Precuing the Target Location in Visual Searching by a Chimpanzee (Pan troglodytes): Effects of Precue Validity

A chimpanzee ( Pan troglodytes ) performed a visual search task using a modified matching-to-sample procedure in which a sample stimulus was followed by the search display, which contained one stimulus identical to the sample (target) and several uniform stimuli different from the sample (distractors). On cued trials, while the subject was observing the sample, a white square (precue) appeared at the location where the target was to be presented (valid trials), or elsewhere (invalid trials). The validity of the precue (correspondence between the cued and the target locations) was changed from 0% to 100% across conditions. Cost-benefit analyses were performed on the difference between valid and noncued trials (benefit) and between invalid and noncued trials (cost). Under the high-validity conditions, the response times were shorter when the cued location corresponded to the target location than when the precue did not appear. When the cued location did not correspond to the target location, on the other hand, the subject took longer to select the target than on noncued trials. When the validity of the precue was relatively low, however, cost of the invalid trials disappeared, while benefit of the valid trials remained. These results confirmed the two-process (automatic and attentional) theory of priming in human information processing; the advance information had the same effects on a chimpanzee's visual search performance as on humans'.     

Comparative assessment of handedness for a coordinated bimanual task in chimpanzees (Pan troglodytes), gorillas (Gorilla gorilla) and orangutans (Pongo pygmaeus)

Hand preferences for a coordinated bimanual task were assessed in a sample of 31 captive gorillas (Gorilla gorilla) and 19 captive orangutans (Pongo pygmaeus) and were compared with chimpanzee (Pan troglodytes) hand preferences in subjects that were matched on the basis of age, sex, and rearing history. The task required that the apes remove food from the inside edges of a symmetrical polyvinyl chloride pipe presented to them in their home cages. The results indicate significant species differences with chimpanzees showing population-level right-handedness and orangutans showing population-level left-handedness. The gorillas showed a nonsignificant trend toward right-handedness. The results are discussed in terms of possible ecological or biomechanical factors that may influence hand preferences in different ape species.     

A Stroop-like effect in color-naming of color-word lexigrams by a chimpanzee (Pan troglodyte)

The Stroop effect (J. R. Stroop, 1935) reflects the difficulty in ignoring irrelevant, but automatically processed, semantic information that is inherent in certain stimuli. With humans, researchers have found this effect when they asked participants to name the color of the letters that make up a word that is incongruent with that color. The authors tested a chimpanzee that had learned to associate geometric symbols called lexigrams with specific colors. When the chimpanzee had to make different responses that depended on the color of stimuli presented to her, she showed a Stroop-like effect when researchers presented to her the previously learned symbols for colors in incongruent font colors. Her accuracy performance was significantly poorer with these stimuli than with congruent color-referent lexigrams, noncolor-referent lexigrams, and nonlexigram stimuli, although there were not any significant differences in response latency. The authors' results demonstrated color-word interference in a Stroop task with a nonhuman animal.     

Conspecific recognition in the chimpanzee (Pan troglodytes): cardiac responses to significant others

The ability of a chimpanzee (Pan troglodytes) to recognize photographs of conspecifics was evaluated with heart-rate measures. Heart rate was recorded before, during, and after viewing photographs of an aggressive chimpanzee, a friendly companion animal, and an unfamiliar chimpanzee. The subject displayed a differential pattern of heart-rate response to the stimulus animals, without prior experience with the photographs. Responses to the aggressive animal were acceleratory, which suggests a defensive response. Respiratory sinus arrhythmia suggested that this response was associated with sympathetic activation. In contrast, responses to the familiar animal were minimal, whereas cardiac deceleration was observed in response to the strange chimp, which likely reflects an orienting response. Results suggest the chimpanzee is able to recognize photographs of individual conspecifics and that heart-rate change can reflect the nature of established social relationships between chimpanzees.     

A procedure for generating differential "sample" responding without different exteroceptive stimuli

Sidman (1994, 2000) suggested that responses as well as stimuli can join equivalence classes, a hypothesis difficult to test because differential responding typically requires different stimuli. The present experiments describe a procedure with pigeons that avoids this potential confounding effect. In Experiment 1, spacing two responses 3 s apart (a differential-reinforcement-of-low-rate [DRL] schedule) to a white stimulus on some trials produced food or the comparison stimuli in a matching task, whereas pecking 10 or more times with no temporal restrictions (a fixed-ratio [FR] schedule) produced the same effect on other trials. Completing the alternative (unscheduled) requirement terminated the white stimulus and repeated the trial. Following such errors, pigeons learned to switch to the alternative response pattern on the repeat trials. In addition, the correct response pattern functioned as a conditional cue for comparison choice. In Experiment 2, mixed DRL-FR training was preceded by two-sample/two-alternative matching-to-sample with DRL and FR sample-response requirements. In a subsequent transfer test in which the correct response pattern to white served as the sample, pigeons preferentially chose the comparison previously reinforced following that pattern in the baseline task. This "unsignaled response" procedure may be useful for assessing whether differential responses can be members of acquired equivalence classes.     

