Acoustic Mechanisms of Note-Type Perception in Black-Capped Chickadee (Poecile atricapillus) Calls.

Acoustic communication in black-capped chickadees (Poecile atricapillus) has been studied intensively, the "chick-a-dee" call being among the most well described. This call consists of 4 note types; chickadees perceive these notes as open-ended categories and do so in a continuous manner, with As more similar to Bs and Bs more similar to Cs. Acoustic features contributing to the note-type differentiation are unknown. Recent analyses suggested that certain acoustic features may play a role in note-type classification. Here, the authors tested black-capped chickadees in an operant-conditioning paradigm to determine which features were controlling note-type perception. The results suggest that the note pitch and the frequency modulation in the initial portion of the note control the perception of note types. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Open-ended categorization of chick-a-dee calls by black-capped chickadees (Poecile atricapilla).

The authors trained black-capped chickadees (Poecile atricapilla) in an operant discrimination with exemplars of black-capped and Carolina chick-a-dee calls, with the goal of determining whether the birds memorized the calls of conspecifics and heterospecifics or classified the calls by species. Black-capped calls served as both rewarded (S+) and unrewarded (S-) stimuli (the within-category discrimination), whereas Carolina chick-a-dee calls served as S-s (the between-category discrimination) in the black-capped chick-a-dee call S+ group. The Carolina call S+ group had Carolina calls as S+s and S-s (within-category) and black-capped calls as S-s (between-category). Both groups discriminated between call categories faster than within a call category. In 2 subsequent experiments, both S+ groups showed transfer to novel calls and propagation back to between-category calls. The results favor the hypothesis that the acoustically similar social calls of the 2 species constitute separate open-ended categories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanisms of call note-type perception in black-capped chickadees (Poecile atricapillus): Peak shift in a note-type continuum.

We report on operant conditioning and artificial neural network (ANN) simulations aimed at further elucidating mechanisms of black-capped chickadee chick-a-dee call note category perception. Specifically, we tested for differences in the speed of acquisition among different discrimination tasks and, in two selected discrimination groups, searched for evidence of peak shift. Earlier, unreported ANN data were instrumental in providing the motivation for the current set of studies with chickadees and are provided here. The ANNs revealed differences in the speed of learning among note-type discrimination groups that is related to the degree of perceptual similarity among the three note types tested (i.e., A, B, and C notes). In many respects, bird and network results were in agreement (i.e., in the observation of peak shift in the same group), but they also differed in important ways (i.e., all discrimination groups showed differences in speed of learning in simulations but not in chickadees). We suggest that the start, peak and end frequency of the chick-a portion of chick-a-dee call notes, which form a graded but overlapping continuum, may drive the peak shift observed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual differentiation during categorization learning by pigeons.

In Experiment 1, pigeons were trained to categorize two sets of variable stimuli (black and white checkerboard patterns), constructed by random distortions of two prototype patterns. They were subsequently trained on new discriminations, between two new exemplars of their positive category, two new exemplars of their negative category, or two control checkerboard patterns. The new exemplars of their familiar categories were easier to discriminate than the wholly novel stimuli, although this difference was significant only for exemplars of their previously negative category. In Experiment 2, pigeons were initially trained on a discrimination between two prototype checkerboards; they subsequently learned to discriminate between two distortions of their negative prototype more rapidly than between two control patterns. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Statistical classification of black-capped (Poecile atricapillus) and mountain chickadee (Poecile gambeli) call notes.

Both black-capped (Poecile atricapillus) and mountain chickadees (Poecile gambeli) produce a chick-a-dee call that consists of several distinct note types. In some regions, these 2 species live sympatrically, and it has been shown that 1 species will respond weakly to songs of the other. This suggests that chickadee song, and potentially other of their vocalizations, contains species-specific information. We tested the possibility that call notes were acoustically sufficient for species identification. Black-capped and mountain non-D notes were summarized as a set of 9 features and then analyzed by linear discriminant analysis. Linear discriminant analysis was able to use these notes to identify species with 100% accuracy. We repeated this approach, but with black-capped and mountain D notes that were summarized as a set of 4 features. Linear discriminant analysis was able to use these notes to identify species with 94% accuracy. This demonstrates that any of the note types in these chickadee calls possesses sufficient information for species classification. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Representation of the numerosities 1–9 by rhesus macaques (Macaca mulatta).

