Compared with many mammals, humans have a pretty weak sense of smell. But olfaction still plays a role in our social communication. By sniffing each other, we can glean information about gender, age, illness, and even whether someone is sad or disgusted, the scientists wrote. People with psychiatric disorders that can make socializing more difficult, such as autism or schizophrenia, tend to have a poorer sense of smell. And people born without a sense of smell—a condition called congenital anosmia—seem to be less socially secure than others. On the other side of the coin, a sensitive nose has been associated with extraversion.