|Photo: Mark Dumont|
Four female bonobos each completed either twenty-five or twenty-six trials in total over thirteen separate testing sessions. They were briefly shown two images and then a dot appeared on the screen which remained there until the individual tapped the dot. Upon tapping the dot, the individual is rewarded with a food item. In half of the trials, the images briefly shown were of a bonobo in some sort of emotional state, such as pant hooting, playing, or in distress. In the other half, the images were of a bonobo in a neutral state.
By looking at the reaction time, Kret and colleagues (2016) were able to determine that bonobos are more captivated by images of other bonobos that are affiliative or protective rather than images with bonobos in distress or aggression, which has found to be the case most often for humans (Vuilleumier and Schwartz, 2001; Williams et al., 2004; Tamietto et al., 2005; Flaisch et al., 2009).
Images of yawning, grooming, and sexual behavior caught the bonobo's attention the most. Reaction time was longest for yawning, followed by grooming and then sexual behaviors. Yawning is a contagious behavior in humans and also for bonobos (Palagi et al., 2014). Grooming and sexual behavior are both types of behavior that reduce tension (Manson et al., 1997; De Waal, 1997; Crockford et al., 2013).
The increased attention devoted to these social behaviors suggest that they are of greater importance to bonobos than aggressive behaviors or actions associated with a threat. Given that this isn't the case with humans and what captures our attention, this study highlights another intriguing difference between the two species.
Links of potential interest:
Paper in PNAS
Are bonobos more peaceful than chimpanzees?
IUCN page on bonobos
Crockford, C., Wittig, R. M., Langergraber, K., Ziegler, T. E., Zuberbühler, K., & Deschner, T. (2013). Urinary oxytocin and social bonding in related and unrelated wild chimpanzees. Proceedings of the Royal Society of London B: Biological Sciences, 280(1755), 20122765.
De Waal, F. B. (1997). The chimpanzee's service economy: food for grooming. Evolution and Human Behavior, 18(6), 375-386.
Flaisch, T., Schupp, H. T., Renner, B., & Junghöfer, M. (2009). Neural systems of visual attention responding to emotional gestures. Neuroimage, 45(4), 1339-1346.
Kret, M. E., Jaasma, L., Bionda, T., & Wijnen, J. G. (2016). Bonobos (Pan paniscus) show an attentional bias toward conspecifics’ emotions. Proceedings of the National Academy of Sciences, 201522060.
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Vuilleumier, P., & Schwartz, S. (2001). Emotional facial expressions capture attention. Neurology, 56(2), 153-158.
Williams, M. A., & Mattingley, J. B. (2004). Unconscious perception of non-threatening facial emotion in parietal extinction. Experimental Brain Research, 154(4), 403-406.