Pii: S0163-6383(01)00079-0

Duchenne and non-Duchenne type of smiles were studied in infants with and without Down syndrome while they looked at their mother’s face or at objects. In infants with Down syndrome the Duchenne smile with open mouth was the most frequent, regardless of the direction of their gaze. The study of different type of smiles may be related to sociocognitive development in children with Down syndrome. © 2002 Elsevier Science Inc. All rights reserved. It is well known that adults from the general population express different types of smiles according to the social context. The common morphology of these smiles is the bilateral or unilateral raising of the lip corners as a part of various more or less complex facial configurations with different functional meaning. The type of smile universally associated most clearly with a discrete positive emotional state is that which includes, in addition to the bilateral raising of the lip corners, the raising of the cheeks (Ekman, Davidson & Friesen, 1990). Although also referred to by other terms, such as “felt smile” or “full smile,” this type of smile is most commonly known as the Duchenne smile, in reference to the nineteenthcentury French anatomist who defined the expression corresponding to frank joy (Ekman, 1989). It is also well known that each type of smile is in some way sensitive to social learning, so that even cultural differences have been described in relation to frequency of Duchenne smiles in typically-developing infants, with higher frequencies being observed in Euro American and Japanese infants than in Chinese infants (Camras et al., 1998). * Corresponding author. Tel.: 34-91-397-45-94; fax: 34-91-397-52-15. E-mail address: [email protected] (F. Carvajal). Infant Behavior & Development 24 (2001) 341–346 0163-6383/01/$ – see front matter © 2002 Elsevier Science Inc. All rights reserved. PII: S0163-6383(01)00079-0 With regard to typically-developing infants, the Duchenne smile and other smile morphologies have been described according to social context as follows: a) when infants direct a smile at their mother they display mainly the Duchenne type (Fogel, Nelson-Goens, Hsu & Shapiro, 2000; Fox & Davidson, 1988; Messinger, Fogel & Dickson, 1997), almost always with the mouth slightly open (Jones, Raag & Collins, 1990); b) when infants are in play situations demanding some visual activity (e.g., looking at a storybook), however, they display non-Duchenne smiles, characterized simply by the oblique retraction of the lip corners with relaxed cheeks, generally with mouth closed (Dickson, Walker & Fogel, 1997); and c) during play situations involving tactile stimulation, infants display Duchenne or non-Duchenne smiles with open mouth and a marked dropping of the jaw (Dickson, Walker & Fogel, 1997; Fogel et al., 2000). In conclusion, it can be stated not only that type of smiles may reflect how young infants differentially perceive diverse elements in their environment, but also that their emotional expressions (at least in relation to type of smiles) constitute well-differentiated facial responses that reflect their particular relationship with that environment. Bearing in mind the above, it may be interesting to analyze the evolution of type of smiles in infants with Down syndrome in order to better define their level of sociocognitive development at a any given point. Considering the cognitive deficit of these children, which manifests itself with time, the studies by Legerstee and cols. (Legerstee & Bowman, 1989; Legerstee, Bowman & Fels, 1992) show that their socioemotional behavior is comparable to that of typically-developing infants, in that they smile and direct their vocalizations more frequently at people than at the objects around them (see also Carvajal & Iglesias, 2000). Nevertheless, these authors did not analyze the kind of smile the infants produced, and we might therefore ask to what extent infants with Down syndrome emit facial expressive responses that are similar to those of typically-developing infants. To date, research has only provided data on type of smiles for children with Down syndrome from age 22 months onwards in child-experimenter interactions, with no differences in frequency of Duchenne smiles reported in comparison to typically-developing infants of equal mental age, although children with Down syndrome do present a higher frequency of non-Duchenne smiles (Kasari, Mundy, Yirmiya & Sigman, 1990). In the light of this result, it would be interesting to determine whether in the first year of life the relative distribution of Duchenne and non-Duchenne smiles in infants with and without Down syndrome is similar to that reported for children over 22 months old. In an attempt to determine whether infants with Down syndrome react differentially, with different type of smiles, to persons and to objects, as a first step we compared Duchenne and non-Duchenne smiles displayed by infants with and without Down syndrome when they look at their mother’s face or when they look at the objects around them in natural interaction conditions with the mother. Despite the differences observed between infants with and without Down syndrome in quantitative parameters such as frequency, duration or intensity of facial expressions associated with emotions, if we assume a similar pattern of emotional development in the two cases (Cicchetti & Sroufe, 1976, 1978, among others; for a review, see Carvajal & Iglesias, in press), it could be expected that both typically-developing infants and infants with Down syndrome direct mainly Duchenne-type smiles at the mother and non-Duchenne type at toys, all of these smiles being mainly with open mouth. 342 F. Carvajal, J. Iglesias / Infant Behavior & Development 24 (2001) 341–346