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The distinctiveness and recognizability of taste-elicited facial expressions in newborns were examined in 2 studies. Sucrose, sodium chloride, citric acid, and quinine hydrochloride solutions were presented to 12 infants at 2 hours of age. In Study 1, the anatomically based Facial Action Coding System adapted for infants (Baby FACS) was used to obtain detailed, objective descriptions of the infants' videotaped facial responses to each solution. Facial responses to sucrose were characterized primarily by facial relaxation and sucking. The responses to salty, sour, and bitter solutions shared the same hedonically negative upper- and midface components but differed in the accompanying lower-face actions: lip pursing in response to sour and mouth gaping in response to bitter. There was no distinctive facial expression for sodium chloride. These findings demonstrate that newborns differentiate sour and bitter from each other and from salt, as well as discriminating sweet versus nonsweet tastes. In Study 2, untrained adults viewing videotapes of the infants' facial reactions made forced-choice judgments identifying the stimuli presented and rated the hedonic tone of the infants' responses. While the judges accurately identified the newborns' responses to sucrose, there were systematic errors in their judgments of the 3 nonsweet stimuli. The judges' hedonic ratings, on the other hand, clearly differentiated between the infants' responses to the bitter stimulus and the other 3 tastes. The findings are discussed in terms of the possible functional origins and communicative value of taste-elicited facial expressions in infants.

Three studies tested whether infant facial expressions selected to fit Max formulas (Izard, 1983) for discrete emotions are recognizable signals of those emotions. Forced-choice emotion judgments (Study 1) and emotion ratings (Study 2) by naive Ss fit Max predictions for slides of infant joy, interest, surprise, and distress. But Max fear, anger, sadness, and disgust expressions in infants were judged as distress or as emotion blends in both studies. Ratings of adult facial expressions (Study 2 only) fit a priori classifications. In Study 3, we coded the facial muscle components of faces shown in Studies 1 and 2 with the Facial Action Coding System (FACS; Ekman & Friesen, 1978) and Baby FACS (Oster & Rosenstein, in press). Only 3 of 19 Max-specified expressions of discrete negative emotions in infants fit adult prototypes. Results indicate that negative affect expressions are not fully differentiated in infants and that empirical studies of infant facial expressions are needed. ' For this reason, the debate about the existence of "basic" or discrete human emotions (cf. Camras, 1991; Fogel & Reimers, 1989; Ortony & Turner, 1990; Scherer, in press) does not hinge on evidence of whether emotions and their expressions are invariant throughout life.

The distinctiveness and recognizability of taste-elicited facial expressions in newborns were examined in 2 studies. Sucrose, sodium chloride, citric acid, and quinine hydrochloride solutions were presented to 12 infants at 2 hours of age. In Study 1, the anatomically based Facial Action Coding System adapted for infants (Baby FACS) was used to obtain detailed, objective descriptions of the infants' videotaped facial responses to each solution. Facial responses to sucrose were characterized primarily by facial relaxation and sucking. The responses to salty, sour, and bitter solutions shared the same hedonically negative upper- and midface components but differed in the accompanying lower-face actions: lip pursing in response to sour and mouth gaping in response to bitter. There was no distinctive facial expression for sodium chloride. These findings demonstrate that newborns differentiate sour and bitter from each other and from salt, as well as discriminating sweet versus nonsweet tastes. In Study 2, untrained adults viewing videotapes of the infants' facial reactions made forced-choice judgments identifying the stimuli presented and rated the hedonic tone of the infants' responses. While the judges accurately identified the newborns' responses to sucrose, there were systematic errors in their judgments of the 3 nonsweet stimuli. The judges' hedonic ratings, on the other hand, clearly differentiated between the infants' responses to the bitter stimulus and the other 3 tastes. The findings are discussed in terms of the possible functional origins and communicative value of taste-elicited facial expressions in infants.

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