Odors and the remembrance of things past.

Three experiments, using ambient odors and incidental learning procedures, examined the effectiveness of odors as memory retrieval cues. Experiment 1 showed that a single ambient odor present on both learning and testing improved recall of a list of words over a no-odor control and a group that received the odor at encoding or retrieval only. Experiment 2 replicated this result and showed that whereas reinstating the odor context improved overall recall, recall of odor-related information was not significantly enhanced by the odor cue. Finally, Experiment 3, employing implicit and explicit retrieval tasks, demonstrated that the same odor must be present on both learning and remembering for the memory benefit to occur. The memory enhancement observed with odors was not due to the effects of semantic mediation. The results are discussed within the framework of encoding specificity of memory (e.g., E. Tulving and D. M. Thomson, 1973), and implications for odor imagery and cuing effects on odor-related material are addressed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exposure to various stressors alters preferences for natural odors in rats (Rattus norvegicus).

Male Sprague-Dawley rats were given choice tests (Test 1) in a maze with the odors of clean bedding, citronella, an alpha colony (ACO), shocked conspecifics (SCO), or a predator cat (PCO). In Exps 1–3, groups were exposed to no stress, defeat by a conspecific, or shocks. During subsequent tests (Test 2), nonstressed rats showed no change in odor preferences; defeated rats showed a nonsignificant reduction in preference for ACO; and shocked rats showed significant preference reductions for SCO and PCO and a significant increase in preference for ACO. In Exp 4, odors of isolated, nonstressed conspecifics (CO) were preferred more than ACO, for rats given shock before Test 2. In Exp 5, rats significantly preferred CO over ACO when exposed to a caged cat during Test 2. Because of exposure to stress, rats later avoided certain fear odors and showed strong preferences for the odors of nonstressed CO. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the relationship between differential outcomes and differential sample responding in matching-to-sample.

Four experiments involving 24 experimental pigeons and 24 experimentally naive pigeons examined control over choice by differential sample responding in matching-to-sample with differential outcomes. In Exp 1, Ss initially learned to match with food vs no-food outcomes. Their performances later transferred to other samples to which responding vs not responding had been explicitly reinforced with a single outcome (food). In Exp 2, Ss initially learned to produce the comparisons by pecking 1 sample but not the other. Transfer was then observed to new samples associated with food vs no food (and thus often vs seldomly pecked). Exps 3 and 4 showed that transfer of matching required differential behavior to each sample set and did not depend on explicit conditioning of that behavior prior to acquisition. Results show that differential sample behavior provides a redundant cue for choice in differential outcome matching-to-sample. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfactory discrimination of mouse strains (Mus musculus) and major histocompatibility types by humans (Homo sapiens).

Examined, in 5 experiments, whether the olfactory differences apparent to mice are also accessible to humans, using a total of 63 human Ss. In Exp I, Ss were asked to distinguish between the whole-body odors of live mice differing genetically only at the major histocompatibility gene complex (H-2). In Exps II and III, the odor source was mouse fecal pellets, and in Exps IV and V, the odor source was mouse urine. Results reveal that humans can use olfaction to discriminate closely related strains of mice. The possibility that excreted metabolites with characteristic odors may have predated the evolution of an adaptive function for these odors in social communication is suggested. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discrimination among colony mates' anogenital odors by guinea pigs (Cavia porcellus).

Three experiments used an aversively motivated learning task to examine the ability of adult guinea pigs to discriminate among odors from nonspecific anogenital swabbings of colony mates. Exps I and II examined the ability of 8 male (M) and 8 female (F) Ss to discriminate among odors of colony mates controlled for age and sex. Both sexes were able to discriminate among individual Ss on the basis of odor. Since individual Ss could be discriminated, Exp III, examining detection of physiological estrus, tested the ability of 6 Ms and 6 Fs to discriminate preserved odor samples from the same F during conditions of estrus and nonestrus. Both Ms and Fs were able to discriminate between the conditions. Results are discussed with reference to the involvement of odor in the social behavior of guinea pigs. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of discrimination training on responding during a compound conditioned stimulus.

Four experiments examined responding in the presence of a triple-element compound ABC after discrimination training in which 2 compounds, AB and BC, signaled the delivery of food and 1 element alone, B, signaled the absence of food. In Exps 1 and 2, using rats, responding during ABC was more vigorous than in a control group for which A and C but not B had been individually paired with food. This finding was replicated in Exp 3, which used pigeons, and in Exp 4, where all 3 stimuli of the control condition were individually paired with food. The results are more consistent with a configural than with an elemental theory of learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus control of copulatory behavior in sexually naive male Japanese quail (Coturnix japonica): Effects of test context and stimulus movement.

