Creating False Memories Using Stimulus Equivalence

Abstract

The misinformation effect occurs when misleading information contradicts details of an originally witnessed event. The phenomenon is reliably produced in cognitive psychology laboratory studies, and is a probable cause of real-world situations where a witness is found to have an altered recollection of an original event. However, in many real-world situations, it is not possible to identify a distinct source of misinformation, and it appears likely that the witness has inferred a false memory by integrating misleading suggestions from a variety of sources. Stimulus equivalence is a learning process of considerable interest to behavioural scientists. In a stimulus equivalence task, a small number of trained relations between some members of the class result in a large number of untrained relations emerging between all members of the class. The potential for emergent relations allows for an inferential process which may underlie creativity, schema development, attitudes, and a number of other psychological constructs. Of interest for this thesis is that stimulus equivalence may underlie some instances of false memory where there is no distinct source of misinformation. Three main experiments were conducted to investigate this hypothesis. The first two used patterns made up of coloured geometric shapes as stimuli, while the third used photographic images. Misinformation was provided by means of a stimulus equivalence task which used two components of the original stimulus and changed a third. At a recognition test, misled participants were more likely to misidentify a pattern or photograph similar to the original, but constructed of the members of the stimulus equivalence class. The equivalence derived misinformation effect was robust and distinct from the effects of familiarity, or partial stimulus control. Having a reliable manifestation of the misinformation effect following inference of misleading information during stimulus equivalence training, it became apparent that differences in strategies reported by the participants may underlie differing results between groups using verbal or non-verbal stimuli. The possibility of two differing behaviours equating to stimulus equivalence is discussed. In summary, stimulus equivalence processes may underlie some real-world manifestations of the misinformation effect, while studying the effects of stimulus equivalence on memory may further understanding of stimulus equivalence itself.