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This study examined the effects of delivery mode on the response to inflammatory pulpal pain and pain-induced changes in cognitive performance in adult rats. Experiments were done on rats born by vaginal or caesarean section (C-section) delivery. Dental pulp was irritated by intradental capsaicin (100 [micro]g) application and then nociceptive scores were recorded for 40 min. Spatial and passive avoidance learning and memory were assessed using the Morris water maze (MWM) and shuttle box tools, respectively. Additionally, in vivo recording of field excitatory postsynaptic potential (fEPSP) in the CA1 of the hippocampus was used to verify synaptic plasticity. Capsaicin produced more significant nociceptive behavior in vaginally delivered rats compared to C-section rats (P < 0.01). C-section-delivered rats show better performance in both MWM and shuttle box tests. Likewise, C-section rats had greater fEPSP slopes compared to the vaginally delivered group (P < 0.05). Capsaicin impairs cognitive performance in rats born by each delivery route. However, capsaicin effects were more significant in rats delivered vaginally than by C-section. Overall, C-section-delivered rats show lower sensitivity to capsaicin-evoked pulpal nociception and better cognitive performance than vaginally delivered rats. These effects are in part mediated by reduced neuroinflammation and enhanced neuronal synaptic plasticity following C-section delivery. Key words: pulpal nociception, vaginal delivery, C-section, learning and memory, fEPSP. Cette etude a porte sur les effets du mode d'accouchement sur la reaction a la douleur inflammatoire de la pulpe et les variations dans les performances cognitives engendrees par la douleur chez le rat adulte. Nous avons procede a des experiences chez des rats accouches par voie vaginale ou par cesarienne. Nous avons provoque une irritation de la pulpe dentaire en appliquant de la capsaicine (100 [micro]g) a l'interieur de la dent, puis note des scores de nociception pendant 40 min. Nous avons evalue l'apprentissage de l'evitement passif et la memoire a l'aide du labyrinthe aquatique de Morris (LAM) et de la boite-navette, respectivement. De plus, nous avons verifie la plasticite synaptique a l'aide de l'enregistrement in vivo de champs de potentiels post-synaptiques excitateurs (fEPSP) dans la region CA1 de l'hippocampe. La capsaicine a entraine des comportements nociceptifs plus importants chez les rats accouches par voie vaginale que chez les rats accouches par cesarienne (P < 0,01). Les performances des rats accouches par cesarienne etaient meilleures dans la PAM comme dans la boite-navette. De la meme maniere, les rats accouches par cesarienne presentaient des pentes de fEPSP plus prononcees que les rats accouches par voie vaginale (P < 0,05). La capsaicine nuit aux performances cognitives des rats accouches par voie vaginale comme par cesarienne. Cependant, les effets de la capsaicine etaient plus marques chez les rats accouches par voie vaginale que par cesarienne. Dans l'ensemble, les rats accouches par cesarienne presentent une plus faible sensibilite a la nociception de la pulpe engendree par la capsaicine, avec de meilleures performances cognitives que les rats accouches par voie vaginale. Ces effets sont en partie medies par un abaissement de la neuro-inflammation et une hausse de la plasticite neuronale synaptique a la suite d'un accouchement par cesarienne. [Traduit par la Redaction] Mots-cles: nociception de la pulpe, accouchement par voie vaginale, cesarienne, apprentissage et memoire, fEPSP., Introduction Pulpalgia, pulpal pain, is one of the most common and widespread problems in primary care. It may occur as a result of reversible or irreversible inflammation of pulp tissue [...]

Social animals, such as primates, must behave appropriately in complex social situations such as dominance interactions. Learning dominance information through trial and error would be dangerous; therefore, cognitive mechanisms for rapid learning of dominance information by observation would be adaptive. We used a set of digitally edited artificial social interactions to examine whether rhesus monkeys (Macaca mulatta) can learn dominance relationships between unfamiliar conspecifics through observation. Our method allowed random assignment of stimulus monkeys to ranks in an artificial hierarchy, controlling for nonbehavioral cues that could indicate dominance. Subject monkeys watched videos depicting 1 stimulus monkey behaving dominantly toward another and were rewarded for selecting the dominant individual. Monkeys rapidly learned this discrimination across 5 behavior types in Experiment 1 and transferred performance to novel videos of new individuals in Experiment 2. In addition, subjects selected the dominant individual more often than expected by chance in probe videos containing no behavioral dominance information, indicating some retention of the relative dominance status of stimulus monkeys from training. Together, our results suggest that monkeys can learn dominance hierarchies through observation of third-party social interactions. Keywords: social cognition, observation, social behavior, hierarchy, computerized testing Supplemental materials: http://dx.doi.org/10.1037/a0019751.supp DOI: 10.1037/a0019751

This study explored the visual discrimination learning ability of fire-bellied toads (Bombina orientalis). Two groups of toads were trained in a simultaneous visual discrimination task involving video footage of either black crickets on a white background (black-cricket toads) or white crickets on a black background (white-cricket toads). Fifteen widely spaced acquisition trials were followed by 12 reversal trials. Successful learning was observed by decreased incorrect snapping and reduced latency to snap at the correct stimulus (S+) during acquisition; however, white-cricket toads executed significantly more incorrect snaps than did black-cricket toads. Both groups of toads could master the reversal task as measured by latency to snap at S+, but not as measured by the proportion of incorrect snaps. Despite the stronger potency of the black-cricket stimulus, the results showed that toads can learn a simultaneous discrimination task and a reversal of its contingency. This elaborate form of learning appears to be conserved among vertebrates. doi: 10.3758/LB.38.4.418

