Novelty and functional equivalence in superordinate categorization by pigeons

Superordinate categorization via association with a common response was studied in pigeons. Original training paired disparate classes (e.g., people + chairs and cars + flowers) with a common response (Responses 1 and 2, respectively). Reassignment training taught new responses (Responses 3 and 4, respectively) to one component class from each pair (e.g., people and cars). Superordinate categorization was documented in testing when the pigeons made the same responses to the stimuli that were withheld in reassignment training (e.g., chairs and flowers) as they did to the reassigned stimuli themselves (e.g., people and cars) and when the birds transferred these discriminative responses to novel stimuli from all four component classes. Reassignment training with novel stimuli produced effects that were similar to those of reassignment training with familiar stimuli. Superordinate categorization via association with a common response is thus a robust effect that generalizes to novel stimuli from each of the component classes.     

Relational learning in pigeons: The role of perceptual processes in between-key recognition of complex stimuli

In Experiment 1, we used six procedures in a series of unsuccessful attempts to obtain relational learning using trial-unique pictorial stimuli in pigeons. The Experiment began by testing conventional (three-key) matching-to-sample (MTS) and nonmatching-to-sample (NMTS); in subsequent stages of the experiment we progressively incorporated features of techniques that do obtain relational learning in a single-key apparatus. In Experiment 2, we found that acquisition of NMTS using pictorial stimuli proceeded no more rapidly than acquisition of a conditional discrimination. Experiment 3 showed that acquisition of NMTS was more rapid than acquisition of MTS when plain colored stimuli were used, but not when pictorial stimuli were used. These three experiments suggest that pigeons do not recognize pictorial stimuli shown on different keys. In Experiment 4, between-key recognition was obtained with familiar but not with novel pictorial stimuli. It is argued that perceptual learning facilitates the detection of the between-key identity of complex stimuli, and that perceptual processes may underlie the difficulty in demonstrating relational learning in pigeons.     

Lexical categorization modalities in pre-school children: Influence of perceptual and verbal tasks

This study investigates how categorical organization functions in pre-school children, focusing on the dichotomy between living and nonliving things. The variables of familiarity, frequency of word use and perceptual complexity were controlled. Sixty children aged between 4 years and 5 years 10 months were investigated. Three tasks were used: a naming task; a concepts deconstruction task; and a concepts construction task. Results indicated that age influences: (a) the picture naming and concepts deconstruction task, with older children performing better, and (b) the prevalence of functional features for the inanimate stimuli. These data show that it would be risky to argue that there is a pre-eminence of one concept component without considering the task involved, which is of particular importance in the educational domain.     

Testing the translational-symmetry hypothesis of abstract-concept learning in pigeons

The translational-symmetry hypothesis of abstract-concept learning was tested in a same/different (S/D) task with pairs of pictures. The translational-symmetry hypothesis proposes that subjects discriminate same trials by the simultaneous repetition of features in the two pictures (and different trials by the lack of feature repetition). Pigeons that had learned a simultaneous S/D task were tested with delays between the two pictures to remove emergent perceptual cues. In Experiment 1, we tested delays of 0 and 1 sec. The results did not show the accuracy decrease expected according to the translational-symmetry hypothesis. In Experiment 2, we expanded the delays to 2 and 6 sec. Even at the longest delay, there was no evidence of the precipitous performance decline or default strategy that would be predicted by translational symmetry. The results provide evidence against translational symmetry (or other perceptually emergent features) that might control these pigeons’ performance in our two-item S/D task.     

The learning of basic-level categories by pigeons: the prototype effect, attention, and effects of categorization

Pigeons were trained to classify composite faces of two categories created by mimicking the structure of basic-level categories, with each face consisting of an item-specific component and a common component diagnostic for its category. Classification accuracy increased as the proportion of common components increased, regardless of familiar and novel item-specific components, with the best discrimination occurring at untrained original faces used as the common components. A no-categorization control condition suggested that categorization gives rise to equivalence for item-specific components and distinctiveness for degrees of prototypicality. When some item-specific components were shared by exemplars of the contrasting categories, those that were not overlapping between the categories became the effective cues for the pigeons’ responses. Implications of these results are discussed in the context of current categorization and associative learning theories.     

