ویژگی ابرازات هیجانی نوزاد برای درک هیجان

Abstract Attachment theory emphasizes the role of negative emotional expression in infancy for establishing proximity to and care of the caregiver. According to Lang's biphasic model of emotions protective reflexes (e.g. startle response) are primed if a defensive motivational set is activated. The aim of the study was to examine whether the perception of an infant emotional expression can prime such defensive behavior. The sample consisted of 48 university students. Startle reflex, corrugator and zygomatic EMG activity and subjective ratings of valence and arousal were assessed as a response to presentation of pictures of different emotional valence. Affective startle modulation was obtained when probes were presented during pictures of the International Affective Pictures System replicating previous findings. By contrast, negative infant emotion pictures did not prompt an augmentation of the startle response, although both the subjective ratings and the mimic EMG activity indicated a clear differentiation between negative and positive infant pictures. This pattern of findings was found only in a between-subject design, but not when the two picture sets were presented in the same session, indicating an interference of contrasting content of pictures.

1. Introduction Infant emotional expression plays an important role for development, because during the first year before the onset of speech and even more during the first months before the up-coming of the first gestures, emotional expression and most of all negative emotional expression is the only way for an infant to communicate his/her needs to the caregiver. Thus, infant emotional expression is a substantial component of the infant-caregiver interaction. In the same way, substantial are the caregiver's responses to infant emotional expression, in particular the ability of the caregiver to perceive these emotional signals and to adequately interpret them, which should enable him/her for an appropriate caregiver behavior. According to attachment theory (Bowlby, 1969 and Ainsworth et al., 1978) negative emotional expression or crying in infants is part of the infant attachment behavior system, which would be activated when the infant is distressed or anxious. The function of attachment behaviors is the activation of the complementary caregiving system of the mother or father in order to gain their support and comfort for emotional regulation (e.g. Spangler et al., 1994). There is plenty of empirical evidence regarding the function and organization of the infant attachment system (e.g. Ainsworth and Wittig, 1969, Main and Solomon, 1990 and Spangler and Grossmann, 1993). Moreover, there is strong empirical support for the important role of the caregiver's behavior on the quality of infant-caregiver attachment in terms of maternal sensitivity (Ainsworth et al., 1978, Grossmann et al., 1985 and Spangler et al., 1996). Regarding the internal regulation of the caregiving behavior, attachment research focused on the role of attachment representation (Main et al., 1985 and van Ijzendoorn, 1995). In contrast, little is known about basic motivational processes regulating the caregiver's responses to infant attachment behavior. According to the biphasic emotion theory of Lang (Lang, 1995 and Lang et al., 1990) emotions are defined as action dispositions, and emotional responses are assumed to be organized on the basis of two opponent motive systems, an appetitive and an aversive system grounded on neurophysiological circuits. According to this approach, the valence of a certain stimulus or a given context defines the general direction of behavior. While unpleasant stimuli activate the aversive motivational system priming defensive behavior to the level of protective reflexes, pleasant stimuli are expected to activate the appetitive behavioral set priming approach behavior. A crucial component of Lang's biphasic theory is the modulatory function meaning that new affective responses are modulated by the ongoing affective valence of behavior or state and that this modulatory effect can be observed on different levels of organization [level of expressive and evaluative language, behavioral level and physiological level (Lang, 1995)]. From this perspective, affective responses are most prominent if there is a match between the emotional foreground and the valence of the new stimulus. Thus, protective reflexes are enhanced if the organism is in an aversive motivational state and are inhibited if the actual valence of the context is positive. Similarly, positive stimuli would activate the appetitive behavioral system stronger given a positive valence of the ongoing context. Empirical support for Lang's biphasic theory comes from a series of studies adopting the startle paradigm, in which the eye-blink response to a probe stimulus (e.g. a sudden loud noise) is investigated, while different affective states are evoked. From their theoretical point of view Lang and coworkers expected that the magnitude of the startle response would be bigger if the startle occurred in a negative context (i.e. if there is a match between stimulus and context), as