Lifelong experience with a sign language and congenital deafness can affect cognitive processes, and these effects can be teased apart by comparing the performance of signers who are either deaf or hearing as well as deaf individuals who do not acquire a sign language. Some cognitive effects have been shown to arise from the acquisition or habitual use of a sign language (enhanced mental imagery ability, increased ability to discriminate facial features, improved spatial memory), whereas other cognitive effects are associated primarily with early and lifelong deafness (faster reactions to visual stimuli, enhanced attention to the periphery of vision, superior ability to infer spatial information by touch).