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Development of infant reaching in the dark to luminous objects and 'invisible sounds'
D M Stack1, D W Muir, F Sherriff
1Department of Psychology, Queen's University, Kingston, Ontario, Canada.
Insights
Human infants do not show a U-shaped developmental function when reaching for invisible sounds. Reaching for auditory targets was less frequent and poorer quality compared to visual targets in infants aged 2-7 months.
Area of Science:
- Developmental psychology
- Auditory perception
- Motor control
Background:
- Previous research suggested a U-shaped developmental function for infants reaching towards invisible sounds.
- Auditory-manual coordination is crucial for infant development.
Purpose of the Study:
- To investigate the U-shaped developmental function for reaching towards invisible sounds in human infants.
- To compare reaching behaviors towards auditory and visual stimuli.
- To examine the effects of practice and stimulus association on reaching accuracy.
Main Methods:
- Two studies were conducted with infants aged 2-7 months.
- Infants were presented with auditory-alone, visual-alone, combined, or conflicting auditory-visual stimuli in darkness.
- Study 2 involved practice trials with varying auditory and visual stimulus presentations.
Main Results:
- No U-shaped function was observed for reaching towards auditory targets.
- Reaching for auditory targets was slower, less frequent, and of poorer quality than for visual targets.
- Auditory reaching developed later and was achieved by fewer infants, even at 7 months.
Conclusions:
- The hypothesized U-shaped developmental function for auditory-manual reaching was not supported.
- Auditory localization and visually guided reaching develop distinctly in sighted infants.
- Findings offer insights into auditory-manual coordination and potential applications for the visually impaired.
Abstract:
Two studies were conducted to investigate the existence of an unusual U-shaped developmental function described by Wishart et al (1978) for human infants reaching towards invisible sounds. In study 1, 2-7 month olds were presented with four conditions: (i) an invisible auditory stimulus alone, (ii) a glowing visual stimulus alone, (iii) auditory and visual stimuli on the same side (ie combined), and (iv) auditory and visual stimuli on opposite sides (ie in conflict). Study 2 was designed to examine the effects of practice and possible associations made when using the 'combined conflict' paradigm. Infants of 5 and 7 months of age were given five trials with the auditory stimulus, with or without prior visual experience, and five trials with the visual stimulus, with the position of the stimulus varied on each trial. Stimuli were presented individually at the midline, and +/- 30 and +/- 60 degrees from the midline. In both studies testing was conducted in complete darkness. Results indicated that the auditory-alone condition was slower to elicit a reach from the infants, relative to the visual-alone one, and reaches were least frequent to the auditory target. No U-shaped function was obtained, and reaching for auditory targets occurred later in age than for visual targets, but even at 7 months of age did not occur as often and was achieved by fewer infants. In both studies the quality of the reach was significantly poorer to auditory than to visual targets, but there were some accurate reaches. This research adds to our understanding of the development of auditory-manual coordination in sighted infants and is relevant to theories of auditory localization, visually guided reaching, and programming for the blind.