compared to a positive context (mismatch). In their experiments they presented acoustic or visual startle probes to the subjects during ongoing presentation of picture slides with different emotional valence. In accordance to the theoretical expectations the magnitude of the eye-blink response to the startle probe was larger during presentation of unpleasant slides than during neutral and pleasant slides, the latter leading to the smallest responses (Vrana et al., 1988 and Bradley et al., 1988). These findings have been replicated in various laboratories (Cook et al., 1992 and Hamm and Vaitl, 1996) using aversive conditioned stimuli (Hamm et al., 1993), imagery (Vrana and Lang, 1990), film scenes stimuli instead of pictures (Jansen and Frijda, 1994), or odors (Ehrlichman et al., 1995). The majority of studies were using picture slides stemming from the international affective picture system (IAPS, Center for the Psychophysiological Study of Emotion and Attention, 1994). These pictures vary widely in content and affective tone and are organized in three affective classes: (1) unpleasant (e.g. pictures of violent death, aimed guns, snakes, angry or starving people); (2) neutral (e.g. common household objects); and (3) pleasant (e.g. attractive nudes, romantic couples, cuddling animals, appetizing foods and happy babies). Usually, broad representative selections of the IAPS were used in most studies adopting the startle paradigm. Moreover, in clinical studies, pictures were selected with respect to specific emotions under study. For example, in a study with high animal fearful subjects (Hamm et al., 1997) included a special set of snake and spider pictures. According to Lang (1995), motivational modulation of the startle reflex is generally robust despite variations in specific foreground content (pg. 373). However, in the same paper he addressed the issue of dual motives, meaning that certain stimuli may activate both the appetitive and the aversive motive system simultaneously. Findings of Balaban and Taussig (1994) indicate that within different groups of negative pictures those provoking pity (e.g. pictures of babies undergoing extreme medical treatments or starving people) produce somewhat smaller startle responses. Perceiving such pity pictures may lead to aversive responses and at the same time may activate an approach disposition to help and care for others (see Lang, 1995). These findings indicate that in addition to the valence of picture stimuli their specific content may play an important role, or at least that there may be specific groups of pictures producing different patterns of startle responses. The current study used this elaborated picture perception paradigm to investigate the basic processes of the regulation of the caregiving system in adults. Either pleasant (e.g. smiling) or unpleasant (e.g. crying) infant emotional expressions were used as picture stimuli to activate the caregivers’ emotional systems. As mentioned above, it is assumed that the magnitude of the startle response depends on whether an aversive or appetitive motivational response system is activated. While positive stimuli would activate the appetitive behavioral set, negative stimuli would activate the defensive behavioral set. On the other hand, pictures which are rated as unpleasant, do not necessarily activate a defensive response set (Lang, 1995). For example, negative emotional expression or crying of a baby may be rated as a highly unpleasant stimulus. According to attachment theory, however, infant crying as part of the infant attachment behavior system deserves the function to activate the complementary caregiving system of the mother or father in order to gain their support for emotional regulation. From this perspective, the function of infant crying is to elicit approach behavior in the caregiver and not to activate defensive behavior. The aim of our study was to investigate the usefulness of the startle paradigm for the study of caregiving behavior within an attachment theory framework. In particular, we wanted to investigate whether a sample of pictures including infant emotion pictures of different emotional expressions would specifically modulate the startle eye-blink response. Assuming a phylogenetic base of the caregiving system (Bowlby, 1969) we expect that specific response patterns may be identified in adults in general rather than only in parents. Thus, in the first step of our investigation we included adults not familiar with infant care, in order to identify general response patterns. Of course, there may be specific eye-blink response patterns in adults depending on caregiving experience (parents vs. non-parents) or in parents depending on the familiarity with the child shown in the picture. Moreover, from an attachment perspective, there may be different response patterns in parents with a secure attachment representation as compared to those with an insecure attachment relationship, as these two groups would exhibit different sensitivity to the child's signals on the behavioral level (Grossmann et al., 1988 and van Ijzendoorn, 1995). This issue will be addressed in a different study (Spangler et al., submitted).

