The success rate for the test protocol was high, with only 2
(6.5%) of 31 infants (one 4-month-old and one 12-month-old) failing to
complete both the radial deformation and grating acuity protocols.
Three typical examples of radial deformation psychometric functions are
shown in
Figure 2 . At low modulation amplitudes, infants show no consistent preference
for either pattern, and the observer’s performance is at chance level
(50% correct). At moderate modulation amplitudes, performance
increases above chance and, in general, reaches an upper asymptote of
100% correct. Overall, infant psychometric functions had high upper
asymptotes (means = 0.98, 0.98, 0.99, and 0.98 for the 4-, 6-, 9-,
and 12-month-old groups, respectively) and steep slopes (means =
20.3, 8.4, 28.3, and 14.8 for the 4-, 6-, 9-, and 12-month-old groups,
respectively).