In a new study, led by Masaki Tomonaga from Kyoto University in Japan, researchers looked at how bottlenose dolphins perceive a range of simple, two-dimensional objects compared with chimpanzees and humans.

Previous studies of dolphin vision have used complicated, three-dimensional shapes, making it hard for researchers to identify the types of visual "cues" — like curves or diagonal lines — that dolphins use to suss out differences or similarities among objects.