Kate Branson, Aista Sobouti, Alison Cook, Cindy Lawrence
RESEARCH SITE:
San Diego Zoo
ABSTRACT:
This study used videotape of naturally-occurring behavior in a triad of adolescent bonobos (2 females and 1 male) on exhibit at the San Diego Zoo. Segments in which all three animals were clearly visible were analyzed, frame-by-frame, for events that began with one animal turning its head toward another. The relative head position of all animals was then tracked until at least one subsequent head turn occurred. Head position for each animal toward every other was scored (1-9) according to the access to eye contact that that head position afforded. These scores were also summed across dyads, and across the triad as a whole, to determine if pairwise or triadic states of access were predictive of subsequent head turns.
We scored each animal's orientation to each other animal, on a scale of 1-9, per the access to eye contact the orientation afforded.
Results of interest include the significant tendency, in events in which the initial head turn brought about a very high level of triadic access, for one of the triad to effect an extremely rapid (Mean = 256 ms) shift away from the others. Furthermore, the triadic sum predicted this outcome better than the dyadic or individual access scores did. Similarly, in randomly sampled events (the first in each two-minute interval of video), the best predictor of whether an animal turned toward another and maintained that position, or turned away before any other head turn occurred, was not that individual's access, nor the access of the animal toward which it turned, but rather the access of the third party to that event. That is, if the third party was monitoring the event, the first animal was significantly more likely to turn away from the second than if the third party was not monitoring the event.
In this frame, the animal on the left has just turned her head toward the others, so that now all three bonobos have a high level of access to each other.
These and related results indicate that the animals in this triad were sensitive to one another's attentional states, and responded not just on the basis of individual tendencies or pairwise relationships, but in terms of the triadic field of attention they co-created.
The bonobos (left to right): Lolita, Congo and Lavern
DISCUSSION:
A variety of converging evidence indicates the importance to primates of detecting and responding to the head orientation of conspecifics. From the field, researchers have described primates' use of threatening stares, the recruitment of eye contact as a prelude to collaborative interactions, and "gaze avoidance" as a means of rejecting a solicitation or otherwise precluding engagement. In the lab, researchers have documented that eye contact elicits strong physiological responses (such as increased heart-rate and pupil dilation), that eyes are the feature of the face most often examined by primate subjects and that specialized cells in the cerebral cortex differentially respond to head orientation and/or gaze directed at, versus from, the subject.
Cells in monkey cortex respond differentially to the sight of faces at different orientations
From Gross, Desimore, Albright & Schwartz (1985)
Researchers interested in the evolution of cognition in primates have argued that the evolution of social intelligence in primates may be related to the occurrence of triadic (or polyadic) interactions. That is, such interactions are probably more cognitively demanding than are the more common dyadic ones. Animals that engage in only dyadic dominance interactions, for example, need only keep track their own relative position to each other animal in the group. In contrast, when coalitions and other polyadic negotiations are possible, an individual must know not only about its own relationships, but also about the relationships that exist between others.
Immediately following (within 3 frames of) the situation on the left, one of the animals in this triad turned away from the others. Such rapid adjustments were observed in 94% of such "high access" contexts.
ACKNOWLEDGEMENTS
San Diego Zoological Society / CRES
Dept of Cognitive Science, UCSD
Dept of Anthropology, UCSD
Christine M. Johnson
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