g. Field, 1992). Handedness was tested by means of a 10-item handedness questionnaire (Van Strien, 1992), in participants to enable selection of fully right-handed participants and their mothers only to enable selection of either fully right-handed or fully left-handed

mothers. The latter was done to increase the likelihood that all mothers, whether right-handed or left-handed, were inclined to bottle-feed by holding the bottle in their dominant hand and the infant on their non-dominant arm, as is the most common pattern of behaviour. Only participants and mothers that were fully right- or left-handed on 10 out of 10 items of the Van Strien checklist were selected. Thus, the group of left-held participants selected all had right-handed mothers – excluding selleck chemicals llc six candidates

with a left-handed mother – and the group of right-held participants all had left-handed mothers – excluding one candidate with a right-handed mother. On the basis of the results LY2109761 of the questionnaires, we excluded the data of a further eleven candidates (and their mothers) from the analyses, mostly for multiple reasons: maternal depression (5), participant depression (4), additional breast-feeding (5), and/or substantial involvement of the father in daily bottle-feeding (3). Fifty-five participants remained: 25 in the left-held (11 male, 14 female) and 30 in the right-held group (15 male, 15 female). The slightly greater number of right-holding mothers was due to the fact that we had especially urged participants

second with left-handed mothers to participate. Age did not differ significantly between groups (Left-held: M = 27.2, SD = 5.1; right-held: M = 25.3, SD = 3.1, t(38.381) = 1.59, p = .120). In both groups the mother had been the primary caregiver, had been the sole or main person involved in feeding, and had fully bottle-fed her child from the very beginning. The stimuli for the tests were constructed from photographs selected from a commercially available database (Lundqvist, Flykt, & Öhman, 1998). For the Emotion test we selected the happy and neutral frontal photographs of five male and five female posers. The photographs of each poser were vertically divided and recombined to form two chimeras: one with the happy face half on the left (from the observer’s point of view) and the neutral face half on the right and the other chimera combining the remaining face halves. The chimeras were transformed into grey-scale images and an oval cut-out of the chimeras was made to obscure (most of) the hair and neck (see Fig. 1a). The chimeras were then rotated vertically to create mirror images of the originals in addition. The resulting eighty images subtended about 9 × 7 cm on the screen. On each of the 40 trials, a chimera and its mirror image were presented simultaneously, one above the other.