Differential effects of familiarity on judgments of sameness and difference

Ss indicated whether pairs of simultaneously presented objects were “same” or “different.” In Experiments 1, 2, and 3 the stimuli were pairs of letters, and familiarity was manipulated by showing the letters in either an upright or an upside-down orientation. In Experiments 4 and 5 the stimuli were pairs of trigrams, and familiarity was manipulated either by rotation or by selection according to rated meaningfulness. Analysis of reaction times indicated that familiar pairs were responded to more quickly than were unfamiliar pairs; however, this was true only for “same” judgments, not for “different” judgments. In addition, Experiment 3 indicated that familiarity influenced discrimination accuracy under conditions of tachistoscopic exposure. Finally, in Experiment 6 an effort was made to disentangle the effects of meaningfulness from the effects of pronounceability. The present results stand in contrast to previous research using perceptual comparison tasks, since the earlier work failed to indicate any effect of familiarity.     

A transfer of functions through derived arbitrary and nonarbitrary stimulus relations

During Experiments 1 and 2, subjects were trained in a series of related conditional discriminations in a matching-to-sample format (A1-B1, A1-C1 and A2-B2, A2-C2). A low-rate performance was then explicitly trained in the presence of B1, and a high-rate performance was explicitly trained in the presence of B2. The two types of schedule performance transferred to the C stimuli for all subjects in both experiments, in the absence of explicit reinforcement through equivalence (i.e., C1 = low rate and C2 = high rate). In Experiment 2, it was also shown that these discriminative functions transferred from the C1-C2 stimuli to two novel stimuli that were physically similar to the C stimuli (SC1 and SC2, respectively). For both these experiments, subjects demonstrated the predicted equivalence responding during matching-to-sample equivalence tests. In Experiments 3 and 4, the conditional discrimination training from the first two experiments was modified in that two further conditional discrimination tasks were trained (C1-D1 and C2-D2). However, for these tasks the D stimuli served only as positive comparisons, and ND1 and ND2 stimuli served as negative comparisons (i.e., C1 × ND1 and C2 × ND2). Subsequent to training, the negatively related stimuli (ND1 and ND2) did not become discriminative for the schedule performances explicitly trained in the presence of B1 and B2, respectively. Instead, the ND1 stimulus became discriminative for the schedule performance trained in the presence of B2, and ND2 became discriminative for the schedule performance trained in the presence of B1. All subjects from Experiment 4 showed that the novel stimulus SND1, which was physically similar to ND1, became discriminative for the same response pattern as that controlled by ND1. Similarly, SND2, which was physically similar to ND2, became discriminative for the same response pattern as that controlled by ND2. Subjects from both Experiments 3 and 4 also produced equivalence responding on matching-to-sample equivalence tests that corresponded perfectly to the derived performances shown on the transfer of discriminative control tests.     

Choice As A Function Of Reinforcement Ratios In Delayed Matching-to-sample

Pigeons were studied in two experiments using a delayed matching-to-sample task. In Experiment 1, 4 subjects were exposed to a task in which the proportion of reinforcement associated with matching and nonmatching, and the overall proportion of reinforcement associated with selecting each choice, regardless of the sample stimulus, were varied. Choice was sensitive to both proportions. A least squares regression analysis showed that Wixted's (1989) proportions of reinforcement model closely fit the data from Experiment 1; however, the model failed to make accurate qualitative predictions for some test conditions. In Experiment 2, 4 subjects were exposed to a delayed matching-to-sample task in which the retention intervals and the reduction in delay to reinforcement signaled by the onset of the sample stimulus were independently varied. When the retention interval was short and when the delay-reduction value of the sample stimulus was high, the sample exerted greater control over choice; the control by the overall proportion of reinforcements for selecting each choice stimulus was correspondingly low. Conversely, when the retention interval was long and the delay-reduction value of the sample stimulus was low, the sample exerted relatively less control over choice; control by the overall proportion of reinforcements obtained for selecting each choice stimulus was correspondingly high. A signal detection analysis found that sensitivity to reinforcement varied directly with retention interval. Data were also consistent with misallocation models. No evidence was found to suggest that pigeons ignore the rate at which selecting individual choice stimuli is reinforced, as has been reported in studies with human subjects.     

