A forced-choice reaction time (RT) task was used to examine the efficiency
of visual filtering (the inhibition of processing of irrelevant stimuli) an
d covert orienting (shifts of visual attention independent of eye movement)
components of attention in persons with Down syndrome (n = 20) and childre
n of average intelligence (n = 20) matched for mental age (MA) (average MA
= approximately 5.4 years). Conditions varied with regard to presence or ab
sence of distracters, and the validity (valid, invalid, or neutral) of loca
tion cues. Contrary to expectations, persons with Down syndrome and MA-marc
hed children of average intelligence at approximately age 5 showed similar
patterns of performance on a task that required filtering distracting stimu
li and searching for relevant information in the visual field. Both groups
responded more efficiently to a target preceded by a valid cue as compared
to a target preceded by an invalid or neutral cue. In addition, performance
was more efficient with a target that was presented without irrelevant inf
ormation as compared to one that was flanked on either side by extraneous,
nontarget information and therefore necessitated filtering for efficient pe
rformance. These two findings indicate that: (1) disengaging from the locat
ion of an incorrect cue, and then searching for, locating, and responding t
o a target requires more time and attention than simply locating and respon
ding to a target that has been validly cued; and (2) processing and respond
ing to a target flanked by extraneous information entails filtering, and th
erefore requires more time and resources than simply responding to a target
without distracters. In general, the development of visual reflexive, cove
rt orienting, and filtering are intact in persons with Down syndrome relati
ve to their level of functioning at an MA level of approximately 5 years, a
period that is critical in the development of attentional processes.