Three rhesus monkeys (Macaca mulatta) were trained to respond to exemplars of 1, 2, 3, and 4 in an ascending, descending, or a nonmonotonic numerical order (1←2←3←4, 4←3←2←1, 3←1←4←2). The monkeys were then tested on their ability to order pairs of the novel numerosities 5–9. In Experiment 1, all 3 monkeys ordered novel exemplars of the numerosities 1–4 in ascending or descending order. The attempt to train a nonmonotonic order (3←1←4←2) failed. In Experiment 2A, the 2 monkeys who learned the ascending numerical rule ordered pairs of the novel numerosities 5–9 on unreinforced trials. The monkey who learned the descending numerical rule failed to extrapolate the descending rule to new numerosities. In Experiment 2B all 3 monkeys ordered novel exemplars of pairs of the numerosities 5–9. Accuracy and latency of responding revealed distance and magnitude effects analogous to previous findings with human participants (R. S. Moyer & T. K. Landaeur, 1967). Collectively these studies show that monkeys represent the numerosities 1-9 on at least an ordinal scale. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative processes in differential outcome discriminations.

This study assessed the role of stimulus–outcome (S–O) and response–outcome (R–O) associations in differential outcome performances. In Experiment 1, pigeons learned one-to-many matching-to-sample with differential R–O associations but with either differential or nondifferential sample-outcome (S–O) associations. Later, both groups showed strong transfer of matching to novel samples that were differentially associated with the same outcomes used in training. Experiment 2 reversed the training conditions for each group. The switch from differential to nondifferential S–O associations produced a large drop in matching accuracy, whereas the opposite switch had only a small effect. Following recovery, both groups again showed positive transfer to novel samples, although transfer was stronger following differential S–O training. These data support a 2-process ("outcome expectancy") account of differential outcome performances but also indicate a contribution of bidirectional R–O associations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

By land or by sea: The role of perceptual similarity in infants' categorization of animals.

In 3 experiments, the authors used an object-examining task to investigate the role of perceptual similarity in infants' categorization. In Experiment 1, infants were familiarized with a set of either perceptually similar or perceptually variable exemplars from 1 category and tested with novel exemplars from both categories. Ten-month-olds did not respond to the category in either condition, and 13-month-olds responded categorically in both conditions but somewhat differently in the 2 conditions. Experiment 2 showed that when 10-month-olds were familiarized with similar exemplars but not with variable exemplars, they responded to the categorical distinction when given tests with typical exemplars. Experiment 3 established that 10-month-olds could differentiate among the exemplars. These results suggest that the perceptual similarity of the exemplars influences infants' recognition of categorical distinctions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multiple levels of representation of song by European starlings (Sturnus vulgaris): Open-ended categorization of starling sing types and differential forgetting of song categories and exemplars.

Four European starlings (Sturnus vulgari) were trained to discriminate among conspecific and heterospecific song segments in a go/no-go operant task. In Experiment 1, the starlings discriminated among novel starling and heterospecific songs, indicating an open-ended category of conspecific song types. The starlings also showed excellent memory for reinforced conspecific songs and discriminated among subordinate categories of conspecific song. In Experiment 2, the starlings were presented with the song segments from Experiment 1 after an 8-month delay period. The starlings retained the discrimination between conspecific and heterospecific songs but not among conspecific songs. The starlings also retained memory for individual singers over the 8-month delay. Starlings categorize song at the level of species, and at subordinate categories of song types, and may have superior long-term retention of song categories relative to song exemplars. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Categorization of speech by infants: Support for speech-sound prototypes.

This study tested 6-month-old infants' categorization of speech stimuli to investigate whether infants organize speech categories around "prototypes." In Experiment 1, infants first discriminated single "good" exemplars from two different vowel categories. They were then tested with 64 novel exemplars, 32 from each vowel category. The test stimuli varied in the degree to which they conformed to adult-defined prototypes of the two categories. The results showed that infants correctly sorted the novel stimuli over 90% of the time. In Experiment 2, we trained two groups of infants, one with a good (prototypical) exemplar from a vowel category and the other with a poor (nonprototypical) exemplar. Then we tested both groups with 16 novel exemplars from that same vowel category. Generalization to novel members of the category was significantly greater following exposure to the prototypical exemplar. Results are consistent with a model of speech perception that holds that young human infants organize vowel categories around prototypes. This may contribute to their seemingly efficient processing of speech information, even in the first half year of life. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is a rose always a rose? The role of social category exemplar change in attitude stability and attitude-behavior consistency.

