Cognitive Evolution: Understanding How Humans Differ from Apes

What changes in thinking accompanied evolution? While there is a significant fossil record that has enabled palaeontologists to reconstruct the strata of the past, it is not possible to know the cognitive processes of different organisms as they evolved, and how this might have influenced evolution.

Or is it?

In a new analog-driven study (published on Sept. 5 2006 in Current Biology), Max Planck Institute researhers found possible answers to these difficult questions through a creative approach using comparative psychology.

It appears that thinking strategies shaped by evolution amongst a wide variety of species cannot explain the unique cognitive development that separates humans from great apes, our closest ancestors.

Here are the details:

At the fundamental level, there are a couple of practices that are important to all species: remembering a food source's location and being able to find it after the initial discovery. Two basic components are involved in remembering location: recalling features of the object (carcass, tree, rock), or knowing the spatial placement (directional in relation to a third object).

The researchers examined a selection of species: (goldfish, toads, chickens, pigeons, rats and human children) all seemed to employ both strategies. However, if the type of recall task is designed so that the two strategies are in opposition, then some species (fish, rats and dogs) have a preference for locational strategies, while others (toads, chickens and children) favor those which use distinctive features.

Fig. 2: Test conditions: A mature male orangutan carries out the tasks. Top: "Place conditions" - the experimenter swaps the objects under which the item (X) is hidden, but the actual place where it is hidden remains unchanged. Bottom: "Feature conditions" - the experimenter moves the object and the item hidden underneath it to a different place. Image: Knut Finstermeier, MPI for Evolutionary Anthropology

Up until recently few significant studies have systematically examined these preferences amongst different members of a species lineage. Recently, however, Daniel Haun and colleagues looked at the cognitive preferences of an entire biological family, the hominids. They compared the five species of great apes - orangutans, gorillas, bonobos, chimpanzees and humans - to establish which cognitive strategies each used to uncover hidden characteristics. Assumption: If all five share a particular preference or set of preferences, than this common element is probably shared amongst all the common ancestors.

In the Leipzig Zoo, researchers hid coveted items using two different strategies (see Fig.2): In the place condition, the item remained in the same place it was hidden in before, but under a different object; in the feature condition the object remained the same, but the place was altered. All 4 great ape species and one-year-old children were found to use the location to find a hidden object, even if it is also disguised under a completely new and different object. This finding suggests that the location preference has probably been part of cognitive structure for 15 million years.

Three year old children, unlike younger children - considered the object under which the item was hidden to be the most reliable indication of its whereabouts, even if the location was changed. Apparently, 1-year-olds simply prefer to use a location-based strategy, even though they have the capability to 'switch' strategies later on.

"The unique human cognitive development seems to replace some of our evolved strategies even before we reach the age of three," says Daniel Haun. "In future experiments, we want to study which areas of cognitive development in humans, for example, language acquisition, are responsible for the restructuring of cognitive preferences."

It would seem that a new methodology has been created for the comparative study of cognitive structures that are closely related to human ancestors unlocking a gateway to a greater understanding of the evolution of human thinking.

Daniel B. M. Haun, Josep Call, Gabriele Janzen, and Stephen C. Levinson
Evolutionary Psychology of Spatial Representations in the Hominidae
Current Biology 16, 1-5, September 5, 2006

Source: Max Planck Institute for Evolutionary Anthropology

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