Behavioral contrast in pigeons and rats: A comparative analysis

The effects of reinforcement rate on behavioral contrast were examined in pigeons and rats. Each species was exposed to a series of 12 multiple variable-interval schedules, divided into four 3-schedule series. Each series consisted of a standard contrast manipulation, and baseline schedules provided a different rate of reinforcement in each of the series. The functions relating reinforcement rate to the magnitude of contrast were different across species. Rats showed a U-shaped function, with reliable contrast occurring only at high reinforcement rates. Pigeons showed an inverted U-shaped function, with contrast occurring on all schedules except the schedule providing the lowest rate of reinforcement. Pigeons discriminated between schedule components better than rats did, although differences in discrimination were probably not responsible for the differences in contrast. The results suggest that behavioral contrast in rats may be a different phenomenon from behavioral contrast in pigeons. The results cannot be explained by current theories, which view contrast as the product of a single general process.     

The nature of discrimination learning in pigeons

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 rulefor determining the shape ofthe 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.     

The future of infant categorization research: a process-oriented approach

We call for a shift from a content-oriented approach to a process-oriented approach to the study of categorization in infancy. Although gains have been made in our understanding of infant categorization by evaluating the categories to which infants respond, further understanding of infant categorization, and how categorization changes with development, requires that we more directly assess infants' category formation. We argue that two directions for future research will continue to enhance our understanding of categorization in infancy (and beyond). First, contextual variations (e.g., the effects of task, stimuli, and other factors) on infants' categorization must be better understood. Second, we must more directly evaluate the kinds of information infants use when forming categories, as well as how their use of such information changes with age, task, and so forth. We argue that these two foci will provide clearer understanding of the origins and early development of categorization.     

The determination of direction in landmark-based spatial search in pigeons: A further test of the vector sum model

In four experiments, pigeons were trained to find hidden food at a constant location with respect to one or two arrays of landmarks. On crucial tests, the birds were presented with conflicting cues associated with two different directions, which were 90° apart from the center of the search space at the same radial distance. The direction-averaging model predicts that the radial distance of search should not change on these tests, compared with radial distance of search on control tests without conflicting cues. The vector-averaging (vector sum) model predicts that when pigeons average the two conflicting cues, the radial distance of search should be shorter. Results support the direction-averaging model and suggest that distance and direction are independently computed in landmark-based search. Multiple sources are averaged by pigeons in determining direction.     

Discrimination of geons by pigeons: The effects of variations in surface depiction

We explored how changes in the depiction of the surface features of a simple volume (a geon) affected the pigeon’s recognition performance. Pigeons were trained to make a different keypeck response to each of four computer-rendered single-geon objects. In Experiment 1, the pigeons were tested with images of the original stimuli in which the light source was shifted from its original position, as well as with silhouettes and line drawings of these objects. All three types of stimulus variations resulted in marked drops in performance: above chance for silhouettes and light-change stimuli, but at chance for line drawings. In Experiment 2, the pigeons were tested with images of the original stimuli in which the contrast levels were either increased or decreased. These transformations resulted in very small drops in performance (except for the complete absence of contrast-a silhouette). These results indicated that the pigeons attended to the shape of the outside contour of an object and to the relative brightness of an object’s surface contours.     

The acquisition of trace supraordinate stimulus control in pigeons

Match-to-sample and oddity-from-sample problems with four colors were acquired by two pigeons under the supraordinate control of a line tilt superimposed on samples, Since the supraordinate stimulus terminated before the comparison stimuli were presented, accurate matching and oddity performance indicated trace stimulus control as well, The temporal extent of trace control was assessed in one subject by presenting probes—trials without a line tilt on the sample—in which the basis of correct responding was the supraordinate stimulus presented on the previous trial, Trace supraordinate control did not extend between trials, Subsequently, the delay between the termination of the supraordinate stimulus and the presentation of the comparison stimuli was gradually increased within a trial, Both subjects were able to perform matching and oddity over longer delays, and eventually on probe trials, although accuracy decreased, Results were discussed in terms of instructional stimulus control and memory.     

