Earlier research established that preschool children pay less attention to television that is sequentially or linguistically incomprehensible. The authors of this study determined the youngest age for which this effect can be found. One hundred and three 6-, 12-, 18-, and 24-month-olds' looking and heart rate were recorded while they watched "Teletubbies", a television program designed for very young children. Experimenters manipulated comprehensibility by either randomly ordering shots or reversing dialogue to become backward speech. Infants watched 1 normal segment and 1 distorted version of the same segment. Only 24-month-olds, and to some extent 18-month-olds, distinguished between normal and distorted videos by looking for longer durations toward the normal stimuli. The results suggest that it may not be until the middle of the second year that children demonstrate the earliest beginnings of comprehension of video as it is currently produced. (Contains 1 table and 3 figures.)