An analysis of emergent simple discrimination in children

In Experiment 1 eight five-year-old children received an arbitrary matching-to-sample task with sample stimuli A1 and A2 and comparison stimuli B1 and B2. This task was mixed with a simple, two-choice discrimination task with stimuli A1 and A2. In subsequent tests with B1 and B2 presented alone, the number of responses to B1 was greater when it had been paired with the correct stimulus of the simple discrimination task than when it had been paired with the incorrect stimulus. In Experiment 2 incorrect comparisons were omitted during the matching-to-sample task. Eight children were taught to point to either A1 or A2 first, and to either B1 or B2 second. Eight other children were taught to point to either B1 or B2 first, and to either A1 or A2 second. The effect of Experiment 1 was replicated with the first but not with the second group. The results of both experiments suggest that the functions of S+ and S- in a simple discrimination task can transfer to test stimuli if the training stimuli precede the test stimuli during paired presentations.     

Correlation between menstrual cycle and cognitive performance in a chimpanzee (Pan troglodytes)

Extensive research on human subjects has tried to investigate whether there is a correlation between cognitive performance and the menstrual cycle. Less is known about the relationship between the menstrual cycle and task performance in other cognitive animals. We test whether the secretion of a sex hormone [luteinizing hormone(LH)] influences the performance of cognitive tasks by a female chimpanzee (Pan troglodytes) who is part of a long-term cognition research program. We focus on two cognitive tasks: an "easy task," which consists of simple numerical ordering, and a "difficult task," which combines numerical ordering with memorizing the numerals' spatial location. Data on the performance of these cognitive tasks, urine samples, and sexual swelling over six menstrual cycles showed that the chimpanzee's performance accuracy decreased and that the intertrial interval was longer during the LH-surge of the menstrual cycle, but only for the performance of the difficult task. These performance attributes seem to reflect a decrease in attention or motivation during ovulation. In summary, the cognitive performance of a chimpanzee was disturbed by hormonal changes despite her long-term experience in the tasks.     

Pragmatic use of stereotyping in teamwork: social loafing and compensation as a function of inferred partner-situation fit

Using 4 experiments, the authors examined how stereotypic information about teammates influences social loafing and compensation during collective tasks. In each experiment, participants performed better on cognitive tasks when there was a poor (vs. good) fit between the stereotypic strengths of their partner and the requirements of the task. This pattern occurred whether participants used gender stereotypes (Experiment 1) or occupational stereotypes (Experiments 2 to 4) and occurred even when participants only anticipated working on a collective task (Experiment 4). In Experiment 3, the pattern occurred only in the collective (not in the coactive) condition, providing direct evidence for social loafing. Together, these results suggest that people use stereotypes to tune their motivation to optimize the ratio of their own individual effort to the team's expected output.     

Discrimination of temporal relations by pigeons

In four experiments, pigeons were tested on a duration comparison task involving the successive presentation of two visual stimuli that varied in duration from trial to trial. Following presentation of the durations, two choice keys were lit, and reinforcement for choices was based on the temporal relation between duration of the pair. In Experiment 1, the range of durations was varied over conditions. Responding changed as an orderly function of the ratio of the two durations. There was a decrease in discrimination accuracy as average duration increased over condition but no difference in accuracy between shorter and longer problems within a duration range. There was no systematic response bias over conditions for all problems within a range, but there was a bias to report the second duration longer than the first for "long" problems within a range. In Experiment 2, the pigeons were transferred from a task involving spatially differentiated choices to one involving hue-differentiated choices. Performance was similar to that of the spatial procedure of Experiment 1. Additional analyses revealed that although information provided by a single duration of the pair was sometimes predictive of the temporal relation between pair members, responding was also based on the relation and comparison of both durations. In Experiment 3, the pigeons were exposed to a single duration range that included many durations from the four ranges of Experiment 1. Discrimination accuracy was comparable in the fourth and longest category. Manipulation of absolute reinforcement rate in Experiment 4 resulted in no chang in discrimination accuracy, suggesting that the decline in accuracy over conditions of Experiment 1 could not be attributed to decreases in reinforcement rate that accompanied lengthier durations. The results are discussed in terms of theories of animal timing, with Staddon's (1983, 1984) temporal perspective model providing the most systematic account of all aspects of performance.     