Three experiments tested whether changes in social category exemplars affect attitude stability, attitude–behavior consistency, or attitude change. In Experiment 1, participants displayed greater attitude stability across 1 month, in several social categories, when they named the same rather than different exemplars. In Experiment 2, participants displayed greater attitude–behavior consistency toward each of 2 social categories when they named the same rather than different exemplars at behavior assessment and at attitude assessment. Participants who named a more likable exemplar behaved more positively, and those who named a less likable exemplar behaved more negatively, than their initial attitudes predicted. In Experiment 3, participants changed their attitudes in the predicted direction after estimating the height of an exemplar who was either more or less likable than the one they had earlier named. The results are interpreted as consistent with recent theory and research on attitude introspection, the matching hypothesis, and models of social judgment. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Remembering Can Cause Inhibition: Retrieval-Induced Inhibition as Cue Independent Process.

Previous experiments have mostly relied on recall as a dependent measure to assess whether retrieval of information from memory causes inhibition of related information. This study aimed to measure this inhibition in a more direct way. In Experiment 1, it was shown that repeated retrieval of exemplars from a category resulted in longer recognition latencies to nonretrieved exemplars from that same category, compared with recognition latencies to control exemplars. Experiment 2 obtained the same pattern of results using a lexical decision task. This was the 1st time that retrieval-induced forgetting was demonstrated on an implicit test of memory. To exclude noninhibitory explanations of the data, the exemplars were presented in both experiments without their categories as cues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discrimination of artificial categories structured by family resemblances: A comparative study in people (Homo sapiens) and pigeons (Columba livia).

Adult humans (Homo sapiens) and pigeons (Columba livia) were trained to discriminate artificial categories that the authors created by mimicking 2 properties of natural categories. One was a family resemblance relationship: The highly variable exemplars, including those that did not have features in common, were structured by a similarity network with the features correlating to one another in each category. The other was a polymorphous rule: No single feature was essential for distinguishing the categories, and all the features overlapped between the categories. Pigeons learned the categories with ease and then showed a prototype effect in accord with the degrees of family resemblance for novel stimuli. Some evidence was also observed for interactive effects of learning of individual exemplars and feature frequencies. Humans had difficulty in learning the categories. The participants who learned the categories generally responded to novel stimuli in an all-or-none fashion on the basis of their acquired classification decision rules. The processes that underlie the classification performances of the 2 species are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Song-note discriminations in zebra finches (Taeniopygia guttata): Categories and pseudocategories.

Sturdy, Phillmore, and Weisman (1999) developed a simple, reliable procedure for classifying zebra finch (Taeniopygia guttata) song notes into types using exemplar notes from 4 captive North American laboratory colonies. In the present experiment, zebra finches learned true-category song-note discriminations based on Sturdy et al.'s note-type classification faster than pseudocategory discriminations based on random assortments of the same notes. Also, birds in the true-category discrimination were able to sort notes not heard during training into the same categories as the training notes. This evidence suggests that zebra finches accurately sort conspecific song notes into the same open-ended categories as Sturdy et al.'s human observers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Picture fragment completion: Priming in the pigeon.

It has been suggested that the system behind implicit memory in humans is evolutionarily old and that animals should readily show priming. In Experiment 1, a picture fragment completion test was used to test priming in pigeons. After pecking a warning stimulus, pigeons were shown 2 partially obscured pictures from different categories and were always reinforced for choosing a picture from one of the categories. On control trials, the warning stimulus was a picture of some object (not from the S+ or S– category), on study trials the warning stimulus was a picture to be categorized on the next trial, and on test trials the warning stimulus was a randomly chosen picture and the S+ picture was the warning stimulus seen on the previous trial. Categorization was better on study and test trials than on control trials. Experiment 2 ruled out the possibility that the priming effect was caused by the pigeons' responding to familiarity by using warning stimuli from both S+ and S– categories. Experiment 3 investigated the time course of the priming effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Superordinate categorization via learned stimulus equivalence: Quantity of reinforcement, hedonic value, and the nature of the mediator.

