For the next 20 years they showcased modern art with an emphasis on African-Americans, including work by abstract expressionist Norman Lewis, Boston-born Lois Mailou Jones (known for incorporating African images into her work) and lesser-known Washington-area artists.
People rely on their spatial knowledge to build many other more complex or abstract representations including time, number, musical pitch, kinship relations, morality and emotions.
They also assessed their physical and neurological health, and carried out tests - including memory, language and abstract reasoning - to evaluate their condition.