Mothers' pupillary responses to infant facial expressions.
BACKGROUND
Human parental care relies heavily on the ability to monitor and respond to a child's affective states. The current study examined pupil diameter as a potential physiological index of mothers' affective response to infant facial expressions.


METHODS
Pupillary time-series were measured from 86 mothers of young infants in response to an array of photographic infant faces falling into four emotive categories based on valence (positive vs. negative) and arousal (mild vs. strong).


RESULTS
Pupil dilation was highly sensitive to the valence of facial expressions, being larger for negative vs. positive facial expressions. A separate control experiment with luminance-matched non-face stimuli indicated that the valence effect was specific to facial expressions and cannot be explained by luminance confounds. Pupil response was not sensitive to the arousal level of facial expressions.


CONCLUSIONS
The results show the feasibility of using pupil diameter as a marker of mothers' affective responses to ecologically valid infant stimuli and point to a particularly prompt maternal response to infant distress cues.
Tampere Center for Child Health Research, School of Medicine, University of Tampere, Lääkärinkatu 1, 33520, Tampere, Finland. santeri.yrttiaho@uta.fi.
Santeri
http://orcid.org/0000-0002-5724-1222
S
Yrttiaho
Department of Psychiatry, Faculty of Health Sciences, Stellenbosch University, Stellenbosch, South Africa.
Dana
D
Niehaus
Department of Psychiatry, Faculty of Health Sciences, Stellenbosch University, Stellenbosch, South Africa.
Eileen
E
Thomas
Tampere Center for Child Health Research, School of Medicine, University of Tampere, Lääkärinkatu 1, 33520, Tampere, Finland.
Jukka M
JM
Leppänen
D000328:Adult; D003463:Cues; D004644:Emotions / Q000502:physiology; D005149:Facial Expression; D000066499:Facial Recognition / Q000502:physiology; D005260:Female; D006801:Humans; D007223:Infant; D009034:Mother-Child Relations / Q000523:psychology*; D009035:Mothers / Q000523:psychology; D011680:Pupil / Q000502:physiology*
Attention; Emotion; Facial expressions; Infant faces; Mothers; Pupil