This illustrated booklet describes research procedures in the Infant Laboratory of the Educational Testing Service to investigate measurable factors in infant behavior which can predict intellectual potential. The research is currently focusing on attending, the manner in which infants respond to various stimuli presented to them during their earliest months. Preliminary findings indicate that the length of time of attention gives evidence of the activity levels of the infant's nervous system. Infant's response to an arresting stimulus includes: opening his eyes, expanding pupils, slowing down breathing, slowing down heart rate, decreasing motor movement, babbling in response to social stimulus, stopping babbling in response to non-social stimulus. Changes in response to stimulus develop about the age of three months. Infants suffering from brain damage do not change their responses. Infants provided with more home environmental stimulation habituate faster to test stimuli, indicating they are more intellectually alive. Experiments relating cognitive development to shortening attentional responses indicate that this factor may be a yardstick of intellectual potential. Further studies will explore cultural implications. (DJ)