Handbook of Psychology, Volume 4: Experimental Psychology

Efficiency of Selection 275

Figure 10.5 Sample cue displays and target displays used to investigate
contingent attentional capture. In these examples, the cues appear in the left-
hand location and the targets in the right-hand location (thus any trials com-
posed from these particular components would be considered invalid trials).
See text for further details. Source:Reprinted from Folk, Remington,
and Johnston (1992), with permission of the American Psychological
Association.

Color cue

Onset cue

Color target

Onset target

was an xor an “=” sign. The target was defined either as a
color singleton target (e.g., the single red item among white
items) or as an onset target (i.e., a unique abruptly onset item
in the display). Two types of distractors were used. A color
distractor consisted of four colored dots surrounding a poten-
tial target location, and arrays of white dots surrounded the
remaining three locations. An onset distractor consisted of a
unique array of four white dots surrounding one of the poten-
tial target locations. The two distractor types were factorially
combined with the two target types, with each combination
presented in a separate block. The locations of the distractor
and target were uncorrelated. The authors reasoned that if a
distractor were to capture attention, a target sharing its loca-
tion would be identified more rapidly than a target appearing
at a different location. Thus, they measured capture as the
difference in performance between conditions in which dis-
tractors appeared at the target location versus nontarget loca-
tions. The question was whether capture would depend on the
match between the salient property of the distractor and the
property defining the target. The results showed that it did:
Whereas capture was found when the distractor and target
shared the same property, virtually no capture was observed
when they were defined by different properties.
The foregoing discussion of attentional capture suggests
that the conditions under which involuntary capture occurs

remain controversial. Studies that reached incompatible con-

clusions usually presented numerous procedural differences.

For instance, Folk (e.g., Folk et al., 1992) and Yantis (e.g.,

Yantis, 1993) disagree on what status should be assigned to

new (or abruptly onset) objects. Yantis claims that abrupt on-

sets capture attention irrespective of the observer’s inten-

tions, whereas Folk argues that involuntary capture by abrupt

onsets happens only when subjects are set to look for onset

targets. Note, however, that Yantis’s experiments typically in-

volved a difficult search, for instance, one in which the target

was a specific letter among distracting letters (e.g., Yantis &

Jonides, 1990) or a line differing only slightly in orientation

from surrounding distractors (e.g., Yantis & Egeth, 1999). In

contrast, Folk’s subjects typically searched for, say, a red tar-

get among white distractors—that is, for a target that sharply

differed from the distractors on a simple dimension (e.g.,

Folk et al., 1992). Thus, the two groups of studies differed as

to how much top-down guidance was available to find the tar-

get. This factor may possibly account for the better selectiv-

ity obtained in Folk’s studies. Further research is needed to

settle this issue.

The main point of agreement seems to be that an irrelevant

feature singleton will not capture attention automatically when

the task does not involve searching for a singleton target. This

finding has been obtained using three different paradigms,

under which attentional capture was gauged using different

measures: a difference between distractor-present versus dis-

tractor-absent trials (Bacon & Egeth, 1994); a difference be-

tween trials in which the target and cue occupy the same versus

different locations in spatial cueing tasks (e.g., Folk et al.,

1992); and the difference between trials in which the target and

salient item do versus do not coincide (e.g., Yantis & Egeth,

1999). Although most of the evidence provided by Theeuwes

(e.g., 1992) for automatic capture was drawn from studies in

which the target was a singleton, his position on whether cap-

ture occurs when the target is not a singleton is not entirely

clear (see, e.g., Theeuwes & Burger, 1998).

Note, however, that in the current state of the literature,

the implied distinction between singleton detection mode,

in which any salient distractor will capture attention, and

feature search mode,in which only singletons sharing a

task-relevant feature will capture attention, suffers from two

problems.

First, it is based on the yet-untested assumption that the

singleton detection mode of processing is faster or less cogni-

tively demanding than is the feature search mode. Indeed, one

observes that subjects will use the feature search mode only if

the singleton detection mode is not an option. For instance,

when the strategy of searching for the odd one out is not

available (e.g., Bacon & Egeth, 1994, Experiments 2 & 3),