Joël Fagot

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 tasks 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.

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.

Orthographic Processing in Baboons (Papio papio)

Monkey See, Monkey Read An orthographic object such as a set of letters, and the ability to recognize such sets as words, is a key component of reading. The ability to develop these skills has often been attributed to the prior acquisition of a complex language. For example, we learn how letters sound and thus recognize when a particular letter makes up part of a word. However, orthographic processing is also a visual process, because we learn to recognize words as discrete objects, and the ability to read may thus be related to an ability to recognize and classify objects. Grainger et al. (p. 245; see the Perspective by Platt and Adams) tested orthographic skills in baboons. Captive, but freely ranging, baboons were trained to distinguish real English words from combinations of similar letters that are not words, and they were able to distinguish real words with remarkable accuracy. Thus, a basic ability to recognize words as objects does not require complex linguistic understanding. Baboons discriminate words from nonwords on the basis of spelling. Skilled readers use information about which letters are where in a word (orthographic information) in order to access the sounds and meanings of printed words. We asked whether efficient processing of orthographic information could be achieved in the absence of prior language knowledge. To do so, we trained baboons to discriminate English words from nonsense combinations of letters that resembled real words. The results revealed that the baboons were using orthographic information in order to efficiently discriminate words from letter strings that were not words. Our results demonstrate that basic orthographic processing skills can be acquired in the absence of preexisting linguistic representations.

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.

Automated testing of cognitive performance in monkeys: Use of a battery of computerized test systems by a troop of semi-free-ranging baboons (Papio papio)

Fagot and Paleressompoulle (2009) published an automated learning device for monkeys (ALDM) to test the cognitive functions of nonhuman primates within their social groups, but the efficiency of the ALDM procedure with large groups remains unknown. In the present study, 10 ALDM systems were provided ad lib to a troop of 26 semi-free-ranging baboons that were initially naive with computerized testing. The test program taught baboons to solve two-alternative forced choice (2AFC) and matching-to-sample (MTS) tasks. A million trials were recorded for the group during a period of 85 days (Experiment 1). Their analysis shows that 75% of the baboons participated at high frequencies and quickly learned the 2AFC and MTS tasks. In Experiment 2, we compared the baboons’ behavior when the ADLM systems were either accessible or closed. ALDM reduced frequencies of object-directed behaviors, but had no overt consequence on social conflicts. In Experiment 3, we tested the process of the global or local attributes of visual stimuli in MTS-trained baboons in order to illustrate the efficiency of ALDM for behavioral studies requiring complex experimental designs. Altogether, the results of the present study validate the use of ALDM to efficiently test monkeys in large social groups. ALDM has a strong potential for a variety of scientific disciplines, including for biomedical research. Supplemental materials for this article may be downloaded from http://brm.psychonomic-journals.org/content/supplemental.

Automatic testing of cognitive performance in baboons maintained in social groups.

Laboratory procedures used to study the cognitive functions of primates traditionally have involved removal of the subjects from their living quarters to be tested singly in a remote experimental room. This article presents an alternative research strategy favoring testing primates while they are maintained in their social group. The automatic learning device for monkeys (ALDM) is a computerized test system controlled by an automatic radio frequency identification of subjects. It is provided ad lib inside the social group of monkeys, for voluntary self-testing on a 24-h schedule. Nine baboons were tested with ALDM during a 7-month period. Experiments were performed to assess learning in motor control and abstract reasoning tasks. The results revealed high trial frequencies and excellent learning performance, even in tasks involving the highest cognitive complexities. A different study using ALDM with a group of 3 rhesus monkeys revealed social influences on learning. Beyond its interest for cognitive psychologists, ALDM is of interest for pharmacologists and cognitive neuroscientists working with nonhuman primates. ALDM also can serve as an enrichment tool for captive animals and may be used to study a variety of species other than primates.

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.

Rotation of Mental Images in Baboons When the Visual Input Is Directed to the Left Cerebral Hemisphere

The mental rotation phenomenon was examined in baboons and humans using a video-formatted mutching-to-sample task. Sample stimuli were presented either centrally or in the right or left visual half-field. Immediately afterward, subjects had to distinguish the previously presented sample stimulus from its mirror image after both had been rotated to the same angular deviation. A mental rotation phenomenon was found in baboons and humans, but in baboons this effect was limited to conditions in which visual input was directed to the right visual half-field. These data represent the first evidence of mental rotation in a nonhuman species.

Visual search for global/local stimulus features in humans and baboons

Fagot and Deruelle (1997) demonstrated that, when tested with identical visual stimuli, baboons exhibit an advantage in processing local features, whereas humans show the “global precedence” effect initially reported by Navon (1977). In the present experiments, we investigated the cause of this species difference. Humans and baboons performed a visual search task in which the target differed from the distractors at either the global or the local level. Humans responded more quickly to global than to local targets, whereas baboons did the opposite (Experiment 1). Human response times (RTs) were independent of display size, for both local and global processing. Baboon RTs increased linearly with display size, more so for global than for local processing. The search slope for baboons disappeared for continuous targets (Experiment 2). That effect was not due to variations in stimulus luminance (Experiment 3). Finally, variations in stimulus density affected global search slopes in baboons but not in humans (Experiment 4). Overall, results suggest that perceptual grouping operations involved during the processing of hierarchical stimuli are attention demanding for baboons, but not for humans.