Pigeons were trained in a forced choice task with four alternatives to categorize arrays consisting of 1, 3, 5, or 8 dots. Before the pigeons chose a comparison stimulus, they were required to peck each dot sequentially. A single peck to a dot, which was defined as an indicating response, changed the color of the dot so that it was differentiated from those that remained to be counted. The pigeons successfully learned to categorize the numerical arrays and then displayed transfer to novel arrays consisting of two, four, six, or seven dots, in a manner according to the order of 1 < 2 < 3 < 4 < 5 < 6 < 7 < 8. Subsequent tests revealed that the pigeons discriminated the stimuli by relying on the number of indicating responses. They also utilized multiple information (surface area, time, and other confounded events), but this was of minor significance, and after training, the pigeons were able to disregard these cues. doi: 10.3758/LB.37.4.365

Using a variation on the standard procedure of conditioned inhibition (Trials A+ and AX-), rats (Rattus norvegicus) in a circular pool were trained to find a hidden platform that was located in a specific spatial position in relation to 2 individual landmarks (Trials A [right arrow] platform and B [right arrow] platform; Experiments 1a and 1b) and to 2 configurations of landmarks (Trials ABC [right arrow] platform and FGH [right arrow] platform; Experiment 2a). The rats also underwent inhibitory trials (Experiment 1: Trials AZ [right arrow] no platform; Experiment 2a: Trials CDE [right arrow] no platform) interspersed with these excitatory trials. In both experiments, subsequent test trials without the platform showed both a summation effect and retardation of excitatory conditioning, and in Experiment 2a rats learned to avoid the CDE quadrant over the course of the experiment. Two further experiments established that these results could not be attributed to any difference in salience between the conditioned inhibitors and the control stimuli. All these results contribute to the growing body of evidence consistent with the idea that there is a general mechanism of learning that is associative in nature. Keywords: landmark learning, conditioned inhibition, rats, Morris water maze DOI: 10.1037/a0015630

Previous studies demonstrate that soft-bodied (coleoid) cephalopods are adept at learning and remembering features of their environment, bur little is known about their primitive relative, nautilus. Nautilus makes nightly migrations from deep to shallow water along coral reef slopes, covering large areas of varied substrate. Memory of its surroundings may be advantageous, but the nautilus brain is the simplest among extant cephalopods, lacking dedicated neural regions that support learning and memory in other cephalopods. The authors hypothesize that the absence of these regions in nautilus may affect memory storage. Here the authors report the first evidence for spatial memory in 2- and 3-dimensional arenas. In a small open-field maze, nautiluses learned the location of a goal within 3 trials, and memory was stable for at least 2 weeks. In 3-dimensional environments, animals habituated within and across trials when their surroundings were unchanged, bur activity increased when the environment changed topographically, although not when the change was visual only. These results are comparable to performances of coleoids in similar tasks and are surprising given the far simpler neuroanatomy of nautilus. Keywords: nautilus, cephalopod, learning, memory, spatial

According to O-R theory of instrumental learning, incongruent biconditional discriminations should be impossible to solve in a goal-directed manner because the event acting as the outcome of one response also acts as a discriminative stimulus for an opposite response. Each event should therefore be associated with two competing responses. However, Dickinson and de Wit (2003) have presented evidence that rats can learn incongruent discriminations. The present study investigated whether rats were able to engage additional processes to solve incongruent discriminations in a goal-directed manner. Experiment 1 provides evidence that rats resolve the response conflict that arises in the incongruent discrimination by differentially encoding events in their roles as discriminative stimulus and as outcome. Furthermore, Experiment 2 shows that once goal-directed control has been established the dorsomedial prefrontal cortex is not directly involved in its maintenance but rather plays a central role in conflict resolution processes. Keywords: instrumental learning, goal-directed action, response conflict, rats, prefrontal cortex

There is a long-standing debate in educational settings on the influence of positive and negative consequences on learning. Although positive rewards seem desirable from an ethical perspective, 1-trial learning has been best demonstrated in the animal literature with tasks using highly salient negative consequences, such as shock or illness, and so far only in tasks requiring the acquisition of a singular stimulus-response association. Here we show that pigeons and baboons can concurrently learn, in a cognitively challenging memorization task, hundreds of picture-response associations after a single exposure and that this rapid learning is better promoted by a positive outcome after the first picture presentation. Further, the early positive outcomes had beneficial effects on the memory of learned acquisitions that was detectable up to 6-8 months after initial training. Beyond their significance for educational policies, these findings suggest that the psychological and brain mechanisms controlling rapid, often 1-trial, learning have a long evolutionary history. They may represent the phylogenetic precursor for the disproportionate impact of first impressions in humans and the phenomenon of fast word learning in children. monkey | positive reinforcement | fast mapping | picture processing | bird

In 2 experiments, dwarf hamsters (Phodopus campbelli) were trained to find palatable foods in an open field. The location of each food patch remained the same throughout each experiment, and only 1 food was available per day. Once subjects had been trained to find each food in its unique location, they progressed to a testing phase in which subjects' mates were allowed to eat and hoard the food that was available in the open field each day. The foods that subjects' mates brought back to the home cages then served as discriminative stimuli signaling which food could be obtained in the open field. Subjects generally approached the patch containing the food hoarded by their mates, suggesting that dwarf hamster burrows could function as information centers. Keywords: information-center hypothesis, dwarf hamsters, foraging behavior, social learning, social influence.

