The effects of distributional learning on rats' sensitivity to phonetic information.

During the first year of life, infants show decreased sensitivity to phonetic differences not used in their native language and increased sensitivity to the differences that are used. It has been shown that this change in speech perception is a function of the distributional properties of the input. The present study explores whether the mechanism responsible for the developmental changes regarding the organization of phonetic categories is a general mechanism shared with other animals. The results demonstrate that the distributional exposure to a phonetic continuum affects the subsequent discrimination of these phonemes in rats, indicating that the ability to use distributional cues to change the phonetic category structure extends beyond humans. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Tufted capuchin monkeys (Cebus apella) spontaneously use visual but not acoustic information to find hidden food items.

Foraging choices in tufted capuchins monkeys are guided by perceptual, cognitive, and motivational factors, but little is known about how these factors might interact. The present study investigates how different types of sensory information affect capuchins' ability to locate hidden food. In two experiments, capuchins were presented with two cups, one baited and one empty. Monkeys were given visual, acoustic, or acoustic-visual information related to the baited cup, the empty cup, or both baited and empty cup. Results show that capuchins spontaneously used visual information to locate food, and that information indicating presence and absence of food led to higher success rates than information indicating only absence of food. In contrast, acoustic information did not lead to success rates above chance levels and failed to enhance performance in combination with visual information. Capuchins spontaneously avoided a visually empty cup, but they did not appear to associate sounds with either the presence or absence of food. Being able to locate food items with the aid of acoustic cues might be a learned process that requires interactive experiences with the task's contingencies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A failure to find socially mediated taste aversion learning in Norway rats (R. norvegicus).

Three studies with 240 Long-Evans rats investigated whether rats would avoid ingesting a diet as the result of interacting with an ill conspecific that had ingested that diet. Observer rats interacted with conspecific demonstrators immediately after demonstrators ate a novel diet and were made ill by LiCl injection. Following their interaction with demonstrators, observers were tested for aversion to their ill demonstrator's diet. Previous research has shown that (a) an observer can extract information from a demonstrator sufficient to permit identification of the demonstrator's diet and (b) a rat ill from LiCl toxicosis is an adequate UCS in a taste aversion learning paradigm. Two of the present experiments demonstrated that cues emitted by an S, reflecting the particular diet it has eaten, were an adequate CS in a toxicosis-induced aversion learning situation. Observer avoidance of a diet previously ingested by an ill demonstrator was, however, not demonstrated. Implications of the failure to find socially mediated aversion learning are discussed. (10 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modality-specific imagery reduces cravings for food: An application of the elaborated intrusion theory of desire to food craving.

Based on converging evidence that visual and olfactory images are key components of food cravings, the authors tested a central prediction of the elaborated intrusion theory of desire, that mutual competition between modality-specific tasks and desire-related imagery can suppress such cravings. In each of Experiments 1 and 2, 90 undergraduate women underwent an imaginal food craving induction protocol and then completed either a visual, auditory, or olfactory imagery task. As predicted, the visual and olfactory imagery tasks were superior to the auditory imagery task in reducing participants' craving for food in general (Experiment 1) and for chocolate in particular (Experiment 2). Experiment 3 replicated these findings in a sample of 96 women using a nonimagery craving induction procedure involving a combination of chocolate deprivation and exposure to chocolate cues. Thus, imagery techniques in the visual or olfactory domain hold promise for treating problematic cravings in disordered eating populations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Domestic dogs (Canis familiaris) use human gestures but not nonhuman tokens to find hidden food.

The authors examined the ability of domestic dogs to use human body cues (gestures) and equivalent-sized nonhuman cues to find hidden food in an object choice paradigm. In Experiment 1 the authors addressed the importance of the human element of the cue, and the effects of size, topography, and familiarity on dogs' success in using cues. Experiment 2 further explored the role of the human as cue-giver, and the impact of a change in the experimenter's attentional state during cue presentation. This included a systematic test of the role inanimate tokens play as cues apart from human placement. Our results indicate that dogs are more sensitive to human cues than equivalent nonhuman cues, and that the size of the cue is a critical element in determining dogs' success in following it. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Failure to find self-recognition in Asian elephants (Elephas maximus) in contrast to their use of mirror cues to discover hidden food.

Only humans, chimpanzees, and orangutans have demonstrated that they recognize their reflections in mirrors. Other mammals (including over a dozen species of monkeys) have failed to show signs of self-recognition. Recent investigations have attempted to discover if the absence of self-recognition is related to a general inability to process mirrored information. This article describes the failure to find self-recognition in two adult Asian elephants (Elephas maximus) along with their spontaneous use of mirrored information to locate otherwise hidden food. Ss responded appropriately on Trial 1 to novel placements of food items, but continued to respond to their images as if confronted by another elephant. Results are discussed in the context of the relationship (or lack thereof) between different types of mirror-mediated behavior and self-recognition. It is concluded that possession of mirror-mediated abilities is not a sufficient condition for the development of self-recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Category learning and change: Differences in sensitivity to information that enhances or reduces intercategory distinctions.

We examined the amenability of abstractions of categories to new and relevant information. In Experiment 1, Ss formed impressions of 2 sets of numbers by periodically estimating the cumulative means of each set. During the 1st half of the procedure, the 2 means were mathematically stable. During the 2nd half of the procedure, the mean of 1 set was modified and the mean of the other set remained unchanged. We predicted and found that the resultant estimates for the modified category changed more when the mean difference between the 2 categories was enhanced than when it was reduced. Experiment 2 suggested that the accentuation effect results from a 2-stage process of category learning (Stage 1) and category change (Stage 2). Experiment 3 replicated the effect with person categories. The relevance of category accentuation is discussed with respect to the modifiability of social beliefs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)