We examined whether visual search for a conjunction target defined by stereoscopic disparity and colour is parallel, as indicated by Nakayama and Silverman [1986 Nature (London) 320 264 – 265]. The stimuli consisted of arrays of variable size, containing either 15, 25, or 35 elements. The elements were squares and bordered with a frame to ensure stereoscopic fusion. They were clearly distinguishable either in terms of stereoscopic depth or colour. The target was an element with a combination of stereoscopic depth and colour that was unique in each display. Before search, subjects were either instructed to find a target with defined properties, or to find the odd target. When the subjects knew the target properties, there was a significant effect of set size, although overall search times were short. When the subjects were asked to search for the odd target, search times were long and increased as a function of set size. These results suggest that conjunction search for stereo and colour is serial.