Research has demonstrated that exposure to a rhythmic auditory stimulus can promote retention of a simple memory task in an avian species. In the current study, day-old domestic chicks (Gallus gallus) were trained on a weakly reinforced discriminative avoidance task for which retention is typically lost 30 min posttraining. Exposure to rhythmic stimuli 5 rain posttraining prevented memory loss, but only when sequences were highly metrical and contained sufficient repetition. These data provide further support for the claim that rhythmicity is a key feature of memory-enhancing auditory stimuli. Keywords: avoidance learning, chickens (Gallus gallus), rhythmicity, repetition, metricality

The ability to use the geometric shape of an environment as an orienting cue for goal location has been shown in many vertebrate groups. Experimentally, however, geometric spatial tasks are typically carried out on horizontal surfaces. The present study explored how learning a geometry task is affected by training on a surface extending in the vertical dimension--a slope. In a reference memory task, pigeons (Columba livia) were trained to locate a goal in an isosceles trapezoid arena. Learning on a slope proceeded more rapidly or with fewer errors than on a flat surface, presumably because of kinesthetic, vestibular, and visual information extractable from an inclined surface. Experiment 1 showed that, although the geometric shape of the arena was encoded, pigeons trained on a slope were guided by a goal representation based on the vertical and orthogonal axes of the slope to solve the task. Experiment 2 revealed that geometric learning was neither overshadowed nor facilitated by training on a slope. The data highlight a potentially important role for slope as an allocentric cue for goal location. Keywords: spatial learning, geometric shape, slope, vertical dimension, Columba livia

One parallel between humans and most songbirds is the fact that young require social interactions with an adult to acquire specific vocalizations. Songbirds are considered good models for comparative studies, although reports to date concern almost exclusively male songbirds. In addition, adult influence on vocal communication is generally investigated only in restricted social contexts (usually dyads). Here, the authors analyzed song learning and spatial associations among young female starlings that were maintained for 1 year in dyads (1 adult, 1 young), triads (2 adults, 1 young) or a larger group (7 young, 2 adults). Segregation by age was seen in the triads and in the larger group. The influence of adults (proportion of songs copied from adults) decreased as the young adult ratio increased. Unusual temporal features were observed in young maintained in triads and young neglected copying adult songs in the presence of peers. These results are among the first to explore the circumstances under which females learn and from whom they learn. They also add new insight to a wide range of questions about social influences on learning. Keywords: female starlings, Sturnus vulgaris, social context, song learning, social preferences

Three pigeons were trained in a three-item simultaneous same/different task. Three of six stimulus combinations were not trained (untrained set) and were tested later. Following acquisition, the subjects were tested with novel stimuli, the untrained set, training-stimulus inversions, and object shape and color manipulations. There was no novel-stimulus transfer--that is, no abstract-concept learning. Two pigeons showed partial transfer to untrained pairs and good transfer to stimulus inversions, suggesting that they had learned the relationship between the stimuli. Lack of transfer by the third pigeon suggests item-specific learning. The somewhat surprising finding of relational learning by 2 pigeons with only six training pairs suggests restricted-domain relational learning that was controlled more by color than by shape features. Individual differences of item-specific learning by 1 pigeon and relational learning by 2 others demonstrate that this task can be learned in different ways and that relational learning can occur in the absence of novel-stimulus transfer.

The role of attention in perceptual learning has been a topic of controversy. Sensory psychophysicists/ physiologists and animal learning psychologists have conducted numerous studies to examine this role; but because these two types of researchers use two very different lines of approach, their findings have never been effectively integrated. In the present article, we review studies from both lines and use exposure-based learning experiments to discuss the role of attention in perceptual learning. In addition, we propose a model in which exposure-based learning occurs only when a task-irrelevant feature is weak. We hope that this article will provide new insight into the role of attention in perceptual learning to the benefit of both sensory psychophysicists/ physiologists and animal learning psychologists.

The goal of the current research was to explore whether monkeys possess conceptual precursors necessary for understanding zero. We trained rhesus monkeys on a nonsymbolic numerical matching-to-sample task, and on a numerical ordering task. We then introduced nondifferentially reinforced trials that contained empty sets to determine whether monkeys would treat empty sets as numerical values. All monkeys successfully matched and ordered the empty sets without any training. Accuracy showed distance effects, indicating that they treated empty sets as values on a numerical continuum. Keywords: zero, empty sets, numerical cognition, distance effects, numerical continuum

The relationship of locomotor behavior in animals to physical objects, such as obstacles, is discussed, along with ideas related to object perception and visual kinesthesis. Meanwhile, apparent space perception is attributed to the animal's visual orientation both to light and to the surfaces of its environment. Consequences of these findings for maze-learning are emphasized.

