ALLENDALE, Mich. -- When it comes to estimating the intelligence of various animal species, it may be as simple measuring overall brain size. In fact, making corrections for a species' body size may be a mistake. The findings were reported by researchers at Grand Valley State University and the Anthropological Institute and Museum at the University of Zrich, Switzerland. The study has now been published online in the journal Brain, Behavior, and Evolution.

"It's long been known that species with larger body sizes generally have larger brains," said Robert Deaner, assistant professor of psychology at Grand Valley and the first author on the study. "Scientists have generally assumed that this pattern occurs because larger animals require larger nervous systems to coordinate their larger bodies. But our results suggest a simpler reason: larger species are typically smarter."

Deaner said the findings imply that a re-evaluation may be in order for many previous studies that have compared brain size across different animal species, including ancestral hominids.

The new results build on a paper by the same researchers, published in the online journal Evolutionary Psychology, in July 2006, which showed that some primate species consistently outperform others across a broad range of cognitive tasks. That finding provided evidence for species differences in intelligence or "domain-general cognition," in the parlance of the field. This intelligence allows an animal to tackle new and unpredictable situations. Domain-general cognitive ability stands in contrast to domain-specific skills that are suited to particular environment challenges, such as a bird remembering where it cached food.

The new study compared how well eight different brain size measures predicted the domain-general cognition variable generated in the earlier study. To the researchers' surprise, overall brain size and overall neocortex size proved to be good predictor
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Contact: Mary Pirkola
pirkolam@gvsu.edu
616-331-2221
Grand Valley State University
18-May-2007