Time-Based and Event-Based Prospective Memory in Autism Spectrum Disorder (ASD): The Roles of Theory of Mind, Executive Functioning, Time Perception, and “Future Thinking”

Background:  Event-based “prospective memory” (EBPM) and time-based prospective memory (TBPM) involve remembering to carry out an intention upon the occurrence of a particular event or at a particular time-point, respectively.  Everyday examples include remembering to turn off the bath taps before the bath overflows, remembering to pay a bill on time, or remembering to keep an appointment.  It is clear that prospective memory is critical for flexible, independent living.  To a greater or lesser extent, both forms of PM may rely on theory of mind, in that both require the retrieval of a previously-formed intention for success.   The link between theory of mind and prospective memory may be mediated by “episodic future thinking” (the ability to mentally project oneself through time to imagine future experiences of self).

Objectives:  To assess the prospective memory profile and its cognitive correlates in ASD.

Methods:  In Study 1, 21 high-functioning children with ASD and 21 age- and IQ-matched comparison participants completed TBPM and EBPM tasks, as well as background measures of executive functioning and theory of mind.  In Study 2, novel EBPM and TBPM tasks, as well as measures of “episodic future thinking” and working memory, were completed by 17 adultswith ASD and 17 age- and IQ-matched comparison participants. 

Results:  In Study 1, a significant Group (ASD/comparison) × PM task (Event-based/time-based) interaction, F(1, 40) = 6.46, p = .02, indicated that children with ASD showed significantly diminished TBPM, but non-significantly better EBPM than comparison participants.  In Study 2, the interaction between Group and PM task observed in Study 1 was replicated exactly in this study, F(1, 31) = 5.87, p= .02, reflecting diminished TBPM, but unimpaired EBPM among individuals with ASD.  In neither study was there any evidence that time perception contributed to diminished TBPM among individuals with ASD.  There was evidence in Study 1 of a specific relation between diminished TBPM and diminished theory of mind.

Conclusions:  These results provide clear (replicable) evidence for a specific profile of prospective memory ability/disability in ASD.  Correlations between prospective memory task performance and background measures will be presented and the nature of cognitive underpinnings of prospective memory discussed.  In particular, the issue of whether individuals with ASD employed compensatory strategies to perform well on EBPM tasks, despite limited/atypical underlying competence, will be addressed.