Modulating Children’s Manual Preference Through Spontaneous Nondominant Hand Use

We evaluated the effect of repeated use of the nonpreferred hand on young children’s manual preference by positioning toys in the left hemifield in egocentric coordinates to induce right-handed 4–5-year-olds to use their left hands spontaneously. We induced motor activities in the laterally biased workspace by presenting tasks in a ludic context over different days, similar to their daily kindergarten experience. Preceding and following these lateralized experiences, the children were tested on a task requiring reaching, grasping, and inserting cards into a slot. In the 1-day retention assessment, we found that repeated use of the nonpreferred left hand in the previous phase led to increased use of the left hand to perform the probing task. Following 14 days of rest, the children with induced left-hand experiences used exclusively their left hands to manipulate the leftmost card positions. We propose that repeated use of the nonpreferred left hand leads to increased confidence to plan left-handed movements for subsequent tasks.

Can Eye Fixation During the Grooved Pegboard Test Distinguish Between Planning and Online Correction?

The Grooved Pegboard Test, in its standard use, has well-documented utility. However, a revised methodology needs further study, leading us to investigate whether duration of eye fixation could predict performance on different task conditions of the Grooved Pegboard Test (place and remove pegs) with the preferred and nonpreferred hands. Fifty-two right-handed undergraduate students (33 male and 19 female), with a mean age of 22.22 (±3.57) years, performed the Grooved Pegboard Test. SensoMotoric eye-tracking glasses with a binocular time resolution of 30 Hz were used to measure eye fixation. The videos were recorded in iView software, and data were analyzed using BeGaze software. The number and duration of eye fixations were statistically different with preferred and nonpreferred hands and also differed across tasks. Simple linear regression showed eye fixation duration to predict movement time in the place task (preferred hand: R2 = 31%; nonpreferred hand: R2 = 41%) and in the remove task (preferred hand: R2 = 11%; nonpreferred hand: R2 = 25%). Thus, duration of eye fixation during the Grooved Pegboard Test differentially predicted performance with each hand and on preferred and different subtests of this instrument.

Ipsilateral and Contralateral Skill Acquisition following Random Practice of Unilateral Mirror-Drawing

The present mirror-drawing experiment was conducted over four months on one healthy female (R.H.) to elucidate the nature of the ipsilateral and contralateral learning curves for 12 sessions of unimanual training of the nonpreferred hand using a random practice schedule. Analysis indicated greater initial improvement for the practising nonpreferred hand with further improvements for both hands in number of errors and time to complete a single transfer test trial. A 4-mo. retention test showed the improvements were greater for the preferred (untrained) hand. Star-tracing records completed for both hands were quite similar to those recorded using the mirror after practice. This may reflect central processing and long-term potentiation influential even after practice ceased.

Reaction Time Crossover with an Interfering Task

The present study investigated reaction time with and without tapping as an interfering task. 66 undergraduate students were instructed to press and hold a button when a stimulus disappeared from a computer screen, then release it as quickly as possible when it reappeared at the end of each preparatory interval, using the preferred hand. Lengths of preparatory intervals were either 1, 2, 4, 8, 16, or 25 sec. and occurred sometimes in a regular sequence of preparatory intervals of the same length and sometimes in an irregular randomly ordered sequence. Half of the participants were assigned to tap the tabletop with the forefinger of the nonpreferred hand throughout the task. A 2 × 6 × 2 analysis of variance showed significant effects for regularity, length of preparatory interval, and the interaction between regularity and length of preparatory interval. A significant main effect for tapping indicated that reaction times were slower in the tapping group. There were no significant interactions between tapping and other variables, indicating that the pattern of reaction times did not differ significantly between the two groups. Tapping produces a dual-task interference that increases reaction time similarly across different conditions.

Finger-Movement Tracking Scores in Healthy Subjects

The purpose of this study was to examine the effects of age, sex, and hand preference on precise control of voluntary movement at the index finger metacarpophalangeal joint in able-bodied volunteers. An electrogoniometer was attached to this joint and connected to a computer. The computer screen displayed a sine wave target that each subject attempted to track with careful extension and flexion finger movements. Accuracy index scores were calculated for the extension phases, flexion phases, and the total sine wave. Each subject performed three tracking trials and the average for each of the above scores was computed. The results showed that younger subjects tracked significantly more accurately than older subjects and men tracked significantly more accurately than women. Also, the subjects tracking with the nonpreferred hand (15 right, 105 left) tracked significantly more accurately than those subjects tracking with the preferred hand (112 right, 8 left) in the flexion phases of the test. The data from these able-bodied subjects provide a base for comparison of patients' data, which may be helpful in the early recognition and monitoring of problems with precision in movement control.

Bilateral Transfer in Mentally Retarded Children of Ages 7 to 17 Years

The purpose of this study was to describe the effect of age on bilateral transfer of mildly mentally retarded girls (IQs of 70 to 90) after practice on a 45-rpm rotary pursuit task. Subjects were 96 girls from 7 to 17 yr. old. Each performed 14 trials on a rotary pursuit task (30-sec. trials, 10 sec. between trials), half performing the first seven trials with the nonpreferred hand, using the preferred hand on the next seven trials. The order was reversed for the remaining subjects. Nonsignificant differences between Trial 1 scores of the two groups indicated that the task was novel. Trial 1 scores of both groups were positively associated with age ( r = 0.5). There was no transfer to preferred hand, with negative transfer occurring to the nonpreferred hand. It was concluded that, for the task used in this study, mentally retarded girls do not experience positive bilateral transfer as do normal, age-matched girls.

Human Handedness: The Influence of Learning

55 subjects were divided by writing-hand preference and further divided into control and experimental conditions. All subjects were administered a manipulative skill at pretest, counterbalanced for starting hand. Experimental subjects were given 5 practice sessions, and then all subjects were administered a posttest. Posttest scores of both hands of experimental subjects indicated significant improvement as a result of practice, with the nonpreferred hand showing no significant difference from the preferred hand. These findings were related to the etiology of handedness which is hypothesized to involve two factors, one verbal and dichotomous, the other nonverbal and continuous.