The role of olfactory familiarization in short-term recognition of odors was investigated. Subjects were asked to make qualitative similarity judgments regarding either identical or dissimilar odors delivered in pairs. Except for control groups, subjects got familiarized with either the first (target) or the second (distractor) or both odors from a pair. Groups also differed according to the number offamiliarization sessions-one, two, or three-taking place prior to the discrimination judgments. There was no significant influence offamiliarization on correct recognition scores for pairs ofidentical odors. The most salient finding was a marked decrease of false alarms as a function of the number of familiarization sessions, which evidenced a positive effect of familiarization on discrimination for pairs of dissimilar odors. These judgments were not dependent on an intensity criterion. False alarms did not vary according to whether subjects had been familiarized with the target or the distractor or both odors from a pair. A positive correlation found between discrimination performances and the number of odors correctly remembered as being presented during familiarization suggested that familiarization resulted in long-term storing of memory traces for familiarized odors. Since familiarization was effective despite conditions unfavorable to the use of semantic encoding, the results argue in favor of a predominantly perceptual encoding of odors in the investigated task.In the olfactory domain, several studies have been carried out in order to investigate the encoding of odors in memory structures (Engen & Ross, 1973;Eskenazi, Cain, & Friend, 1986;Lawless, 1978;Lyman & McDaniel, 1986, 1990 Murphy, Cain, Gilmore, & Skinner, 1991;Rabin, 1988;Rabin & Cain, 1984;Schab, 1990). Some of these studies have indicated that the familiarity of subjects with the tested odors seems to be a determinant variable in a type of experimental procedure developed in order to evaluate olfactory memory in terms of odor recognition (Cain, 1984;Rabin & Cain, 1984). In principle, this procedure consists ofpresenting subjects with odors throughout the first part ofthe experiment, and then presenting the same subjects with the same odors, called targets, interspersed with other ones, called distractors, during the second part ofthe experiment. Hence, the task consists ofrecognizing, among the distractors, the target odors that have initiaIIy been delivered during the first part.The influence of familiarity is expressed by an increase in performance, which depends on subjects' experience with the tested odors before the experiment has even begun. To study the effect of subjects' prior experience with tested odors, Rabin (1988) examined the ability of subjects to discriminate odors-that is, to recognize the odors as being the same or different when they are presented in pairs after having been learned. Rabin observed Correspondence should be addressed to loP. Royet, Universite Claude-Bernard Lyon I, Laboratoire de Physiologie Neurosensorielle, 43, ...

The role of verbal encoding in odor recognition memory was investigated using odors of low familiarity to subjects before the experiment began. The experimental procedure included two phases--odor learning (first phase) and odor memory testing (second phase)--separated by a delay of 7 days. Five experimental conditions were established: three conditions of odor learning with names (labeling conditions), one condition of odor learning without names (sensory familiarization), and one condition of no learning prior to testing (control conditions). The labeling conditions differed from each other regarding label characteristics. The names were those of odor sources (veridical names), those personally generated by subjects (generated names), or those derived from the chemical names of the odorants (chemical names). Subjects were required to learn 20 fixed associations between odors (targets or distractors) and 20 names during two daily sessions. The learning sessions included two identification tests and ended by a verbal memory test in which subjects recalled odor names. The odor memory test was split into two parts separated by a retention interval of either 20 min (short-term memory) or 24 h (long-term memory). Data showed that olfactory recognition memory was enhanced in subjects who associated veridical or generated names to odors during the learning session. Chemical names were not appropriate to facilitate odor recognition. Similarly, the level of odor identification was higher for veridical and generated names than for chemical names, though the level of verbal memory for chemical names was substantial. Recognition response latencies were systematically longer for a target odor implying a positive response than for a distractor odor implying a negative response. Together, these data suggest that odor recognition and identification are sensitive to the semantic content of labels associated with odors. Odor memory was adversively influenced by time, but this influence was less pronounced when the names were endowed with a rich semantic content.

An investigation of very short term olfactory recognition memory was made with odors of low familiarity to subjects. The experimental procedure was that currently used to make qualitative similarity judgments on odors delivered in paired succession. Subjects made similarity judgments in a yes/no recognition paradigm on odors that were either identical or different. The dependence of recognition performance upon the degree of qualitative similarity was assessed by using two sets of dissimilar odor pairs: slightly dissimilar pairs (S1) and very dissimilar pairs (S2). Performance in terms of correct judgments (hits, correct rejections) was rather good for identical pairs in both sets and was nearly perfect for very dissimilar pairs with a delay of 2-300 sec, suggesting no effect of time or similarity on performance. However, for slightly dissimilar pairs, false alarms increased in number, thereby indicating a dependence of the recognition score on the qualitative distance between odors. In addition, false alarms tended to increase with the lengthening of the retention interval. It was suggested that the subjects based their responses on their capability to detect differences between odors rather than recognizing their similarities. Correct identifications were thus preserved at the cost of increasing false alarms when the discrimination task was made more difficult by closer similarity 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 view that recognition performances had some cognitive/semantic basis.

The child version of the California Odor Learning Test (COLT) was designed to assess cognitive functioning in impaired and healthy children. The COLT's rationale was based on two assumptions. First, measures of cognitive functioning are a good index of severity or extent of brain damage if compared between normal and clinical populations. Second, the cognitive-mediated tasks of verbal odor recall, recognition and identification were suitable to evaluate cognitive functioning. The focus of this study was to determine the COLT's ability to detect developmental differences in odor learning and memory. The participants were 51 healthy children who were twice administered the COLT with a weekly delay between tests. They were ascribed to two age-groups (7-10 and 11-15 years old) according to levels of cognitive development. The COLT employed 22 common odors and included two sessions. In the first session, children learned two sets of six odors. The first set was presented three times, the second one once, during a single learning episode. Following learning, children recalled the odors of the first set by name at free recall and category-cued recall. The second session included the following tasks: long-term free odor recall and category-cued odor recall, odor recognition-memory and verbal odor identification. A series of analyses of variance (ANOVAs, p < 0.05) with age as between-subject variable and repeated measurements on recall revealed significant differences between the two groups on the number of odors correctly recalled by name both at free recall, category-cued recall, recognition and identification. There were differences in false alarms at odor recognition between the two groups. Children from both groups benefited from a learning effect over odor trials. A gender effect was found for odor free recall at retest. These results suggest that the COLT has the potential to serve as a useful tool in the assessment of cognitive functioning in children.