Age-related differences in the acute pain facial expression during infancy

The ontogenetic perspective on the development of emotional expressions in infants holds that infants' facial and vocal expressions evolved to serve crucial communicative functions in infancy and contribute to infants' survival. Infants' facial expressions should be contextualized by their own developmental stage rather than presuppositions from verbal populations. The overall aim of this paper was to examine age differences in the temporal patterning of elucidated facial expressions in the first minute following vaccination injections.

One hundred infants were videotaped longitudinally (2, 4, 6 and 12 months) from 2007-2012 during their routine vaccination appointment over the first year of life and five major negative facial configurations were identified using BabyFACS. In the current study, facial configurations were graphed in 5-s epochs for 1-min post-vaccination and subsequently analysed for facial expression by time effects using Repeated Measures ANOVAs at each age.

Clear differences in temporal patterns were displayed as infants aged. ANOVA analyses indicated significant facial expression by time interactions at each age.

Facial expressions illustrating intense/moderate distress and sensory overload were prominent in the first 15 s at the 2-, 4- and 6-month vaccination. However, expressions showing regulation of distress occurred progressively earlier over 1 min post-needle in older infants, suggesting a significant shift in regulatory capacity of pain-related distress occurs after 6-months of age.

An important developmental milestone was identified in infants' ability to regulate distress at 6 months. Supporting parents' infant pain management is particularly critical in the first months of life as infants' initial facial expressions appear to be more reflective of an organism overwhelmed by distress.