CONTEXT-DEPENDENT RETRIEVAL CUES, MEMORY SYSTEMS, AND SELF-REFERENT KNOWLEDGE

The effectiveness of context-dependent retrieval cues is evident when evaluating individuals’ memory for stressful and traumatic events. Con- text-dependent retrieval occurs when some circumstance that was present during a to-be-remembered event later cues memory of the event. Thus, retrieval can be triggered by circumstances that bear some relevance to the circumstances of the to-be-remembered event. One victim of repeated childhood molestation offers an example. The first time he recalled the previously unrecalled episodes, he experienced a sudden return of memo- ries of three different instances as a child lying naked on the bathroom floor. These memories returned on a hot and humid day, which probably was the same sort of humidity that may have been present in a slightly steamy bathroom (Terr, 1994). Another example of context-dependent cues triggering the return of memory consists of a woman who suffered from psychogenic amnesia following a rape that occurred a few months earlier while she was jogging. She was jogging for the first time since the assault in a different area and caught sight of a pile of bricks. The bricks cued memory of her running on a path covered with crushed bricks dur- ing a frantic attempt to escape the rapist (Christianson & Nilsson, 1989). As suggested by these case studies, it may not necessarily be the same or a highly similar physical environment that serves as the context-dependent memory cue. Sensory associations (visual, auditory, tactile, and olfactory) may equally serve as context-dependent retrieval cues.

Several studies on trauma patients have, however, shown that these types of sensory cues may lead to behavioral responses suggestive of memory, whether or not the same cues lead to conscious, verbal recall of the episode. A case study of a woman who had been sitting in her car when another driver bumped into her from the rear offers an example. Fortunately, she had no other injuries than a concussion and bruising on her forehead. She had, however, mentioned that she had heard car tires breaking right before the impact, and that she, in that second, had felt con- vinced she would die. For a long time after the accident, she suffered from

panic attacks whenever she heard the sound of tires squealing (de L Horne, 1993). Another woman who had been assaulted and raped in her home avoided taking the subway because the smell in the underground area reminded her of the rapists and made her nauseous (McMurran, 1988).

The occurrence of context-dependent retrieval, and the effectiveness of sensory cues as well as physical cues, may be explained, in part, by con- sidering that different types of memory exist. On the basis of empirical findings, Johnson and colleagues envision sensory retrieval cues as medi- ated by nonverbal, so called “perceptual subsystems” of the brain, that stem from early evolution of humans (Johnson, Kim, & Risse, 1985; John- son & Multhaup, 1992). These can be contrasted with later developing “re- flective subsystems.” In a slightly different classification of memory, Squire (1995) suggested that there is an implication that emotional aspects of an event may be stored separately from other aspects of an event (e.g., factual, self-referent information) at a nondeclarative or procedural level, and memory of these emotional aspects may then be expressed through behavior. Other researchers have proposed dual representations of auto- biographical events. Conway (1992) has, for instance, proposed that repre- sentations consist of a “phenomenological record” containing online phe- nomenal experiences of specific events, on the one hand, and “thematic knowledge” containing more semantic or abstract knowledge about the events in the personal history of an individual, on the other hand. Brewin, Dalgleish, and Joseph (1996; see also Brewin, 1989) have specifically fo- cused on trauma in their theoretical distinction between “situationally ac- cessible knowledge” and “verbally accessible knowledge.” The former indeliberately triggers emotional responses, as originally conditioned, in situations where some aspects may be reminiscent of the traumatic event. These aspects may well include sensory cues. This situationally-accessible knowledge is not available to consciousness or verbal recall. In contrast, “verbally accessible knowledge” consists of generic knowledge that en- ables an individual to appraise the implications of the traumatic event from both a personal and a general point of view. Finally, Tulving and others have made distinctions between implicit and explicit memory. Im- plicit memory consists of learned behaviors and responses, does not oper- ate at a conscious level, and is expressed through behaviors and ac- tions. By contrast, explicit memory includes deliberate, conscious recall of events and information.

