ABSTRACT
The organization of infants' reaching skill for stationary and moving targets was examined. While 58 term, healthy infants at 5.5, 8.5, and 11.5 months of age reached for and grasped a cloth-covered dowel, their reaches were videotaped for later slow-motion analysis. Analyses addressed infants' anticipatory adjustment of hand alignment, use of information from spinning and oscillating targets to update ongoing reaches, and ability to capture targets moving in depth. Infants at all ages made anticipatory adjustments of hand alignment, although the effectiveness of these adjustments improved with age. Regardless of age, infants also used dynamic information from spinning and oscillating targets to update ongoing reaches, but the way infants used this information was related to age. Developmental constancy characterized infants' reaches for approaching targets. By observing infants' reaches for stationary, spinning, and approaching targets, the study expands the range of conditions under which adaptive reaching skill has been examined and provides insight into the roles of anticipation and updating in the development of early manual skill.
Subject(s)
Child Development/physiology , Hand/physiology , Motion Perception/physiology , Movement/physiology , Age Factors , Female , Humans , Infant , Male , Time Factors , Videotape Recording , Visual Perception/physiologyABSTRACT
The microdevelopment of infants' visual expectations was examined by analysis of the eye movements that 80 three-month-old human infants made during interstimulus intervals (ISIs) of an alternating picture sequence. For comparison, identical eye movement data were gathered from 10 infants who watched an irregular sequence. Shifts during ISIs were exhibited by all infants and occurred on 48% of all trials. Initially, infants' ISI shifts repeated saccades that had successfully located the preceding picture; during the course of the alternating session, repetitive saccades declined while alternating and anticipatory saccades increased. For infants who saw the irregular sequence, the frequency of ISI shifts did not vary systematically over trials. Analysis of saccade latencies suggested that infants quickly learned to inhibit a prepotent tendency in order to execute task-appropriate saccades.
Subject(s)
Psychomotor Performance , Saccades , Visual Perception , Female , Humans , Infant , Infant Behavior , Male , Motion Perception , Photic Stimulation , Reaction TimeABSTRACT
We tested the applicability of concepts and measures from information theory to studies of the development and operation of collative motivation. Three variables nominated by Berlyne as potential motivators of information seeking--uncertainty, variety, and novelty--were put into correspondence with three informational theoretic measures--average uncertainty in bits, number of possible outcomes, and outcome probability--to investigate the incentive properties of each variable for first and fourth graders. Increasing bit levels of uncertainty by adding alternatives to the set of possible outcomes was generally positively related to cover choices; however, increasing bit values by varying outcome probabilities from unequal to equal had no effect on choice. Without uncertainty, variety provided a weak source of collative motivation, systematically related to the choice of the transparent cover only for the older children when rewards occurred equally frequently. In contrast, the transparent cover was chosen significantly more frequently when the outcome probability of the associated reward was low. We obtained developmental stability in motivational effects except for variety operating in the absence of uncertainty.
