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In a test of the hypothesis that the dominant arm would be more active than the nondominant arm, 70 young adults (including 34 left-handers) wore instrumented motion recorders on both wrists for 48 hours. Participants' left arms made approximately 80 more movements per hour than did their right arms, which was unexpected. This mean difference reflected a generalised leftward shift in the distribution of the frequency of arm movements. Two-thirds of the individuals in the sample were characterised by a sinistral bias in arm movement frequencies. Degree of sinistral bias in arm movement frequency was unrelated to hand preference as measured by the Waterloo Inventory. Implications of this new asymmetry are discussed.

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One element of Coren and Halpern's controversial theory [Psychological Bulletin, 109, 90-106 (1991)] that left-handedness is associated with shorter lifespans is the hypothesis that sinistrality is accompanied by a developmental lag. Perinatal traumas could interfere with the normal developmental shift to right-sided lateral preferences during childhood, leading to an association between maturational lag and left-handedness. In a test of this hypothesis, we assessed current stature, predicted adult stature and relative stature, an index of physical maturity, for elementary school-aged children in three separate, large-sample studies. No relations between hand preference and the three measures of physical status were found. Repeated failures to confirm the hypothesis with pre-adolescent samples raise serious doubt about the viability of the left-handed developmental lag hypothesis.

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OBJECTIVE: To determine whether prepartum and postpartum emotional distress in first-time mothers is associated with crying and fussing behavior and activity level in 6-week-old infants, after eliminating potential biases. DESIGN: Observational study examining predictive and concurrent associations between maternal emotions and infant behaviors. SETTING: General community. PARTICIPANTS: Expectant primiparas attending obstetricians' offices for routine prenatal care were recruited in the third trimester. Mothers and babies were required to be free of medical complications to complete the study. Of 113 mothers who enrolled, complete crying/fussing data were obtained in 88 dyads. Activity data were obtained in a designated subgroup of 50 infants. MEASUREMENTS: Mothers completed a self-report scale of emotional distress, the 28-item General Health Questionnaire, at 34 weeks of gestation and at 6 weeks postpartum. Crying/fussing data were obtained using a previously validated parent diary of infant behavior during the sixth week of life. Motor activity was measured objectively in the home setting with actometers. RESULTS: Third-trimester distress was not related to either infant crying/fussing or activity. Postpartum distress was significantly related to crying/fussing duration and bout frequency (r[88] = .45 and .28, respectively; both P < .01). These relations were not diminished after controlling statistically for background and/or potential mediating variables, nor could they be accounted for by different diary-recording styles in the mothers. Postpartum distress was not, however, related to activity level (r[50] = -.09; not significant). Furthermore, the pattern of maternal distress was associated differentially with crying levels. Distress levels increased from prepartum to postpartum among mothers of infants who met predefined clinical criteria for "colic," while decreasing in the others ("colic" status x period interaction: F(1,86) = 8.2; P < .01). Also, infant crying varied among four groups of mothers who differed according to presence and timing of clinically significant emotional disturbance (one-way analysis of variance, F (3,86) = 9.4; P < .001). Infants of mothers who became significantly distressed postpartum ("reactive") cried more than those in the other groups, even mothers who had been distressed both prepartum and postpartum ("depressed") (3.7 vs 2.7 h/d; P = .05, post hoc Tukey). CONCLUSIONS: Maternal emotional distress and infant crying behavior are associated in the postpartum period independent of reporting or referral biases. Clinically significant levels of crying (or "colic") are differentially associated with different patterns of clinically significant maternal distress. Reported concern about either maternal mood or infant crying behavior should be taken seriously as a possible indicator of a stressed mother-infant relationship.

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Child temperament theories generally presume genetic contributions to behavioral differences, but empirical support is based largely on parent ratings of twins. These subjective ratings may be biased by parental exaggeration of dizygotic differences or of monozygotic similarities. An objective assessment of the genetic hypothesis was undertaken with motor activity level, a core dimension of most temperament theories. The activity level of 60 infant twin pairs was measured both by parent ratings and by motion recorders over a 2-day period. Data from the motion recorders showed evidence of genetic influences (RMZ = .76, RDZ = .56), as did parent ratings (RMZ = .82, RDZ = .21). The motion recorder results confirm with instrumentation a critical assumption of temperament theories and identify the presence of genetic contributors to temperamentally relevant behavioral differences in infancy.

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By virtue of being farther along a developmental path for motor activity level, girls may appear to be the less active sex when compared to less physically mature but same-aged boys. If so, observed sex differences in activity level may be an epiphenomenon of sex differences in maturity related declines in AL. To test this hypothesis and the associated premise that females would be more mature and less active than males, the customary activity levels and relative physical maturities of 83 5-8-year-olds were assessed. Relative maturity (percentage of estimated adult height attained) was negatively related to activity level, and girls were both less motorically active and more mature than boys. Though reduced in magnitude, the sex effect remained significant after maturity was added as a predictor of AL. Thus, sex differences are not due only to maturity differences but may be partially mediated by them.

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The impact of a respite program on the cognitive and physical functioning of dementia and nondementia patients, and on the burden perceived by their caregivers, was assessed in a pretest-posttest design. A total of 55 caregivers were interviewed twice, 5 weeks apart. In the respite group, the caregiver's patient experienced a 2-week respite stay in a nursing home during the 5-week interval, whereas in the waiting-list comparison group, the patient experienced ongoing in-home care during the interval. We hypothesized that patient diagnosis (dementia vs. nondementia) would interact with respite exposure, with nondementia patients showing more improvement from respite than dementia patients. Regardless of diagnosis, however, positive effects from respite exposure were found for caregiver reports of the patient's memory and behavior.

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Mentally retarded and nonretarded individuals matched for MA were assessed on gender understanding with the expectation that the two groups would show similar sequencing and attainment. The nonretarded subjects' data mirrored previous cross-sectional findings, but the retarded respondents displayed significantly better gender constancy performance than did their nonretarded counterparts. This unexpected superiority on the constancy component implied different attainment sequences for the groups. Two interpretations were discussed, one attributing the constancy superiority to guessing, the other to greater CA-related knowledge of gender. Present results partially support the hypothesis of similar sequencing in MA-matched groups.

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