We're slower to direct our attention to the same location twice in succession, a well-established phenomenon that cognitive psychologists call 'inhibition of return' (IoR). It's thought the mechanism may act to make our search of the visual scene more efficient by deterring us from looking at the same spot twice. Now Paul Skarratt and his colleagues have documented a new 'social' form of inhibition of return, in which people are slower to attend to a location that social cues, such as gaze direction, suggest another person has already attended to.
Twelve participants sat at a table with an animated character projected opposite. Each participant and their animated partner had two lights and two buttons in front of them, near the middle of the table (see figure above). One light/button pair was to the left, the other pair was to the right. The basic task was to press the corresponding button as fast as possible when its light came on. Participants were slower to respond to a light when the animated partner had just responded to the adjacent light on their side of the table - this is what you might call a weak version of social inhibition of return. However, when two large vertical barriers were put up with a gap in the middle, so that the participants could only see their partner's eyes and initial reaching action, and not their actual button presses, this social IoR disappeared.
In a second experiment, the animated partner was replaced with a human. This time, the social IoR effect occurred even when the barriers were erected and only the partner's eye gaze and initial hand movement could be seen. In other words, inferences about where the partner was going to attend, based on their eyes or early hand movement, seemed to be enough to inhibit a participant's own attention to the same location. For some reason, this strong version of social IoR only occurred with a real, human partner, not the animated, computer-controlled partner of the first experiment.
The final experiment added yet another visual barrier, which left only the partner's eyes or only their early hand movement visible. This was to try to establish which cue was the more important for provoking social IoR. The answer was that both cues were equally effective.
It's only supposition at this stage, but Skarratt and his team think social IoR could be supported by the postulated mirror neuron system. Monkey research has shown, for example, that there are mirror neurons in the premotor cortex that fire whether a monkey sees another person grasp an object or if they just see the initial part of that grasping movement.
'Although the critical mechanisms underlying social IoR remain to be discovered,' the researchers said, 'the current study indicates that it can be generated independently of direct sensory stimulation normally associated with IoR, and can occur instead on the basis of an inference of another person's behaviour.'
Skarratt, P., Cole, G., & Kingstone, A. (2010). Social inhibition of return. Acta Psychologica, 134 (1), 48-54 DOI: 10.1016/j.actpsy.2009.12.003
Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.
Figure courtesy of Paul Skarratt.