This study investigated the nature of selective
attention deficits after severe closed head injury (CHI).
Twenty participants with severe CHI (greater than 1 year
postinjury) and 20 matched controls completed search and
nonsearch visual selective attention tasks under conditions
of low (Experiment 1) and high (Experiment 2) target–distractor
similarity. In the search situations, participants searched
visual displays that contained 1, 4, or 8 items for the
targets. In the nonsearch situations, the location of the
targets was visually cued with a peripheral arrow. The
results revealed that in both the low and high target–distractor
similarity search conditions, CHI participants required
a longer time than controls to locate and identify the
target. In contrast, in the nonsearch condition, CHI participants
were able to successfully ignore irrelevant task information
when target–distractor similarity was low. However,
when target–distractor similarity was high, CHI participants
had more difficulty than controls ignoring the irrelevant
information. These results suggest that, in comparison
to controls, CHI participants may be at a disadvantage
in selective attention situations when visual search is
required and when the discriminability between targets
and distractors is difficult. (JINS, 1998, 4,
144–159.)