John M. Gardiner’s research while affiliated with City, University of London and other places

Adults with autism spectrum disorder (ASD) show intact recognition (supported procedure) but impaired recall (unsupported procedure) of incidentally-encoded context. Because this has not been demonstrated for temporal source, we compared the temporal and spatial source memory of adults with ASD and verbally matched typical adults. Because of difficulties with temporal processing in ASD, we predicted ASD adults would benefit from test support for location but not temporal occurrence of studied words. We found similar levels of recognition and source memory for both groups but there was a greater effect of support on memory for location source in the ASD group. The lack of an effect of support for temporal source may simply reflect a difficulty in operationalising temporal cues.

Rehearsal strategies of adults with autism spectrum disorders (ASDs) and demographically matched typically developed (TD) adults were strategically manipulated by cueing participants to either learn, or forget each list word prior to a recognition task. Participants were also asked to distinguish between autonoetic and noetic states of awareness using the Remember/Know paradigm. The ASD group recognised a similar number of to-be-forgotten words as the TD group, but significantly fewer to-be-learned words. This deficit was only evident in Remember responses that reflect autonoetic awareness, or episodic memory, and not Know responses. These findings support the elaborative encoding deficit hypothesis and provide a link between the previously established mild episodic memory impairments in adults with high functioning autism and the encoding strategies employed.

Diminished episodic memory and diminished use of semantic information to aid recall by individuals with autism spectrum disorder (ASD) are both thought to result from diminished relational binding of elements of complex stimuli. To test this hypothesis, we asked high-functioning adults with ASD and typical comparison participants to study grids in which some cells contained drawings of objects in non-canonical colours. Participants were told at study which features (colour, item, location) would be tested in a later memory test. In a second experiment, participants studied similar grids and were told that they would be tested on object-location or object-colour combinations. Recognition of combinations was significantly diminished in ASD, which survived covarying performance on the Color Trails Test (D'Elia et al. Color trails test. Professional manual. Psychological Assessment Resources, Lutz, 1996), a test of executive difficulties. The findings raise the possibility that medial temporal as well as frontal lobe processes are dysfunctional in ASD.

Considerable evidence suggests that the episodic memory system operates abnormally in autism spectrum disorder (ASD) whereas the functions of the semantic memory system are relatively preserved. Here we show that the same dissociation also applies to the domain of order memory. We asked adult participants to order the names of famous historical figures either according to their chronological order in history (probing semantic memory) or according to a random sequence shown once on a screen (probing episodic memory). As predicted, adults with ASD performed less well than age- and IQ-matched comparison individuals only on the episodic task. This observation is of considerable importance in the context of developmental theory because semantic and episodic order memory abilities can be dissociated in typically developing infants before they reach the age at which the behavioural markers associated with ASD are first apparent. This raises the possibility that early emerging memory abnormalities play a role in shaping the developmental trajectory of the disorder. We discuss the broader implications of this possibility and highlight the urgent need for greater scrutiny of memory competences in ASD early in development.

The advantage in long-term recognition memory of words vocalized at study over those read silently was investigated by requiring subjects to indicate when recognizing a word whether or not they could consciously recollect its prior occurrence. The advantage for vocalization occurred only for words which subjects indicated were accompanied by recollective experience, and the results were not affected by whether subjects vocalized the test words or read them silently. It is concluded that this modality effect, and possibly other similar ones, originate in episodic memory and not in a procedural or ‘quasimemory’ system. Differences between the present results and those obtained elsewhere using intentional learning instructions are discussed.

To test the effects of providing relational cues at encoding and/or retrieval on multi-trial, multi-list free recall in adults with high-functioning autism spectrum disorder (ASD), 16 adults with ASD and 16 matched typical adults learned a first followed by a second categorised list of 24 words. Category labels were provided at encoding, retrieval, both or not at all. Both groups showed enhanced recall when labels were available during encoding or throughout the task. ASD individuals showed reduced recall of the second list and reduced clustering. Clustering and recall were correlated in both groups, which also showed similar levels of subjective organisation. The findings are discussed in relation to theories of frontal and medial temporal lobe contributions to memory in ASD.

Background: Bowler, Gardiner & Berthollier (2004) demonstrated intact recognition by adults with ASD of incidentally-encoded sources of studied words such as location on screen, voice of presentation or actions performed on the words. Recall of source, by contrast was diminished in comparison with that of a matched typical comparison group. Source recall difficulties are also seen in multi-list recall paradigms such as the California Verbal Learning test where individuals with ASD make more intrusions from earler-studied lists into the recall of later lists (Bennetto et al, 1996), raising the question of whether support at retrieval would facilitate memory for which list a particular word belonged to at study. We predicted that adults with ASD would benefit from support at test for memory for the location of studied words on the screen but that support for which block of the word belonged to (first, second or third) would be less effective. Objectives: To compare the effects of task support at test on memory for spatially and temporally-defined source in adults with ASD. Methods: 18 adults with ASD and 18 verbal ability matched typical adults took part. Participants studied a list of 27 words consisting of three temporally-distinct blocks of 9 words labelled ‘List 1’, ‘List 2’, ‘List 3’. Within each block, three words were presented at the top, middle or bottom of the computer screen. Words were presented at a rate of one every 4 seconds with a 6-second pause between each block. The test consisted of a yes/no recognition procedure where studied words were presented randomly interspersed with lures. If participants made a ‘yes’ response they were either asked to state where on the screen the word had been presented or in which list it appeared (unsupported trials), or to select from source cues (TOP, MIDDLE, BOTTOM or LIST 1, LIST 2, LIST 3) presented on the screen (supported trials). Order of supported and unsupported test and spatial and temporal source were systematically varied. Results: : Overall recognition memory was similar for both groups, replicating the majority of existing findings on recognition. The source memory data were analysed using a 2 (Group) x 2 (Temporal/Location) x 2 (Support/No Support) ANOVA. There was no group difference in overall source memory, but memory for temporal source was superior to that of spatial source. No other main effect was significant. The only significant interaction was for Group x Source x Support. This showed a marginally superior effect for support for location source in the ASD group but the reverse in the typical group. Presence of support had no effect on temporal source memory in either group. Conclusions: The findings on the effect of support for memory of source location replicates those of Bowler et al. (2004). The lack of an effect of support for temporal source goes against our prediction and may simply reflect a difficulty in experimentally operationalising temporal cues.

In a re-examination of the recognition memory of Jon, a young adult with developmental amnesia due to perinatal hippocampal damage, we used a test procedure that provides estimates of the separate contributions to recognition of recollection and familiarity. Comparison between Jon and his controls revealed that, whereas he was unimpaired in the familiarity process, he showed abnormally low levels of recollection, supporting the view that the hippocampus mediates the latter process selectively.