Abstract
When stimuli are presented in rapid succession, processing of the first target stimulus interferes with the processing of the second - a phenomenon known as the attentional blink (AB). This interference is thought to reflect a lack of processing resources left for dealing with the second target. However, processing of the second target is not always impaired: in cases of Lag-1 sparing, a target stimulus that appears directly after the first is processed effectively, and observers correctly identify both targets. By presenting targets in separate RSVP streams on either side of fixation, Jefferies and Di Lollo (2007) used the phenomenon of Lag-1 sparing as a tool of convenience for monitoring how the extent of a spatial window of attention shrinks and expands over time. The window initially encompasses both possible target locations, then reflexively narrows to the location of the first target. If the second target is presented directly after the first in the opposite stream, the incidence and magnitude of Lag-1 sparing may be used to evaluate how quickly the attentional window narrows to the location of the first target. In this study, we compared the time course of the narrowing of the attentional window in older and younger observers. Older observers are slower to detect and/or process the first target presented in the RSVP streams, delaying initiation of the shrinking of the attentional window. This leads to greater Lag-1 sparing in older observers than in younger observers. Although older observers are slower to start shrinking the window, the time course of shrinking once started is similar to that of younger observers. Consistent with previous findings, older observers experience a larger AB deficit at Lag-3 when the targets appear in the same stream, implying that intervening distractors disrupt processing of the second target to a greater degree with age.