Use of number by crows: investigation by matching and oddity learning

Hooded crows were trained in two-alternative simultaneous matching and oddity tasks with stimulus sets of three different categories: color (black and white), shape (Arabic Numerals 1 and 2, which were used as visual shapes only), and number of elements (arrays of one and two items). These three sets were used for training successively and repeatedly; the stimulus set was changed to the next one after the criterion (80% correct or better over 30 consecutive trials) was reached with the previous one. Training was continued until the criterion could be reached within the first 30 to 50 trials for each of the three training sets. During partial transfer tests, familiar stimuli (numerals and arrays in the range from 1 to 2) were paired with novel ones (numerals and arrays in the range from 3 to 4). At the final stage of testing only novel stimuli were presented (numerals and arrays in the range from 5 to 8). Four of 6 birds were able to transfer in these tests, and their performance was significantly above chance. Moreover, performance of the birds on the array stimuli did not differ from their performance on the color or shape stimuli. They were capable of recognizing the number of elements in arrays and comparing the stimuli by this attribute. It was concluded that crows were able to apply the matching (or oddity) concept to stimuli of numerical category.     

Ordinal judgments of symbolic stimuli by capuchin monkeys (Cebus apella) and rhesus monkeys (Macaca mulatta): the effects of differential and nondifferential reward

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.     

Sequential responding and planning in capuchin monkeys (Cebus apella)

Previous experiments have assessed planning during sequential responding to computer generated stimuli by Old World nonhuman primates including chimpanzees and rhesus macaques. However, no such assessment has been made with a New World primate species. Capuchin monkeys (Cebus apella) are an interesting test case for assessing the distribution of cognitive processes in the Order Primates because they sometimes show proficiency in tasks also mastered by apes and Old World monkeys, but in other cases fail to match the proficiency of those other species. In two experiments, eight capuchin monkeys selected five arbitrary stimuli in distinct locations on a computer monitor in a learned sequence. In Experiment 1, shift trials occurred in which the second and third stimuli were transposed when the first stimulus was selected by the animal. In Experiment 2, mask trials occurred in which all remaining stimuli were masked after the monkey selected the first stimulus. Monkeys made more mistakes on trials in which the locations of the second and third stimuli were interchanged than on trials in which locations were not interchanged, suggesting they had already planned to select a location that no longer contained the correct stimulus. When mask trials occurred, monkeys performed at levels significantly better than chance, but their performance exceeded chance levels only for the first and the second selections on a trial. These data indicate that capuchin monkeys performed very similarly to chimpanzees and rhesus monkeys and appeared to plan their selection sequences during the computerized task, but only to a limited degree.     

Controlling relations in conditional discrimination and matching by exclusion.

Normally capable adults learned two-choice identity matching of three-digit numerals and arbitrary matching of physically dissimilar nonsense syllables. The stimuli were displayed on a computer terminal, and responses consisted of typing on the terminal's keyboard. In Experiment 1, every trial displayed a sample numeral, a comparison numeral, and three equal signs (= = =). The comparison stimulus was to be selected if it was identical with the sample; otherwise the equal sign was to be selected. This "single comparison" method was then used to show that arbitrary matching could be based upon either sample-S+ or sample-S- relations. In Experiment 2, a series of probe trials displayed a novel sample, a comparison stimulus from the arbitrary matching baseline, and = = =. Subjects typically selected = = =; they apparently were excluding the baseline comparison stimulus. Experiments 3 through 5 investigated which variables in training would lead to the selection of baseline comparison stimuli in response to novel samples. Behavior was usually unchanged when baseline training included relating comparison stimuli to as many as four different samples. Punishment contingencies were effective, but performance did not generalize unless those contingencies were applied in relation to more than one baseline comparison stimulus.     

Ordinal judgments of numerical symbols by macaques (Macaca mulatta)

Two rhesus monkeys (Macaca mulatta) learned that the arabic numerals 0 through 9 represented corresponding quantities of food pellets. By manipulating a joystick, the monkeys were able to make a selection of paired numerals presented on a computer screen. Although the monkeys received a corresponding number of pellets even if the lesser of the two numerals was selected, they learned generally to choose the numeral of greatest value even when pellet delivery was made arrhythmic. In subsequent tests, they chose the numerals of greater value when presented in novel combinations or in random arrays of up to five numerals. Thus, the monkeys made ordinal judgments of numerical symbols in accordance with their absolute or relative values.     