Sexually experienced male quail (Coturnix japonica) are more likely to engage in copulatory behavior than sexually naive ones. These experiments suggest that sexual experience in a particular place may facilitate later copulatory responding because of increased familiarity with the contextual cues of the environment. Male quail in Exp 1 did not copulate reliably with taxidermic models of females in a novel context, even though some of the subjects were allowed to copulate with female quail in their home cages. In contrast, sexually naive males in Exps 2 and 3 copulated vigorously with taxidermic models of females in a familiar context. In Exp 4, sexually naive males tested in an unfamiliar context were more likely to copulate with a moving than with a static model. The stimulus control of copulatory behavior in sexually naive male quail was similar to that in sexually experienced ones but only in familiar contexts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfaction and the "data" memory system in rats.

Conducted studies to characterize the memory system involved in successive olfactory discrimination learning in rats. Two odors emanated from different arms of a radical maze; 1 of the arms contained a water reward. After training on 4 to 5 pairs of odors Ss learned to discriminate the members of a new pair in 5–20 trials. Experiments in which either member of the pair was compared with a novel cue indicated that the Ss learn both positive and negative odors, rather than ignoring the negative cue. The memories for the odors were apparently persistent, and no evidence for retroactive interference from subsequent training was obtained. Animals trained on 3 component odors with 2 in common did not recognize the elements that were unshared when these were presented by themselves. Even when 1 of the 2 shared components was combined with the differentiating component into a cue the new cue was treated as a novel odor. Inclusion of a previously learned simple odor in a complex odor did affect the learning of that odor. Findings, combined with those of previous studies in which lesions were used, suggest that learning that a series of odor discriminations involves a version of the "data" memory system described by cognitive psychologists. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Manipulating odor cues facilitates add-on fostering in sheep

Manipulating the odor of a ewe's own and alien lambs has been used to facilitate fostering a second lamb on ewes with a single offspring (add-on fostering). Previous research has demonstrated that familiar odor cues must be present on the own and alien young to achieve successful and rapid adoptions. Familiar odors may consist of natural own-lamb odors or artificial odors previously applied to the lambs involved. In the present study (Exp. 1), an artificial odorant (neatsfoot oil) was applied to the own and alien lambs shortly after birth to establish a common familiar odor. Acceptance tests were conducted daily over a 72 h period. In Exp. 2, neatsfoot oil was again used as a common artificial odorant to facilitate add-on fostering, but, in addition, the natural odors of own and alien lambs were transposed by exchanging cloth stockinette jackets worn by the lambs. In Exp. 1, 9 of 18 ewes (50%) met the criteria for accepting their own and alien lambs within 72 h. Seven of these nine ewes (78%) accepted the alien lamb immediately. In Exp. 2, 24 of 30 ewes (80%) accepted their own and alien young, and 20 of the 24 acceptances (83%) were immediate. We conclude that add-on fostering may be limited only by our inability to properly match familiar-odor cues on own and alien lambs.     

Recognition of conspecific odors by laboratory rats ( Rattus norvegicus) does not show context specificity.

This experiment investigated how contextual cues affect recognition of conspecific odors in laboratory rats (Rattus norvegicus). Rats received 5 encounters with the same odor in the same context. For the 6th test encounter, all rats received a simultaneous presentation of the original odor and a novel odor. The authors tested 1 group of rats (context same) in the same context as before. For the remaining 2 groups, the test encounter was in a different context that 1 group (context different) had experienced but that 1 group (context novel) had not. A significant preference to investigate the novel odor by context-same and context-different rats, but not by context-novel rats, suggests that odor recognition can occur following transfer to a different, but familiar, test context, indicating a lack of context specificity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Instrumental responding remains sensitive to reinforcer devaluation after extensive training.

