VERY SHORT-TERM RECOGNITION MEMORY FOR ODORS

An investigation of very short term olfactory recognition memory was m ade with odors of low familiarity to subjects. The experimental proced ure was that currently used to make qualitative similarity judgments o n odors delivered in paired succession. Subjects made similarity judgm ents in a yes/no recognition paradigm on odors that were either identi cal or different. The dependence of recognition performance upon the d egree of qualitative similarity was assessed by using two sets of diss imilar odor pairs: slightly dissimilar pairs (S1) and very dissimilar pairs (S2). Performance in terms of correct judgments (hits, correct r ejections) was rather good for identical pairs in both sets and was ne arly perfect for very dissimilar pairs with a delay of 2-300 sec, sugg esting no effect of time or similarity on performance. However, for sl ightly dissimilar pairs, false alarms increased in number, thereby ind icating a dependence of the recognition score on the qualitative dista nce between odors. In addition, false alarms tended to increase with t he lengthening of the retention interval. It was suggested that the su bjects based their responses on their capability to detect differences between odors rather than recognizing their similarities. Correct ide ntifications were thus preserved at the cost of increasing false alarm s when the discrimination task was made more difficult by closer simil arity between odors (S1) or by the fading of memory traces with time. Studying the congruence between the similarity judgments and the kind of evocations associated with paired odors gives some support to the v iew that recognition performances had some cognitive/semantic basis.