Three experiments examined superordinate categorization via stimulus equivalence training in pigeons. Experiment 1 established superordinate categories by association with a common number of food pellet reinforcers, plus it established generalization to novel photographic stimuli. Experiment 2 documented generalization of choice responding from stimuli signaling different numbers of food pellets to stimuli signaling different delays to food reinforcement. Experiment 3 indicated that different numbers of food pellets did not substitute as discriminative stimuli for the photographic stimuli with which the food pellets had been paired. The collective results suggest that the effective mediator of superordinate categories that are established via learned stimulus equivalence is not likely to be an accurate representation of the reinforcer, neither is it likely to be a distinctive response that is made to the discriminative stimulus. Motivational or emotional mediation is a more likely account. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social values and social conflict in creative problem solving and categorization.

Participants were led to expect either cooperation or conflict, and then performed K. Duncker's (1945) functional-fixedness task (Experiment 1) or E. Rosch's (1975) categorization task (Experiment 2). Those who expected cooperation, compared with those who expected conflict, were more likely to solve Duncker's task and used categories more inclusively, that is, rated low-prototypic exemplars of a category as better members of the category. In Experiment 3, the direct experience of cooperation and conflict had the same effect on categorization. In Experiment 4, participants were classified as having cooperative, competitive, or individualistic social values, and were led to expect either cooperation, conflict, or neither in a control. In the control, cooperators used categories more inclusively than competitors or individualists. Competitors used categories least inclusively in the conflict condition; in the cooperation condition, they used categories most inclusively. These results are interpreted in terms of the possible mediating role of cognitive organization in individual and intergroup conflict resolution. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of comparison in the extension of novel adjectives.

Previous research has documented that basic-level object categories provide an initial foundation for mapping adjectives to object properties. Children ranging from 21 months to 3 years can successfully extend a novel adjective (e.g., transparent) to other objects sharing a salient property if the objects are all members of the same basic-level category; if the objects are members of different basic-level categories, they fail to extend adjectives systematically (R. S. Klibanoff & S. R. Waxman, 2000a; S. R. Waxman & D. B. Markow, 1998). The present study proposed that the process of comparison is instrumental in children's ability to move beyond this foundation. To promote comparison, 2 target objects were introduced to 3-year-olds. In Experiment 1, the targets had contrastive properties (e.g., 1 transparent and 1 opaque object); in Experiment 2, the targets had consistent properties (e.g., 2 transparent objects). The results of both experiments illustrate that comparison—a general psychological process—operates in conjunction with naming to support the extension of novel adjectives to properties of objects from diverse basic-level categories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of exclusivity in perceptually based categories of young infants

The exclusivity of perceptually defined categorical representations for natural animal categories in young infants was investigated. Previously, as well as in Experiment 1, evidence was obtained for a categorical representation for cats in 3- and 4-month-old infants that excluded dogs but included perceptually similar female lions after a number of different familiarization procedures. However, in Experiment 2 both dogs and female lions were found to be excluded when the initial familiarization with cats alone was followed by six pairings of familiar cats and novel lions intermingled with two added pairings of familiar cats. The present results indicate that a categorical representation can attain a high level of exclusivity during early infancy as a consequence of experience with exemplars of the contrasting categories that accents the perceptual similarities among members of a category and the perceptual differences among exemplars from different categories.     

Retrieval from semantic memory and its implications for Alzheimer's disease.

In 3 experiments, participants generated category exemplars (e.g., kinds of fruits) while a voice key and computer recorded each response latency relative to the onset of responding. In Experiment 1, mean response latency was faster when participants generated exemplars from smaller categories, suggesting that smaller mental search sets result in faster mean latencies. In Experiment 2, a concurrent secondary task increased mean response latency, suggesting that slowed mental processing results in slower mean latencies. In Experiment 3, the mean response latency of Alzheimer's participants was faster than that of elderly controls, which is consistent with the idea that the semantic memory impairments of Alzheimer's disease patients stem primarily from a reduction in available items (as in Experiment 1) rather than retrieval slowing (as in Experiment 2). (PsycINFO Database Record (c) 2010 APA, all rights reserved)