Stern (1977) developed a model showing various degrees of adult-infant contact, which has been later used by a number of scientists testing his original hypothesis of mother-child cognitive interaction. Several experimental studies have been conducted that support Stern’s (1977) model. In two separate studies, Pelaez-Nogueros and colleagues (Pelaez-Nogueros et al., 1997) had adult females interact with infants in a standardized manner, to examine the effects of different forms of contingent responsiveness on infant behaviour. In both studies, experimenters responded dissimilarly to infant looks with various forms of stimulation, and examined their effects on infant behaviour over time. In the first study (Pelaez-Nogueros et al., 1996), contingent physical stroking paired with smiling and vocalizing at the infant led to more eye contact, more positive affect, and less negative affect over time than did contingent smiling and vocalizing alone. In the second (PelaezNogueras et al., 1997), contingent stroking led to more eye contact, more positive affect, and less negative affect than did tickling and poking.
Field (1977) also provided some support for Stern’s (1977) model. In a study of full-term, preterm, and post-term infants, she noted that when mothers of full-terms were instructed to try to get their infant’s attention, the mothers increased their level of stimulation over that of free play, and the amount of time that their infants looked at them actually decreased.
The most common type of experimental study in this area involves use of Tronick and colleagues’ (Tronick, Als, Adamson, Wise, & Brazelton, 1978) ‘still-face’ procedure. In the studies conducted by Kogan and Carter (1996), parents play with their infant for a short period and then terminate normal social interaction and present a motionless ‘still-face’ (usually for about 2 minutes). Infants in these situations usually show decreases in smiling and looking at the parent, increases in motor activity, and in fussiness or crying. If this disinterest or distress is the result of boredom from insufficient stimulation, then these results support Stern’s (1977) model in that infant positive affective involvement is dependent on the presentation of interesting patterns of parental stimulation.
We used the coding approach that was initially employed by Kogan and Carter (1996) in their ‘still-face’ experiment. Unlike the original research conducted by these scholars, in which different people (specifically trained in coding) were asked to record and systemize mothers’ and infants’ behaviours, one person coded the study participants’ actions and responses to stimuli, presented on the video. Similarly to Kogan and Carter (1996), gaze and affect were coded across baseline play, still-face, and re-engagement. We systemized affect as “positive,” “neutral,” or “negative.” In turn, gaze was recorded as “leaning towards mother” or “withdrawing”. It should be noted that if mothers or babies’ faces were not visible on the screen, we recorded the affect as missing. Three types of gazes were coded: looking at the mother’s face; looking at the toy present in the settings; and looking away or closing eyes. Relying on the experiment conducted by Kogan and Carter (1996), gaze data was coded according to one of six sorts of behaviour recorded in real time.