Response to commentaries by Leslie B. Cohen and Alan Slater

Abstract

The clear message running through the target article and commentaries is thatthe preference procedure can yield both familiarity and novelty effectsdepending on the experimental setting, and that this bidirectionality can makeit difficult to interpret infants’ behaviour in terms of the knowledge driving it.The commentators share our concerns about the interpretation of data obtainedfrom modifications of the original habituation and preference procedures, andprovide further examples of cases where uncertainty about the direction of aneffect has led to differing conclusions about infants’ cognitive abilities.The commentators usefully add ideas on how to avoid the problem wedescribe. Our own suggestion was to follow the course of infants’ looking overtime. In the light of Hunter and Ames’ (1988) model of infant attention, weargued that if infants are found to pass from a preference from one stimulus to apreference for the other, the former might more confidently be identified as afamiliarity preference, and the latter as a novelty preference. Slater takes issuewith this suggestion on two grounds: first, because evidence suggests that thepattern of preferences described by Hunter and Ames is not always found, andsecond, because the insertion of ‘probe trials’ testing infants’ preferences mightinterfere with the habituation process. We address these points in turn.We see the validity of Hunter and Ames’ model as an empirical question. Thepoint we wish to emphasise is the importance of assessing its validity in differentexperimental contexts, as we believe that regularities in the direction of infants’shifts in attentional preferences over time are not only potentially theoreticallyrevealing but may also prove a useful experimental tool. Where a significantpreference in a single direction does not allow a definitive conclusion to be drawn,as in Houston-Price (2002), obtaining preferences in both directions over timecould solve the problem, if Hunter and Ames’ model is correct.However, as Slater notes, a familiarity effect is not always observed prior to anovelty effect. For instance, Fantz (1964) measured infants’ looking times towardsfamiliar and novel stimuli during 10 1-min intervals, and found no period offamiliarity preference. Similarly, when Rose and Slater (1983) familiarized 3- and 5-month-olds to a visual stimulus for 20 and 10s respectively, infants showed anovelty preference on subsequent testing with no preceding preference forfamiliarity. While these studies may appear to fail to support the model ofdynamic attentional preference presented by Hunter and Ames, they are also goodexamples of where the failure to find aneffecttells us little about whether thateffect