The sensory input of humans is not outstanding compared with that of some other animal species. Compared with many animals, humans have a poor sense of smell. It is signiﬁcant that the olfactory centre is one of the few brain centres that is smaller in humans than it is in closely related species. Butterﬂies can pick up the scent of other butterﬂies over a distance of miles. Whales and dolphins can communicate by sound with members of their own species over a distance of miles. Nocturnal predators are much better at seeing in the dark than humans. On a beach where there are thousands of penguins and their young, the parent penguins can locate their young by recognising the sound that they make. The visual acuity of monkeys that leap from branch to branch at great speed is better than that of humans. Humans have used their ingenuity (outer me) to create devices such as spectacles, microscopes, telescopes, hearing aids, radar, radiography and underwater sonar devices to vastly enhance their sensory input in certain areas.