The transfer of specific and general consequential functions through simple and conditional equivalence relations

The purpose of this study was to examine the transfer of consequential (reinforcement and punishment) functions through equivalence relations. In Experiment 1, 9 subjects acquired three three-member equivalence classes through matching-to-sample training using arbitrary visual forms. Comparison stimuli were then given conditioned reinforcement or punishment functions by pairing them with verbal feedback during a sorting task. For 8 of the 9 subjects, trained consequential functions transferred through their respective equivalence classes without additional training. In Experiment 2, transfer of function was initially tested before equivalence testing per se. Three of 4 subjects showed the transfer without a formal equivalence test. In Experiment 3, 3 subjects were given training that gave rise to six new three-member conditional equivalence classes. For 2 of the subjects, the same stimulus could have either a reinforcement or punishment function on the basis of contextual cues that defined its class membership. Experiment 4 assessed whether equivalence training had established general or specific consequential functions primarily by adding novel stimuli in the transfer test. Subjects treated even novel feedback stimuli in the transfer test as consequences, but the direction of consequential effects depended upon the transfer of specific consequential functions through equivalence relations.     

Parallel and competitive processes in hierarchical analysis: perceptual grouping and encoding of closure.

The role of perceptual grouping and the encoding of closure of local elements in the processing of hierarchical patterns was studied. Experiments 1 and 2 showed a global advantage over the local level for 2 tasks involving the discrimination of orientation and closure, but there was a local advantage for the closure discrimination task relative to the orientation discrimination task. Experiment 3 showed a local precedence effect for the closure discrimination task when local element grouping was weakened by embedding the stimuli from Experiment 1 in a background made up of cross patterns. Experiments 4A and 4B found that dissimilarity of closure between the local elements of hierarchical stimuli and the background figures could facilitate the grouping of closed local elements and enhanced the perception of global structure. Experiment 5 showed that the advantage for detecting the closure of local elements in hierarchical analysis also held under divided- and selective-attention conditions. Results are consistent with the idea that grouping between local elements takes place in parallel and competes with the computation of closure of local elements in determining the selection between global and local levels of hierarchical patterns for response.     

Bias in self-evaluation: Signal probability effects

Two experiments examined apparent signal probability effects in simple verbal self-reports. After each trial of a delayed matching-to-sample task, young adults pressed either a “yes” or a “no” button to answer a computer-presented query about whether the most recent choice met a point contingency requiring both speed and accuracy. A successful matching-to-sample choice served as the “signal” in a signal-detection analysis of self-reports. Difficulty of matching to sample, and thus signal probability, was manipulated via the number of nonmatching sample and comparison stimuli. In Experiment 1, subjects exhibited a bias (log b) for reporting matching-to-sample success when success was frequent, and no bias or a bias for reporting failure when success was infrequent. Contingencies involving equal conditional probabilities of point consequences for “I succeeded” and “I failed” reports had no systematic effect on this pattern. Experiment 2 found signal probability effects to be evident regardless of whether referent-response difficulty was manipulated in different conditions or within sessions. These findings indicate that apparent signal probability effects in self-report bias that were observed in previous studies probably were not an artifact of contingencies intended to improve self-report accuracy or of the means of manipulating signal probability. The findings support an analogy between simple self-reports and psychophysical judgments and bolster the conclusion of Critchfield (1993) that signal probability effects can influence simple self-reports much as they do reports about external stimuli in psychophysical experiments.     

Effects of auditory stimulus intensity on response force in simple, go/no-go, and choice RT tasks

In four experiments, increasing the intensities of both relevant and irrelevant auditory stimuli was found to increase response force (RF) in simple, go/no-go, and choice reaction time (RT) tasks. These results raise problems for models that localize the effects of auditory intensity on purely perceptual processes, indicating instead that intensity also affects motor output processes under many circumstances. In Experiment 1, simple RT, go/no-go, and choice RT tasks were compared, using the same stimuli for all tasks. Auditory stimulus intensity affected both RT and RF, and these effects were not modulated by task. In Experiments 2-4, an irrelevant auditory accessory stimulus accompanied a relevant visual stimulus, and the go/no-go and choice tasks were used. The intensity of the irrelevant auditory accessory stimulus was found to affect RT and RF, although the sizes of these effects depended somewhat on the temporal predictability of the accessory stimulus.     

