Episodic memory in adults with autistic spectrum disorders: Recall for self- versus other-experienced events
Introduction
Memory involves storage and recall of different forms of information (Tulving, 2000). In addition to the distinction between working, short and long-term memory, ‘semantic memory’ (knowledge about the world) can be distinguished from ‘episodic memory’ (recollection of events from an individual's personal past characterised by the conscious experience of ‘remembering’) (Tulving, 1985). A further distinction is made between the subjective experiences of ‘remembering’ (i.e. mentally returning to an event and re-experiencing it) and ‘knowing’ (i.e. recognition without recall of the original experience). ‘Autonoetic consciousness’ is the conscious awareness of one's own existence and identity “… in subjective time extending from the personal past through the present to the personal future” (Tulving, 1985). This facilitates ‘mental time-travel’ to past events, which can then be re-experienced (Gardiner, 2002). The linkage of episodic recall and autonoetic consciousness has implications for understanding of the ‘self’ and the extent to which self concept develops from episodic experiences (Klein, 2001). Conway (2002) further proposes that the recollective experience associated with episodic memories indicates that the mental image generated is a reflection of a self-experienced event, rather than dreams or fantasy, and that ‘experiences with strong self-reference may receive privileged encoding that render them highly accessible’.
If episodic memory is dependent upon autonoetic consciousness, then episodic memory requires a ‘self’ that is continuing through time, with past and present experiences relating to the same ‘self’. Episodic recollection is dependent on recollection of specific events and recognising that the event happened in one's own past. Thus, without reference to the past and self-continuity across time, individuals would exist in a ‘permanent present’ (Baddeley, 1999). Self-continuity through time does not develop until the age of 4 years, when episodic memory is first observed (Perner, 1990, Welch-Ross, 1995). Klein (2001) argues that impaired self concept leads to impaired memory, rather than vice-versa, and proposes that people with autistic spectrum disorders (ASD) might experience impaired self continuity related to observed autobiographical episodic memory dysfunction (Boucher & Lewis, 1989; Klein, Chan, & Loftus, 1999; Ozonoff, Pennington, & Rogers, 1991).
Perner (1990) proposes that episodic memory in typically developing children is dependent on mentalisation abilities. Therefore, people with ASD would be expected to exhibit episodic memory deficits and children with ASD have been found to have difficulties in recalling self-participation in events (Boucher, 1981; Boucher & Lewis, 1989). Powell and Jordan (1993) explain deficits in episodic memory associated with ASD by reference to an impaired ‘experiencing self’ that ‘encodes events as part of a personal dimension’. Without this specialised encoding, spontaneous retrieval is hindered, impairing free recall of personal episodic memories. They further posit a difference between ‘knowing’ that one is engaged in an event and ‘experiencing’ it as happening to oneself, the latter involving evaluating personal feelings about the event and the personal significance of the event.
Episodic memories can be recalled by cued recall or by spontaneous free recall, which requires re-experiencing (Conway, 2002). Powell and Jordan (1995) suggest people with ASD will not be impaired on cued recall of personally experienced events, only on free recall, as their ability to deliberately place themselves back in an experience is impaired, which results in events not being encoded as part of a personal dimension.
Conway (2002) proposes experiences directly involving the self may receive ‘privileged’ encoding that makes them more easily searched for and retrieved, i.e. events involving the self should be more easily remembered than events observed (Baker-Ward, Hess, & Flannagan, 1990; Conway & Dewhurst, 1995). Therefore, people with ASD who have deficits in processes involving the self should not demonstrate this superiority for self-experienced events.
Section snippets
Concepts of ‘self’ in autistic spectrum disorders
Although there is limited research into concepts of self in ASD, impaired functions of ‘self’ can be identified, e.g. refer to self in the third person and confusion of personal pronouns ‘I’ and ‘you’ (Lee, Hobson, & Chiat, 1994). Loveland (1993) suggests that pronoun confusion results from difficulties in understanding the differing view-points of others, i.e. ‘you’ and ‘I’ are simultaneously both ‘I’ to oneself and ‘you’ to another person.
Powell and Jordan (1995) propose that self-concept
Method
A 2 × 2 n experimental design was employed, with two groups of participants (ASD and ID, and ID only) and two experimental conditions viz.:
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Personal—participant performing a series of table-top tasks and then recalling those tasks
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Companion—participant and researcher taking turns to perform a series of table-top tasks and the participant then recalling those tasks and who performed each one.
Participants were recruited from 3-day services for people with moderate to severe ID and from statutory and
Procedure
To counter-balance procedures across participants, the participants were allocated consecutive positions from a table listing all possible combinations of task list, experimental condition and verbal ability test. An alternative list, condition and test were administered in session 2. Sessions were scheduled 1 week apart to reduce retroactive interference. To minimise confounds due to different physical environments, sessions were conducted in a quiet room containing two separate tables with
Results
A total of 12 participants with ASD and 14 participants with ID achieved age equivalent verbal ability scores of 4 years or above and completed the study. Verbal abilities were indicated as age-equivalent BPVS and TROG scores. TROG scores of five participants [three ASD; two ID] were too low to compute age-equivalent scores and were counted as missing data.
All data was normally distributed and within-group equality of variances was assumed for verbal ability (F = 0.87, p = 0.360) and for
Discussion
No between-group differences were found for ‘free recall’ under any of the three recall conditions, providing no support for hypothesis 1. Three participants with ASD and two participants with ID scored ‘0’ for free recall in one or both experimental conditions, indicating possible floor effects. Caution is therefore required in interpreting these findings. Hypothesis 2 was supported, as no within-group differences between the recall conditions were found for the participants with ASD. As per
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