Size matters: impact of item size and quantity on array choice by chimpanzees (Pan troglodytes)

The authors previously reported that chimpanzees (Pan troglodytes) showed a striking bias to select the larger of 2 candy arrays, despite a reversed reward contingency in which the animals received the smaller, nonselected array as a reward, except when Arabic numerals were used as stimuli. A perceptual or incentive-based interference occurred that was overcome by symbolic stimuli. The authors of the present study examined the impact of element size in choice arrays, using 1 to 5 large and small candies. Five test-sophisticated chimpanzees selected an array from the 2 presented during each trial. Their responses were not optimal, as animals generally selected arrays with larger total mass; thus, they received the smaller remaining array as a reward. When choice stimuli differed in size and quantity, element size was more heavily weighted, although choices reflected total candy mass. These results replicate previous findings showing chimpanzees' difficulties with quantity judgments under reverse reward contingencies and also show that individual item size exerts a more powerful interference effect.     

Choice with probabilistic reinforcement: effects of delay and conditioned reinforcers.

Two experiments measured pigeons' choices between probabilistic reinforcers and certain but delayed reinforcers. In Experiment 1, a peck on a red key led to a 5-s delay and then a possible reinforcer (with a probability of .2). A peck on a green key led to a certain reinforcer after an adjusting delay. This delay was adjusted over trials so as to estimate an indifference point, or a duration at which the two alternatives were chosen about equally often. In all conditions, red houselights were present during the 5-s delay on reinforced trials with the probabilistic alternative, but the houselight colors on nonreinforced trials differed across conditions. Subjects showed a stronger preference for the probabilistic alternative when the houselights were a different color (white or blue) during the delay on nonreinforced trials than when they were red on both reinforced and nonreinforced trials. These results supported the hypothesis that the value or effectiveness of a probabilistic reinforcer is inversely related to the cumulative time per reinforcer spent in the presence of stimuli associated with the probabilistic alternative. Experiment 2 tested some quantitative versions of this hypothesis by varying the delay for the probabilistic alternative (either 0 s or 2 s) and the probability of reinforcement (from .1 to 1.0). The results were best described by an equation that took into account both the cumulative durations of stimuli associated with the probabilistic reinforcer and the variability in these durations from one reinforcer to the next.     

Chimpanzee responding during matching to sample: control by exclusion

Three chimpanzees performed a computerized matching-to-sample task in which samples were photographs of items and comparison stimuli were geometric symbols called lexigrams. In Experiment 1, samples were either defined (i.e., they represented items that were associated already with a specific lexigram label by the chimpanzees) or undefined (i.e., they did not have an already learned association with a specific lexigram). On each trial, the foil (incorrect) comparison could be either a defined or an undefined lexigram. All 3 chimpanzees selected the correct comparison for undefined samples at a level significantly better than chance only when the foil comparison was defined. In Experiment 2, three comparisons were presented on each trial, and in Experiment 3, four comparisons were presented on each trial. For Experiments 2 and 3, the foil comparisons consisted of either defined or undefined comparisons or a mixture of both. For these two experiments, when the chimpanzees were presented with an undefined sample, they typically made selections of only undefined comparisons. These data indicate that the chimpanzees responded through use of exclusion. A final experiment, however, indicated that, despite the use of exclusion to complete trials with undefined samples correctly, the chimpanzees did not learn new associations between undefined samples and comparisons.     

Attentional set interacts with perceptual load in visual search

In the present study, we examined the hypothesis that perceptual load is the primary factor that determines the efficiency of attentional selection. Participants performed a visual search task under conditions of high- and low-load. In line with the perceptual load hypothesis, presenting conditions of highand low-load in separate blocks of trials resulted in processing of to-be-ignored stimuli only in the lowload condition (Experiment 1). However when high- and low-load conditions were randomly mixed in blocks of trials, the participants showed processing of to-be-ignored stimuli in both conditions, suggesting that high perceptual load is not necessarily sufficient to obtain perceptual selectivity (Experiment 2). An analysis of intertrial transition effects showed that on high-load trials, processing of to-be-ignored stimuli occurred only when the previous trial was a low-load trial. The results suggest that low perceptual load can engender broad attentional processing. On the other hand, when a high-load trial was preceded by another high-load trial, little processing of task-irrelevant stimuli was observed. The present results are discussed in terms of the interaction between expectancies and bottom-up factors in the efficiency of attentional selection.     

