The repeatability of cognitive performance: a meta-analysis

Behavioural and cognitive processes play important roles in mediating an individual's interactions with its environment. Yet, while there is a vast literature on repeatable individual differences in behaviour, relatively little is known about the repeatability of cognitive performance. To further our understanding of the evolution of cognition, we gathered 44 studies on individual performance of 25 species across six animal classes and used meta-analysis to assess whether cognitive performance is repeatable. We compared repeatability (R) in performance (1) on the same task presented at different times (temporal repeatability), and (2) on different tasks that measured the same putative cognitive ability (contextual repeatability). We also addressed whether R estimates were influenced by seven extrinsic factors (moderators): type of cognitive performance measurement, type of cognitive task, delay between tests, origin of the subjects, experimental context, taxonomic class and publication status. We found support for both temporal and contextual repeatability of cognitive performance, with mean R estimates ranging between 0.15 and 0.28. Repeatability estimates were mostly influenced by the type of cognitive performance measures and publication status. Our findings highlight the widespread occurrence of consistent inter-individual variation in cognition across a range of taxa which, like behaviour, may be associated with fitness outcomes.This article is part of the theme issue 'Causes and consequences of individual differences in cognitive abilities'.

Other better versus self better in baboons: an evolutionary approach of social comparison

Comparing oneself with others is an important characteristic of human social life, but the link between human and non-human forms of social comparison remains largely unknown. The present study used a computerized task presented in a social context to explore psychological mechanisms supporting social comparison in baboons and compare major findings with those usually observed in humans. We found that the effects of social comparison on subject's performance were guided both by similarity (same versus different sex) and by task complexity. Comparing oneself with a better-off other (upward comparison) increased performance when the other was similar rather than dissimilar, and a reverse effect was obtained when the self was better (downward comparison). Furthermore, when the other was similar, upward comparison led to a better performance than downward comparison. Interestingly, the beneficial effect of upward comparison on baboons' performance was only observed during simple task. Our results support the hypothesis of shared social comparison mechanisms in human and non-human primates.

Processing of above/below categorical spatial relations by baboons (Papiopapio)

Three video-formatted experiments investigated the categorization of 'above' and 'below' spatial relations in baboons (Papio papio). Using an identity matching-to-sample task, six baboons correctly matched line-dot stimuli based on the 'above' or 'below' location of the dot relative to the line (Experiment 1). Positive transfer of performance was then observed when the line-dot distance depicted in the sample stimulus differed from that of the two comparison stimuli (Experiment 2). Using a go/nogo procedure, two baboons were further trained to discriminate whether a 'B' character was displayed 'above' or 'below' a '3' character (Experiment 3). After training, a positive transfer of performance was observed with the same type of stimuli depicted in different type fonts. Altogether, these results suggest that baboons may form conceptual representations of 'above' and 'below' spatial relations, and categorize visual forms on that basis.

Hemispheric lateralisation and global precedence effects in the processing of visual stimuli by humans and baboons (Papio papio)

This paper examines the effect of global precedence (GPE: Navon, 1977) and its lateralisation from a comparative perspective. Using a divided field matching-to-sample task with compound stimuli, Experiment 1 demonstrated consistent patterns of lateralisation in humans and baboons, corresponding to a right-hemisphere advantage for global processing and a left- but nonsignificant advantage for local processing. Species differences emerged in terms of GPE; humans showed a global precedence effect, and baboons were better for local than for global matching. In Experiment 2, a visual search task was used to assess the origin of species differences in terms of GPE. Humans processed the global structure of the forms pre-attentively, whereas baboons used an attentional search strategy. From this finding, it is argued that lateralisation in Experiment 1 was rooted in early perceptual mechanisms. So far, consistent patterns of lateralisation for global/local processing have been found in baboons, chimpanzees, and humans, suggesting that this phenomenon has a long evolutionary history.

