Giuliana Bucci-Mansilla¹ (), I. Hawkins^2,3, V. Ajuwon², N. S. Clayton¹, Jason Fischer^4,1, C. Krupenye¹; ¹Johns Hopkins University, ²University of Cambridge, Cambridge, UK, ³University of Oxford, Oxford, UK, ⁴University of Coimbra

Humans have an intuitive understanding of the physics of the world that allows them to make inferences about how a scene will unfold. While nonhuman animals may share some capacities for making inferences about the physical world, the underlying representations remain unclear. One open question is how animals represent the weight of objects and whether they understand that heavier objects produce greater impacts when dropped. To address this, we tested whether Eurasian Jays (Garrulus glandarius) can infer the identity of occluded objects based on how the objects affect the bearing of a balance beam. In our experiment, we hid two objects with different weights in cups and placed them on opposite sides of a balance beam. We hypothesized that Eurasian Jays would use a representation of weight as a force to infer that the heavier object tilts the balance, allowing them to predict the desired object’s location. Our design had two conditions: in Condition 1 the desired object was paired with a lighter object, causing it to be at the lower end of the beam, and in Condition 2, it was paired with a heavier object, making it end at the higher position. We found that jays differentiated between conditions: they selected the lower option more often when the desired object was the heavier of the two but chose according to chance when the desired object was the lighter of the two. These findings suggest that jays may have mental representations of weight that extend beyond inflexible responses to perceptual cues.

Acknowledgements: johns hopkins University, psychological and brain science; Animal behavioral society.