In an open-field search task, pigeons (Columba livia) were trained to search for a goal located at the midpoint of the hypothetical line connecting two discrete visual landmarks positioned 60 cm apart. In Experiment 1, global orienting cues were absent. After reaching training criteria, pigeons were tested with novel interlandmark distances. Search location and error on test trials suggested pigeons learned relative distance. In Experiment 2, a global orienting cue was present. After reaching training criteria, pigeons were again tested with novel interlandmark distances. Results suggested pigeons learned relative and absolute distances. In Experiment 3, pigeons searched at the midpoint of rotated arrays in both the presence and absence of an orienting cue indicating learning of relative direction. In Experiment 4, pigeons searched in the appropriate goal direction when presented with a single landmark in the presence of the orienting cue but not in its absence indicating learning of absolute direction. Results implicate a stable frame of reference as critical to spatial coding strategies and suggest pigeons are able to code location based on absolute and relative distance and direction from discrete visual landmarks. Keywords: open field, pigeon, spatial, learning, landmark

Capuchin monkeys (Cebus apella) were tested on a reverse-reward task involving different quantities of the same food, or an identical quantity of different foods. All monkeys tested first on the qualitative version spontaneously mastered the task, whereas only one of four spontaneously mastered the quantitative version. No monkey reached criterion when the tasks were switched, although almost all did so following remedial procedures after the study. The results suggest that (a) qualitative reverse-reward is easier than quantitative versions of the problem, (b) quality and quantity dimensions are processed differently in food-related tasks, and (c) capuchin monkeys can show rapid and spontaneous learning of reverse-reward contingencies. Keywords: self-control, food preference, inhibitory control, choice

Only recently have researchers studied the ability of ants to learn and remember individual heterospecific odors. Cataglyphis cursor adults have the capacity to learn these odors, but the duration of their memory and the factors that affect its formation remain unknown. We used a habituation/discrimination paradigm to study some of these issues. C. cursor adult workers were familiarized to an anesthetized Camponotus aethiops on four successive encounters. Then they were either isolated or placed with 20 nestmates for a certain length of time before undergoing a discrimination test that consisted of reintroducing the familiar C. aethiops, as well as introducing an unknown member of the same colony. The results showed that adult C. cursor ants can retain in memory a complex individual odor for at least 30 min, as well as differentiate it from the odor of another closely related individual. However, when ants were replaced in a rich social background between the habituation and the discrimination trials, we did not observe a significant discrimination between the known and unknown C. aethiops ants. Our study shows, for the first time, the existence of long-term memory for individual odors in mature ant workers.

In two experiments, two groups of rats were trained in a navigation task according to either a continuous or a partial schedule of reinforcement. In Experiment 1, animals that were given continuous reinforcement extinguished the spatial response of approaching the goal location more readily than animals given partial reinforcement--a partial reinforcement extinction effect. In Experiment 2, after partially or continuously reinforced training, animals were trained in a new task that made use of the same reinforcer according to a continuous reinforcement schedule. Animals initially given partial reinforcement performed better in the novel task than did rats initially given continuous reinforcement. These results replicate, in the spatial domain, well-known partial reinforcement phenomena typically observed in the context of Pavlovian and instrumental conditioning, suggesting that similar principles govern spatial and associative learning. The results reported support the notion that salience modulation processes play a key role in determining partial reinforcement effects.

Two groups of rats were trained for 50 days on different discriminations in a magazine approach paradigm. One group was trained with a negative patterning schedule and a positive patterning schedule concurrently: they received intermixed trials of A +, B +, AB-, C-, D-, CD + (A, B, C, and D are four distinct stimuli; the plus sign denotes reinforcement with food, and the minus sign denotes nonreinforcement). The second group of rats was trained with the same four stimuli arranged as compounds and reinforced according to the biconditional schedule AB +, CD +, AC-, and BD-. The first group learned the positive patterning schedule much more quickly than the negative patterning schedule, but they learned the negative patterning schedule more effectively than the second group learned the biconditional schedule. The authors discuss the implications of these findings for models of stimulus representation.

The classic evidence for vocal production learning involves imitation of novel, often anthropogenic sounds. Among mammals, this has been reported for dolphins, elephants, harbor seals, and humans. A broader taxonomic distribution has been reported for vocal convergence, where the acoustic properties of calls from different individuals converge when they are housed together in captivity or form social bonds in the wild. Vocal convergence has been demonstrated for animals as diverse as songbirds, parakeets, hummingbirds, bats, elephants, cetaceans, and primates. For most species, call convergence is thought to reflect a group-distinctive identifier, with shared calls reflecting and strengthening social bonds. A ubiquitous function for vocal production learning that is starting to receive attention involves modifying signals to improve communication in a noisy channel. Pooling data on vocal imitation, vocal convergence, and compensation for noise suggests a wider taxonomic distribution of vocal production learning among mammals than has been generally appreciated. The wide taxonomic distribution of this evidence for vocal production learning suggests that perhaps more of the neural underpinnings for vocal production learning are in place in mammals than is usually recognized. Keywords: vocal learning, vocal production learning, vocal convergence, noise compensation

The results from five experiments are considered in relation to two of Spence's (1937, 1938) proposals concerning discrimination learning. In Experiments 1 and 2, we investigated whether his ideas about the interaction between excitatory and inhibitory generalization gradients can be used to understand how animals solve a complex patterning discrimination. The results supported a development of his proposals as put forward by Pearce (1994), provided a modification was made to Pearce's rule for determining the shape of the generalization gradient. In Experiments 3, 4, and 5, we examined whether animals would pay more attention to stimuli that are relevant, rather than irrelevant, to the solution of a discrimination. The results supported this proposal for stimuli comprising visual patterns, but not for those comprising plain colors. The results also indicated that change of attention was a consequence of preliminary receptor-exposure acts, as envisaged by Spence, and not of more central changes in attention.

