Neurons in intermediate visual cortical areas such as V2 and V4, unlike those in V1, respond preferentially to texture images containing naturalistic image statistics common to natural images. We wondered whether and how representations of these image statistics, which we term “naturalness”, changed during development. We made longitudinal behavioral and neural measurements from 2 infant macaque monkeys at the ages of 6 and 12 mo, using texture stimuli that were parametrically varied in naturalness. We used a novel visual search task to efficiently measure behavioral naturalness sensitivity. We also implanted multielectrode recording “Utah” arrays in areas V1/V2 and V4, and recorded neural responses to the same stimuli in interleaved testing sessions. We found a robust increase in behavioral naturalness sensitivity across the ages tested. Neural sensitivity was greater in V4 than in V1 or V2, at both the unit and population levels. In contrast to the behavioral data, neural naturalness sensitivity did not change consistently with age. We analyzed the time course of responses, measuring the dynamics of the response to textures and of the differential response to naturalness. In V2, the response to naturalness emerged later than the texture response, while in V4 the texture response and the naturalness response began together. The naturalness signal in V4 preceded the naturalness signal in V2. Both visual and naturalness latencies in V4 shortened with age. In summary, our longitudinal data suggest that developmental performance improves at least in part as a result of changes downstream to V2 and V4. Our analysis of response dynamics suggests that naturalness sensitivity in the ventral visual stream may emerge first in V4 and be fed back to earlier areas.