Chimpanzee (Pan troglodytes) relational matching: playing by their own (analogical) rules

Chimpanzees (Pan troglodytes) have been known to exhibit rudimentary abilities in analogical reasoning (Flemming, Beran, Thompson, Kleider, & Washburn, 2008; Gillian, Premack, & Woodruff, 1981; Haun & Call, 2009; Thompson & Oden, 2000; Thompson, Oden, & Boysen, 1997). With a wide array of individual differences, little can be concluded about the species' capacity for analogies, much less their strategies employed for solving such problems. In this study, we examined analogical strategies in 3 chimpanzees using a 3-dimensional search task (e.g., Kennedy & Fragaszy, 2008). Food items were hidden under 1 of 2 or 3 plastic cups of varying sizes. Subsequently, chimpanzees searched for food under the cup of the same relative size in their own set of cups--reasoning by analogy. Two chimpanzees initially appeared to fail the first relational phase of the task. Meta-analyses revealed, however, that they were instead using a secondary strategy not rewarded by the contingencies of the task--choosing on the basis of the same relative position in the sample. Although this was not the intended strategy of the task, it was nonetheless analogical. In subsequent phases of the task, chimpanzees eventually learned to shift their analogical reasoning strategy to match the reward contingencies of the task and successfully choose on the basis of relative size. This evidence not only provides support for the analogical ape hypothesis (Thompson & Oden, 2000), but also exemplifies how foundational conceptually mediated analogical behavior may be for the chimpanzee.     

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     

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.     

Choice Between Two Discrimination Tasks in Chimpanzees (Pan troglodytes)

The purpose of the present study was to investigate the effects of cognitive effort on a chimpanzee's choice between discrimination tasks. The tasks were of the matching-to-sample type. In Experiment 1, the chimpanzee was required to choose between a task providing a high reinforcement rate with high cognitive effort and a task providing a low reinforcement rate with low cognitive effort. Her choice depended on the reinforcement rate more than the cognitive effort. Experiments 2, 3, and 4 examined whether the kind of cognitive effort influenced the chimpanzee's choice. Experiment 2 manipulated the sample-choice relationship, so-called symmetry in the matching-to-sample tasks. Experiment 3 manipulated the number of comparison stimuli. Experiment 4 manipulated the delay interval between the sample and the comparison stimuli. In Experiments 2 and 3, the effects of the cognitive effort were confounded with those of the reinforcement rates. However, in one condition of Experiment 4, the chimpanzee preferred the simultaneous task to the delayed task, despite the lack of a significant difference in reinforcement rates between the two tasks. The present study demonstrated that the chimpanzee's choice of discrimination task depended on the cognitive effort involved, in addition to the reinforcement rate.     

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.     

A COMPARATIVE STUDY OF INSTRUMENTAL LEARNING BY PRESCHOOL CHILDREN IN PAPUA NEW GUINEA AND AUSTRALIA1

Instrumental learning of preschool children in Papua New Guinea (PNG) and Australia (AUST) was compared using two tasks (imitative and nonimitative) and two rewards (social and nonsocial). There were no differences between the two groups in the rate of acquisition measure of trials to criterion. PNG children made more late responses during acquisition and, for nil responses, there were group x task and group x reward x task effects. In the extinction phase, there were two main effects for trials to criterion: PNG children were more resistant to extinction than AUST children, and there was greater persistence in responding after social reward regardless of nationality. Reward x group, reward x task, and reward x group x task interactions also were observed in the extinction trials to criterion. In addition, there were three main task effects during extinction for other responses: on the imitative task, more wrong responses were made, and on the nonimitative task, more extra responses and more paired responses were made. A subsidiary analysis compared the two culturally different but educationally similar groups comprising the PNG sample: no major differences were isolated in acquisition or extinction.     

