ترجیح طرف جایگاهی با پردازش جانبی حالات صورت نوزاد در زنان در ارتباط است

Abstract Women’s cradling side preference has been related to contralateral hemispheric specialization of processing emotional signals; but not of processing baby’s facial expression. Therefore, 46 nulliparous female volunteers were characterized as left or non-left holders (HG) during a doll holding task. During a signal detection task they were then asked to detect the emotional baby faces in a series of baby portraits with neutral and emotional facial expressions, presented either to the left or the right visual field (VFP). ANOVA revealed a significant HG × VFP interaction on response bias data (p < .05). Response bias was lowest when emotional baby faces were presented in the visual field of cradling side preference, suggesting that women’s cradling side preference may have evolved to save cognitive resources during monitoring emotional baby face signals.

. Introduction The vast majority of women (60–80%) prefer to cradle a baby on the left side of their body (Bogren, 1984, Harris et al., 2006, Lucas et al., 1993 and Manning and Chamberlain, 1991). This behavior cannot be fully explained by handedness (Harris et al., 2001 and Saling and Bonert, 1983). Left-side preference has been found in female preschoolers (De Château and Andersson, 1976 and Saling and Bonert, 1983) and in never-pregnant adult females (Saling & Tyson, 1981), and is thus neither due to maternity nor previous experience with children, although it might be enhanced by these factors. Left holding preference is present when actually holding a baby or a doll, and also during imagining of holding a baby (Harris, Almerigi, & Kirsch, 2000) or a kitten (Almerigi & Harris, 2002). The left cradling preference was present in every culture investigated (Harris et al., 2006, Lockard et al., 1979 and Saling and Cooke, 1984). Left cradling preference has also been found in monkeys (for an overview see Hopkins, 2004 and Tomaszycki et al., 1998), and great apes (Manning & Chamberlain, 1990). Studies of historical human trans-generational family picture sets indicated baby holding similarities within female relatives (Manning, 1991 and Manning and Denman, 1994), suggesting that the development of cradling side preferences may rely on a biological basis and provide evolutionary advantages. Holding the baby is everyday activity in a caregivers’ life, not only for the need to transport them, but also for various other reasons, such as monitoring, communicating, and regulating their emotional state. The interaction between caregiver and child consists of reciprocal signals, such as touches, sounds and vocals, as well as facial expressions. These signals can elicit caregiver behavior (Spangler, Geserick, & von Wahlert, 2005), which is influenced by individual experience and intuition about the baby’s needs (Papousek & Papousek, 1995). Neutral state information indicates that the baby may feel safe, and no urgent response is necessary. The caregiver’s perceptual sensitivity in distinguishing between the baby expressing emotional vs. neutral state signals, as well as responding to them appropriately and promptly, may be considered an important prerequisite for the establishment of a ‘secure’ bonding (Ainsworth et al., 1978 and De Wolff and van Ijzendoorn, 1997). This corresponds to the finding that the mother’s sensitivity in perceiving the infant’s emotional state predicts mother–child interactions (Donovan, Leavitt, Taylor, & Broder, 2007), and that the mother’s appropriate response to baby signals determines mother–child attachment (Seifer, Schiller, Sameroff, Resnick, & Riordan, 1996), which is known to influence child development (Sroufe, 2005). Thus, mechanisms supporting the caregiver’s optimal recognition of affective child signals may be beneficial for future child development. From an evolutionary viewpoint it seems evident that the integration of spatial and functional relations between central nervous system structures offers some adaptive potential to optimize efficacy of operating neural networks. As such, a right hemisphere specialization with respect to the processing of emotional stimuli was suggested (Basu and Mandal, 2004, Borod et al., 1998, Burton and Levy, 1989 and Duda and Brown, 1984), particularly relevant during the processing of emotional faces (Best et al., 1994 and Buchtel, 2001). Because the right hemisphere receives the visual input directly from the (contralateral) left perceptual field, right brain damaged patients are expected to show impaired visual perception of emotional stimuli presented in the left visual field (Borod et al., 1998 and Buchtel, 2001), but other theories may offer explanations for this finding, too. When caregivers hold the baby on the left side of their body, the baby’s face lies in their left visual field. Thus, visual information originating from the baby will be first transmitted to the right hemisphere. A right hemispheric specialization may thus facilitate the monitoring of the child’s emotional state (Manning and Chamberlain, 1991 and Vauclair and Donnot, 2005) and improve mother–child communication (Sieratzki & Woll, 2002). Several previous studies (Bourne and Todd, 2004, Donnot and Vauclair, 2007, Harris et al., 2001, Lucas et al., 1993 and Vauclair and Donnot, 2005) investigated the association between holding preference and left/right hemispheric processing advantage for emotional faces by presenting chimeric adult faces. Chimeric faces are produced by combination of one half of a neutral face with the other half of a happy face of the same portrayed person. Participants see two faces, one with the happy half on the left side, one with the happy half on the right side. They have to choose the face that looks happier to them. Individuals with a typical right hemisphere advantage choose that face more often when the happy half of the face is in their left visual field. Most of these studies found a right hemispheric processing advantage in women holding the doll on the left side (left holders), and no clear hemispheric advantage in non-left holders (Bourne and Todd, 2004, Harris et al., 2001 and Vauclair and Donnot, 2005). However, there are also studies, which did not find an association between holding side and hemispheric processing advantage (Donnot and Vauclair, 2007 and Lucas et al., 1993). The present literature on cradling preference and hemispheric advantage is characterized by some limitations. First, the use of adult face stimuli may be inappropriate and baby faces would be more authentic. Functional imaging studies support this view. Studies have shown that stimulation with child faces produces different activation patterns of brain regions than stimulation with adult faces (Leibenluft, Gobbini, Harrison, & Haxby, 2004), especially of those brain areas being associated with attention and processing of empathy. Second, cradling behavior has not yet been investigated with respect to the recognition of negative facial expressions. This is noteworthy, since a right hemisphere advantage for processing baby faces was observed for negative facial expressions, only (Best et al., 1994). Third, cradling side preference studies have not considered response accuracy, response bias and reaction time data concerning the detection of emotional faces (Bourne and Todd, 2004, Harris et al., 2001, Lucas et al., 1993 and Vauclair and Donnot, 2005), but these measures may represent crucial factors during mother–child interaction. The aim of this study was to determine whether women who prefer to hold a doll on the left side of their body recognize emotional face expressions better when baby face portraits are presented in their left visual field, and whether non-left holders show the opposite pattern. We hypothesized that such an association would be identifiable as a significant two-way interaction of the between subject factor ‘holding group’ and within subject factor ‘visual field of presentation’. Further, processing differences of positive and negative face expressions would be seen as a three-way interaction of the former and the within subject factor ‘emotional baby face expression’ (positive vs. negative).

5. Conclusion Women’s holding side preference is related to a contralateral hemispheric specialization, guaranteeing a lower response bias to judge neutral baby faces erroneously as expressing an emotion. Our data supports our hypothesis that saving cognitive resources when detecting emotional baby face expressions is involved in determining cradling side preference.