304 Action Selection
the mapping of the stimulus locations to responses was ma-
nipulated. Each trial was preceded by no warning or a 50-ms
warning tone, followed at intervals of 50, 100, 200, 400, and
800 ms by a stimulus to the left or right of fixation. RT was a
U-shaped function of foreperiod, reaching a minimum at the
200-ms interval. Error rate showed an opposing, inverted
U-shaped function, being highest at the 100-ms interval. The
main effect of compatibility was significant in the RT and
error data, but compatibility did not interact with foreperiod.
These results suggest that the warning tone altered alertness,
or readiness to respond, but did not affect the rate at which
the information built up in the response-selection system.
RT continues to increase as the foreperiod increases be-
yond 800 ms, up to at least 5 s. Sanders and Wertheim (1973)
failed to find an effect of foreperiod between 1 and 5 s for au-
ditory stimuli, although they found the standard increase in
RT for visual stimuli. However, Sanders (1975) demonstrated
that the critical factor seems to be stimulus intensity:
Auditory stimuli below 70 dB showed foreperiod effects
similar to those shown by visual stimuli, and there was a
trend toward smaller effects for high-intensity visual signals.
Precuing Effects
Leonard (1958) was the first to demonstrate that subjects can
use advance information to prepare for a subset of S-R alter-
natives. He tested himself in a six-choice reaction task in
which six stimulus lights were mapped compatibly to six re-
sponse keys pressed by the fingers of each hand. In the six-
choice condition, all six stimuli were lit, and the target light
went off 100 ms later. In a three-choice condition, only the
left or right set of three stimuli was used. Of most interest
was a precue condition in which the subject did not know
whether the choice would involve the three left locations or
the three right locations until the lights designating those lo-
cations were lit (i.e., those locations were precued). RT de-
creased as a function of the precuing interval, with RT at the
500-ms interval being equivalent to that of the three-choice
task.
Subsequent studies using four-choice tasks have obtained
similar results, in which the benefit for precuing the two
left or two right locations occurs within the first 500 ms of
precue onset (Miller, 1982; Reeve & Proctor, 1984). How-
ever, when other pairs such as alternate locations are precued,
the maximal benefit is not evident until a longer interval.
Reeve and Proctor (1984) showed that the advantage for pre-
cuing the two left or two right locations does not depend on
the fact that they typically involve responses from different
hands. With an overlapped hand placement in which the index
and middle fingers from the two hands are alternated, the two
left or right locations show a similar precuing advantage
relative to other pairs of locations. These and other findings
imply that the time needed to obtain the maximal benefit
from a precue varies as a function of how long it takes to
translate the precue information. Proctor and Reeve (1986)
attributed this pattern of differential precuing benefits to the
salience of the left-right distinction.
Kantowitz and Sanders (1972) distinguished between two
types of precue: utilityandnecessity. Utility precues, as in the
studies just discussed, are helpful in reducing the number of
alternatives, but do not provide information that is necessary
for responding. Necessity precues tell subjects what informa-
tion is relevant for the current trial (e.g., whether they are to
respond to stimulus color or shape). RT is longer when the
precue is a necessity than when it is only useful. Because the
information provided by necessity precues must be used at all
intervals, it is more difficult to respond at shorter ISIs. With
utility precues, subjects use the information at longer inter-
vals but not shorter ones.RELEVANT AND IRRELEVANT
STIMULUS INFORMATIONNoncorrespondence of Relevant and
Irrelevant InformationEffects of irrelevant information on performance have been
studied extensively in many areas of experimental psy-
chology. Three such effects studied in the choice reaction
literature—the Stroop color-naming effect, the Eriksen
flanker effect, and the Simon effect—involve correspondence
of relevant and irrelevant stimulus information.The Stroop EffectThe best-known example of irrelevant information affecting
response selection is the Stroop color-naming task (see
MacLeod, 1991, for a review). In this task, color words are
presented in different ink colors, and subjects are instructed
to name the ink color while ignoring the color word. In
Stroop’s (1935/1992) study, subjects took 110 s to name a list
of 100 colors presented in incongruent color words, com-
pared to 63 s to name a list of 100 colors presented in solid
squares. Thus, conflicting color words nearly doubled the
naming time, a phenomenon known as the Stroop effect.
Stroop also reported that the time to read 100 color words in
incongruent ink colors was 43 s, compared to 41 s when the
words were presented in black ink. Thus, the interference
with color naming was asymmetric: Irrelevant words inter-
fered with naming ink colors, but irrelevant ink colors did not
interfere with reading color words.