On estimating the difference limen in duration discrimination tasks: a comparison of the 2AFC and the reminder task

This article assesses whether the two-alternative forced-choice (2AFC) and the reminder tasks (i.e., method of constant stimuli) yield identical estimates of the difference limen (DL). In a series of six experiments, participants discriminated between two duration stimuli. Experiments 1-5 employed auditory stimuli, and Experiment 6 employed visual stimuli. Experiments 1 and 2 combined each of the two tasks with an adaptive and a nonadaptive procedure for threshold estimation. Experiment 3 varied the distribution of the comparison levels, whereas Experiment 4 employed random interstimulus intervals. Experiments 5 and 6 examined the influence of the presentation order of the standard and comparison stimuli. Results indicate that both the adaptive and the nonadaptive procedures yield virtually identical DL estimates; yet, the 2AFC task produces consistently larger DLs than does the reminder task. In addition, DL increases when the standard occurs in the second rather than in the first stimulus position. In order to account for these results, we assume that participants use an internal standard instead of the actually presented standard as a reference for their judgment.     

TESTS FOR CONTROL BY EXCLUSION AND NEGATIVE STIMULUS RELATIONS OF ARBITRARY MATCHING TO SAMPLE IN A “SYMMETRY-EMERGENT” CHIMPANZEE

In the present experiments, controlling relations in arbitrary matching-to-sample performance were tested in a 9-year-old female chimpanzee who showed statistically significant emergence of symmetry in previous two-choice conditional discrimination experiments. In Experiment 1, a novel (undefined) sample stimulus was followed by a pair of trained (defined) and undefined comparison stimuli to assess the control by exclusion in arbitrary matching. The chimpanzee selected the undefined shape comparison, excluding the defined one, in color-sample-to-shape-comparison probe trials, although stimulus preferences were relatively stronger than control by exclusion in shape-sample trials. An additional test for control by relations of the sample to the positive comparison (S+ control) showed that her behavior was also under the control of relations of the sample to the positive comparison. In Experiment 2, a defined sample was followed by a pair of negatively defined and undefined comparisons to test control by the relations of the sample to the negative comparison. (S- control). The subject selected undefined comparisons in both color-shape and shape-color test trials. These results clearly indicate that the conditional discrimination behavior of this “symmetry-emergent” chimpanzee was under both S+ and S- control. Furthermore, her performance was also under control by exclusion in color-shape arbitrary matching, unlike other chimpanzees who showed no evidence of symmetry but only S+ control of arbitrary matching.     

Differential vocalization in budgerigars: towards an experimental analysis of naming.

In Experiment 1, 3 budgerigars (Melopsittacus undulatus) were trained with food reinforcement to make low- or high-frequency calls in response to different color stimuli, C1 and C2 (a color-naming task), using a gradual response-differentiation procedure and an automatic call-recognition system. Thus, a call within a certain frequency band was reinforced in the presence of C1 ("C1 call"), and a call within a different band was reinforced in the presence of C2 ("C2 call"). In Experiment 2, all 3 budgerigars were trained in a form-to-color matching-to-sample task, alternating trial by trial with either the color-naming task (2 birds) or an identity color matching-to-sample task (1 bird). Sample stimuli for the new matching-to-sample task were forms (F1 or F2) and comparisons were the same two colors (C1 and C2). Given Sample F1 or F2, birds had to make a call to produce Comparison Pair C1 and C2. With F1 as the sample, a peck on C1 was reinforced; with F2 as the sample, a peck on C2 was reinforced. Although no particular call was specified in the presence of F1 and F2, 2 birds made the C1 call in the presence of F1 and the C2 call in the presence of F2. In Experiment 3, the bird that failed to match form and color calls in Experiment 2 and another bird were first trained in a color-to-form matching-to-sample task: C1 to F3 and C2 to F4. In this task, to produce the comparison pair of forms, a high call (or low for the other bird) was required in the presence of C1, and a low call (or high) was required in the presence of C2. Both birds were then trained with an identity matching-to-sample task in which sample and comparison stimuli were the same two forms, F3 and F4. Trials on the identity task alternated with the color-to-form trials. Although no particular call was required in the presence of Samples F3 and F4, both birds came to make the C1 call in the presence of F3 and the C2 call in the presence of F4. Our technique promises to be useful for the study of emergent vocal relations in budgerigars and other animals.     

Temporal control of internal states in pigeons

To understand how animals serially organize complex competing behaviors, we tested pigeons in a sequential task-switching procedure. Daily sessions involved two conditional discrimination tasks that were presented in sequence. In Experiment 1, the first half of a session employed a matching-to-sample task, and the second half tested an oddity-from-sample task. Because the same colors were used for both tasks, these tasks could be solved only by employing a modulating sequential cue. The results of the first experiment revealed that the pigeons could learn this task-switching procedure and that an internal clock was the critical modulator between the tasks. In Experiment 2, we tested a three-alternative choice task. By examining the pattern of errors among choices, the results of this experiment revealed that pigeons learned and used different representations of the choice rules for each half of the experiment. This modulation of the pigeons’ internal states by time has implications for how animals organize their behavior in different settings and holds clues as to the evolution of the serial organization of behavior.     

