Administering nebulized oxytocin is an increasingly popular technique (with no reported side effect) to examine the effect of this evolutionary-old neuropeptide affecting various sides of social behavior in humans, dogs, and monkeys. We for the first time administered nebulized oxytocin (and control placebo saline) to humans' two closest relatives, bonobos and chimpanzees and examined the changes in social attention, in particular the frequency of eye contact to conspecific images. We found that, as reported in other species, bonobos increased eye looking in response to oxytocin. However, interestingly, there was a significant species difference in the effect of oxytocin between bonobos and chimpanzees. Chimpanzees rather decreased eye looking and instead increased mouth looking. It was previously identified that bonobos make more eye contacts than chimpanzees (see below). Thus, oxytocin can be suggested as one of the drivers that could enhance the divergence of social behavior (an existing species difference) in hominoids. 

In this outreach project, we asked professional contemporary artists to make movies 'for chimpanzees' and compared chimpanzees' and humans' responses to the movies in eye-tracking. Both chimpanzees and humans looked at similar elements of movies, such as the appearance of animal figures, targets of actions, and the center of abstract concentric figures. The differences between chimpanzees and humans were also pronounced; for example, human showed strong 'center bias' by keeping their gaze around the center of the screen, while chimpanzee did so to a lesser extent. This study not only offered comparative knowledge about responses to (artistic) movies in chimpanzees and humans but demonstrated how non-scientists can learn comparative psychology through an outreach project.

We showed that great apes can use their self experiences to infer whether the actor can see through the barrier in a false belief task. Two groups of great apes have first experienced different properties of a barrier in reality. One group experienced that the barrier cannot be seen through (normal barrier). The other group experienced that the barrier can be seen through (see-through barrier). The barrier looks untransparent and identical from afar. After this, both groups have watched the same video in which an actor hid behind the barrier while his object of interest is translocated. When the actor tried to retrieve the objects, the apes who have experienced the normal barrier have anticipated the actor's action as if he has a false belief and the other apes who have experienced the see-through barrier anticipated the actor's action as if he has a true belief. This result shows that apes can integrate their own experiences in their understandings about what the actor knows, therefore do not simply use superficial behavioural cues of the actor. Featured in The AtlanticSmithonian, An introductory article by Alia Martin (Martin A (2019) Belief Representation in Great Apes. Trends Cogn. Sci. 23(12):985-986.)

Kano F., Walker J., Sasaki T., Dora B. (2018) Head-mounted sensors reveal visual attention of free-flying homing pigeons. Journal of Experimental Biology, 221(17), jeb183475.
We developed 'pSensor', that can record free-flying pigeons' head movement (as a proxy for gaze) with IMU (Inertial Measurement Unit) and flight trajectories with GPS. Pigeons changed the pattern of head movement according to the visual needs; 1) increased head movement as they established their own navigation routes, 2) decreased head movement when they flew across obvious landmarks (e.g. roads), 3) decreased head movement when they flew with a partner. Thus, it seems that they decreased their head movement when they attended to an object of interest (as if a primate 'fixates'). This study opened up many possibilities in testing visual attention of free-flying birds in ecologically-valid conditions.
Featured in JEBCosmos

Kano F., Moore R., Krupenye C., Hirata S., Tomonaga M., Call J. (2018) Human ostensive signals do not enhance gaze following in chimpanzees, but do enhance object-oriented attention. Animal Cognition, 21(5), 715-728. 
We tested if chimpanzees respond appropriately to the human experimenter's 'ostensive' cues; the cues that a human adult often uses to indicate her/his intention of informing something useful to others. Previously, human 6-month-olds and domestic dogs followed the experimenter's gaze more often after they saw the ostensive signals, such as eye contact and calling names. We found that chimpanzees did not behave in the same way as human infants and dogs; they followed the gaze equally often after they saw the ostensive signals. However, they, especially those chimpanzees who had kept close relationships with human experimenters since youth, looked the objects (both looked- and non-looked-objects) more often when they saw the ostensive signals vs. the control cues. The results indicate both limitations and potentials in the chimpanzees' ability to understand humans' intention to communicate.

Kano F., Shepherd S.V., Hirata S., Call J. 2018 Primate social attention: Species differences and effects of individual experience in humans, great apes, and macaques. PLOS ONE 13(2), e0193283. 
We examined if there are differences among species and individuals in attention to social video stimuli in great apes, monkeys, and humans by testing more than 40 nonhuman primate individuals. Indeed, apes, monkeys, and humans were clearly distinguished from one another. Among great apes, bonobos were distinguished from the other species. We also found that individual experiences such as rearing history (institute-reared, zoo-reared, biolab-reared) affected social attention among chimpanzees. Interestingly, we also found the effect of expertise in human primatologists and non-primatologists; they clearly differ in their viewing patterns for chimpanzees in the videos (an effect of expertise).