Discriminating the relation between relations: the role of entropy in abstract conceptualization by baboons (Papio papio) and humans (Homo sapiens)

Two baboons (Papio papio) successfully learned relational matching-to-sample: They picked the choice display that involved the same relation among 16 pictures (same or different) as the sample display, although the sample display shared no pictures with the choice displays. The baboons generalized relational matching behavior to sample displays created from novel pictures. Further experiments varying the number of sample pictures and the mixture of same and different sample pictures suggested that entropy plays a key role in the baboons' conceptual behavior. Two humans (Homo sapiens) were similarly trained and tested; their behavior was both similar to and different from the baboons' behavior. The results suggest that animals other than humans and chimpanzees can discriminate the relation between relations. They further suggest that entropy detection may underlie same-different conceptualization, but that additional processes may participate in human conceptualization.

Cross-modal integration and conceptual categorization in baboons

This study investigates concept formation and cross-modal integration in baboons. Response times were recorded in a categorical task involving discrimination between human and baboon vocalizations. We show that a brief presentation of human or baboon prime pictures conceptually related to the target sound shortened response speed of one baboon. Cross-modal priming effects were replicated with degraded pictures, and were also found in a sample of humans. Cross-modal priming demonstrates that this baboon had formed amodal abstract concepts of the human and baboon categories.

Perception of partly occluded figures by baboons (Papio papio)

Comparative literature provides conflicting findings whether animals experience amodal completion. Five experiments were conducted to verify if baboons perceive partly occluded objects as complete. The first three experiments used a go/no-go procedure and a video monitor for stimulus presentation. These experiments failed to reveal amodal completion, suggesting that the stimuli were processed as 2-D images rather than 3-D objects. In contrast, completion was demonstrated in a fourth experiment with cardboard stimuli in a two-alternative forced-choice (2AFC) discrimination task presented in a Wisconsin General Test Apparatus. Although in experiment 5 the same 2AFC procedure was used as in experiment 4, completion was absent when the stimuli were shown with a computer graphic system. The results suggest that baboons share with humans the ability for amodal completion, but also underline some procedural factors that might affect the elicitation of this capacity.

Same-different conceptualization by baboons (Papio papio): the role of entropy

The authors trained 6 baboons (Papio papio) to make 1 of 2 report responses to 16-icon same arrays versus 16-icon different arrays. In the same arrays, the icons were all the same as one another, whereas in the different arrays the icons were all different from one another. In Experiment 1, the baboons discriminated the same arrays from the different arrays, and they transferred their discriminative responding to arrays of novel icons. In Experiments 2 and 3, the baboons exhibited strong sensitivity to the degree of display variability when they were shown mixed arrays that comprised some same and some different items. The information theoretic measure "entropy" systematically described these results and outperformed several rival metrics. Finally, in Experiments 4 and 5, the baboons' responses to displays that contained jittered and blurred icons suggested that their same-different conceptual behavior was not based on the spatial orderliness of the visual arrays.

Comparative assessment of distance processing and hemispheric specialization in humans and baboons (Papio papio)

This comparative study explored the ability to process distance and its lateralization in humans and baboons. Using a conditional matching-to-sample procedure in a divided-field format, subjects had to decide whether or not the distance between a line and a dot belonged to a short- or a long-distance category. Experiments 1, 2, and 4 demonstrated the ability of baboons to process and categorize distances. Moreover, humans showed better distance processing for right visual field/left hemisphere presentations than for left visual field/right hemisphere (LVF-RH) displays (Experiments 1-2). The same bias was found in baboons (Experiment 1), but in a weaker way. In Experiment 3, naive human individuals were tested and the difficulty of the discrimination was enhanced. There was a LVF-RH advantage which vanished with practice. Results are discussed by referring to theories (i.e., Kosslyn, 1987) of visuospatial processing for coordinate and categorical judgments.

Processing of global and local visual information and hemispheric specialization in humans (Homo sapiens) and baboons (Papio papio)

Global precedence was examined in 8 baboons and 14 humans using compound stimuli presented in the left visual hemifield (LVF) or the right visual hemifield (RVF). Humans showed a global advantage and global-to-local interference. Baboons showed a local advantage and no interference. For humans and baboons, a LVF advantage appeared for global matching and an unsignificant RVF advantage appeared for local matching. The local advantage in baboons still emerged when the memory load of the task was removed and when the local elements were connected by lines or were adjacent. Moreover, global precedence in humans persisted with unfamiliar forms. Species differences suggest that global precedence is not a universal trait and that this effect in humans does not have a purely perceptual or sensory basis.

