Data is from a short-term longitudinal study conducted at the Institute of Human Development which involved presenting two weeks of a special contingency experience to infants between their eighth and tenth weeks. (Authors/MB)

Portions of this paper were read as part of a symposium on The Meaning of Smiling and Vocalizing in Infancy'' at the 1970 meeting of the American Psychological Association, Miami Beach, Florida, September, 1970. (Editor)

In order to determine if infants possessed contingency awareness and if it were related to a temporal unit, two hypotheses were constructed. (1) Reinforcement of a response would probably lead to emission of that response only if the infant's next response occurred within a period of time during which he could remember the preceding…

Tests the hypothesis that, while the difference in rate of smiling to O degree v non-O degree orientations will diminish with increasing age with silent and/or unfamiliar faces, infants over 14 weeks of age should continue to discriminate between a talking familiar 0 degree face, and all other combinations of orientation, familiarity, and silent…