International audienceFagot 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

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Reversal performance in the transfer index (TI) task is known to improve from prosimians to apes, suggesting that this task is a marker of cognitive evolution within the primate taxa (Rumbaugh, 1970). However, the cognitive processes recruited by this task remain unclear. In the present study, 19 socially-housed baboons (Papio papio) from 1.6 to 14.3 years of age were tested on a computerized version of the TI task, using an automated self-testing procedure. Age was a significant factor in the level of success, with the younger baboons outperforming the adults. The younger baboons learned the pre-reversal discrimination faster and improved their post-reversal performance more rapidly than adult baboons. As 17 of these baboons had already been tested in previous studies on inhibitory control and cognitive flexibility tasks, comparison across tasks provide indicators of the underlying cognitive processes. Age variations in performance were similar between the TI task and in an adaptation of the Wisconsin Card Sorting Task (WCST) measuring cognitive flexibility (Bonté et al., 2011). This contrasts previous results from a task requiring motor inhibitory control (Fagot et al., 2011). Therefore, these findings suggest that cognitive flexibility was a central component of the cognitive system that evolved within non-human primates. They also implicate a decline in executive control with age that begins during early adulthood in this baboon species.

A computerized visual search task was presented to 18 guinea baboons (Papio papio) ranging from 2.7 to 14.3 years of age. The task, inspired from Hick’s (1952) task, required detection of a target among a variable number of distractors equidistant to a start button. The reaction times (RTs) and movement times both increased with the number of distractors expressed in bits of information. However, the slope of RT per bit function correlated positively with age, whereas a negative correlation was found for the movement time slopes. In Experiment 2, the same baboons were required to inhibit an ongoing manual pointing toward a target stimulus, to reengage in a new point as a consequence of a change in target location. Results revealed a more accurate performance in the adults, suggesting that differences in behavioral strategies in Experiment 1 can be accounted for by a greater inhibitory control of the adult participants. Implications of these results are discussed regarding the relation between attention, inhibitory control, and behavioral strategies in monkeys, and the general significance of RT slopes in visual search tasks.