Recognition of rotated objects and cognitive offloading in dogs _ Lonardo et al.
We trained pet dogs on a visual discrimination task between two geometrical shapes presented on a touchscreen. We subsequently tested the dogs on the rotated (±45°, ±90°, ±135°) versions of the same stimuli. We analysed dogs' accuracy and head tilts both at the group and at the individual level. During the recognition test, all dogs performed significantly above chance level with upright stimuli, consistently with the strict learning criteria they had to meet before entering the test phase. Females were more accurate than males. With rotated stimuli, on average dogs' accuracy dropped to chance level and we did not find evidence for a human-like mental rotation effect of the angle of stimulus rotation on performance. Indeed, dogs' accuracy was not modulated by the angular disparity between stimulus and reference, nor by the direction of stimulus rotation (clockwise or counter clockwise). With rotated stimuli, the female advantage disappeared and we found no sex difference in the accuracy. At the individual level, only 3 (38%) out of 8 dogs performed differently from chance level with rotated stimuli. Of these, one male and one female dog performed above chance level and one female dog performed significantly below chance level. We interpret these data as evidence that dogs use individual strategies to solve the mental rotation task and that some of them were likely focusing their attention on local parts of the stimuli rather than considering the stimuli globally. In our controlled setting, in which dogs had to lay their head on a chinrest before observing the stimuli, we found that dogs only rarely exhibited head tilting. Rather, they made small adjustments of their head position on the chinrest following the stimuli onset (average amplitude of head tilt observed after stimulus onset: ca. 5°; range: 0°- ca. 26°). Although dogs' head tilts after the stimulus onset followed the same direction as the stimulus rotation and were wider for wider stimulus rotations, there was no evidence that tilting their head influenced dogs' accuracy, probably due to the challenging task and relatively small sample size. We conclude that these data do not support the hypothesis that dogs, similarly to humans, try to offload the demands of the mental rotation task by using their bodies. This work paves the way to the study of cognitive offloading in non-human animals.
Steps to reproduce
All R scripts containing the code used for analysing and plotting the data, R workspaces and data files are provided. The data files are explained more in detail in the paper