The representation of objects becomes increasingly complex at higher levels of the human visual cortex. Shapes of intermediate complexity serve as a step in the representation of such intricate constructs. Healthy aging has adverse effects on cortical function, and we sought to determine the effects of age on the efficacy and speed of neuronal mechanisms underlying shape processing. Using deformed circular shapes, we probe object representation by varying the characteristics that define the shape and by assessing lateral interactions among shapes. Results indicate that performance declines with age for shapes defined by texture but not by luminance. However, there is no age-related slowing for the processing of shape, and probes of lateral interactions reveal spared function for complex shape combinations. Findings suggest that the effect of age on shapes defined by texture arises from lower stages of visual processing, and that the representation of shape combinations is spared because of its robust nature.

*SD*± 2.9, range 20–30) and eighteen community dwelling older observers (mean age 65.2 years,

*SD*± 4.3, range 60–76) participated in this study. Older observers were screened for general health and for medications that could affect visual or brain function. They also underwent complete eye exams by an optometrist and only those with healthy eyes participated in these experiments. Corrected visual acuity was 20/20 or better in all participants with the exception of one observer in each group, who had visual acuity of 20/25. Older observers were corrected for the viewing distance of 131 cm. Participation was voluntary, and the study was approved by York University's Human Participants Review Committee.

^{2}.

*r*and

*θ*are the polar coordinates of the contour, and

*r*

_{mean}is the average radius (radius of the base circle). The remaining three parameters control various aspects of the shape's geometry, where

*ω*is the radial frequency, which represents the integer number of sinusoidal modulation cycles (peaks and troughs about the circle),

*ϕ*is the phase, which represents the overall orientation of the shape, and

*A*is the amplitude and represents the size of these deformations as a proportional change of the radius. The radial frequency of all contours was 5 cycles/circumference, and the mean radius was 1° of visual angle.

*α*level set to <0.05.

*F*= 0.34;

*p*= 0.56) and no interaction between age and target duration (

*F*= 0.47;

*p*= 0.71). The main effect of target duration was highly significant (

*F*

_{[1,17]}= 111.2,

*p*< 0.0001) with performance declining at shorter exposures. Post-hoc tests revealed that performance showed a significant improvement between exposure durations of 40 and 120 ms and between 120 and 500 ms but not between 360 and 500 ms. To achieve an estimate of asymptotic performance on this task, the geometric means for each group were fit with an exponential function that decays to an asymptotic level. The asymptotic thresholds for young and older groups were 10.5 and 10.6 s of arc, respectively; the associated time constants were 42.1 and 43.2 ms.

*F*= 10.99;

*p*< 0.002) and exposure time (

*F*= 103.2;

*p*< 0.0001) but no interaction between age and exposure time (

*F*= 0.008;

*p*= 0.81). Performance of older subjects was worse than that of younger individuals at all stimulus durations. As was the case for first-order stimuli, post-hoc comparisons revealed that performance with second-order stimuli showed a significant improvement between exposure durations of 40 and 120 ms and between 120 and 360 ms but not between 360 and 500 ms. When decaying exponential functions were fit to the means, asymptotic thresholds for the second-order stimuli were estimated at 22.4 s and 27.5 s of arc for young and older subjects, respectively (time constants: 49.2 and 40.4 ms). Using the pooled variance from all second-order test conditions, we calculated the 95% confidence limits around the estimated mean for the young group (22.4 s) and found that the estimate for the older subjects (27.5 s) lies outside the upper bound of this confidence interval.

*F*

_{[6,204]}= 63.95,

*p*< 0.0001); however, the effect of age was not statistically significant (

*F*= 0.2518;

*p*= 0.61), nor was the interaction between age and mask condition (

*F*= 1.19;

*p*= 0.31). Post-hoc comparisons using Tukey's method were employed to examine the relative strengths of various mask configurations.