Growth curve analyses are best suited to examine the relation between developmental pathways and selective breeding: comment on Hofer, Shair, Masmela, & Brunelli, "Developmental effects of selective breeding for an infantile trait: the rat pup ultrasonic isolation call".

Hofer, Brunelli, Shair, & Masmela (2001) provide valuable information about the effects of selective breeding on rat-pup behaviors and physiology. Although the design and statistical analytic techniques employed are typical of those used to evaluate behavioral development in animals, I offer several suggestions about how to evaluate the influence of selective breeding on developmental pathways using modern statistical techniques. As Hofer et al. demonstrate, the development of rat behavior and physiology can be an excellent model for examining the relation between selection and development.

A developmental-psychobiological approach to developmental neuropsychology.

Although both developmental psychobiology and developmental neuropsychology examine the interface between biological and psychological processes, they differ in conceptual framework. This article argues for the incorporation into developmental neuropsychology of certain aspects of the conceptual framework of developmental psychobiology. Three principles of dynamic psychobiological interaction are described and applied to four issues in neuropsychology (handedness, sex differences in behavior, critical periods, and modularity of structure-function relations). Then, it is proposed that developmental psychobiology can make four direct contributions to developmental neuropsychology. Finally, it is argued that the value of the conceptual framework provided by developmental psychobiology depends, in part, on how well it translates into procedures that can be applied in the clinical settings of the developmental neuropsychologist.

Effect of certain task characteristics on performance of two neuropsychological tests of spatial ability.

Certain neuropsychological assessments of spatial ability assume that the processing of diagonality and nondiagonality of patterns is equivalent and that processing 2-D representations is equivalent to processing 3-D objects. The Stick Test and the Locomotor Maze Test also assume that successful performance requires the use of mental rotation. Normal adult subjects received either 2-D or 3-D versions of the Stick Test (n = 45) or an unlabeled or labeled version of the maze test (n = 25). Both tests used either nondiagonal or diagonal patterns. More errors were made on 2-D representations of sticks than on the 3-D sticks. Also, more errors occurred with the diagonal than with the orthogonal patterns on both tasks. When maze paths were labeled, fewer subjects made errors on the orthogonal paths than on the diagonal paths. Few subjects reported using mental rotation to perform these tasks. The performance of normal adults may violate the assumptions usually made about a test's measure of spatial ability.

Sex differences in parental influences on children's story-telling skills.

Acquisition of story-telling skills is an aspect of language development that is influenced by hearing parental story telling. Because discourse between parent and child is affected by the sex of both parent and child, we hypothesized that sex differences would affect parental story telling and children's acquisition of story-telling skills. For this study, 24 children (12 girls, 12 boys) told a story from a picture book both before and after hearing a parent (12 mothers or 12 fathers) tell the story. Children's stories improved after hearing a parent tell the story. Sons told stories containing more evaluatives (linguistic forms believed to promote better comprehension and memory of stories) after hearing mother's rather than father's story telling, and daughters told stories containing more evaluatives after hearing father's, rather than mother's, story telling. There were no differences in mothers' and fathers' use of evaluatives when telling stories to sons as compared with daughters.

Maternal influences on infant hand-use during play with toys.

Infant hand-use preferences are related to mother's, but not father's, handedness. Since infants match mother's hand-use during toy play, maternal handedness can affect infant hand-use. Twenty-eight mother-infant pairs (14 left-handed and 14 right-handed infants but all right-handed mothers) were videotaped while playing with six toys on the infant's 7-, 9-, and 11-month birthdays. Play was analyzed for five kinds of hand-use biasing situations, but maternal hand-use was the dominant influence. Infant matching of maternal hand-use increased with age and right-handed infants and female infants matched maternal hand-use more frequently. Concordance of hand-use preference between mother and infant seemed to account for both the matching and the stronger preferences of the right-handed compared to the left-handed infants.

Rate variables and automatized naming in developmental dyslexia.