Processing of global and local visual information and hemispheric specialization in humans (Homo sapiens) and baboons (Papio papio)

Global precedence was examined in 8 baboons and 14 humans using compound stimuli presented in the left visual hemifield (LVF) or the right visual hemifield (RVF). Humans showed a global advantage and global-to-local interference. Baboons showed a local advantage and no interference. For humans and baboons, a LVF advantage appeared for global matching and an unsignificant RVF advantage appeared for local matching. The local advantage in baboons still emerged when the memory load of the task was removed and when the local elements were connected by lines or were adjacent. Moreover, global precedence in humans persisted with unfamiliar forms. Species differences suggest that global precedence is not a universal trait and that this effect in humans does not have a purely perceptual or sensory basis.

Hand-movement profiles in a tactual-tactual matching task: effects of spatial factors and laterality

We examined the effect of spatial factors and hemispheric lateralization upon hand-scanning strategies in 14 right-handed men tested in a tactual-tactual matching task. The experiment involved comparisons (judgments of same or different) between two objects sequentially touched by the fingertips of the left or right hand. Stimuli were made of smoothly joined cubes whose junctions were not haptically discernible. Exploratory strategies were inferred from the durations and locations of hand contacts with any of the cubes composing the stimuli. Accuracy was greater when the same stimulus was touched twice by the same hand than when different hands were used to feel it. With regard to strategies, both hands touched the upper parts of the object longer than the lower parts. Subjects also inspected more portions of the objects ipsilateral to the hand used. Overall differences in time spent touching cubes were greater for the right hand than for the left hand, showing that touch times were less evenly distributed on object parts for the former than for the latter. In this study, the process of information gathering by touch appears to be determined by the intertwining integration of contextual factors (e.g., stimulus position in space), biomechanical constraints on hand movements, and such cognitive factors as hemispheric differences on the ability to encode spatial pattern information.

Eye movements in baboons performing a matching-to-sample task presented in a divided-field format

We examined eye saccades in a baboon solving a video-formatted matching-to-sample (MTS) task. In that task, the animal had to place a cursor by way of joystick manipulation within the boundaries of a fixation point (FP) displayed on a monitor. A sample stimulus was then flashed in either the left or right of FP. Immediately thereafter, two comparison forms were displayed and the animal had to select the comparison form matching the sample. A new video technique requiring no specific head or body constraints was employed to monitor eye movements. Expt. 1 indicated that the gaze was centered on FP during the fixation procedure. However, some goal-directed express saccades, with mean latencies of 100 ms, were observed during sample presentation. Expt. 2 used an overlap procedure in which FP remained visible during sample presentation. Latencies of express saccades increased by approximatively 20 ms. Expt. 3 showed in four baboons that the overlap procedure did not affect scores. It is concluded that the computerized MTS task is a valuable tool for the assessment of hemispheric lateralization in visual processing in intact primates, as long as the sample is not displayed longer than 120 ms.

Video-task assessment of stimulus novelty effects on hemispheric lateralization in baboons (Papio papio)

In a video matching-to-sample task, we examined the effects of stimulus novelty on hemispheric specialization in 6 baboons (Papio papio). After familiarization with a set of 8 composite stimuli, baboons were tested with either familiar stimuli paired in a novel way, novel stimuli composed of familiar elements, or novel stimuli differing in structure from the previous stimuli. Analyses focused on visual field differences between initial and later trials in each condition. The findings reflected shorter left than right visual half-field response times for initial but not for terminal trials. With regard to accuracy, scores were smaller for the initial trials than for the later ones, but there was no significant difference between left and right visual half-fields. Overall, this study suggests that hemispheric lateralization changes with practice and that the right hemisphere of the baboon plays a critical role in the processing of novelty.

