A temporary functional blindness to the second of two spatially separated targets has been identified in numerous studies of temporal visual attention. This effect is known as attentional dwell time and is maximal 200 to 500 ms after presentation of the first target (e.g. Duncan, Ward, Shapiro, 1994).

In most studies of attentional dwell time, two masked targets have been used. Moore et al. (1996) have criticised the masking of the first target when measuring the attentional dwell time, finding a shorter attentional dwell time when the first mask was omitted. In the presented work, the effect of the first mask is further investigated by including a condition where the first mask is presented without a target. The results from individual subjects show that the findings of Moore et al. can be replicated. The results also suggest that presenting the first mask without a target is enough to produce an impairment of the second target. Hence, the attentional dwell time may be a combined effect arising from attending to both the first target and its mask.