The rate variable in rapid automatized naming (RAN) was investigated in 50 adolescent and 40 adult students with developmental dyslexia, in matched normal controls, and in learning-disabled students without reading difficulties. Visual stimuli depicting familiar colors and common objects were presented in isolation at three film speeds and three exposure times. Film speed and exposure time contributed as independent variables to error rate; and dyslexic subjects of both age groups made significantly more naming errors than controls. Dyslexic subjects also responded with longer naming latencies than controls when the same RAN stimuli were presented in a continuous sequential mode as a matrix of rows and columns. Naming latencies in the sequential presentation were highly correlated with naming errors in the film version. The implications of reduced naming rates for nongraphological stimuli in developmental dyslexia are discussed.

The timing of syllable repetitions in developmental dyslexia.

The temporal organization of motor speech was examined in dyslexic adolescents and adults without overt speech difficulties, matched normal readers, and learning disabled adolescents without reading difficulties. Subjects were asked to repeat nonsense two- and three-syllable strings in time to each of four metronome speeds. Speech samples were analyzed for repetition rates, time coherence between prescribed and actual performance, and serial ordering of three-syllable strings. Dyslexic subjects deviated more from the prescribed rate, repeated syllables too slowly at all metronome speeds, and made more speech sequencing errors than normal or learning disabled controls. Repetition rate and syllable sequencing contributed as independent variables to the temporal organization of motor speech. The relevance of motor speech deficits for reading impairment in dyslexia is discussed.

Restricting the field of view: perceptual and performance effects.

Visual perception involves both the high acuity of foveal vision and the wide scope of overlapping peripheral information. The role of peripheral vision in competent performance of the adult visuomotor activities of walking, reaching, and forming a cognitive map of a room was examined using goggles which limited the scope of the normal field of view to 9 degrees, 14 degrees, 22 degrees, or 60 degrees. Each restriction of peripheral field information resulted in some perceptual and performance decrements, with the 9 degrees and 14 degrees restriction producing the most disturbance. In addition, bodily discomfort, dizziness, unsteadiness and disorientation, were reported as the subjects moved around with restricted fields of view.

Evidence for a maternal effect on infant hand-use preferences.

Left-handed offspring occur more frequently when one or both parents are left-handed. Among parental pairs with discordant handedness, left-handed mothers have more left-handed offspring than do left-handed fathers. No previous study has looked for this maternal effect in the hand-use preferences of infants. Handedness of 42 infants (21 females) 6-13 months of age (M = 10 months) was assessed by a reliable and valid procedure that provides hand-use preference scores separately for reaching and unimanual manipulation of objects. Equal numbers of age-matched male and female infants were formed into three groups representing different patterns of parental handedness: neither parent left-handed, father left-handed, mother left-handed. Infants of left-handed mothers showed more left hand-use than infants of left-handed fathers or infants of right-handed parents. Indeed, 64% of infants with left-handed mothers had significant left hand-use preference scores whereas none of the infants in the other groups had significant left hand-use preference scores. Possible mechanisms for this maternal effect on infant hand-use preferences are discussed.

Postural and lateral asymmetries in the ontogeny of handedness during infancy.

Ten newborn infants who preferred to lie with their heads turned rightward and ten who preferred to lie with their heads turned leftward had their hand-use preferences for reaching assessed at 8 different ages during the period 12-74 weeks postpartum. Eighteen infants maintained stable hand-use preferences throughout this period and the direction of their neonatal head orientation preference predicted the hand they preferred to use. The neonatal head-turn preference was maintained through the first 2 months and induced lateral asymmetries in visual regard and motor control of the hands. These lateral asymmetries are plausible contributors to mechanisms linking neonatal headturn preference to infant hand-use preference. Thus, the dextral bias in handedness may be derived, in part, from the rightward bias in neonatal head-turn preference.

Spatiotemporal linkage in infant interlimb coordination.

Timing and direction of movement of the arms and hands of 7- and 11-month-old infants were examined during bimanual reaching for a transparent cube. Videotape analysis of frames from release of the hands to initial contact of one hand with the cube revealed that hand movement was more often temporally linked for 7-month infants than for 11-month infants. Also, at 7 months, the hands moved toward the cube in the same direction, whereas at 11 months, they moved in opposite (complementary) directions. Thus, although both 7- and 11-month infants perform bimanual reaching, at 7 months the 2 hands are linked both in timing and direction of movement in a fashion different than at 11 months.