We studied transposition in pigeons by training them to select the smaller (or the larger) of a pair of circles. In training, different groups of pigeons were given one pair, two pairs, or three pairs of circles along the size dimension. Testing included two stimulus pairs for which, according to theoretical postdiscrimination generalization gradients, transposition should decrease from one-pair to two-pair to three-pair training. On the basis of the results of our earlier study (Lazareva, Wasserman, & Young, 2005) and contrary to these predictions, we expected that transposition should increase from one-pair to two-pair to three-pair training. We found that multiple-pair discrimination training enhanced transposition, which, on average, rose from 47% (one-pair training) to 52% (two-pair training) to 64% (three-pair training). In addition, we found that the overall similarity of the testing pair to the training pair(s) modulated the strength of relational responding. These results demonstrate that encountering multiple instances of a rule leads to stronger relational learning, even when reinforcement history predicts the opposite trend. These results also provide strong evidence against stimulus generalization as the sole determinant of relational responding in transposition.

Successful adaptation to changes in an animal's emotional and motivational environment depends on behavioral flexibility accompanied by changes in bodily responses, e.g., autonomic and endocrine, which support the change in behavior. Here, we identify the orbitofrontal cortex (OFC) as pivotal in the flexible regulation and coordination of behavioral and autonomic responses during adaptation. Using an appetitive Pavlovian task, we demonstrate that OFC lesions in the marmoset (i) impair an animal's ability to rapidly suppress its appetitive cardiovascular arousal upon termination of a conditioned stimulus and (ii) cause an uncoupling of the behavioral and autonomic components of the adaptive response after reversal of the reward contingencies. These findings highlight the role of the OFC in emotional regulation and are highly relevant to our understanding of disorders such as schizophrenia and autism in which uncoupling of emotional responses may contribute to the experiential distress and disadvantageous behavior associated with these disorders. behavioral inhibition | emotion | reversal learning

Nut cracking is restricted to communities of wild chimpanzees living in West Africa, suggesting it is an example of a socially transmitted tradition. Detailed study of the acquisition of nut cracking in wild chimpanzees is consistent with this conclusion. However. only 2. small-scale experiments have been carried out in captivity to explore the role of social transmission in the acquisition of this behavior. The study presented here does this with a comparatively larger, statistically viable sample of 11 sanctuaryliving chimpanzees (Pan troglodytes schweinfurthii), permitting both between- and within-subjects experimental manipulations. Results confirmed that nut cracking can be acquired in a matter of days by social learning, but only in chimpanzees 3 to 4 years old and older. Direct comparisons are made with a study carried out in the wild, revealing striking similarities in developmental profiles. Keywords: tool use, social learning, nut cracking, chimpanzees

Primates' understanding of tool functionality has been investigated extensively using a paradigm in which subjects are presented with a tool that they must use m obtain an out-of-reach reward. Alter being given experience on an initial problem, monkeys can transfer their skill to tools of different shapes while ignoring irrelevant tool changes (e.g., color). In contrast, monkeys without initial training perform poorly on the same tasks. Compared to most monkeys, great apes show a clear propensity for tool using and may not require as much experience to succeed on tool functionality tasks. We investigated this question by presenting 171 apes (Pan troglodytes, Pan paniscus, Gorilla gorilla, and Pongo pygmaeus) with several tool-use problems without giving them initial training or familiarizing them with the test materials. Apes succeeded without experience, but only on problems based on basic properties such as the reward being supported by an object. However, only minimal experience was sufficient to allow them to quickly improve their performance on more complex problems in which the reward was not in contact with the tool. Keywords: tool use, tool properties, object choice task, problem solving, causal knowledge

We tested 6 chimpanzees (Pan troglodytes), 3 orangutans (Pongo pygmaeus), 4 bonobos (Pan paniscus), and 2 gorillas (Gorilla gorilla) in the reversed reward contingency task. Individuals were presented with pairs of quantities ranging between 0 and 6 food items. Prior to testing, some experienced apes had solved this task using 2 quantities while others were totally naive. Experienced apes transferred their ability to multiple-novel pairs after 6 to 19 months had elapsed since their initial testing. Two out of 6 naive apes (1 chimpanzee. 1 bonobo) solved the task--a proportion comparable to that of a previous study using 2 pairs of quantities. Their acquisition speed was also comparable to the successful subjects from that study. The ratio between quantities explained a large portion of the variance but affected naive and experienced individuals differently. For smaller ratios, naive individuals were well below 50% correct and experienced ones were well above 50%, yet both groups tended to converge toward 50% for larger ratios. Thus, some apes require no procedural modifications to overcome their strong bias for selecting the larger of 2 quantities. Keywords: inhibition, perseveration, quantity discrimination, relative numerousness, reversal learning

In two experiments, we developed a new methodology for studying complex stimulus control by spatial sequences of letters generated by artificial grammars. An artificial grammar is a system of rules that defines which letter sequences or strings are 'grammatical.' In Experiment 1, pigeons learned to respond differently to strings conforming to a grammar versus strings that were nongrammatical distortions. Several different criteria all suggested that performance was controlled both by some short chunks of strings shared between reinforced training strings and novel transfer strings and by more complex sequential regularities. In Experiment 2, pigeons quickly and accurately learned to respond differently to strings conforming to one or the other of two different artificial grammars. As in Experiment 1, performance was controlled both by some short chunks and by more complex sequential regularities. The results are interpreted in terms of family resemblance and pose new goals for theories of complex stimulus control.

In three experiments, rats were given concurrent exposure to a compound flavor (AX) and to one of the elements of the compound (X). The perceptual effectiveness of A was then assessed by a test involving generalization of a conditioned aversion. Comparison was made with a preexposure procedure in which the compound and the common element were presented on separate trials, either in alternation or in separate blocks of trials. The effectiveness of the unique cue was less after blocked preexposure than after either of the other procedures; concurrent preexposure did not produce a greater effect than did alternating preexposure. These results challenge the suggestion that concurrent preexposure engages a special comparison process that will facilitate this form of perceptual learning.