Krupenye, C.*, Kano, F.*, Hirata, S., Call, J., Tomasello, M. (2016). Great apes anticipate that other individuals will act according to false beliefs. Science, 354(6308): 110-114. (*shared first-authors, co-correspondence). 

We examined if great apes anticipate, with their looks (so-called anticipatory looks), an agent’s action based on the agent’s false beliefs. We followed a seminal infant study (Southgate, Senju, Csibra, 2007) for the general design to test false-belief understanding and also followed Kano & Hirata (2015, Current Biology) to make optimized videos for apes. We created two videos having the same general design (after the seminal infant study) but differing in scenarios. Apes reliably anticipated that the agent would act according to false beliefs in two scenarios. 

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Kano, F., Hirata, S., Deschner, T., Behringer, V., & Call, J. (2016). Nasal temperature drop in response to a playback of conspecific fights in chimpanzees: A thermo-imaging study. Physiology & Behavior, 155, 83-94. 

We applied an infrared thermo-imaging to examine the chimpanzee's emotional responses to a playback of conspecific fights. Chimpanzees dropped their nasal-tip temperature in response to the stimuli. A remote measurement of skin temperature is a promising technique in this field.

Kano F, Hirata S (2015) Great Apes Make Anticipatory Looks Based on Long-Term Memory of Single Events. Current Biology 25(19): 2513-2517.
We used a novel eye-tracking task to study great apes’ long-term memory shaped through single experiences. We found that, when watching the same video again with a 24-hr delay, great apes make anticipatory looks to the critical, emotional events based on where-what information.

Featured in The New York Times, New Scientists, The Gurdian, etc.
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Kano F, Hirata S, Call J (2015) Social Attention in the Two Species of Pan: Bonobos Make More Eye Contact than Chimpanzees. PLoS ONE 10(6): e0129684. doi:10.1371/journal.pone.0129684

Bonobos and chimpanzees are known to differ in many interesting ways. For example, bonobos are in general more affiliative and tolerant to the conspecifics than chimpanzees. I tested if bonobos make more eye contacts than chimpanzees, because, in humans, people with more needs for affiliation tend to make more eye contacts. Indeed, bonobos focused on the eyes of conspecifics better than chimpanzees in my eye-tracking experiment.

Kano, F., & Call, J. (2014). Great apes make goal-directed action prediction by eye movements, Psychological Science, 25(9): 1691-1698.

I tested if great apes (chimps, bonobos, orangs), like human adults and infants, predict reaching actions by eye movements. Apes were familiarized to movie clips of a human hand reaching to grasp one of two objects. Then object locations were swapped, and the hand made an incomplete reach between the objects. In a control condition, a mechanical claw performed the same action. Apes predictively looked at the familiarized goal object rather than the familiarized location when viewing the hand action. However, they did make no prediction when viewing the claw action. 

Kano, F., & Call, J. (2014). Cross-species variation of gaze following and conspecific preference among great apes, human infants and adults. Animal Behaviour 91: 137-150.. 

Gaze following was compared between four hominoid species.  All species followed the gaze of own species model. The species differences were that 1) bonobos followed the gaze more sensitively than chimpanzees, and that 2) chimpanzees and human infants followed only own-species gaze but not other-species gaze, while bonobos, orangutans, and human adults did follow other-species gaze.

Kano, F., & Tomonaga, M. Head-Mounted Eye Tracking of a Chimpanzee under Naturalistic Conditions. PLoS ONE, 8(3), e59785, 2013
Media article (
Pan, the chimpanzee, wearing the eye-tracker

Spontaneous scanning of faces by orangutan, gorilla, and human participants.
Gap-overlap task revealed the similarities and differences of basic eye-movement properties between great apes and humans
Chimpanzees scanned visual scenes more quickly and more widely than humans. 

Chimpanzees were similar to humans in their pattern of viewing complex and abstract scenes. 
Among many video contents, chimpanzees viewed fighting scenes most strongly.
Humans extensively viewed eyes. Chimpanzees also viewed eyes but viewed mouth relatively more often. 
Humans viewed eyes when presented with any facial expressions, while chimpanzees viewed mouth expressions more often.
Chimpanzees followed only chimpanzee gaze, while human adults followed both chimpanzee and human gaze.
A chimpanzee on the eye-tracking setting.
Typical scanpaths by chimpanzees and humans.
A chimpanzee recognized the emotional scene better in a memory task.
A chimpanzee on the touch-panel setting.