We document a new phenomenon: participants' eye movements are influenced by the belief that they are either looking at pictures alone, or that a person next door is looking at the same pictures. The pictures were in sets of four. One had a positive and one a negative valence, and others were neutral. On a trial by trial basis, eye movements to the negative versus the positive pictures were modulated by participants' belief that they were looking alone or jointly. A second experiment manipulated

more »

... the beliefs participants had about the person in the next cubicle, in an attempt to tease apart possible explanations for this effect of 'joint perception'. In each case, a minimal sense of cooperation with another appears to produce distinct cognitive effects, in manner similar to that found in studies of 'joint action'. We conclude that there may be a pervasive effect of social context upon cognitive and perceptual processes.