The concurrent task benefit in the attentional blink: The effect of stimulus similarity and concurrent task difficulty.

When two targets are presented in a rapid sequence, attending to the first target (T1) hinders detection of a second target (T2) between 200 ms to 500 ms after T1. This attentional deficit known as 'attentional blink' (AB) represents an attentional capacity limitation in information processing. The present experiments varied stimulus nature and task difficulty in the concurrent task in order to manipulate task-relevance and task difficulty respectively. Experiment 1 investigated the effects of task-irrelevant additional stimuli. Participants were randomly allocated to either 'task' or control conditions. In both conditions participants viewed the same concurrent stimuli presented with the RSVP stream, however participants in the task condition were asked to notice the extraneous stimuli while in the control condition, participants were asked to ignore the stimuli. The experiment was split into four blocks of trials consisting of two high difficulty and two low difficulty blocks. Experiment 2 consisted of the same conditions except participants were presented with task-relevant extraneous stimuli. It was hypothesized that AB attenuation would be found in Experiment 1, AB would be impaired in Experiment 2 and difficulty conditions would exacerbate this effect. While T2 accuracy results supported these hypotheses, T1 accuracy data raised several important questions regarding the validity of the results