Results 3.1. Reliability of affective judgements for IAPS pictures To test whether computer displayed IAPS pictures elicited the same picture evaluation than slides, retest correlations were calculated between the German normative valence and arousal ratings of the 60 IAPS pictures (Hamm and Vaitl, 1993) and the mean ratings obtained in the current study. Retest reliability was (r=0.94) for valence and (r=0.82) for arousal indicating a high correspondence. For the infant pictures, retest correlations were calculated between the valence and arousal ratings of 36 of the 60 pictures already used in a former study ( Spangler et al., submitted) and the mean ratings obtained in the current study. Retest reliability was (r=0.94) for valence and (r=0.83) for arousal indicating a high correspondence. The mean valence and arousal ratings for the IAPS and infant pictures obtained in this study are presented in Table 1 together with the German normative IAPS ratings and infant picture ratings from the Spangler et al. (submitted) study. As can be seen, the affective ratings are within the usual range (see Lang, 1995) and are quite similar for the different samples and different picture sets. 3.2. Valence and arousal judgements of IAPS and infant pictures For a comparison of valence ratings of IAPS pictures and infant pictures three-way MANOVAs with a priori valence (positive, neutral, negative), picture type (IAPS, infant) and the subjects’ gender (male, female) as factors were conducted for the valence and arousal ratings. As can be seen from Fig. 1 there was a similar pattern of findings for the between-subjects and the within-subjects analysis. First, with respect to the a priori valence of pictures the valence ratings of both picture types were as expected (between-subjects: F2,40=171.45, P<0.01, ε=0.67; within-subjects: F2,44=160.4, P<0.01, ε=0.71. Positive pictures received the highest and negative pictures the lowest valence ratings, neutral pictures were in-between (Duncan, P<0.05). Secondly, the infant pictures were generally rated as more pleasant than the IAPS pictures (between-subjects: F1,20=11.0, P<0.01; within-subjects: F1,22=37.59, P<0.01. As indicated in Fig. 1 this seems to be specifically the case for neutral and negative pictures. The interaction between valence and picture type, however, was significant only for the within-subjects comparison F2,44=9.95, P<0.01, ε=0.71. It should be noted, however, that nevertheless, clear differences depending on the a priori valence of the pictures were given for the infant pictures. Thirdly, in both analyses an interaction between gender and valence occurred (between-subjects: F2,40=3.96, P<0.05, ε=0.67; within-subjects: F2,44=2.92 P<0.10, ε=0.71. Post-hoc analyses showed that female subjects exhibited a wider range of valence ratings. Positive pictures were rated more positive and negative pictures more negative in females as compared to males. Affective judgements of valence and arousal for positive, neutral and negative ... Fig. 1. Affective judgements of valence and arousal for positive, neutral and negative infant and IAPS pictures. Figure options Unpleasant and pleasant pictures were rated as more arousing than neutral contents (see Fig. 1). The arousal ratings were larger for the negative pictures and lowest for the neutral ones, the ratings for positive pictures being in-between. This rating pattern was obtained both in the between-group and within-group comparison. F2,40=52.33, P<0.01, ε=0.90 and F2,44=102.74, P<0.001, ε=0.72, respectively. As indicated by the significant interaction between picture type and valence in the within group comparison F2,44=23.79, P<0.001, ε=0.97 the arousal rating of the infant pictures showed a slightly different pattern than those of the IAPS pictures. While unpleasant IAPS pictures ware rated as most arousing, negative infant pictures obtained only slightly larger arousal judgements than positive pictures. To test whether the exclusive presentation of infant or IAPS pictures, respectively, in one session as compared to a simultaneous presentation of different types in one session affected the subjective ratings, the valence and arousal ratings were compared using a two-way MANOVA with valence (positive, neutral, negative) and type of session (same, mixed). There were no significant effects regarding type of session indicating that the subjective ratings were not affected by presenting a different picture type. Thus, different emotional expressions of infants prompted the same different evaluations as standard affective materials both in the within and between comparison. 