| |
Abstract:
Saccadic reaction times (SRTs) are reduced when the fixation
point (FP) is extinguished prior to the onset of a target. This
facilitatory effect has been called the 'gap effect', and has
variously been attributed to 1) a facilitated disengagement of
active fixation, 2) disengaged attention or 3) warning signal
effects. To further clarify the factors contributing to the gap
effect, we recorded SRTs and MRTs (simple Manual Reaction Times).
The premise is that disengagement of active fixation should
selectively influence saccades, whereas warning effects and
disengaged attention could influence both SRTs and MRTs. There were
3 task conditions (MRT alone, SRT alone and dual task MRT/SRT), two
fixation conditions (an OFFSET condition in which the FP was
extinguished and a COLOR CHANGE condition in which the FP changed
color) and two gap durations (0 and 200 ms). Our main findings
were: 1) no difference between single and dual task conditions; 2)
SRTs faster than MRTs, 3) 200 ms gap faster than 0 ms gap, and 4)
4) the difference between the OFFSET and the CC condition was only
significant for SRT at gap200. Thus, FP OFFSETs can serve as a
significant warning signal, but at 200 ms gap durations, FP OFFSETs
also produce an effect that is selective for saccades. Supported by
CNPq, FAPERJ, FINEP, PRONEX/MCT, Brazil.
|
