Do chimpanzees seek explanations? Preliminary comparative investigations

Canadian Journal of Experimental Psychology, Jun 2001 by Daniel J Povinelli, Sarah Dunphy-Lelii

The most important results concern the children's bouts of visual and/or tactile inspection of the bottom of the sham block. Sixty-one percent (11/18) of the children engaged in at least one visual inspection of the bottom of the sham block, 50% (9/18 children) engaged in at least one tactile inspection, 50% engaged in both, and 61% engaged in at least one tactile or visual inspection.

Finally, coding of the children's verbal responses indicated that 89% (14/18) described the ongoing state of affairs (e.g., "This one keeps falling"), 22% used mentalistic terminology to describe the block, 11% (2/18) asked "Why?" at some point during the trial, and 11% offered a specific physical cause for why the block would not stand up.

DISCUSSION

Again, there were both similarities and differences in the manner in which the apes and the 5-year-old children manipulated the sham blocks. Both the children and the apes spent most of the time available attempting to stand up the sham block, and made a number of attempts to switch the sham block to the other location. This would seem to reflect a motivation in both species to pursue the task to its completion. However, whereas 61% of the children engaged in at least one form of inspection of the bottom of the sham block, and 50% engaged in both visual and tactile inspections, there were no instances in which the apes performed either - nor were there any instances in which the apes unambiguously inspected the blocks by some other means (e.g., orally). Thus, when there were no detectable perceptual differences between the sham blocks and the functional blocks, only the children inspected the sham blocks. One obvious limitation of this research is that the same chimpanzees were used in both experiments, whereas different children were used. However, it should be noted that (a) four months elapsed between Experiment 1 and 2, and (b) the chimpanzees' interest in attempting to stand the sham blocks was not negatively affected; indeed, if anything, they displayed greater motivation in Experiment 2 than in Experiment 1 (see Figure 2).

GENERAL DISCUSSION

The results of these preliminary experiments point to an important potential difference in the way in which humans and chimpanzees think about and explore the world. Our data suggest (in a preliminary manner) that although chimpanzees are motivated to explore even small, perceptually novel features of objects when their attention is drawn to them (see Experiment 1), this may not reflect a drive for explanation as much as a drive for general object exploration (perhaps by already wellunderstood mechanisms related to the orientation to perceptual novelty; e.g., Pavlov, 1927; Sokolov, 1963). In contrast, they may not exhibit such explorations in situations where an explanation is clearly warranted (from a human perspective), but no perceptual novelty is present.

In contrast, humans may develop a kind of explanatory drive (see Gopnik, 2000) that has evolved in parallel to more ancient psychological systems that support object exploration and manipulation (see Povinelli, 2000). Thus, although many species (especially chimpanzees and certain other nonhuman primates) may display robust evidence of an intrinsic interest in the functional and perceptual properties of the objects they encounter, it may be that our species alone develops an intrinsic interest in why objects have the properties that are apparent to the primary senses. Indeed, we have previously proposed that precisely such a human psychological specialization - although subtle in its overt manifestation in spontaneous behaviour - could account for what may turn out to be fairly profound differences in how humans and other primates understand both the social and the physical world (Povinelli, 2000).