In three experiments, we examined the effect on the patterns of responding noted on fixed interval (FI) schedules of prior exposure to a range of interval and ratio schedules. Rats leverpressed for food reinforcement on random ratio (RR), random interval (RI), or variable interval (VI) schedules prior to transfer to FI schedules. In Experiment 1, prior exposure to an RR schedule retarded the development of typical FI patterns of responding. Exposure to a yoked RI schedule produced even greater retardation of typical FI performance. This effect was replicated in Experiment 2, using a within-subjects design. Rats responded on a multiple RR-RI schedule prior to a multiple FI-FI schedule. Typical FI performance emerged more slowly in the component previously associated with the RI than with that associated with the RR. In Experiment 3, exposure to an RR schedule retarded the development of FI performance to a greater extent than did exposure to a VR schedule. The latter schedule was programmed to allow the possibility that inhibitory control would develop after reinforcement. These results confirm that ratio schedules independently result in the disruption of FI responding. This effect was not long lasting and cannot be used plausibly to explain species differences in responding to FI schedules. However, it does suggest that temporal control--as manifested by the transfer of inhibitory control from one schedule to another---could facilitate movement between interval schedules.

Three experiments used a compound test procedure to evaluate whether superior conditioning results from the pairing of stimuli that are related to each other. In each case, a stimulus compound was tested after its component conditioned stimuli (CSs) had been conditioned by the same unconditioned stimuli (USs) arranged such that either related or unrelated CSs and USs were paired. Experiment I explored auditory and gustatory stimuli conditioned by LiC1 or shock, using rats. Experiments 2 and 3 used second-order conditioning in pigeons to pair stimuli that were similar by virtue either of qualitative features or of shared physical location. In each case, the compound test provided clear evidence that pairing related stimuli produces superior associative learning.

The authors analyze the shape categorization of rhesus monkeys (Macaca mulatta) and the role of prototype- and exemplar-based comparison processes in monkeys' category learning. Prototype and exemplar theories make contrasting predictions regarding performance on the Posner-Homa dot-distortion categorization task. Prototype theory--which presumes that participants refer to-be-categorized items to a representation near the category's center (the prototype)--predicts steep typicality gradients and large prototype-enhancement effects. Exemplar theory--which presumes that participants refer to-be-categorized items to memorized training exemplars--predicts flat typicality gradients and small prototype-enhancement effects. Across many categorization tasks that, for the first time, assayed monkeys' dot-distortion categorization, monkeys showed steep typicality gradients and large prototype-enhancement effects. These results suggest that monkeys--like humans--refer to-be-categorized items to a prototype-like representation near the category's center rather than to a set of memorized training exemplars. Keywords: categorization, prototypes, exemplars, comparative cognition, monkeys

Four experiments examined the effects of varying the conditioned stimulus--unconditioned stimulus (CS-US) interval (and US density) on learning in an appetitive magazine approach task with rats. Learning was assessed with conditioned response (CR) measures, as well as measures of sensory-specific stimulus--outcome associations (Pavlovian-instrumental transfer, potentiated feeding, and US devaluation). The results from these studies indicate that there exists an inverse relation between CS-US interval and magazine approach CRs. but that sensory-specific stimulus-outcome associations are established over a wide range of relatively long, but not short. CS-US intervals. These data suggest that simple CR measures provide different information about what is learned than measures of the specific stimulus--outcome association, and that time is a more critical variable for the former than latter component of learning. Keywords: CS-US interval, S-O associations, Pavlovian-instrumental transfer, motivational processes, timing processes

Three experiments showed that 2 associatively activated stimulus representations may engage in excitatory or inhibitory learning, depending on their temporal relationship. Experiment 1a suggested that simultaneously activated stimulus representations show evidence of inhibitory learning in an acquisition test. Experiment 1b showed similar evidence of inhibition in a summation test. Experiment 2 found that activation of 2 stimulus representations in a serial compound resulted in excitatory learning between the antecedent and the subsequent (forward) and inhibitory learning between the subsequent and the antecedent (backward). The results show the dynamic influence of temporal contiguity on mediated learning. Keywords: conditioning, mediated learning, rats

Six experiments used rats to study blocking and unblocking of fear learning. An excitatory stimulus (A) blocked tear learning to a neutral stimulus (B). Unblocking of B occurred if the AB compound signaled an increase in unconditioned stimulus (US) intensity or number. Assessments of associative change during blocking showed that more was learned about B than A. Such assessments during unblocking revealed that more was learned about B than A following an increase in US intensity but not US number. These US manipulations had no differential effects on single-cue learning. The results show that variations in US intensity or number produce unblocking of fear learning, but for each there is a different profile of associative change and a potentially different mechanism. Keywords: associative change, surprise, prediction error

Monkeys received discrimination training in which the choice of either a simultaneous or a serial compound of two visual images was rewarded before we assessed the monkeys' conditioned preference for one of the images from the compound. This preference was reduced or blocked if the other image had been associated with reward rather than nonreward prior to compound training. By contrast, the preference was enhanced if the other image was associated with reward rather than nonreward after compound training. The magnitudes of the blocking and enhancement were unaffected by the temporal structure, simultaneous or serial, of the stimulus compound. These results are discussed in terms of the representation of stimulus compounds, the role of within-compound associations, and the similarities between serial and simultaneous visual compounds as processed by monkeys.