Four experiments, with 140 male rats, investigated performance of an instrumental response following postconditioning devaluation of the reinforcer. Exps I and II, which examined whether extended training would make the instrumental response insensitive to such devaluation, found substantial decreases in the performance of both moderately and extensively trained instrumental responses when their reinforcers were paired with an intraperitoneal injection of LiCl (.5 mg/kg). Both experiments revealed that there was some residual performance of a response whose reinforcer had been devalued. Exp III showed residual responding to be attributable neither to unconditioned levels of responding nor to the inadequacy of the devaluation procedure, while Exp IV revealed the amount of residual responding to be the same whether or not the reinforcer was earned by another response during aversion training. Results suggest that a portion of instrumental responding depends on response–reinforcer learning even after extensive training. However, with both moderate and extensive training, some portion of responding is independent of the current value of the reinforcer. (47 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spontaneous configuring in conditioned flavor aversion.

Four experiments with 202 rats investigated spontaneous configuring, using the conditioned flavor-aversion paradigm. In Exp I, extended training of a 2-flavor compound stimulus did not produce spontaneous differentiation of conditioned responding to that compound and its elements. In Exp II, it was found that extended nonreinforced exposure to a compound stimulus generated spontaneous element–compound differentiation when the elements were later conditioned. Ss that received extended preexposure to the compound showed less conditioned responding to the compound than to either of its elements. However, Ss that had not received preexposure to the compound showed greater conditioned responding to the compound than to either of its elements (summation). In Exp III, nonreinforced preexposure to a compound stimulus prior to minimal reinforced compound training produced spontaneous compound–element differentiation, but extended reinforced compound training eliminated that differentiation. In Exp IV, extended partial reinforcement training with a compound produced differentiation of the compound from its elements. Implications of these data for the mechanisms responsible for spontaneous configuring, and for the summation assumptions common to most learning theories, are discussed. (38 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Representation-mediated overshadowing and potentiation of conditioned aversions.

Examined the ability of CS-evoked representations of flavored substances to modulate the conditioning of LiCl-based aversions to simultaneously presented flavors or odors. In Exps I–III, 156 thirsty Sprague-Dawley rats first received pairings of an auditory CS with a flavored-water UCS; they then received pairings of a compound stimulus with a toxin. Exp IV examined the potentiation of aversion conditioning to a novel odor using 32 Ss. In Exp I, conditioning of a flavor was partially overshadowed when it was presented in compound with a tone that had been previously paired with another flavor. Exp II replicated that result and also found that conditioning to a flavor was not overshadowed when the flavor was presented in compound with a tone that had been paired with that same flavored substance. In Exps III and IV, conditioning to an odor stimulus was potentiated when it was presented in compound with either a tone or another odor that had been previously paired with a flavor stimulus. Results suggest that evoked representations of stimuli may substitute for those events themselves in a variety of associative functions. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The hide-and-seek of retrospective revaluation: Recovery from blocking is context dependent in human causal learning.

In a typical blocking procedure, pairings of a compound consisting of 2 stimuli, A and X, with the outcome are preceded by pairings of only A with the outcome (i.e., A+ then AX+). This procedure is known to diminish responding to the target cue (X) relative to a control group that does not receive the preceding training with blocking cue A. We report 2 experiments that investigated the effect of extinguishing a blocking cue on responding to the target cue in a human causal learning paradigm (i.e., A+ and AX+ training followed by A– training). The results indicate that extinguishing a blocking cue increases conditioned responding to the target cue. Moreover, this increase appears to be context dependent, such that increased responding to the target is limited to the context in which extinction of the blocking cue took place. We discuss these findings in the light of associative and propositional learning theories. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Age of first appearance of simultaneous and successive negative contrast in infant rats.

Simultaneous (SimNC) and successive (SNC) negative contrast, 2 paradoxical effects that are related to shifts in reward magnitude, were studied in 148 rat pups. In Exps I and II, 11-, 14-, and 17-day-old Ss were able to discriminate between the large (milk suckling) and small (dry suckling) reward odor cues as measured by attachment latencies, but only the 14- and 17-day-olds showed SimNC. At none of the 3 ages was a discrimination formed to the differential odor cues in the alley in terms of runway speeds. In Exp III, Ss were placed directly on the dam's ventrum to facilitate attachment. As in the earlier experiment, the 11-day-olds discriminated between the odors signaling the 2 reward conditions but did not show the SimNC effect. In Exp IV, SNC was shown at 17 days but not at 14 days in the attachment latency measure and at neither age in the run measure. These 4 experiments extend earlier findings that the paradoxical effects that emerge out of intermittent schedules of reward magnitude occur earlier than those associated with single abrupt shifts in reward magnitude. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memory for individual scent in hamsters (Mesocricetus auratus) as assessed by habituation methods.

