Spatial relations: capuchins are their own frame of reference
Consider an imaginary square delimited by four identical landmarks. Gal, a male capuchin, is trained to search in the middle to obtain a food reward. Now the square is stretched by moving away the landmarks. Where will he search? Not in the middle, but near one of the landmarks, thus preserving the relative distances and orientations from each one. With such a complex configuration, capuchins are not able to taking into account the spatial relations between all landmarks. But with simpler configurations.
We investigated capuchins’ use of different spatial reference frames to locate objects in space. Researchers usually recognize two basic frames of spatial reference humans use to find objects: an egocentric frame, which relies on the body (e.g., on my left, in front of me, below me), and an allocentric frame, which is based on the relation between objects (e.g., the object is near the wall, in a tree, under a bush). Which one do capuchins rely on? Up to now, the results suggest that capuchins mainly rely on a self-referenced spatial frame to code and remember positions of objects in space. In particular, our experiments results suggest that capuchins search next to individual landmarks to find hidden food, but they do not exploit landmarks’ configurations. However, they can use landmarks’ configurations given a series of conditions: that is if only two landmarks are present in a small scale space and their position can vary but the line connecting them has always the same orientation (e.g. vertical) with respect to the subject’s point of view.
Figure. Configuration 1 (left): Gal has learned that in the central hole of the imaginary square delimited by four red sticks (references) is a hidden reward. Configuration 2 (right): if the sticks are moved away, Gal is no longer seeking the center hole of the new configuration but close to the reference, taking from them the same distance as he learned during training (a hole).
Inter-objects spatial relations: capuchins are not so good architects
Which is the best way to investigate primates’ comprehension of spatial relations between objects? Give them some blocks to play with and observe the constructions they made...
We investigated primates’ constructing inter-object spatial relations as indicated by spontaneous play with blocks. Findings indicate that species and age influence the degree to which primates rely on their own action and body to place objects in space. In particular, capuchins and young chimpanzees move and place objects together with the same part of the body and/or using their body as a support surface, so that inter-object relations are coincidental to forming relations between objects and their body. Older chimpanzees produce more complex constructions but, compared to human children, they too are relatively impaired in constructing object relations that cannot be directly supported by action coordination or functional relations (i.e. containment and support relations).
Video. Researchers try to understand how chimpanzees realize on spatial relationships between objects, from the way they combine theme. The video shows how Panzi builds a tower by placing the bowls on top of each other.
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