Hand-use preference for reaching and object manipulation in 6- through 13-month-old infants.

Validity, reliability, and stability of separate assessment of hand-use preferences for reaching, object manipulation, and complementary bimanual action were determined for 6 through 13 month-old male and female infants. Only hand-use preferences for complementary bimanual action varied with age. Females had more distinct hand-use preference than males but only for object manipulation. Comparison of hand-use preference among these different sensorimotor skills can provide a richer evaluation of infant handedness status required for systematic study of the development of neuropsychological functions during infancy.

Contribution of nesting experience to progesterone-induced incubation in ring doves (Streptopelia risoria).

Injections of progesterone induce incubation behavior in gonadally intact ring doves only if the doves have had previous experience with at least the nest-building phase of a breeding cycle. The present study was designed to determine whether exposure to progesterone during the nest-building phase is sufficient to account for the ability of progesterone to induce incubation at a later time or whether some other factor provided by experience with this phase of the cycle is needed. Six groups of 10 pairs of doves each were provided with different combinations of experience and progesterone priming. Progesterone priming combined with social isolation or with courtship experience had no significant effect on subsequent progesterone-induced incubation. However, doves that participated in the nesting phase of the cycle during progesterone priming later incubated in response to progesterone treatment. Nesting activity, which may or may not include building the nest, seemed to be the relevant experience.

Head Orientation position during birth and in infant neonatal period, and hand preference at nineteen weeks.

This study of lateral preferences of normal full-term infants found, as predicted, that infants who were delivered from a left occiput anterior or transverse birth position (head turned to the right) exhibited a neonatal right supine head orientation and a right-hand preference in visually guided reaching tasks at 19 weeks. Contrary to prediction, infants delivered from a right occiput anterior or transverse birth position (head turned to the left) did not exhibit a left-sided preference in either neonatal head position or hand preference. Results are discussed in relation to other research which found a right shift in neonates' head orientations and in the distribution of hand preference in the human population. The findings suggest further investigation into the relationship between prenatal and postnatal postural asymmetries and the continuing development of laterality.

Right-handedness: a consequence of infant supine head-orientation preference?

Most newborn infants (65 percent) preferred to lie with their heads turned to the right, whereas 15 percent showed a distinct preference for the left. Orientation preference is maintained for at least 2 months and predicts preferential hand use in reaching tasks at both 16 and 22 weeks. Right head-orientation preference in early infancy may contribute to the early development of right-handedness.

Experience and progesterone in ring dove incubation.

Doves were tested for progesterone-induced incubation after they had acquired previous experience with from one to five different phases of their initial breeding cycle. A sixth group had no previous breeding experience. Previous breeding experience inclusive of at least the nestbuilding phase of the cycle is a significant facilitator of incubation behaviour induced by injected progesterone, but previous experience with only the courtship phase was not sufficient. Experience with phases additional to nestbuilding increased overall nest-responsiveness without significantly increasing the number of birds incubating. The nature of a ring dove's previous experience is therefore an important influence in its behavioural response to exogenous progesterone.

Role of mate's previous experience in ring dove hormone-induced incubation.

Progesterone-induced incubation was examined in 40 pairs of adult ring doves, differing in their previous reproductive experience (courtship vs. nest building) and the previous reproductive experience of their mates (courtship vs. nest building) during testing. Only the previous experience of the experimental subject significantly affected the establishment of incubation during the 24-hr test period. More doves experienced with nest building established incubation than did courtship-experienced doves. The latency to enter the nest area and the latency to stand on the nest were affected by both the previous breeding experience of the subject and the previous breeding experience of its mate. Nest-building-experienced mates decreased the latencies of courtship-experienced subjects, and courtship-experienced mates increased the latencies of nest-building-experienced doves. Males were not more affected by their mates' experience than were females. Time spent on the nest was affected only by the subject's previous experience and sex. While the hypothesis that the behavior of the mate can affect a dove's progesterone-induced incubation was not confirmed, the mate's behavior can affect some of the components of nest responsiveness.