Contact causality is one of the fundamental principles allowing us to make sense of our physical environment. From an early age, humans perceive spatiotemporally contiguous launching events as causal. Surprisingly little is known about causal perception in nonhuman animals, particularly outside the primate order. Violation-of-expectation paradigms in combination with eye-tracking and pupillometry have been used to study physical expectations in human infants. In the current study, we establish this approach for dogs (Canis familiaris). We presented dogs with realistic 3D animations of launching events with contact (regular launching event) or without contact between the involved objects. In both conditions, the objects moved with the same timing and kinematic properties. The dogs tracked the object movements closely throughout the study but their pupils were larger in the No-contact condition and they looked longer at the object initiating the launch after the No-contact event compared to the Contact event. We conclude that dogs have implicit expectations about contact causality.

We used the EyeLink1000 eye-tracking system (SR Research, Canada) to record the dogs’ eye movements and pupil size at 1000 Hz. In each session, the dogs first completed a 5-point calibration with animated calibration targets (24–64 px) subtending visual angles of 0.77 – 2.05 degrees depending on the used target stimulus. Following the calibration, we presented a central fixation target (a white expanding circle; max diameter: 90 px; visual angle: 2.88 degrees). The video started once the dogs fixated the target for 50 msec.

Each subject was presented with two test conditions, the Contact and No-contact conditions. Each session consisted of three identical familiarization trials followed by one test trial.

The data and R scripts associated with this manuscript are also available at: https://github.com/cvoelter/dog_causal_perception.