Comparison of sensitivity to first- and second-order local motion in 5-year-olds and adults.
We compared sensitivity to first- versus second-order motion in 5-year-olds and adults tested with stimuli moving at slower (1.5 degrees s(-1)) and faster (6 degrees s(-1)) velocities. Amplitude modulation thresholds were measured for the discrimination of the direction of motion (up vs. down) for luminance-modulated (first-order) and contrast-modulated (second-order) horizontal sine-wave gratings. At the slower velocity (1.5 degrees s(-1)), the differences in threshold between 5-year-olds and adults were small but significant for both first- and second-order stimuli (0.02 and 0.05 log units worse than adults' thresholds, respectively). However, at the faster velocity (6 degrees s(-1)), the differences in threshold between the children and adults were 8 times greater for second-order motion than for first-order motion. Specifically, children's thresholds were 0.16 log units worse than those of adults for second-order motion compared to only 0.02 log units worse for first-order motion. The different pattern of results for first-order and second-order motion at the faster velocity (6 degrees s(-1)) is consistent with models positing different mechanisms for the two types of motion and suggests that those mechanisms mature at different rates.
Groupe de Recherche En Neuropsychologie Expérimentale, Université de Montréal, Montréal, Quebec, Canada. dave.ellemberg@staff.mcgill.ca
Dave
D
Ellemberg
Terri L
TL
Lewis
Karim S
KS
Meghji
Daphne
D
Maurer
Jean-Paul
JP
Guillemot
Franco
F
Lepore
D000328:Adult; D002675:Child, Preschool; D015350:Contrast Sensitivity; D006801:Humans; D009039:Motion Perception / Q000502:physiology*; D010364:Pattern Recognition, Visual; D010775:Photic Stimulation / Q000379:methods; D012684:Sensory Thresholds / Q000502:physiology; D014792:Visual Acuity