To represent the environment meaningfully, human vision must group those parts of the retinal image relating to a single object, and segregate that object from others in the image. Grouping and segregation are often considered in spatial terms, such as continuity and proximity. Lee and Blake now show that grouping can be achieved by purely temporal information 1 Lee S-H. Blake R. Visual form created solely from temporal structure. Science. 1999; 284: 1165-1168 Crossref PubMed Scopus (144) Google Scholar . They created a scattered array of local motion elements that were random in phase, orientation and spatial location, and whose motion directions oscillated back and forth irregularly. An array like this appears highly incoherent. Yet, when the oscillating elements from a given region were made to change direction simultaneously, they grouped into a vivid spatial form that stood out from the surrounding elements. Verifying this observation, observers easily judged the orientation of virtual rectangular regions undergoing synchronized change, even when only a proportion of the elements changed direction synchronously while the remainder changed randomly. This might sound reminiscent of ‘structure from motion’, a phenomenon whereby discontinuities in speed or direction of motion create perceived forms. But Lee and Blake’s demonstration is more subtle. First, the oscillating elements in the synchronized rectangular region all differed in direction and orientation. Second, an element within this region and one from the surrounding region are indistinguishable: both oscillate irregularly in direction and are assigned location, phase and orientation randomly. This randomization removes spatial cues to the region’s orientation. What, then, makes the directional oscillations within the region group into a clearly seen form? Simply that their changes in direction over time are correlated. A more apt term would be ‘structure from correlated change’. For a real-life example, consider a gusting breeze causing a tree to sway to and fro. The leaves move locally in many directions, but all change together with each gust of wind and a coherently swaying tree is perceived. Similarly, in the laboratory, Lee and Blake have shown that the brain can exploit purely temporal information to create spatial structure 2 Demonstrations can be found at: http://www.psy.vanderbilt.edu/faculty/blake/Demos/TS/TS.html Google Scholar .