r results demonstrated that T2 detection was higher when participants completed the single-detection task compared to the dual-detection task. T2 detection performance was also better in the long delay condition, when T2 was presented 700ms after T1, in both the single-detection and dual-detection task. (Figure 3)

Figure 3 also shows the greatest percentage of participants, 76.8%, correctly detected T2 in the condition comprised of the single-detection task and long delay. While, the lowest percentage of participants correctly detecting T2, 57.3%, occurred during the dual-detection task with short delay.

Figure 3. Percentage of participants who correctly detected letter X (T2) in the different conditions.

Discussion

Our results support the hypothesis proposed and as predicted T2 detection was less accurate in the dual-detection task and when there was a shorter delay of 300ms between T1 and T2. This could suggest that AB is affected by task difficulty, and only occurs in a specific period of time.

Our findings are also in line with existing literature. For instance, Raymond et al. (1992) also reported that participants had no difficulty only detecting one letter, the T2, and in the single-detection task 85% of participants were able to correctly identify T2 in They also found that only 60% of participants could detect T2 in a dual-detection task between 180-450ms after T1 was presented. This is similar to our finding that T2 detection was worse when there was a dual-detection task and T2 was presented 300ms after T1. This consistency with results from previous studies indicates a high level of external reliability and supports the work by Raymond et al. (1992).

The findings in this study however, may be limited as they cannot offer conclusive evidence to support some of the existing theories explaining AB. For example, each trial in this study used RSVP with a stream of 12 letters. But to prove the interference theory proposed by Shaprio et al. (1997a) trials with a varying number of distractors may be needed to demonstrate that AB in due to competition between the targets and masks in the buffer. Similarly, to support the 2-stage model by Chun & Potter (1995) a modification to the study may be needed so it is possible to determine how much processing T2 undergoes. This could involve the use of EEG or priming techniques as seen in previous studies (Luck et al. 1996 ; Shapiro et al., 1997b) or alternatively the use of other neuroscience techniques such as fMRI to see if brain areas linked to processing meaning are active during the period when T2 is presented.

Furthermore, there are a number of questions left unanswered by both the present