To investigate the brain's limitations in processing this information, Raymond, Shapiro, and Arnell (1992) used a task in which letters where presented rapidly to participants, and where participants were asked to identify a target letter and then to indicate whether a probe letter was present or absent in the stream of letters after the target. Raymond, Shapiro, and Arnell found that there was a 270 ms interval starting 180 ms after the target, in which probes were poorly detected. This deficit was not found when a brief blank interval followed the target, or when participants were not asked to identify the target. It was therefore suggested that interference at the time when the letter was being recognised made the system realise there was potential for confusion and uncertainty, and that this led to suppression of visual attention mechanisms; the suppression was dubbed an attentional blink (AB). .
A modern, full-blown theory of consciousness needs to be grounded on a solid base of empirical data. The aim of the present study was to investigate the notion of an AB, in an attempt to solidify a small part of the basis for a beginning theory of consciousness. It was hypothesised that there would be a deficit in probe detection until after approximately 450 ms, as this was the extension of the AB as found by Raymond, Shapiro, and Arnell (1992). .
Method .
Participants .
There were 25 participants, all second year psychology students at La Trobe University. All participants were nave as to the aims and the hypothesis of the experiment. .
Materials .
A Macintosh computer was used to present the visual stimuli. .
Procedure .
Participants (P) were seated in front of the computers; all stimuli consisted of letters flashed at the same location of the screen. Distracter letters were black, target letters were red, and the probe was a black 'x'. A stream of letters appeared on the screen, Ps were asked to identify the target letter, and to indicate whether the probe had appeared after the target.
