A small region of the hippocampus known as CA2 is essential for social memory, the ability of an animal to recognize another of the same species, a new study concludes. In humans, the importance of the hippocampus for social memory was famously illustrated by the case of Henry Molaison, who had much of his hippocampus removed by surgeons in 1953 in an attempt to cure severe epilepsy. Molaison was subsequently unable to form new memories of people. A better grasp of the function of CA2 could prove useful in understanding and treating disorders characterized by altered social behaviors, such as autism, schizophrenia, and bipolar disorder.