The senses of "Psittacosaurus" can be inferred from the endocast. Large olfactory bulbs are present, indicating the genus had an acute sense of smell. The size of these bulbs are comparable to large predatory theropods, although they likely evolved to avoid predators instead of to seek out prey. The sclerotic rings in reptiles directly show the size of the eyeball. The rings are not well preserved in "Psittacosaurus", with one individual preserving them likely contracted postmortem, but if they are similar to those of "Protoceratops", "Psittacosaurus" would have had large eyes and acute vision. The curvature of the semicircular canals is related to the agility of reptiles, and the large curved canals in "Psittacosaurus" show that the genus was much more agile than later ceratopsians. Comparisons between the scleral rings of "Psittacosaurus" and modern birds and reptiles suggest that it may have been cathemeral, active throughout the day and for short intervals at night.