The memory of hamsters (Mesocricetus auratus) for the flank scent of older male hamsters was investigated in a series of habituation experiments. In 2 types of habituation tasks (Exps 1 and 2), male hamsters habituated to the flank scent of 1 male and then increased their level of investigation to that of a novel male; similar results were obtained when the intervals between trials ranged from 1 sec to 2 days. When the test trial was 10 or 21 days after habituation (Exp 3), males discriminated between familiar and novel flank scents at 10 days but not at 21 days. The results demonstrate recognition of familiar and unfamiliar individual odors and excellent memory for these differences. Habituation techniques yield extremely robust results and may be useful for investigations of other aspects of individual signatures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive resources and dual-task interference effects at retrieval in normal people: The role of the frontal lobes and medial temporal cortex.

Conducted 3 experiments to examine the hypothesis that concurrent secondary tasks at retrieval will interfere more with long-term, episodic memory functions involving the frontal lobes than those involving the medial temporal lobes hippocampus (MTL/H). The rationale is that strategic retrieval processes mediated by the frontal lobes place greater demands on cognitive resources than do relatively automatic associative retrieval processes (ecphory) mediated by the temporal lobes. In Exps 1 and 2, sequential finger tapping was performed at encoding, at retrieval, at both, or at neither. Recall of a categorized list of 16 words from the California Verbal Learning Test in Exp 1, and release from proactive inhibition (PI) in Exp 2, both being tests that involve the frontal lobes, were impaired if normal Ss tapped at both encoding and retrieval. Concurrent tapping had little effect on rate of learning in Exp 1 and on total words recalled during the buildup of PI in Exp 2, both of which are indices that are affected more by MTL/H than by frontal lesions. In Exp 3, tapping by normal Ss affected letter fluency, a test more sensitive to frontal lobe than temporal lobe damage, but not category fluency, for which the reverse is true. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective hippocampal lesions abolish the contextual specificity of latent inhibition and conditioning.

The contextual specificity of the CR and latent inhibition (LI) was examined in rats with selective hippocampal lesions. Acquisition of the CR to a novel CS was equally rapid in control and hippocampal rats (Exps 1 and 2), and CS preexposure disrupted acquisition (i.e., produced LI) to an equal extent in both groups (Exp 2). In control Ss, however, the CR established in one context transferred incompletely to a 2nd context (Exp 1), and LI was attenuated when CS preexposure and conditioning occurred in different contexts (Exp 3). This context specificity of the CR and LI was not apparent in hippocampal rats; the CR and LI transferred readily from one context to another. In addition, hippocampal rats were impaired in a spatial learning task (Exp 2) but were unimpaired in learning a Pavlovian contextual discrimination (Exp 3). Results suggest that a common contextual retrieval process underlies the contextual dependence of the CR and of LI and that this process is mediated by the hippocampus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Biological significance in forward and backward blocking: Resolution of a discrepancy between animal conditioning and human causal judgment.

Similarities between Pavlovian conditioning in nonhumans and causal judgment by humans suggest that similar processes operate in these situations. Notably absent among the similarities is backward blocking (i.e., retrospective devaluation of a signal due to increased valuation of another signal that was present during training), which has been observed in causal judgment by humans but not in Pavlovian responding by animals. The authors used rats to determine if this difference arises from the target cue being biologically significant in the Pavlovian case but not in causal judgment. They used a sensory preconditioning procedure in Exps 1 and 2, in which the target cue retained low biological significance during the treatment, and obtained backward blocking. The authors found in Exp 3 that forward blocking also requires the target cue to be of low biological significance. Thus, low biological significance is a necessary condition for a stimulus to be vulnerable to blocking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reactions of deer mice (Peromyscus maniculatus) and white-footed mice (Peromyscus leucopus) to homospecific and heterospecific urine odors.

Examined approach and withdrawal behaviors to homospecific and heterospecific urine odors in 2 experiments with 64 sexually naive mice from sympatric populations of Peromyscus maniculatus and Peromyscus leucopus. In Exp I, P. maniculatus females preferred homospecific male urine odor to air during both estrus and diestrus, and air to P. leucopus male urine odor under comparable conditions. P. leucopus females did not show similarly consistent behavior in the presence of these stimuli. In Exp. II, 32 P. leucopus Ss avoided male urine odors of both species, whereas 32 P. maniculatus Ss showed neither attraction nor avoidance to these odors. Results suggest urine might be used by P. maniculatus, but probably not by P. leucopus, for intra- and interspecific communication. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)