Tuesday, November 21, 2006

An inherited primate baseline for spatial cognition.

Haun et al report some interesting experiments that suggest that human infants inherit many of the same cognitive preferences and biases as our primate cousins but then go on to build cognitive structures that may diverge in various ways from this primate base under the influence of language and culture. Their experiments examine the spatial frames of reference (FoRs) used by children and adults in a Dutch village and a Khoisan hunter-gatherer community in Namibia, as well as by representative of the three major great ape genera (orangutans, gorillas, and chimpanzees; using animals in the Leipzig Zoo). Extensive field research in over 20 languages reveal that just three FoRs seem to be used. Some languages mainly use a relative EGOCENTRIC, viewpoint-dependent FoR with terms like front, back, left, and right: "The ball is to the left of the tree" (from my point of view). Some languages mainly use an intrinsic OBJECT CENTERED relational FoR, which makes reference to faceted objects, e.g., "The ball is at the front of the house." Some languages mainly use a third, so-called absolute GEOCENTRIC FoR in which linguistic descriptions use cardinal-direction type systems such as our North, South, East, and West: "The hot water is in the northern tap." Although most languages have several FoRs in their repertoire, egocentric relative constructions are predominant in European languages, whereas the geocentric absolute FoR is dominant, for example, in several indigenous languages of Australia, Papua New Guinea, Mexico, Nepal, and south West Africa.

Here is the experimental setup used for Dutch and Khosian children and adults:

Legend ((Click figure to enlarge)) Experimental setup in two consecutive example trials. Ten exactly identical cups were placed on two tables (five cups on each table). Participants were watching while a target was hidden under the cup depicted as white (HIDING). Then the participants moved to the other table and indicated where they thought a second target might be hidden (FINDING). The three differently striped cups show the different contingencies rewarded in the three consecutive blocks of trials.

Both children and adults were more accurate (made fewer errors) and were faster to learn the finding pattern that matched the FoR dominant in their language (egocentric for the Dutch, geocentric for the Khosian). This correlation is fully robust by age 8 and persists into adulthood.

Because of the shorter attention span of the ape participants, and because of their known limitations with respect to abstract reasoning, experimental conditions were simplified, so that three instead of five cups were on each table. As a result, the object-centered and geocentric conditions were collapsed. The three identical cups in a straight line offer only two alternative strategies: The egocentric one and an allocentric one, which could be based on either object-centered or geocentric cues. Experiments precisely analogous to the human experiment ware done, but more clear results were obtained in further experiments when rewards (food in one cup) were incorporated.

The bottom line, according to the authors: "All great ape genera prefer to process spatial relations based on environmental cues and not self. The standard methods of comparative cognition thus suggest a common phylogenetic inheritance of a preference for allocentric spatial strategies from the ancestor shared by all four existing genera of Hominidae (Pongo, Gorilla, Pan, and Homo). Based on this result, we argue that, at least for small-scale spatial relations, the inherited cognitive mode of operation is not, as argued by Kant and others, egocentric but preferably deploys environmental cues as common reference between objects."

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