Source Memory Difficulties Under Varying Task Demands in ASD

Background: It is well established that Autism Spectrum Disorder (ASD) is characterised by a profile of memory strengths and weaknesses that parallels the pattern seen in neuropathologies of the frontal and medial temporal lobes. Specifically, individuals with ASD experience difficulties in recollecting the spatial and temporal relations amongst elements of experience that uniquely define a prior episode, whilst their factual knowledge is relatively preserved (see Boucher et al., 2012). This pattern would predict source memory difficulties in ASD (where, when, how or from whom one has learned something) but the evidence in this context is surprisingly mixed as well as limited. Here we examine source memory systematically under varying task demands to establish whether difficulties in this domain in ASD might relate to task characteristics such as the number of to-be-remembered items and/or the number of to-be-remembered source locations.

Objectives: To establish which task characteristics render source memory experiments difficult for individuals with ASD.

Methods: 10 ASD and 10 typically developing (TD) comparison participants, matched on chronological age, gender and Full-Scale IQ have been tested so far. Each participant completed four versions of a source memory task that varied orthogonally with respect to the number of to-be-remembered items and the number of to-be-remembered source locations. Specifically, either 16 or 32 items were presented in either 4 or 8 locations on the screen. The instructions specified that participants should try to remember the objects as well as the locations at which they appeared on the screen. During test, participants were first asked to decide whether or not they had seen a particular object (33% of objects were new) and if they responded positively they then had to choose the coloured location at which they thought it had appeared during study.

Results: Performance on the item recognition part of the test was above 70% in both groups and a 2 (group) x 2 (4 vs. 8 source locations) x 2 (16 vs. 32 items) ANOVA revealed no main effects or interactions (p > 0.1). Source memory was computed as the proportion of correct source identifications for correctly recognised items and an ANOVA of these proportions showed significantly worse performance in the ASD group (F(1,18) = 10.41, p < .01) and significantly worse performance in the 8 as compared to the 4 source location conditions (F(1,18) = 4.97, p < .05). A lack of significant interactions suggests that both groups were affected similarly by the experimental manipulations.

Conclusions: Consistent with the broader pattern of memory strengths and weaknesses evident in ASD we observed preserved object recognition but compromised source memory in ASD adults. Both groups responded similarly to manipulations of task difficulty in terms of the number of to-be-remembered items (which had surprisingly little effect in both groups) and the number of to-be-remembered source locations, suggesting that these factors are unlikely to be the source of inconsistent findings in previous studies. Further studies are required to determine what factors might facilitate source memory in ASD.