated his last birthday.) Given the finding that an age-related decrement is likely for episodic, but not for semantic, memory, we hypothesized that episodic memory and semantic memory are differentially responsible for certain components of the distribution of older adults' autobiographical recall.

In the present experiment, we asked the participants to write down the first personal memory that came to mind when they read each of a number of cue words. Then we gave the participants detailed instructions about how to categorize each autobiographical memory as something they remembered (R response) or something they knew (K response) from their personal past. Finally, the participants dated each memory. We expected that the reminiscence component of older adults' autobiographical recall would obtain for R responses (episodic memory) but not for K responses (semantic memory). Alternatively, we expected that the retention component of older adults' autobiographical recall would obtain for K responses (semantic memory) but not for R responses (episodic memory).

METHODPARTICIPANTSWe contacted by mail 200 older men from the Hamilton College (Clinton, NY) classes of 1944 and 1945 and asked them to complete memory questionnaires for real-life experiences and to provide basic demographic information. From that pool, 40 older men (mean age = 72.5 years, SD = 1.1) agreed to participate and completed all of the materials requested. The 40 participants had completed, on average, 18.6 years (SD = 1.2) of formal education. On a Likert-type scale ranging from 1 (poor health) to 9 (excellent health), the mean rating for self-reported health status was 7.6 (SD = .81). The demographic data suggest that participants in the present research were a highly selective group of older men who were exceptionally well educated and very healthy relative to the other members of their birth cohort.

MATERIALS AND PROCEDUREEach member of the prospective participant pool received a cover letter asking if he would be willing to take part in a questionnaire study about memory for real-life personal experiences. The men who decided to participate were instructed to open a sealed packet and to complete a consent form, a demographic questionnaire, a self-report health measure, and an Associative Memory Questionnaire (AMQ; developed and first used in the present study).

We told the participants that their memory for real-life experiences would be measured by the AMQ, which took the form of a word association task. More specifically, the AMQ consisted of 18 cue words drawn from the pool developed by Robinson (1976); each word was laser printed in 24-point Times bold font on standard U.S. letter paper. Immediately below each cue word, we provided the participants with two 20-cm horizontal lines on which they could write a brief description of the first experience or event from their personal lives that "popped into mind" as soon as they read each cue word. We emphasized that the participants could describe experiences from any points in their lives.

Next, we informed the participants that memories of past events may reveal themselves in dramatically different ways. More specifically, we told them that when people recall life events, they sometimes feel as if they have been mentally transported back in time so that they are actually reliving the events--they seem to reexperience some of the same emotions, perceptions, and thoughts that accompanied the original events. This type of recollective experience, we told them, is called an R response. Furthermore, we emphasized that an R response is accompanied by a very personal, intimate, and vivid feeling that an event from the past has just magically reoccurred in the mind.

We also informed them that on other occasions, memory of a personal life event may be categorized as a K response, which is relatively impersonal and objective. A memory qualifies as a K response if people know a great deal about the details of a previous event but do not mentally reexperience the exact perceptual, contextual, and emotional details of the original event. Most important, we emphasized that in the case of a memory classified as a K response, people do not feel as if they have traveled back in time to reexperience the event.

After the participants had read about the distinction between R responses and K responses, we instructed them to decide if the memory triggered by each cue word should be characterized as an R response or a K response. They made their decisions by circling an R or a K positioned near each cue word on the AMQ. Last, we told the participants to indicate how old they were when each R or K response occurred. They provided this information by writing the appropriate age in a box that was positioned near each cue word. We emphasized that in some instances, participants might find it difficult to pinpoint their exact age at which an event happened. Whenever they felt unsure about dating a memory, they gave us their best estimate of how old they were when each event occurred.

Two different versions of the AMQ were developed. Each version contained the same 18 cue words, although the ordering of the cue words was randomly varied within each version.

RESULTSWe began our data analysis by calculating the proportion of memories that participants classified as R responses and K responses within eight different age intervals: 0-5 years, 6-15 years, 16-25 years, 26-35 years, 36-45 years, 46-55 year, 56-65 years, and 66-75 years. Preliminary inspection of the means and standard deviations within the various cells of the data set revealed that the homogeneity of variance assumption that underlies analysis of variance (ANOVA) was in doubt. Thus, we adopted a conservative approach to our statistical analyses. More specifically, we carried out an arcsin transformation on the raw proportional data, and we used the Greenhouse-Geisser (1959) correction to determine the p value of our F tests.

