Socio-spatial cognition in vervet monkeys
Experiments done in the Loskop Dam nature reserve, South-Africa
This paper reports two experiments that Marion Laporte, then a master student at the Université de Strasbourg, France, and I designed together. They were performed by Marion Laporte with free-ranging vervet monkeys in the Loskop Dam Nature Reserve, South-Africa back in 2005. With this experiment we showed that vervet monkeys mentally track their group-members when the latter are out-of-sight. We did this by playing back their voices from impossible locations and showed that this leads to monkeys reacting as if they are taken by surprise quite a bit more often than control playbacks that come from directions where the group-member, whose voice was used in the playback, just disappeared from view. It does not look like a complicated experiment but in reality this is bloody hard to do with monkeys that move around in their natural environment.
Experiment A (left): The voice of an animal that disappeared from the subject's field of vision is played back from a hidden loudspeaker.
Control: the voice owner passes within 45° at either side of the loudspeaker.
Test: the voice owner disappears in any other direction.
Experiment B (right): The subject hears two different calls from the same recording of a single group member with a short time interval from two different loudspeakers.
Control: the two hidden loudspeakers are placed less than 1 m apart that are both in a direction in which the invisible owner of the voice could plausibly be.
Test: The first call (BT1) comes from a loudspeaker as in the Control condition, but the second call (BT2) comes from a loudspeaker hidden in the opposite direction.
Why a separate page for this single paper?
This study has nothing to do with biological market theory, which is probably why I initially did not dedicate a separate page to it on this site. I was reminded of our work on socio-spatial cognition (also written as 'social spatial cognition') by the publication of “Takagi, S., Chijiiwa, H., Arahori, M., Saito, A., Fujita, K. & Kuroshima, H. (2021). Socio-spatial cognition in cats: Mentally mapping owner’s location from voice. PLOS ONE, 16(11), e0257611”, a paper that led to an amazing media-hype. Is an experiment done on captive cats more interesting than one done on vervet monkeys in the wild, or because primates are expected to be able to do this while cats are not, or is it just that cats do well in the popular press? To avoid any misunderstanding: The cat-paper authors, who cited us correctly and gave us all the credit for the methods used and more, are quite welcome to the media-interest their paper got. I thank them for bringing our paper to the attention of those who actually read theirs rather than only the pop-press stories. That is the audience we like to reach.
last update (editing only): 8 JAN 22