Ordinal learning was investigated in capuchin monkeys (Cebus apella) and rhesus monkeys (Macaca mulatta). In Experiment 1, both species were presented with pairings of the Arabic numerals 0 to 9. Some monkeys were given food rewards equal to the value of the numeral selected and some were rewarded with a single pellet only for choosing the higher numeral within the pair. Both species learned to select the larger numeral, but only rhesus monkeys that were differentially rewarded performed above chance levels when presented with novel probe pairings. In Experiment 2, the monkeys were first presented with arrays of 5 familiar numerals (from the range 0 to 9) and then arrays of 5 novel letters (from the range A to J) with the same reward outcomes in place as in Experiment 1. Both species performed better with the numerals, suggesting that an ordinal sequence of all stimuli had been learned during Experiment 1, rather than a matrix of two-choice discriminations. Keywords: ordinality, capuchin monkeys, rhesus monkeys, cebus apella, macaca mulatta

Learning styles in capuchin monkeys were assessed with a computerized reversal-learning task called the mediational paradigm. First, monkeys were trained to respond with 90% accuracy on a two-choice discrimination (A+B-). Then the authors examined differences in performance on three different types of reversal trials (A-B+, A-C+, B+C-), each of which offered differing predictions for performance, depending on whether the monkeys were using associative cues or rule-based strategies. Performance indicated that the monkeys mainly learned to avoid the B stimulus during training, as the A-C+ condition produced the best performance levels. Therefore, negative stimuli showed greater control over responding after reversal and reflected a more associative rather than rule-based form of learning., Reports of cognitive abilities in a variety of animal species have surged in recent years (e.g., Wasserman & Zentall, 2006). Many of these reports emerged from studies with nonhuman primates, [...]

Concepts--rules that transcend training stimuli--have been argued to be unique to some species. Pigeons, a focus of much concept-learning research, were tested for learning a matching-to-sample abstract concept. Five pigeons were trained with three cartoon stimuli. Pigeons pecked a sample 10 times and then chose which of two simultaneously presented comparison stimuli matched the sample. After acquisition, abstract-concept learning was tested by presenting novel cartoons on 12 out of 96 trials for 4 consecutive sessions. A cycle of doubling the training set followed by retraining and novel-testing was repeated eight times, increasing the set size from 3 to 768 items. Transfer performance improved from chance (i.e., no abstract-concept learning) to a level equivalent to baseline performance (>80%) and was similar to an equivalent function for same/different abstract-concept learning. Analyses assessed the possibility that item-specific choice strategies accounted for acquisition and transfer performance. These analyses converged to rule out item-specific strategies at all but the smallest set-sizes (3-24 items). Ruling out these possibilities adds to the evidence that pigeons learned the relational abstract concept of matching-to-sample. Keywords: matching-to-sample, same/different, abstract-concept learning, generalized matching, pigeon

When two conditioned stimuli (CSs) are presented in compound, the response is typically stronger than to the individual CSs, implying that their associative strengths combine. However, to identify exactly how associative strengths combine requires an accurate description of the relationship between associative strength and responding. The authors have used the delta rule (Rescorla & Wagner, 1972) to constrain the predicted growth of associative strength (V) to identify the relationship between V and responding across the course of Pavlovian conditioning of two CSs (one auditory, one visual). Responding to the compound was best predicted as 0.6 x V(CSI) + 0.6 x V(C[S.sub.2]), suggesting that only 60% of the associative strength of each CS generalized to the compound. A second experiment confirmed this result and additionally showed that summation of responding between two same-modality CSs (both auditory or both visual) declined across training. A third experiment applied the procedure to compound conditioning, showing that responding to the compound was equal to the sum of the response rates to the individual CSs. The results are discussed in terms of configural and elemental models of Pavlovian conditioning. Keywords: Pavlovian conditioning, configural, elemental, associative learning, rat

Exposure to a solution composed of an odor (almond) and a taste (salt) produced a context-independent preference when rats were subsequently tested with almond under a salt appetite. Postcompound exposure to either the almond or the salt alone reduced almond preferences but only when rats were tested in the extinction context. Exposure to either the almond or the salt in 1 context in advance of exposure to the compound in a different context also reduced preferences but only when the rats were tested in the context in which the element had been pre-exposed. These results show that extinction and latent inhibition of within-event learning are context specific. Keywords: within-event learning, extinction, latent inhibition, context, within-compound

In two experiments, rats received minimal (16) pairings of one auditory conditioned stimulus (CS) cue with a sucrose reinforcer, and extensive (112) pairings of another auditory CS with that reinforcer. After sucrose was devalued by pairing it with lithium chloride in some rats (Devalue groups) but not others (Maintain groups), taste reactivity (TR) and other responses to unflavored water were assessed in the presence of the auditory CSs alone. The minimally trained CS controlled substantially more evaluative TR responses than the extensively trained CS. Those TR responses were hedonic (positive) in the Maintain groups, but aversive (negative) in the Devalue groups. By contrast, food cup entry and other responses thought not to reflect evaluative taste processing were controlled more by the extensively trained cue. These responses were reduced by sucrose devaluation comparably, regardless of the amount of training. The results suggest rapid changes in the content of learning as conditioning proceeds. Early in training, CSs may be capable of activating preevaluative processing of an absent food reinforcer that includes information about its palatability, but that capability is lost as training proceeds. Keywords: associatively activated event representations, contents of learning, devaluation, taste reactivity