With the aforementioned considerations in mind, we performed a 2 (memory type: remember or know) (times) 7 (age interval: 6-15, 16-25, 26-35, 36-45, 46-55, 56-65, or 66-75 years) repeated-measures ANOVA on the proportion of memories categorized as R responses or K responses within each of the seven age intervals.(FN1) The ANOVA revealed a main effect for age interval, F(6, 234) = 16.19, p < .0001. Most important, the main effect for memory type, F(1, 39) = 2.08, p < .15, and the Memory Type (times) Age Interval interaction proved to be unreliable, F < 1 (see Figure 1). Contrary to our hypotheses, Figure 1 clearly shows that a reminiscence bump and a retention effect were obtained for both R responses and K responses.

To examine more closely episodic and semantic contributions to the reminiscence bump and the retention effect, we conducted two further ANOVAs. First, we performed a 2 (memory type: remember or know) (times) 2 (age interval: 6-15 years or 16-25 years) repeated-measures ANOVA on the proportion of memories categorized as R responses or K responses within the age interval that represents the reminiscence bump (6-15 years) and the age interval just after the reminiscence bump (16-25 years). The ANOVA yielded a main effect for age interval, F(1, 39) = 7.45, p < .009, with more memories reported in the 6-15-years interval than in the 16-25-years interval. This main effect validates the existence of the reminiscence bump; however, the main effects for memory type, F < 1, as well as for the Memory Type (times) Age Interval interaction, F < 1, were not significant. These null findings suggest that the reminiscence bump was just as pronounced for R responses as for K responses. Second, we performed a 2 (memory type: remember or know) (times) 2 (age interval: 56-65 years or 66-75 years) repeated-measures ANOVA on the proportion of memories categorized as R responses or K responses within the age interval that represents the retention effect (66-75 years) and the age interval just before the retention effect (56-65 years). The ANOVA revealed a main effect for age interval, F(1, 39) = 17.84, p < .0001; more memories were reported in the 66-75-years interval than in the 56-65-years interval. This finding indicates the expected retention effect; however, the main effect for memory type, F(1, 39) = 1.30, p < .27, and the Memory Type (times) Age Interval interaction, F(1, 39) = 2,14, p < .16, were unreliable. Thus, the retention effect was just as pronounced for R responses as for K responses.

DISCUSSIONOur goal in the present study was to test the hypotheses that episodic memory is responsible for the reminiscence component of older adults' autobiographical recall, whereas semantic memory underlies the retention component of older adults' autobiographical recall. The results did not support our hypotheses: We observed a reminiscence bump and a retention effect for both R responses and K responses. Our results strongly suggest that the Crovitz technique is a not direct measure of the autobiographical-episodic memory system. Personal memories elicited by cue words may reflect the operation of either the autobiographical-episodic or the semantic memory system. Thus, the distribution of autobiographical memories across the life span seems to reflect the operation of both the episodic and the semantic memory systems; it does not seem to be differentially affected by the episodic versus the semantic memory systems as measured by the R-K paradigm. This last point is consistent with the argument set forth by Wheeler et al. (1997). They maintained that performance on purported laboratory tasks of episodic memory (e.g., recall and recognition) could reflect the operations of the episodic memory system, the semantic memory system, or both. Thus memory researchers, regardless of whether they work in the laboratory or in the "real" world, need to become aware of the complex relationship between memory tasks and memory systems. Autobiographical memory tasks do not necessarily reflect the operation of the autobiographical-episodic memory system.

Another important point to consider is that we found no difference in the overall proportion of R responses and K responses within our sample of well-educated, healthy older men. This finding suggests, at least when older adults' autobiographical recall is considered, that aging is not necessarily accompanied by a decline in episodic memory that is compensated for by an over-reliance on semantic memory. The speculation that older adults are likely to "know the present" but "remember the past" may be applicable only to the findings from laboratory studies of memory aging (e.g., Parkin & Walter, 1992) in which researchers have examined the recall or recognition of rather arbitrary and nonpersonal stimulus materials (see Jacoby, Jennings, & Hay, 1996, for a somewhat similar position).

Another point to consider about our findings involves exactly what we measured by R responses and K responses. Some researchers (for details, see Yonelinas, Kroll, Dobbins, Lazzara, & Knight, 1998) are of the opinion that R responses measure explicit memory, whereas K responses index implicit memory. We believe that this stance has some merit within the context of various models of recognition memory where R responses and K responses might be regarded as measures of recollection and familiarity, respectively. In the present study, however, there does not seem to be anything even remotely "implicit" in the memories we obtained from our participants. We presented participants with cue words, and we asked them to report the first memory they consciously recollected after they read the cue word. Thus, consistent with the comments made by Wheeler et al. (1997), we take the position that R responses and K responses in our research assessed the output of both the episodic and the semantic memory systems.

