Component visual features of objects are registered by distributed patterns of activity among neurons comprising multiple pathways and visual areas. How these distributed patterns of activity give rise to unified representations of objects remains unresolved, although one recent, controversial view posits temporal coherence of neural activity as a binding agent. Motivated by the possible role of temporal coherence in feature binding, we devised a novel psychophysical task that requires the detection of temporal coherence among features comprising complex visual images. Results show that human observers can more easily detect synchronized patterns of temporal contrast modulation within hybrid visual images composed of two components when those components are drawn from the same original picture. Evidently, time-varying changes within spatially coherent features produce more salient neural signals.Early vision entails local feature analyses of the retinal image carried out in parallel over the entire visual field. By virtue of the receptive-field properties of the neurons performing this analysis, visual information is registered at multiple spatial scales, ranging from coarse to fine, for different contour orientations (1-3). Moreover, different qualitative aspects of the visual scene engage populations of neurons distributed among numerous, distinct visual areas (4, 5). Yet we perceive objects whose constituent features are, at least metaphorically speaking, bound together coherently. One popular but controversial hypothesis posits as a binding agent temporal synchronization of neural activity among cortical cells registering object features (6-11). In experiments reported here, we have discovered that synchronized modulations over time in the contrast of separate components of complex images are easier to detect when those components form a meaningful object. These findings are compatible with the notion that temporal and spatial coherence are involved in the promotion of perceptual binding.Several recent experiments have tried to assess whether patterns of neural activity coincident in time promote perceptual grouping, by determining whether visual features flickering in temporal synchrony more readily promote figure͞ ground segregation. Results from those experiments, however, have led to contradictory conclusions (12-14). To pursue this question of figural binding from a complementary perspective, we tested for enhanced detectability of temporal synchrony among spatial features that define a visual object. To understand the rationale for our study, imagine a picture composed of two components each selected to activate separate populations of visual neurons. Suppose further that the contrast of each component can be independently varied over time (Fig. 1), with the temporal pattern of contrast modulations of the components being either identical (i.e., synchronized) or uncorrelated (i.e., unsynchronized). Physiological work (16)(17)(18) shows that fluctuations in contrast amplitude over time will evo...