We used Signal Detection methodology to examine how cognitiveset affects mothers' response to an infant cry. We asked whether a cry from a "difficult" versus an "easy" infant would elicit a change in sensitivity or response bias in mother processing of these cries. Thirty-eight mothers of 4- to 6-month-old infants participated in a Signal Detection task in which they were asked whether they could detect differences between a standard cry and 1 to 4 cry variants. Cry variants differed from the standard cry in small, systematic changes in fundamental frequency. The task was conducted in 2 parts; each part constituted a condition wherein mother received a cognitive set manipulation that labeled the identical cry as coming from either a''difficult''or an "easy" infant. An increase in mothers' sensitivity was associated with the "difficult" infant cognitive set. We examined as well how a coping strategy(illusion of control) affected cry signal processing. Mothers who Exhibited high illusory control were least -sensitive in detecting differences between cries. Two information-prcessing, measures response time and heart rate, were also collected and showed that greater sensitivity was associated with more efficient processing of the cry signal.