Responsive social exchanges are critical for infants' bio-behavioural regulation and healthy development. Parental smartphone use may disrupt early parent-infant interactions, leading to frequent interruptions. The impact of these interruptions on mother-infant behaviours and stress physiology is unclear. Infrared thermal imaging (ITI) offers a non-invasive approach to assess stress-related skin temperature changes reflecting autonomic activation. This study investigates mother-infant behavioural and thermal affective responses to parental digital and non-digital distractions. Thirty-eight mother-infant dyads (22 males) participated in a modified Still-Face Paradigm with five conditions: Free Play, Technoference Exposure (TF-E), Technoference Reunion (TF-R), Paperference Exposure (PF-E), Paperference Reunion (PF-R). During TF-E and PF-E mothers completed questionnaires on a smartphone or paper and were unresponsive to the infant. Mother-infant behaviours were coded microanalytically, while FLIR cameras detected changes in forehead and nasal tip temperatures. Maternal habitual smartphone use was assessed by self-report and passive sensing. Infants showed increased behavioural distress during TF-E and PF-E. ITI revealed lower infant forehead temperatures during TF-E compared to free play and reunions, while no significant changes at the nasal tip. Maternal forehead temperature dropped significantly during PF-E, compared to other episodes. Greater maternal habitual phone use was linked to infant responses and maternal behaviours. Parental unresponsiveness due to digital and non-digital distractions leads to infant behavioural distress, with digital disruptions also triggering a distinct thermal affective response. Findings highlight the impact of different parental distractions on early interactions and stress responding, with potential long-term implications.