Hand movements and hemispheric specialization in dichhaptic explorations

Dichhaptic testing has been widely used to assess lateralization in tactile processing. The rationale of dichhaptic testing is that simultaneous exploration of two objects enhances competition between relevant cortical areas in the right and left hemispheres. The synchronization of hand movements in a dichhaptic situation was investigated to determine whether both hands explore the two shapes simultaneously. Fourteen men were tested with the aid of a dichhaptic intermodal task. Tactile stimuli were composite shapes and the activity of each hand was assessed through analysis of hand contacts on each part of the shape. Only 20% of the total exploration time was devoted to simultaneous investigation of the two shapes. In addition, it was found that (i) the recognition accuracy was greater when the target shape was explored by the left hand compared with the right, and (ii) the left hand touched a greater number of parts of the stimuli than the right. Overall, comparison of the present data with those from a previous, monohaptic, task with the same stimuli suggests an advantage of dichhaptic over monohaptic testing to demonstrate laterality differences in accuracy of recognition. However, it is suggested that this advantage is due to cognitive factors rather than to competition between homologous cortical areas.

Mirror-image matching and mental rotation problem solving by baboons (Papio papio): unilateral input enhances performance

Three experiments, using a matching-to-sample procedure, were conducted to examine hemispheric specialization in mirror-image discrimination and mental rotation in baboons (Papio papio). In Experiment 1, no significant difference was found in discrimination of mirror-image and asymmetric pattern stimuli. In Experiment 2, orientation discrimination was assessed within the left (LVF) and right (RVF) visual half-fields. An RVF advantage was found in accuracy for asymmetric patterns, whereas an LVF advantage was found for discrimination of mirror-image stimuli. No significant relation was found between angular disparity of the stimuli and response time. Experiment 3 examined the effect of bilateral visual input on accuracy and response time. Significantly lower accuracy and longer response times were found for bilateral compared with unilateral visual input.

Laterality in cats: paw preference and performance in a visuomotor activity

Laterality in paw use was investigated over a period of 6 years in 44 domestic cats trained to perform a reaching movement toward a moving spot of light. Both paw preference and paw performance were recorded. At a 50 percent criterion, no significant paw preference was found at the level of the group. When a 90 percent criterion was considered, 23 subjects had a significant preference for one paw. Among these strongly lateralized animals, there were more left- (N = 17) than right-pawed (N = 6) cats. The analysis of visuo-motor performances included reaction time, movement time, and reaching accuracy. Lateralized cats had a faster reaction time than nonlateralized cats. The more-used paw had a shorter reaction time, a shorter movement time, and was also more accurate than the less-used paw. Thus, the findings demonstrate a functional advantage of being lateralized. Moreover, the results confirm the existence of an asymmetry of paw preference in cats and show a consistent relation between paw preference and performance.

Haptic discrimination of nonsense shapes: hand exploratory strategies but not accuracy reveal laterality effects

Studies on haptic processing show inconsistent results concerning sex and hand differences. We present a novel approach in which manual exploratory strategies were examined. Twenty-four right-handed adults of both sexes had to monohaptically explore unseen meaningless stimuli and then to recognize their visually presented outline drawings among drawings of different stimuli. Tactual stimuli were composed of eight smoothly joined cubes whose junctions were not haptically discernible. The computer recorded number and duration of hand contacts on each cube. Analyses included the accuracy of the recognition phase, the number and duration of exhaustive explorations of the stimulus, and the number of cubes simultaneously touched. Neither hand nor sex differences were found for the accuracy measurement. The number and duration of exhaustive explorations also provide no evidence of hand differences. However, the left hand touched simultaneously more cubes than the right and this asymmetry was more pronounced in males than in females. Such an asymmetry was apparent in the very first contact of the hand with the shape. It is suggested that exploratory strategies may be more sensitive measures in revealing hand lateralization than the accuracy measurement.

Mirror-image matching and mental rotation problem solving by baboons (Papio papio): unilateral input enhances performance

Three experiments, using a matching-to-sample procedure, were conducted to examine hemispheric specialization in mirror-image discrimination and mental rotation in baboons (Papio papio). In Experiment 1, no significant difference was found in discrimination of mirror-image and asymmetric pattern stimuli. In Experiment 2, orientation discrimination was assessed within the left (LVF) and right (RVF) visual half-fields. An RVF advantage was found in accuracy for asymmetric patterns, whereas an LVF advantage was found for discrimination of mirror-image stimuli. No significant relation was found between angular disparity of the stimuli and response time. Experiment 3 examined the effect of bilateral visual input on accuracy and response time. Significantly lower accuracy and longer response times were found for bilateral compared with unilateral visual input.

