Sex differences in neonatal state and lateralized head orientation

Abstract

Abstract:Sex differences in state and head orientation were examined 10 to 22 hours after birth for 50 healthy, full-term, normal, vaginally delivered neonates. None of the males had been circumcised at the time of testing. The procedure required videotaping for 30 min in three different conditions: supine, seated in an infant seat (inclined 35°), and seated in an assistant,s lap after having arms or legs manipulated for 10 s. Videotapes were analyzed for direction of infant,s head orientation and state. Males spent more time in sleep states than females, and females spent more time than males in alert states. The left or right direction of head orientotion was more associated with alert states for females and with sleep states for males. This sex difference may be relevant for sex differences in handedness and other forms of hemispheric specialization of function. Article:State is the dominant characteristic of the newborn behavioral repertoire, influencing the infant's display of specific behaviors and reflexes, orientation and responsivity to environmental stimulation, and posture (Casaer, 1979;Korner, 1969Korner, , 1972Prechtl, 1974;Wolff, 1966Wolff, , 1987. Of particular interest have been reports of the relation between the infant's state and pattern of supine head orientation (Cornwell, Fitzgerald, & Harris, 1985;Michel & Goodwin, 1979). The heads of supine infants are more likely to be oriented laterally during quiet-alert and active-alert states than during a fussy or crying state (Cornwell et al., 1985;Michel & Goodwin, 1979). The present study examines the relations of newborn state and sex to supine lateral head orientation.The designs of the Cornwell et al. (1985) and the Michel and Goodwin (1979) studies limited the generality of their conclusions about the influence of state on newborn supine head orientation. Both studies assessed state during a very short time period (4 and 3 min, respectively). Cornwell et al. provided no data before the 2-week assessment. Therefore, the data from Cornwell et al. are not very revealing about the influence of state on newborn supine head orientation. The Michel and Goodwin study did focus on the newborn; however, not only was the assessment period extremely short, but the influence of state on head orientation was only a minor aspect of that study. In order to assess the influence of state on newborn behavior, either the length of the observation period must be long enough to insure alert states or procedures must be employed to provoke the alert states.Control for potential differences between the sexes also must be made when assessing newborn state. Korner et al. (1988) reported that preterm males were more frequently in states of sleep or waking activity (fussiness) at 34 weeks postconceptual age, whereas same-aged preterm females slept less than males and were more often in a quiet-awake state. These sex differences were also found to be consistent across assessment examinations. Some previous reports of sex differences in irritability, responsiveness, and f...

Visually guided reaching and waking behavior in early infancy

“…The organization of state behavior has often been used as an index of the integrity of the central nervous system [8,23]. The sex differences in waking behavior reported here and in previous studies [8,9] suggest sex differences in the maturation of the central nervous system.…”

“…Similarly, Harkins, et. al [9] found that female infants remain in "quiet alert" states longer than male infants who exhibit more crying and sleeping as well as more frequent state transitions. Taken together, these studies suggest that the integrity of the female nervous system provides briefer and calmer transitions into wakefulness thereby providing longer periods of quiet alertness.…”

“…Past studies found relation of sex differences in the maintenance of no distress wakefulness [8,9] such that preterm males exhibit more fussiness at 34 weeks post-conceptual age than females [8] and females exhibit a more "quiet alert" states for longer durations than males. However, both studies involved handling the neonate for neurobehavioral assessment and maneuvering of the limbs, and may therefore, represent differences in ability to sustain non-distress wakefulness in response to handling rather than in a free-field situations.…”

Our Sexy Brain; Our Compelling Environment: Interactionism in Female Development

“…Female infants continue to show increased attention, focusing, and perceptual sensitivity when compared to males (Else-Quest, Shibley Hyde, Hill Goldsmith, & Van Hulle, 2006). With the male infants' more irritable, fussy state, they show an increased tendency to sleep less, cry more, grimace, show anger, fuss, want to be picked up, kick, and use more motor movements (Michel, Harkins, & Meserve, 1990;Silverman, 1987;Weinberg et al, 1999, p. 16). Male infants appear to have more difficulty selfcomforting, and more trouble with states of overarousal and excitement, and, in general, demonstrate greater lability in their emotions and problems regulating their affectivity when com-pared to females (Weinberg et al, 1999).…”

The development of motor asymmetries in 1-month-old infants who were prenatally exposed to cocaine

“…Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/termsand-conditions Michel, Harkins, & Meserve, 1990;Ronnquist & Hopkins, 1998), demonstrate greater grasping strength in their right hand (Petrie & Peters, 1980;Tan, Ors, Kurkcuoglu, & Kutlu, 1992), and will grasp an object for significantly longer in their right hand than in their left hand (Caplan & Kinsbourne, 1976;Petrie & Peters, 1980). In addition, some research shows that young infants are more likely to step with their right foot first during elicitation of a stepping reflex (Melekian, 1981;Peters & Petrie, 1979).…”