3.3. Startle reflex For a comparison of the startle response to IAPS and infant pictures, three-way MANOVAs with a priori valence (positive, neutral, negative), picture type (IAPS vs. infant) and gender (male, female) as factors were conducted. The between-subjects comparison of the magnitude of the startle reflex revealed a significant interaction between picture type and valence F2,44=4.39, P<0.05, ε=0.95. Simple main effect analyses revealed that the startle response varied in the expected way only for the IAPS pictures F2,44=6.07, P<0.01, ε=0.95, but not for the infant pictures F2,44=0.60, N.S.. As can be seen from Fig. 2, for the IAPS pictures the response was highest for the unpleasant ones and lowest for the pleasant ones, the neutral ones lying in-between. Their linear component was significant F1,22=7.32, P<0.05. The difference was significant between pleasant and unpleasant as well as between neutral and unpleasant (Duncan, P<0.05). The startle responses to both pleasant and neutral and unpleasant infant pictures were on the level of the positive IAPS pictures and were significantly lower than the startle responses to the neutral and negative IAPS pictures (P<0.05). Magnitude of the startle response for positive, neutral and negative infant and ... Fig. 2. Magnitude of the startle response for positive, neutral and negative infant and IAPS pictures. Figure options Regarding the within-comparison of the startle response no significant valence effects could be identified indicating a lack of startle modulation in this context. Although Fig. 2 indicates a higher level of startle response in subjects of the within-comparison, this group difference, which is due to a somewhat higher variance in the within-group, is not significant. 3.4. Facial muscle activity For the corrugator and zygomatic response again three-way MANOVAs with a priori valence, picture type and gender as factors were conducted for the between-subject and the within-subject analysis. The between-subject comparison of corrugator activity for infant and IAPS pictures revealed a significant main effect for valence F2,40=9.58, P<0.01, ε=0.59, which was qualified by two-way interactions between valence and picture type F2,40=3.60, P<0.05, ε=0.59 and between valence and gender F2,40=5.89, P<0.01, ε=0.59. The within-subject comparison of corrugator activity resulted in main effects for picture type F1,22=9.16, P<0.01 and valence F2,44=10.04, P<0.001, ε=0.54. Valence effects occurred in both designs. As can be seen from Fig. 3 (upper panel) the data indicate — as expected — a decrease in corrugator activity during positive pictures and an increase during negative ones. This response pattern was obtained for both picture types in the between-subject design as well as in the within-subject design. Nevertheless, there are obvious differences with respect to picture type and design. For IAPS pictures, the corrugator decrease for positive pictures is only minimal. In contrast, there is a marked corrugator increase during negative pictures which is significantly higher than during neutral and positive pictures (Duncan, P<0.05). This pattern is almost the same for the two different designs. Quite differently for the infant pictures (at least for the within-subject design), there is a marked corrugator decrease for positive and also for neutral pictures which statistically differs significantly from the small corrugator increase during presentation of negative infant pictures (P<0.05). Although for the between-subjects design the pattern is similar, the differences between the values are too small to be significant. In sum, as is expressed by the main effects for picture type, infant pictures have a bias for corrugator decrease, while IAPS pictures have a bias for increase. Gender effects only occurred in the between-subjects design. Post-hoc analyses indicated that the valence effect is more pronounced for the female subjects. Corrugator and zygomatic response for positive, neutral and negative infant and ... Fig. 3. Corrugator and zygomatic response for positive, neutral and negative infant and IAPS pictures. Figure options The zygomatic responses to positive, neutral and negative infant and IAPS pictures are depicted in the lower panel of Fig. 3. Although zygomatic activity seems to be higher during presentation of positive pictures as compared to negative pictures, both the between-subjects and the within-subjects comparison of zygomatic activity did not reveal any significant effect. It should be noted, however, that there was a tendency for a main effect for picture type in the within-subjects analysis F1,22=3.13, P<0.10 indicating higher zygomatic responses during infant pictures as compared to IAPS pictures which again speaks for a bias for positive evaluation of infant pictures.