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College students exhibited impulsivity if, in the first of 2 sessions,
they consistently chose an immediate, small rein·forcer (15-s cartoon
video followed by 75 s of waiting) over a delayed, large reinforcer (55-
s prereinforcer delay, 25-s video, 10 additional s of waiting), or selfcontrol
if they showed the opposite preference. Previously, Navarick
(2001) found that informing impulsive participants in Session 2 that
the viewing time was longer on their non preferred schedule reduced
impulsive choice to about .50; informing self-controlled participants
that the video started sooner on their nonpreferred schedule had no
effect. In addition to facilitating discrimination between reinforcers,
the instructions to impulsive participants could have implied a
request to choose the indicated schedule (a demand characteristic)
or that the non preferred schedule was somehow more
advantageous. Effects of these potentially implicit instructions were
assessed by presenting them as explicit instructions to determine if
they again produced a decrease in impulsive choices in impulsive
participants and no change in self-controlled participants. In contrast
to the previous pattern, impulsive and self-controlled participants
conformed similarly to the experimenter's stated schedule
preference, and showed similar, variable preferences in response to
the general schedule characterization. The previous instructions
reduced impulsivity by facilitating discrimination between the large
and small reinforcers and not by conveying these implicit messages.