654

WHAT’S DIFFERENT ABOUT BABIES WHO ‘FAIL TO PROVIDE DATA’ IN HABITUATION EXPERIMENTS?

John Oates

Centre for Human Development and Learning, Open University, Walton Hall, Milton Keynes MK7 6AA, U.K.

A significant proportion of young infants recruited for cognitive/perceptual experiments fail to engage fully or disengage by fretting, crying, or falling asleep before completing trials. The possibility of such behaviours being caused by more than random state changes has become a matter of some concern because of the potential biasing effects of such selective data loss.

43 mothers (mean age 30 yrs, SD=5) and their infants (mean age 56 days, SD=17.5) were recruited through Health Visitors and attended laboratory sessions. These sessions included computer-controlled habituation experiments, 5minute video recordings of mother-infant interaction and a structured interview which elicited mothers’ accounts of pregnancy, delivery and relationship with infant.

The experiments presented one-second digitised video clips of female actors speaking a standard phrase with different facial and vocal expressions, under infant control through conjugate reinforcement of high amplitude sucking. A complete experiment comprised ten 45 second trials. Each trial was video-recorded and coded for level of infant engagement (visual attention) with the stimulus display. The mother-infant interaction videos were coded for infant engagement level in 45 second time samples.

20 infants completed all ten trials (‘completers’). Of the 23 non-completers, 2 infants failed to complete the first trial and 2 1 completed between 1 and 8 trials. The shape of the distribution of number of trials completed suggested that the completers and non-completers represented distinct groups and subsequent analysis focussed on factors associated with this grouping.

Three correlated factors were strongly associated with non-completion: the administration of medication during labour, mothers’ reports that they had not identified with their foetus during the first months of pregnancy and mothers’ descriptions of their infants (at the time of testing) as having only rudimentary capacities for cognition and emotion. In contrast, mothers of completers were unlikely to have received medication during labour, were more likely to report that they had identified positively with their unborn infants early in pregnancy and to describe their infants as currently having capacities for a range of thoughts and feelings.

While non-completion was unrelated to infant age, age was strongly associated with variation in infant engagement: infants older than the sample mean showed much higher sustained attention. Engagement level was also associated with mothers’ identification with their unborn child and reports of their infants’ cognitive and social capacities; this effect was independent of infant age.

Differences in infants’ levels of engagement with their mothers during play interaction were strongly correlated with differences in engagement during the experiments and were associated with independent effects of infant age and mothers’ identification during pregnancy with their unborn infants. Older infants and infants whose mothers reported early identification showed higher levels of engagement during play.

In summary, these data suggest that non-completion and low levels of engagement in habituation experiments with young infants are not randomly distributed, but are associated with stable factors which mark important developmental processes.

Research supported by Economic and Social Research Council grant R000234331