ABS 2023
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The research of mental rotation in a killer whale (Orcinus orca)
Ayumu Santa1, Koji Kanda2, Ikuma Adachi1. 1Center for the Evolutionary Origins of Human Behavior, Kyoto University, Inuyama, Aichi, Japan; 2Port of Nagoya Public Aquarium, Nagoya, Aichi, Japan

Cetaceans (e.g., dolphins and whales) have been highly adapted to the underwater environment, and are frequently observed that they swim with their bodies tilted or sometimes completely upside down. Then, how do they recognize the rotated visual information? It is known that we humans have the ability, called ‘mental rotation,’ to rotate the image mentally. The purpose of this study was to investigate whether mental rotation occurred in a killer whale. Identity matching-to-sample task was performed in a captive killer whale (Orcinus orca) by using a method in which visual stimuli were displayed on a monitor through an underwater window. The error rate and reaction time at the rotational angles of 0-90 degrees were examined in the discrimination of four geometric figures and their mirror images. The reaction time increased linearly along with the rotation angle, this result suggested the possibility of mental rotation in killer whales. On the other hand, the increasing error rate also suggested that the spontaneous rotation of mental images was difficult to occur in this killer whale. This difficulty may be related to the greater freedom of postures and movements in underwater.