Development of vocal protest from 3 to 18 months

Cry sounds change in both form and function during infancy. The present study investigated how cry sounds are used, not to request care, but to protest maternal behaviors. Infants\u27 vocal protests of maternal caregiving and maternal prohibitions were examined in a cross-sectional design across the ages of 3 to 18 months. Naturalistic observations of 75 infants in 5 age groups (3, 6, 8, 12, and 18 months) were videotaped and coded for every instance of maternal caregiving and prohibition. Whether and how infants protested these behaviors were also coded. The rate of maternal caregiving behavior decreased over age, whereas the rate of maternal prohibitions increased. More importantly, the conditional probability that infants would protest a maternal prohibition also increased over age, but the conditional probability of protesting caregiving behavior remained relatively constant. When age was controlled, mothers prohibited crawling infants more often, and crawling infants protested prohibitions more often than non-crawling infants. Finally when the types of sounds infants used to protest were examined. The results showed that older infants were more likely to cry during prohibitions and to fuss during caretaking. Also, older infants often screamed during their protests. Not only do the causes, and the frequency of vocal protests change in the second half-year, but infants use different vocal protests in different social contexts. Further, the onset of locomotion appears to play an important role in this developing communicative skill. The use of cry sounds as vocal protests of maternal behavior provides one window into the qualitative changes taking place in the second half year in infants\u27 early communication skills.