Abstract
Memory for odors is believed to be longer-lasting than memory for visual stimuli, as is evidenced by flat forgetting curves. However, performance on memory tasks is typically weaker in olfaction than vision. Studies of odor memory that use forced-choice methods confound responses that are a result of a trace memory and responses that can be obtained through process of elimination. Moreover, odor memory is typically measured with common stimuli, which are more familiar and responses may be confounded by verbal memory, and measure memory in intentional learning conditions, which are ecologically questionable. Here we demonstrate the value of using tests of memory in which hit rate and correct rejection rate are evaluated separately (i.e., not using forced-choice methods) and uncommon stimuli are used. This study compared memory for common and uncommon odors and pictures that were learned either intentionally (Exp. 1) or incidentally (Exp. 2) and tested with either a forced-choice or a one-stimulus-at-a-time (“monadic”) recognition task after delays of 15 min, 48 h or 1 week. As expected, memory declined with delay in most conditions, but depended upon the particular measure of memory and was better for pictures than odors and for common than uncommon stimuli. For common odors, hit rates decreased with delay but correct rejection rates remained constant with delay. For common pictures, we found the opposite result, constant hit rates and decreased correct rejection rates. Our results support the ‘misfit theory of conscious olfactory perception’, which highlights the importance of the detection of novelty in olfactory memory and suggests that olfactory memory should be studied using more ecologically valid methods.
Highlights
Memory for odors has long been believed to be robust and long-lasting [1]
In this paper we address the question: Does olfactory memory rely on different mechanisms than visual memory? In particular, we ask whether “novelty detection” is an important mechanism in long-term olfactory memory? We address this by examining memory for common and uncommon pictures and odors for up to one week in both intentional and incidental learning conditions, by giving participants the option of a “neither” response in a forced-choice task and by examining performance in a “monadic” test paradigm
In this paper we addressed the question: Does olfactory memory rely on different mechanisms than visual memory? In particular, we asked whether “novelty detection” is an important mechanism in long-term olfactory memory
Summary
Memory for odors has long been believed to be robust and long-lasting [1]. The longevity of olfactory memory is sometimes taken as evidence that it is special or unique compared to other forms of memory. The Proustian phenomenon has generated scientific interest and a recent review conducted by Hackländer et al [9] seems to demonstrate the olfactory system’s resistance to forgetting Another form of long-term olfactory memory is odor recognition memory, e.g., [10,11,12,13]. The results of Engen and Ross [16], as shown, and those of Lawless [17], as shown, demonstrate relatively little forgetting of odors over time In the latter case, the flat forgetting curves follow an initial rapid decline for odors and free form pictures and a significant decline for pictures at longer delays. This study was motivated by the question: Does odor memory rely on the same mechanisms as visual memory? Before addressing this question, we first outline a set of methodological and theoretical considerations
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