Acquisition of auditory–visual intermodal matching-to-sample by a chimpanzee (Pan troglodytes): comparison with visual–visual intramodal matching

A chimpanzee acquired an auditory–visual intermodal matching-to-sample (AVMTS) task, in which, following the presentation of a sample sound, the subject had to select from two alternatives a photograph that corresponded to the sample. The acquired AVMTS performance might shed light on chimpanzee intermodal cognition, which is one of the least understood aspects in chimpanzee cognition. The first aim of this paper was to describe the training process of the task. The second aim was to describe through a series of experiments the features of the chimpanzee AVMTS performance in comparison with results obtained in a visual intramodal matching task, in which a visual stimulus alone served as the sample. The results show that the acquisition of AVMTS was facilitated by the alternation of auditory presentation and audio-visual presentation (i.e., the sample sound together with a visual presentation of the object producing the particular sample sound). Once AVMTS performance was established for the limited number of stimulus sets, the subject showed rapid transfer of the performance to novel sets. However, the subject showed a steep decay of matching performance as a function of the delay interval between the sample and the choice alternative presentations when the sound alone, but not the visual stimulus alone, served as the sample. This might suggest a cognitive limitation for the chimpanzee in auditory-related tasks. Accepted after revision: 11 September 2001 Electronic Publication     

Alertness and cognitive control: Is there a spatial attention constraint?

Congruency effects in arrow flanker tasks are often larger when subjects are more alert, suggesting an unusual connection between alertness and cognitive control. Theoretical accounts of the alerting–congruency interaction differ with respect to whether and how spatial attention is involved. In the present study, the author conducted eight experiments to determine whether there is a spatial attention constraint linking alertness to cognitive control. Alertness was manipulated in color-word Stroop tasks involving stimuli that were spatially integrated (Experiments 1–3) or separated (Experiments 4 and 5), as well as in Stroop-like tasks involving spatially separated stimuli for which the irrelevant stimulus features were spatial words (Experiments 6 and 7) or arrows (Experiment 8). All experiments yielded effects of alerting and congruency, but none produced the alerting–congruency interaction typically found with arrow flanker tasks. The results suggest that there is a spatial attention constraint on the relationship between alertness and cognitive control, part of which might involve having a task goal associated with spatial information processing.     

Effects of attention and external stimuli on duration estimation under aprospective paradigm

The study examined whether there are two independent cognitive factors affecting duration estimation. In two experiments, we manipulated simultaneously and independently two variables, namely, the level of attention to the lapse of time and the quantity of perceived changes, and examined their effects on duration estimation under a prospective paradigm. The duration was estimated to be longer when subjects attended to the lapse of time than when they attended to tasks during the target interval (Experiments 1 and 2). The characteristics of external stimuli irrelevant to the tasks, namely, the rate of presentation of sounds (Experiment 1) and the velocity of moving dots (Experiment 2), affected duration estimation, even though the attention level was little changed by these stimuli. These findings suggest that there are at least two independent cognitive factors that affect duration estimation.     

Duration discrimination of filled and empty auditory intervals: cognitive and perceptual factors.

Adult subjects were presented with two auditory stimuli per trial, and their task was to decide which of the two was longer in duration. An adaptive psychophysical procedure was used. In Experiments 1, 2, and 4, the base duration was 50 msec, whereas in Experiment 3, the base duration was 1 sec. In Experiments 1, 2, and 4, it was found that filled intervals (continuous tones) were discriminated more accurately than empty intervals (with onset and offset marked by clicks). It was concluded that this difference was perceptual rather than cognitive in nature, since performance on filled and empty intervals was not affected by increasing cognitive load in a dual-task procedure (Experiment 2) but was affected by backward masking (Experiment 4). In contrast, the results of Experiment 3 showed that duration discrimination of filled auditory intervals of longer duration was cognitively influenced, since performance was impaired by increasing cognitive load. Implications for notions of perceptual processing and timing mechanism underlying differences in duration discrimination with filled and empty intervals are discussed.