Integration and representation in rats' serial pattern learning in the T-maze

Rats were exposed to three-trial series consisting of reinforced (R) trials and one nonreinforced (N) trial in a fixed order, RRN and RNR (Experiments 1 and 2) or NRR and RRN (Experiment 3), on extended visually distinct runways in a T-maze. When initially presented with the same sequence on each series in a session (separate presentations) with the same runway on all trials within a series (Experiments 1 and 3), all the rats developed slower running speeds on N than on R trials. When a runway was sometimes changed between the first and next two trials during separate presentations training (Experiment 2) or both sequences were later intermixed within each session in each experiment, only rats exposed to each sequence on a specific runway maintained these serial running patterns. Rats displayed serial running patterns on a test RNN sequence similar to that on the RNR sequence (Experiment 2), as would be predicted by an intertrial association model of serial pattern learning (Capaldi & Molina, 1979), but responded on test RRR and NRN sequences (Experiment 3) as would be predicted by an ordinal-trial-tag/intratrial association model (Burns, Wiley, & Payne, 1986). Results from test series of free-choice trials in Experiments 1 and 2 failed to support a prediction of the intratrial association model that these rats would integrate RRN and RNR sequences. Rather than always selecting a baited runway on both the second and the third free-choice trials, the rats only selected a baited runway on the third trial on the basis of their choice on the second trial, as would be predicted by the intertrial association model. Only after experiencing all possible outcome sequences during forced-choice training in Experiment 3 did these rats predominantly select a baited runway on every free-choice trial.     

Comparing the effects of two correction procedures on human acquisition of sequential behavior patterns

Thirty-one college undergraduates learned to touch abstract stimuli on a computer screen in arbitrarily designated “correct” sequential orders. Four sets of seven stimuli were used; the stimuli were arrayed horizontally on the screen in random sequences. A correct response (i.e., touching first the stimulus designated as first) resulted in that stimulus appearing near the top of the screen in its correct sequential position (left to right), and remaining there until the end of the trial. Incorrect responses (i.e., touching a stimulus out of sequence) terminated the trial. New trials displayed either the same sequence as the one on which an error had occurred (same-order correction procedure), or a new random sequence (new-order correction procedure). Whenever all responses occurred in the correct sequence, the next trial displayed a new random sequence. Each phase ended when five consecutive correct response sequences occurred. Initially, the same-order correction procedure increased control by the position as well as by the shape of the stimuli; also, it produced more errors, more total trials, more trials to mastery, and more individual patterns of reacquisition than were produced by the new-order procedure.     

整体-局部范式下的负启动效应

在通常的负启动范式基础上 ,以小数字构成的大数字 ,即以同时具有整体特征和局部特征的复合数字为实验材料 ,采用数字命名任务 ,将刺激画面中复合数字的数目和注意指向作为变量进行实验。大学生充任被试。结果发现 ,在单个复合数字条件下对同一客体的非注意指向的特征进行忽略重复 ,注意整体时出现负启动 ,而注意局部时不出现负启动 ;在两个复合数字条件下对启动刺激中充当干扰项的复合数字进行忽略重复 ,则注意整体与注意局部都出现了负启动。该研究表明 ,在不同注意指向时 ,整体 -局部范式下的负启动效应具有知觉组织的层次性 ,并显示出客体内选择和客体间选择对负启动的不同影响。     

Ordinal-list integration for symbolic, arbitrary, and analog stimuli by rhesus macaques (Macaca mulatta)

Two numeral-trained monkeys learned to produce 3 5-item lists of Arabic numerals, colors, and arbitrary signs in the correct sequence. The monkeys then responded at above-chance levels when the authors tested them with nonrewarded pair-wise comparisons of items from different lists, indicating their use of ordinal-position information. The authors also tested the monkeys with nonrewarded pair-wise comparisons of an analog quantity and an item from 1 of the 3 learned lists. Although the monkeys were not trained to serially order analog quantities, 1 monkey correctly integrated the analog quantities with the lists of numerals, colors, and signs. The consistent use of an ordinal rule, despite different types of training and varying degrees of experience with the 4 types of stimuli, suggested that the monkey had a robust concept of ordinality.     