Previous work from our laboratory has demonstrated that rats display a preference for directional responding over true place navigation in the Morris water task. The present study evaluated the range of situations in which this preference is observed and attempted to identify methods that favor navigation to the precise location of the escape platform in the room. A preference for directional responding over place navigation was observed in a wide range of procedures that included providing extensive training (Experiment l), providing only platform placement experience in the absence of active swim training (Experiment 2), training navigation to multiple platform locations in a moving platform variant of the task (Experiment 3), and explicitly training navigation to a precise location in the room, versus navigation in a particular direction, regardless of the pool's position in the room (Experiments 4-5). A modest preference for navigation to the precise spatial location of the platform was observed when the pool wall was virtually eliminated as a source of control by filling it to the top with water (Experiment 6). Keywords: spatial learning, place navigation, cognitive mapping, hippocampus, water maze

Two recent studies testing navigation of rats in swimming pools have posed problems for any account of the use of purely geometric properties of space in navigation (M. Graham, M. A. Good, A. McGregor, & J. M. Pearce, 2006; J. M. Pearce, M. A. Good, P. M. Jones, & A. McGregor, 2004). The authors simulated 1 experiment from each study in a virtual reality environment to test whether experimental results could be explained by view-based navigation. The authors recorded a reference image at the target location and then determined global panoramic image differences between this image and images taken at regularly spaced locations throughout the arena. A formal model, in which an agent attempts to minimize image differences between the reference image and current views, generated trajectories that could be compared with the search performance of rats. For both experiments, this model mimics many aspects of rat behavior. View-based navigation provides a sufficient and parsimonious explanation for a range of navigational behaviors of rats under these experimental conditions. Keywords: spatial learning, view-based navigation, computer simulation, rats, geometry Supplemental materials: http://dx.doi.org/10.1037/0097-7403.34.1.15.supp

Using an automated learning device, we investigated 'learning to learn' by dwarf goats (Capra hircus) in what was for them a familiar environment and normal social settings. Nine problems, each consisting of four discriminable black symbols, each with one [S.sup.+] and three different [S.sup.-], were presented on a computer screen. Mean daily learning success improved over the course of the first four problems, and the improvement was maintained throughout the remaining five problems. The number of trials to reach the learning criterion decreased significantly beginning with problem four. Such results may be interpreted as evidence that the goats were developing a learning set. In the present case, the learning set appeared to have two components. One involved gaining familiarity and apparent understanding of the learning device and the basic requirements of the discrimination task. The second component involved learning potential error factors to be ignored, as well as learning commonalities that carried over from one problem to the next. Among the error factors, evidence of apparent preferences for specific symbols was seen, which had a predictable effect on performances. Keywords: dwarf goats, automated learning device, visual discrimination, learning to learn, learning set

A single tortoise (Geochelone carbonaria) was trained in an eight-arm radial maze, with the apparatus and general procedures modeled on those used to demonstrate spatial learning in rats. The tortoise learned to perform reliably above chance, preferentially choosing baited arms, rather than returning to arms previously visited on a trial. Test sessions that examined control by olfactory cues revealed that they did not affect performance. No systematic, stereotyped response patterns were evident. In spite of differences in brain structure, the tortoise showed spatial learning abilities comparable to those observed in mammals. Keywords: tortoise, Geochelone carbonaria, spatial learning, radial maze

The generalization hypothesis of abstract-concept learning was tested with a meta-analysis of rhesus monkeys (Macaca mulatta), capuchin monkeys (Cebus apella), and pigeons (Columba livia) learning a same/different (S/D) task with expanding training sets. The generalization hypothesis states that as the number of training items increases, generalization from the training pairs will increase and could explain the subjects' accurate novel-stimulus transfer. By contrast, concept learning is learning the relationship between each pair of items; with more training items subjects learn more exemplars of the rule and transfer better. Having to learn the stimulus pairs (the generalization hypothesis) would require more training as the set size increases, whereas learning the concept might require less training because subjects would be learning an abstract rule. The results strongly support concept or rule learning despite severely relaxing the generalization-hypothesis parameters. Thus, generalization was not a factor in the transfer from these experiments, adding to the evidence that these subjects were learning the S/D abstract concept. Keywords: generalization, concepts, same/different, monkeys, pigeons

In serial reversal learning, subjects learn to respond differentially to 2 stimuli. When the task is fully acquired, reward contingencies are reversed, requiring the subject to relearn the altered associations. This alternation of acquisition and reversal can be repeated many times, and the ability of a species to adapt to this regimen has been considered as an indication of behavioral flexibility. Serial reversal learning of 2-choice discriminations was contrasted in 3 related species of North American corvids: pinyon jays (Gymnorhinus cyanocephalus), which are highly social; Clark's nutcrackers (Nucifraga columbiana), which are relatively solitary but specialized for spatial memory; and western scrub jays (Aphelocoma californica), which are ecological generalists. Pinyon jays displayed significantly lower error rates than did nutcrackers or scrub jays after reversal of reward contingencies for both spatial and color stimuli. The effect was most apparent in the 1st session following each reversal and did not reflect species differences in the rate of initial discrimination learning. All 3 species improved their performance over successive reversals and showed significant transfer between color and spatial tasks, suggesting a generalized learning strategy. The results are consistent with an evolutionary association between behavioral flexibility and social complexity. Keywords: behavioral flexibility, complexity, modularity, cognitive evolution, innovation