Manual and hemispheric specialization in the manipulation of a joystick by baboons (Papio papio)

Manual performance asymmetries were examined in 8 baboons (Papio papio). Using a joystick, monkeys had to track and hit with a cursor a randomly moving target on a monitor. The left or right hand was tested first, depending on group assignment, followed by a transfer to the other hand. A transfer effect is reported for the total number of trials to criterion and total number of successful trials. No effect was found for response time. However, for both test and transfer, the group initially tested with the left hand exhibited more controlled movements as demonstrated by shorter cursor's paths. Overall, it appears that the spatial components of the task are more sensitive to laterality effects than response times or learning scores.

Asymmetrical hand use in rhesus monkeys (Macaca mulatta) in tactually and visually regulated tasks

Asymmetrical hand use by rhesus monkeys (Macaca mulatta) was investigated in a series of tactually and visually guided tasks. The 1st experiment recorded manual preferences of 29 monkeys for solving a haptic discrimination task in a hanging posture. There was a left-hand population bias: 21 monkeys had a left-hand bias, 4 a right-hand bias, and 4 no bias. The 2nd experiment, 4 tasks with 23 to 51 monkeys, investigated the critical components of the 1st experiment by varying the posture (hanging, sitting, or tripedal) and the sensory requirements (tactile or visual). Posture influenced hand bias, with a population-level left-hand bias in hanging and sitting postures, but an almost symmetrical distribution in the tripedal posture. A left-hand bias was found for both sensory modalities, but the bias was stronger in the tactual tasks. Results suggest a possible right-hemisphere specialization in the rhesus for tactile, visual, or spatial processing.

Manual laterality in nonhuman primates: a distinction between handedness and manual specialization

This article examines individual and group manual lateralization in nonhuman primates as a function of task's demands. It is suggested to distinguish low- from high-level manual activities with respect to the novelty variable and to the spatiotemporal scale of the movements. This review shows that low-level tasks lead to (a) symmetrical distributions of hand biases for the group and (b) manual preferences that are not indicative of the specialization of the contralateral hemisphere. In contrast, behaviors expressed in high-level tasks (a) show asymmetrical distribution of hand biases for the group and (b) seem to be related to a specialization of the contralateral hemisphere. Two types of lateralization, handedness and manual specialization, correspond to the 2 levels of tasks that are distinguished.

Handedness and bimanual coordination in the lowland gorilla

One could hypothesize from previous studies that gorillas, as a group, might show a right-hand preference, making this species an exception among nonhuman primates. A study of 10 captive gorillas observed while reaching for food and tested on unimanual and bimanual tasks does not support this conclusion. Instead, the present study found (a) a symmetrical distribution of subjects with right-hand (n = 3), left-hand (n = 3), and no hand preference (n = 4) when simply reaching for food and (b) a left-hand preference by 7 of 8 gorillas tested on a spatial task requiring precise alignment of two openings. These results stress the importance of considering the kind of task employed in the assessment of lateral preferences. Furthermore, it is suggested that it might be useful to distinguish between the handedness of a gorilla when simply reaching and its manual specialization for novel and complex tasks.

Handedness and manual specialization in the baboon

Manual preferences of six baboons were tested with three kinds of experimental tasks: (1) a simple reaching on a board or in a hole; (2) a box opening; (3) two visuo-spatial tasks requiring precise alignments of apertures. The distribution of right and left hand preferences was found to be symmetrical for the simple reachings (3 right- and 3 left-handers) and was consistent with the preferences in the box opening task. However, manual tasks with strong visuo-spatial components gave a unimodal distribution with a left hand preference for the group for aligning and adjusting the apertures. These results suggest the coexistence within an individual of two types of preferences according to the distinction between handedness and manual specialization.

Spontaneous hand usage and handedness in a troop of baboons

Hand usage was studied in a troop of 18 Guinea baboons (10 adults and 8 young) for spontaneous activities. Handedness was determined by an analysis of unimanual activities and bimanual asymmetric activities. The distribution of preferential biases gave 5 right-handers and 2 left-handers, other subjects being ambidextrous. Main effects were age related: the strength of the preference was greater for adults than for young; moreover, bimanual activities performed by the adult group were more asymmetric than those realized by the subgroup of young. Laterality thus appears to develop during ontogeny in baboons.