Form perception at birth: Cohen and Younger (1984) revisited

Cohen (1988; Cohen & Younger, 1984) has suggested that there is a shift in the perception of form sometime after 6 weeks of age. Prior to this age infants can remember the specific orientations of line segments, but cannot process and remember the angular relations that line segments can make. Experiment 1 used simple line stimuli with newborn infants to test this suggestion. Following habituation to a simple two-line angle the newborns dishabituated to a change of orientation but not to a change in angle, confirming Cohen and Younger's suggestion that orientation is a powerful cue in early shape perception. In Experiments 2 and 3 newborns were familiarized either to an acute or to an obtuse angle that changed its orientation over trials. On subsequent test trials the babies gave strong novelty preferences to a different angle. Alternative interpretations of the results are discussed, but these experimental findings are compatible with the suggestion that newborns can quickly learn to process angular relations, and that rudimentary form perception may not be dependent on a lengthy period of learning and/or maturation for its development.     

Heart-Rate responses (HRR) to lateralized visual stimuli

Direction of changes in heart-rate responses (HRR) were investigated in three separate experiments as a measure of differential cognitive and emotional specialization of the cerebral hemispheres. Visual stimuli were presented via the visual half-field technique in all three experiments. Slides with different contents were flashed for 200 msec on each trial either to the left or right of a center LED fixation point. The LED went on 5 seconds prior to slide onset. HR changes were scored as second-by-second deviations during 10 seconds after LED onset from pre-LED base line. In the first experiment it was hypothesized that emotionally relevant stimuli initially projected to only the right hemisphere would result in more anticipatory acceleration than when the same stimulus was initially projected to the left hemisphere. A picture of a snake and of a geometric figure were repeatedly briefly flashed to the right of the LED for half of the subjects, and to the left for the other half. There were 25 trials with an intertriai interval of 25–40 seconds. Results showed significant effects of deceleration as a function of the slide stimulus in all groups on seconds 5, 6, or 7 after onset of the center LED. Furthermore, an anticipatory acceleration was observed during the first trial-block on seconds 3 and 4 in the right hemisphere groups only with no differences between the neutral and emotional stimuli. In Experiments 2 and 3, a letter-string of six letters and a complex symmetric pattern were used as stimuli. These stimuli were chosen because previous research has clearly implicated the hemispheres to be differentially specialized in their ability to process verbal and visuo-spatial stimuli. The set-up was identical to Experiment 1, with the exception that differences in response to the two types of stimuli were evaluated on a within-subjects basis. The results from Experiments 2 and 3 showed stimulus-related deceleration, peaking on seconds 5–7 in all groups and an anticipatory acceleration peaking on seconds 3 and 4 in the right hemisphere groups, with decelerations during the corresponding seconds in the left hemisphere groups. The results are discussed in relation to recent findings by Walker and Sandman (1982) about the possibility of hemispheric specialization in psychologic influences on heart rate changes in response to environmental demands.     

单一启动单一探测中基于相关低比例的负启动效应

启动和探测刺激相同试次低比例时可出现类似负启动的抑制现象。本研究采用不同于以往研究的单一探测范式,并操纵相关项（启动与探测词语义相关）的比例及刺激集的大小研究这一抑制机制的特点。实验一在低比例时发现了显著的负启动效应。实验二在低比例时,发现小的刺激集能诱发负启动,而大的则不能。表明在单一探测范式中启动与探测相关试次的低比例确实能诱发抑制控制,该抑制控制由忽视策略所致,并受刺激集大小的影响,支持了干扰项的凸显能够诱发强抑制的观点。     

Acquisition and memory of sequence order in young and adult chimpanzees (Pan troglodytes)