Event memory could thus be regarded as organized at multiple levels, and, various types of information contained in those levels may be differ- ently accessible depending on the retrieval cues. The following case stud- ies, one about a girl who had not yet developed an episodic memory sys- tem, the other about a woman whose episodic memory was blocked, may

provide useful examples. In the first case, an 18-month-old girl had a fish- bone stuck in her throat, which had to be removed by a physician. After the incident, the girl refused to eat fish and would only reluctantly have her throat examined. At the age of 2 years and 1 month, that is, 7 months after the incident, she could identify the physician from a series of photos, but she could not explicitly recall the incident (Howe, Courage, & Peter- son, 1994). In the other case, a former rape victim was at a medical clinic due to a sore throat. Although the woman had no conscious recollection of the assault, when the doctor pressed down her tongue to examine it, she suddenly pushed him away, cried hysterically, and left the clinic. At home, she still could not understand her own behavior at the clinic, but she was compelled to dial a phone number. She reached the policeman who explained to her that he had investigated her rape 3 years earlier (Hartman & Burgess, 1993). As she supposedly had called the police im- mediately after the assault, the affective reaction experienced at the clinic may have reactivated this behavior.

These two cases demonstrate, of course, conditioned reactions, but also suggest memory on some levels, but lack of memory on others. In other words, there appeared to be dissociations between different levels of memory (cf. Graf & Schacter, 1985; Schacter, 1987). The lack of conscious recollection was to some extent compensated by implicit retrieval in both cases of event information in the form of emotional and behavioral reac- tions. Implicit memory may have been automatically activated by external stimuli, such as contextual components of the past event that were ac- cessed by means of perceptual and tactile, trauma-related cues. For the ep- isodic memory representation to be cued, however, it would have been necessary to retrieve contextual information that by definition was self- referent, thus pointing to “the central role played by the self in the reexperienced past: In episodic remembering the rememberer is always an observer or a participant in the mentally recreated earlier real-life hap- penings” (Tulving, 1987, p. 72). In the case of the 18-month-old girl, her sense of self was not yet fully developed, and thus the incident with the fishbone may not have been encoded as an episodic memory. In the case of the woman at the medical clinic, the rape may have carried too heavy an implication for her integrity and ultimately her individual sense of self. She may have blocked episodic memory of the rape event. In any case, for both the young girl and the woman, because the connection to the self could not be made at retrieval (see Kihlstrom, 1995), episodic memory was inaccessible.

A third example also demonstrates both the dissociation between types of memory as well as the importance of self-referent encoding for reten- tion and the effectivenes of context cues. An Italian woman suffered se-

1987). Semantic memory consists of general and personal knowledge that is not related to memory of specific events and experiences. Memory of specific events and personal experiences is referred to as episodic mem- ory. Despite the woman’s loss of semantic memory, her episodic memory was still intact. Thus, she could not recall figures of great significance in the history of Italy, such as Mussolini. The few public events she could re- call were those that seemed to be associated with some personal signifi- cance. For instance, she remembered the nuclear accident in Chernobyl because this disaster meant that she had not been able to eat the vegeta- bles that she had grown in her garden.

Interestingly, it is possible that events that have implications for the in- dividual’s sense of self, including stressful events, may promote elabora- tive rehearsal that would then facilitate memory in the long run. Heuer (1987) argued that the recall pattern for emotional events centers around the causes of the evoked emotions. This circumstance prompts the indi- vidual to personalize a narrative account around the critical elements of the experience. There is a natural correspondence between a person’s feel- ings and the emotion-eliciting information in emotionally arousing situa- tions. Neutral situations do not normally elicit feelings that are intrinsic to information about the event. Elaboration, such as thinking about and re- acting to details in the emotion-provoking sequence of events, will pro- mote memory for the core information, or the gist of the event.