Hemispheric differences in semantic processing: Category matching is not the same as category membership

Two closely related semantic processing tasks were studied under identical procedural conditions in order to examine lateral visual field effects on reaction times. In Experiment 1, reaction times did not differ as a function of visual field when subjects decided whether a lateral word was a member of a foveally presented category word (category membership task). On the other hand, reaction times were faster for right than for left visual field stimulus presentations when subjects decided whether two words, one lateral and one foveal, belonged to the same category (category matching task), although this advantage did not occur immediately. In Experiment 2, the laterality effect in the category matching task was studied as a function of word familiarity. Two groups of subjects performed the matching task for two blocks of trials, one group receiving the same word list in each block and the other receiving different lists. No visual field differences in reaction times were observed for either group during the first block of trials, but a distinct right field advantage appeared for both during the second block. The data from these experiments suggest that category matching strategies rely upon structures or processes localized in the left hemisphere, although their influence is not immediate. Category membership strategies, on the other hand, do not depend upon such localized structures.     

Establishing Functional Classes In A Chimpanzee (Pan troglodytes) With A Two-item Sequential-Responding Procedure

A 9-year-old female chimpanzee was trained on a two-item sequential-responding task. Attempts were made with successive-reversal training to establish functional classes. In Experiment 1, the subject was exposed to between-session successive-reversal training in which one of two pairs of stimuli was reversed, and transfer of reversal responding to the other pair was tested with nonreinforcement probe trials. She did not show transfer during the course of reversals. Stimulus control established in the original training was maintained on nonreinforcement probe trials. In Experiment 2, within-session reversals were introduced. She showed transfer from the initially reversed pair to the other. The results were consistent with Vaughan's (1988) results with pigeons on successive discriminations, which indicated the formation of functional classes. In Experiment 3, crossover and wild-card tests were conducted to clarify the stimulus control of sequential responding. The results suggested that the sequential responding was controlled only by the first stimulus of each pair. To establish control by both first and second stimuli, trial-unique stimuli or wild cards were substituted for one of the items of the lists in Experiment 4. Further transfer tests, in which stimuli for the two new pairs appeared, were also given to the subject. She successfully responded to these two merged lists and reversed the order as the result of reversal training.     

线索聚焦性影响前瞻记忆意向维持与提取：来自眼动追踪的证据

研究以眼动追踪的方法探讨线索聚焦性对前瞻记忆(prospective memory, PM）加工过程的影响。实验1中,28名被试完成了线索聚焦和非聚焦两类PM眼动追踪任务。结果发现,个体在聚焦和非聚焦两类PM任务意向维持、意向提取阶段上均表现出不同的眼动加工特征。实验2中,研究进一步对线索聚焦和非聚焦两个PM任务中PM线索词重复次数进行平衡,并重复了实验1的研究结果,说明实验1所观测到的效应不是PM线索词重复造成的混淆,线索聚焦性影响PM的意向维持、意向提取过程,研究结果支持多重加工理论。     

Enhanced recognition of emotional stimuli in the chimpanzee (<Emphasis Type="Italic">Pan troglodytes</Emphasis>)

Humans often have a better memory of emotional events than neutral events. From the comparative-cognitive perspective, we explored the enhancement of recognition memory by emotion in chimpanzees (Pan troglodytes) using a serial probe recognition task. In this task, we sequentially presented a list of pictures to subjects and then tested their recognition of specific pictures from within the list. We selected pictures of aggressive chimpanzees as emotional stimuli and less tensed, relaxed chimpanzees as neutral stimuli. In Experiment 1, we gave four-item lists to two young chimpanzees; one showed significantly greater recognition of pictures depicting aggressive chimpanzees than neutral ones. In Experiment 2, this chimpanzee was further tested using a recognition task with eight-item lists. The subject again showed better recognition of emotional stimuli than neutral. Furthermore, the presence of an emotional stimulus in the list also facilitated recognition of the neutral item immediately following it. Overall, although only one of the two chimpanzees showed enhanced recognition memory by emotional stimuli, this is the first demonstration of such a response in the chimpanzee. The findings are discussed in comparison with those of human studies.     

预知任务转换的内源性准备和外源性调节

采用ERP探究在预知条件下任务转换的神经机制。使用“任务转换”实验范式,以汉字（名词/动词）或数字（奇数/偶数）的归类为任务。被试执行任务重复（AA,BB,…）或在两个任务间转换（AB,BA,…）,每个任务序列为连续的两个任务（任务1,任务2）。结果发现,任务1中,在刺激呈现后300ms左右,数、词的转换序列与重复序列出现显著差异;在中央区,320ms左右,任务1中转换序列比重复序列、任务2中转换任务比重复任务都产生一个更为负走向的波。这些结果表明,在预知条件下,简单任务转换的内源性准备可能开始于任务1呈现后300ms左右;内源性准备和外源性调节可能都反映了认知冲突过程,此认知冲突可能是转换代价的主要来源     

Training domestic dogs (Canis lupus familiaris) on a novel discrete trials odor-detection task