The recency effect in pigeons’ long-term memory

Four experiments are reported in which pigeons first learned one wavelength discrimination (green S+, yellow S?) and then the reversal; finally, after various delays, they were tested for wavelength generalization in extinction. In Experiment 1, the two problems were learned in different contexts; testing in Context 1 produced maximal responding to green in only half of the subjects, even when testing was delayed 30 days. In Experiment 2, testing of the subjects repeatedly in both contexts showed good control by each context after a 30-day delay. In Experiment 3, both problems were learned in the same context, and all gradients showed recency, peaking at yellow, even after 30 days. In Experiment 4, the subjects learned a series of reversals in the same context, terminating in yellow, S+, green, S?, and their gradients peaked at yellow, even after a 30-day delay. In Experiments 3 and 4, the gradients became flatter with increasing delays, and they were flatter in Experiment 4 (after three reversals) than in Experiment 3 (after one reversal). The location of the peak was not affected by delay, but only by testing in a context that had been uniquely associated with Problem 1 (Experiments 1 and 2). It is proposed that the location of gradient peaks indicates what is being remembered, whereas the slope of the obtained gradients indicates how well the target memory has been retrieved.     

The role of inhibitory associations in perceptual learning

Preexposure to two compound flavors (AX and BX) typically enhances their discriminability: An aversion conditioned to AX will generalize less to BX, especially if the preexposure regime has involved alternated presentations of AX and BX rather than presenting all AX trials before BX trials (or vice versa). One possible explanation of this finding is that alternating preexposure establishes inhibitory associations between the two unique features A and B, thus counteracting the generalization produced by excitatory associations between X and A and between X and B, which might result in either the retrieval of B on a conditioning trial to AX, or the retrieval of A on a test trial to BX. Three experiments on flavor aversion conditioning in rats tested these predictions. Experiment 1 suggested that the more important of these excitatory associations was that which allowed X to retrieve A on the test trial to BX. Experiment 2 suggested that the more important inhibitory association was that which allowed B to inhibit the representation of A on this test trial. Experiment 3 provided direct evidence of the role of this inhibitory B⊣A association.     

Directed forgetting in pigeons: Analysis of cue functions

In delayed matching-to-sample with pigeons, brief postsample cues signaled different trial outcomes. The normal comparison stimuli followed the cue to remember (R cue). In the comparison-omission procedure, comparison stimuli and reinforcement were omitted following the cue to forget (F cue). In the comparison-substitution procedure, comparison stimuli were replaced by a single stimulus and reinforcement for a single response following the F cue. Infrequent probe trials revealed that F cues disrupted matching, with the amount of accuracy loss dependent on the length of the cue-comparison delay. These results, however, were found only with the comparison-omission procedure (Experiment 1). Replacing the comparison stimuli with another simultaneous (unconditional) discrimination revealed no accuracy loss in F-cue probes (Experiment 2), even though choice latencies were again lengthened by F cues. These results suggest that, while the F cue interferes with performance at the time of a retention test by slowing choices, it also interferes with sample retention. Alternative models of the cuing effect and its apparent dependence on end-of-trial reward are outlined.     

人类起源新学说——海豚说

自从有了人,人们就不断的探索人类的起源,不断地争论人类产生的源头。随着科学技术的发展和人们认识能力的不断提高,科学家对人类的起源又有了新的学说。     

范畴化理论的演进

范畴化是语言学界,乃至哲学界和心理学界一直关注和研究的问题。范畴化理论的不断更新也对语言研究的范式产生了诸多影响。国外的范畴化理论较多,而国内相关研究较少;让更多语言研究者了解各种范畴化理论,并为汉语研究服务,这是本文翻译的初衷。总的说来,范畴化研究经历了传统观点、传统观点批判、梯度结构批判和范畴理论等4个阶段。随着认知科学和语言学的发展,以事件为基础的新范畴化阶段已经出现。文章逐一介绍了不同的范畴化理论的核心观点、存在的问题以及对其批判,并对后续研究进行了展望。