ATTENTIONAL BLINK

Attentional Blink

Attentional Blink

Introduction

Attentional Blink (AB, or 'blink') is the phenomenon that the second of two targets cannot be detected or identified when it appears close in time to the first. The 'attentional blink' (AB) was first described by Raymond, Shapiro, & Arnell (1992), though reports published prior to this revealed the existence of the same outcome (e.g., Broadbent & Broadbent, 1987) but did not use this term. The basic AB paradigm employs a method known as rapid serial visual presentation (RSVP) where stimuli such as letters, digits, or pictures are presented successively at a single location at rates between 6 - 20 items per second. In the procedure derived by Raymond et al. (1992), participants were required to identify the only white letter (first target; T1) in the 10-item per second RSVP stream of black letters (non-targets or distractors), then to report whether the letter 'X' (second target; T2) occurred in the subsequent letter stream (see Figure 1 for a static example and Figure 2 for a slowed dynamic example). T2 was presented on only 50% of trials and when presented, occurred with an interval separating the two targets of between 100 to 800 ms. Report of both targets was required after the stimulus stream ended. The AB is defined as having occurred when T1 is reported correctly but report of T2 is inaccurate at short T1/T2 intervals, typically between ~100 to 500 ms, but recovers to the baseline level of accuracy at longer intervals (see Figure 2).

Although the similarity between these two outcomes is obvious, various investigators (Chun, 1997; Ward, Duncan, and Shapiro, 1997) have shown the two effects to be dissociable. Another phenomenon similar to the AB is known as the psychological refractory period (PRP). In the PRP paradigm, two targets separated by a varying interval and often from different modalities are required to be identified as quickly as possible after each is presented. The targets do not occur as part of an RSVP stream and are not masked. The basic finding is that whereas RT to the first target remains unaffected by the temporal separation between the two targets, RT to the second target is substantially lengthened the closer the two targets occur in time to each other. The requirement to make a reaction time response to both targets differentiates the PRP from the AB in an important way that has implications for their respective underlying mechanisms (cf. Arnell, Helion, Hurdelbrink & Pasieka, 2004).

AB Approaches

In addition to the behavioural approach, upon which virtually all of the experiments discussed thus far have been based, a variety of other approaches have proved useful for studying the AB phenomenon. Cognitive neuropsychological investigations have revealed, for example, that individuals with lesions in the amygdala fail to show a reduced AB for highly emotional words, such as that shown by individuals without such lesions (Anderson & Phelps, 2001). Moreover, patients with hemineglect due to parietal or frontal lesions suffer from an abnormally prolonged AB (Husain et ...