Dogs can be trained to reliably detect a wide variety of odors. Little scientific research, however, has been published on the rate at which dogs can learn to detect an odor, the variables influencing this rate, and how this rate may vary across dogs. In two experiments, we developed a procedure that allows the study of individual differences in the acquisition of an odor detection task in dogs. We demonstrate that differential reinforcement can be used to train a rooting response in a bin under the control of a novel odorant in discrete trials. In initial testing, we showed that as a group, twenty dogs performed significantly above chance within 24 trials, with two dogs meeting an individual criterion for above chance performance. In a follow-up experiment, we compared burying accessible food inside the target bin (with inaccessible food in the non-target bin) to the experimenter delivering food by hand following correct responses. We assessed the effect of this procedural variation on both an odor discrimination and a visual discrimination. Dogs learned faster on the odor task when the experimenter delivered food, compared to when food was placed directly in the bins. Performance on the visual task was lower than on the odor task and was unaffected by how food was delivered. Our discrete-trials procedure with experimenter-delivered food may be a useful method to study rapid acquisition of an odor-detection in dogs.     

Distinct neural correlates for two types of inhibition in bilinguals: response inhibition versus interference suppression

To examine the effects of bilingualism on cognitive control, we studied monolingual and bilingual young adults performing a flanker task with functional MRI. The trial types of primary interest for this report were incongruent and no-go trials, representing interference suppression and response inhibition, respectively. Response times were similar between groups. Brain data were analyzed using partial least squares (PLS) to identify brain regions where activity covaried across conditions. Monolinguals and bilinguals activated different sets of brain regions for congruent and incongruent trials, but showed activation in the same regions for no-go trials. During the incongruent trials, monolinguals activated the left temporal pole and left superior parietal regions. In contrast, an extensive network including bilateral frontal, temporal and subcortical regions was active in bilinguals during the incongruent trials and in both groups for the no-go trials. Correlations between brain activity and reaction time difference relative to neutral trials revealed that monolinguals and bilinguals showed increased activation in different brain regions to achieve less interference from incongruent flankers. Results indicate that bilingualism selectively affects neural correlates for suppressing interference, but not response inhibition. Moreover, the neural correlates associated with more efficient suppression of interference were different in bilinguals than in monolinguals, suggesting a bilingual-specific network for cognitive control.     

Effects of response selection on the task repetition benefit in task switching

A task switch typically leads to worse performance than a repetition does. This shift cost can be reduced with sufficient task preparation time, but a residual cost usually remains. We propose that a large part of this residual cost is caused by an activation bias produced by response selection processes in the preceding trial. In our experiments, we manipulated response selection requirements using a go/no-go methodology. The residual shift cost disappeared after no-go trials, suggesting that response selection is crucial to establish an activation bias for the current category-response rules and that this bias persists into the next trial. A comparison with a go-only group confirmed this analysis by revealing no differences in preparatory strategy due to the inclusion of no-go trials. In addition, no-go trials had no significant effects on subsequent trials in a single-task experiment, suggesting that no-go trials are not coded as a task different from go trials and that there is no inhibition of the prepared task in a no-go trial. We thus conclude that a persisting activation bias of response rules plays a major role in task switching.     

Metamemory in tufted capuchin monkeys (Cebus apella)

Whereas evidence for metacognition by nonhuman primates has been obtained in great apes and old world monkeys, it is weaker in new world monkeys. For instance, capuchin monkeys may fail to recognize their own knowledge of the location of invisible bait. In the present study, we tested whether tufted capuchin monkeys would flexibly change their behavior in a delayed matching-to-sample (DMTS) test depending upon the strength of their memory trace of the sample. In Experiment 1, two monkeys were tested on a modified 9-alternative DMTS task with various delays on a computerized display. In some trials, the monkeys could choose whether to go for a memory test or for a simple key touch as an escape from the test. In other trials, they were forced to go for the memory test. Both monkeys escaped from the memory test more often when their matching accuracy on forced tests was lower. In one of the monkeys, the matching accuracies on chosen memory tests decreased more slowly as a function of delay length, and were higher after long delays than those on forced memory tests. This suggests that at least one capuchin monkey was able to recognize the strength of his own memory trace. Experiment 2 employed occasional no-sample tests, in which the monkeys faced the task choice without presentation of any sample for the trial. The monkey who was successful in Experiment 1 declined the memory test more often in no-sample trials than regular trials, further indicating metamemory in this individual. In Experiment 3, this successful monkey received a task, in which he was sometimes able to choose between shape MTS or texture MTS tasks. However, his matching accuracies did not differ between chosen tasks and forced tasks. Thus, the metamemory possessed by this new world monkey species may be more like a flag, showing strength of memory trace, than an elaborate representation showing details of the memory trace.