Visual Perception of Photographs of Rotated 3D Objects in Goldfish (Carassius auratus)

SIMPLE SUMMARY: The ability to visually recognize objects at different viewpoints is known as object constancy and is very important to animals, including humans. By presenting six goldfish with photographs of plastic turtles and frogs at different viewing angles, we were able to better understand object constancy abilities in goldfish. All the fish had successful performance, showing that they were able to distinguish between the turtle and frog photographs, which is evidence of object constancy. This study was the first to look at fish’s ability to identify photographs of objects they had previously seen, known as object-picture recognition. ABSTRACT: This study examined goldfishes’ ability to recognize photographs of rotated 3D objects. Six goldfish were presented with color photographs of a plastic model turtle and frog at 0° in a two-alternative forced-choice task. Fish were tested with stimuli at 0°, 90°, 180°, and 270° rotated in the picture plane and two depth planes. All six fish performed significantly above chance at all orientations in the three rotation planes tested. There was no significant difference in performance as a function of aspect angle, which supported viewpoint independence. However, fish were significantly faster at 180° than at +/−90°, so there is also evidence for viewpoint-dependent representations. These fish subjects performed worse overall in the current study with 2D color photographs (M = 88.0%) than they did in our previous study with 3D versions of the same turtle and frog stimuli (M = 92.6%), although they performed significantly better than goldfish in our two past studies presented with black and white 2D stimuli (M = 67.6% and 69.0%). The fish may have relied on color as a salient cue. This study was a first attempt at examining picture-object recognition in fish. More work is needed to determine the conditions under which fish succeed at object constancy tasks, as well as whether they are capable of perceiving photographs as representations of real-world objects.