Olfactory short term memory: understanding perceptual representations of odours and the role of encoding strategies in working memory.

Abstract

This project examined the representation of odours in working memory. There is a paucity of research examining specific olfactory working memory ability, and there are equivocal findings concerning the availability of an internal representation to consciousness and the extent and influence of verbal coding. This thesis first describes the creation of a comprehensive database of odour normative data, which contributes to the future control and manipulation of olfactory stimuli in experimental research. Individual differences were assessed across these odour ratings, and four dimensions identified as suitable for future stimulus control. Olfactory working memory was then examined using the n-back task with verbalisable and hard-to-verbalise odours. A working memory advantage for verbalisable odours was replicated (Jönsson et al., 2011), but this advantage was unrelated to the adoption of a verbal rehearsal strategy. Instead, effects from a concurrent rotation task provided tentative evidence for an attentional refreshing process. Controlled working memory processes were shown to be reduced for low verbalisability odours, though there was no evidence in a remember- know task for a switch to more automatic processes (i.e. familiarity). However, in an individual-differences analysis of multi-modal n-back performance, only low verbalisable odours were unrelated to verbal and visual working memory. The n-back working memory findings may therefore reflect a perceptual memory that is unavailable to consciousness, and an important role of semantic information in the generation of an internal representation that can be manipulated in working memory. Finally, this thesis provided a first examination of item-specific proactive interference effects in a memory task, which showed absent proactive interference effects for low verbalisability odours and which supports mediation of an olfactory representation through odour verbalisability. It was suggested that a ‘fuzzy’ representation for low verbalisability odours results in a weak link between an item and a conflicting familiarity signal.