There is no research about age difference in the process of sequential learning in non-human primates. Is there any difference between young and adults in sequential learning process? Six chimpanzees (Pan troglodytes), 3 young and 3 adults, learned the Arabic numeral sequence 1 to 9 by touching the numerals on a touch-screen monitor in ascending order. Initially, the sequence always started with the numeral 1, i.e. ‘start-fixed task’. Training began with the sequence 1–2, 1–2–3, and continued sequentially up to 1–2–3–4–5–6–7–8–9. Later, the subjects were introduced to sequences that started with a random numeral, but always ended with 9, i.e. ‘end-fixed task’. Performance in the end-fixed task was worse relative to the familiar start-fixed task. After training with various sequences of adjacent numerals, the subjects were given a transfer test for the non-adjacent numerals. The results suggested that all chimpanzees indeed mastered sequential ordering, and although there was no fundamental difference in the acquisition process between the two age groups, there was a significant age difference in memory capacity. Based on their knowledge of sequential ordering, the subjects were then asked to perform a masking task in which once a subject touched the lowest numeral, the other numeral(s) turned to white squares. Performance of the masking task by young chimpanzees was better than that of adults in accuracy and degree of difficulty (number of numerals). Taken together, these data clearly demonstrate a similarity among subjects in the way chimpanzees acquire knowledge of sequential order regardless of age differences in sequential learning. Moreover, they reveal that once knowledge of sequential order is established, it can be a good index used to evaluate memory capacity in young and adult chimpanzees.

     

Hemispheric asymmetry in the identification of four-letter names traced in the right and left palms

Forty right-handed males were asked to identify four-letter names traced in either the right or left palms while their eyes were closed. The name stimuli were traced in a right-side-up or upside-down orientation (i.e., vertical or rotated 180 degrees). Mean percentage of errors served as the dependent variable. On the first block of 40 trials, the left palm/right hemisphere (LP/RH) was significantly more accurate than the right palm/left hemisphere (RP/LH) at identifying these names. This advantage, however, was only manifest when the name stimuli were traced in the upside-down orientation. On the second block of 40 trials, as the name stimuli became more familiar and the subjects became more practiced, a similar LP/RH advantage was observed; however, the impact of the rotation variable was no longer in evidence (i.e., the LP/RH was slightly more accurate on both upright and inverted names). These results are interpreted in light of a process-oriented tactile asymmetry as proposed by M. W. O'Boyle, F. Van Wyhe-Lawler, and D. A. Miller (1987, Brain and Cognition, 6, 474-494).     

Reinforcer frequency and restricted stimulus control.

Stimulus control was evaluated in 3 individuals with moderate to severe mental retardation by delayed identity matching-to-sample procedures that presented either one or two discrete forms as sample stimuli on each trial. On pretests, accuracy scores on one-sample trials were uniformly high. On two-sample trials, the correct stimulus (i.e., the one that subsequently appeared in the comparison array) varied unpredictably, and accuracy scores were substantially lower, suggesting that both sample stimuli did not exert stimulus control on every trial. Subjects were then given training sessions with the one-sample task and with a new set of four stimuli. For two of the stimuli, correct matching responses were followed by reinforcers on a variable-ratio schedule that led to a high reinforcer rate. For the other two stimuli, correct responses were followed by reinforcers on a variable-ratio schedule that led to a substantially lower reinforcer rate. Results on two-sample tests that followed showed that (a) on trials in which comparison arrays consisted of one high reinforcer-rate and one low reinforcer-rate stimulus, subjects most often selected the high-rate stimulus; and (b) on trials in which the comparison arrays were either two high reinforcer-rate stimuli or two low reinforcer-rate stimuli and the samples were one high reinforcer- and one low reinforcer-rate stimulus, accuracy was higher on trials with the high-rate comparisons. These results indicate that the frequency of stimulus control by high reinforcer-rate samples was greater than that by low reinforcer-rate samples. Following more training with the one-sample task and reversed reinforcement schedules for all stimuli, the differences in stimulus control frequencies on two-sample tests also reversed. These results demonstrate experimental control by reinforcement contingencies of which of two sample stimuli controlled selections in the two-sample task. The procedures and results may prove to be relevant for understanding restricted stimulus control and stimulus overselectivity.