FUTURE DIRECTIONSIn the present study, we asked participants to report the first experience or event from their personal lives that "popped into mind" as soon as they read a cue word on the AMQ. These instructions, along with the results they generated, may be considered in light of Moscovitch's (1992, 1994) distinction between associative retrieval and strategic retrieval from declarative memory as well as Schacter and colleagues' (Schacter, 1996; Schacter, Savage, Alpert, Rauch, & Albert, 1996) position that associative retrieval is less vulnerable than strategic retrieval to the effects of aging. Associative retrieval is regulated by the hippocampal formation and involves the involuntary, automatic retrieval of a past event (e.g., the memory of the event automatically comes to mind because of the presentation of a specific environmental cue). Strategic retrieval, in contrast, is controlled by the prefrontal cortex and involves the deliberate and effortful memory search (e.g., the generation of internal cues that help a person remember the event; see Nyberg, Cabeza, & Tulving, 1996, for a similar position).

It could be argued that use of the Crovitz cue-word task in autobiographical memory research engenders associative rather than strategic retrieval: "Tell me about the first memory that comes to mind in response to a particular cue word." One problem with that line of reasoning is that several researchers (e.g., Jansari & Parkin, 1996) have shown that it typically takes several seconds for participants to respond to the cue words in the Crovitz paradigm. Thus, some autobiographical memories may, in fact, "pop into mind" because of associative retrieval, whereas other memories might represent the culmination of a more deliberate process marked by strategic retrieval. Unfortunately, previous researchers have not systematically examined how associative versus strategic retrieval contributes to older adults' autobiographical recall, to the distribution of R responses and K responses, or to both. One interesting avenue of research on this topic may have its basis in Moscovitch's (1994) finding that division of attention affects strategic retrieval more than it affects associative retrieval (Moscovitch, 1994; Troyer, Moscovitch, & Winocur, 1997). This finding, applied to the focus of our investigation, suggests that it is reasonable to ask the following questions: If the Crovitz autobiographical memory task was performed under conditions of divided attention, would older participants exhibit a reduction in the frequency of R responses but not of K responses? Would such a pattern of results signify that R responses and K responses are driven by strategic and associative retrieval, respectively? Would the reduction in R responses attributable to a divided-attention task be more prevalent for the recency, reminiscence, or infantile amnesia components of older adults' autobiographical recall? Would performance on tasks of frontal-lobe function be correlated with the proportion of R responses versus K responses exhibited by participants who perform the Crovitz autobiographical memory task under full attention versus divided attention?

SUMMARY AND CONCLUSIONSIn summary, our results lead to the conclusion that older adults may use either the episodic system or the semantic memory system when they engage in the standard Crovitz autobiographical memory task. Thus, older adults are just as likely to "remember" as to "know" about personal events from the near or distant past. This finding has implications for extant theories of two of the most provocative and perplexing components of older adults' autobiographical recall: the reminiscence bump and the retention effect. We suggest that both reminiscence and retention can be supported by either episodic or semantic memory. Future researchers may wish (a) to investigate more closely the phenomenological qualities of older adults' recollective experiences for personal life events and (b) to relate these different types of conscious experience to the integrity of different memory systems, retrieval processes, and neural systems.

Added material.

JOHN M. RYBASH.

BRYNN E. MONAGHAN.

Department of Psychology Hamilton College.

Address correspondence to John M. Rybash, Department of Psychology, Hamilton College, 198 College Hill Road, Clinton, NY 13323; e-mail: jrybash@hamilton.edu.

FIGURE 1. Mean proportion (and standard error) of remember (R) responses and know (K) responses for personal memories dated within specific age intervals. Open circle = R response. Filled square = K response.

FOOTNOTE1 We collected data on memories that participants recalled from birth to 5 years of age. The proportion of memories recalled from this time period is presented in Figure 1. We did not include, however, data from the 0-5-years period in this or any subsequent ANOVAs. We decided to exclude those data from our analyses because we were interested primarily in the reminiscence and retention components of autobiographical recall, not in the infantileamnesia component. Thus, we assumed that inclusion of those data might unnecessarily weaken or cloud our ability to explore the episodic and semantic dimensions of the reminiscence bump and retention effect. Furthermore, exclusion of the 0-5-years interval solves the potential problem of having a single age interval that is half the size of the other age intervals.

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