Suppose you want to hide something and you place it under some object. At a later time you return for the item but the environment has changed to a certain degree. Things have moved from their original places. Where would you search for your item, under the object you have placed it (although the object has now moved) or in the location where you have placed it (although a different object lies there now)?

Faced with this dilemma various animals choose differently. For example fish, rats and dogs consider the location more trustworthy. On the other hand, toads or chickens care more about the object under which the item has been hidden. This doesn't mean that they are not able to use the other search strategy as well, but when the two strategies (location-based and feature-based) come to terms they have the tendency to prefer one over the other.

Researchers at the Max Planck Institute for Psycholinguistics and their colleagues at the Max Planck Institute for Evolutionary Anthropology wanted to find out whether the five species of great apes (orangutans, gorillas, bonobos, chimpanzees and humans) prefer the same search strategy. They assumed that if all hominids share particular preferences, these are probably a part of the evolutionary legacy of our most recent common ancestors, who died out some 15 million years ago.

The image shows a mature male orangutan carrying out the tasks. "Place conditions": the experimenter swaps the objects under which the item (X) is hidden, but the actual place where it is hidden remains unchanged. "Feature conditions": the experimenter moves the object and the item hidden underneath it to a different place. Credit: Knut Finstermeier, MPI for Evolutionary Anthropology

Researchers established that all four great ape species and one-year-old children use the location as a way of finding something hidden, even if it is hidden under a completely different object. According to the scientists this outcome suggests that this preference has been part of our cognitive structure for 15 million years and has probably characterized the mind of our common ancestor.

Scientists had also investigated three-year-old children and discovered that they considered the object under which the item was hidden rather than its location. Thus it seems that humans reassess these preferences and change their strategy from a location-based to a feature-based one as their cognitive development continues.

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