Kaminski, B. J., & Ator, N. A. (2001).
Behavioral and pharmacological variables affecting risky choice in rats.
Journal of the Experimental Analysis of Behavior,
75, 275-297.
The effects of manipulations of response requirement, intertrial
interval (ITI), and psychoactive drugs (ethanol, phencyclidine,
and d-amphetamine) on lever choice under concurrent
fixed-ratio schedules were investigated in rats. Responding on
the "certain" lever produced three 45-mg pellets,
whereas responding on the "risky" lever produced either
15 pellets (p = .33) or no pellets (p = .67). Rats
earned all food during the session, which ended after 12 forced
trials and 93 choice trials or 90 min, whichever occurred first.
When the response requirement was increased from 1 to 16 and the
ITI was 20 s, percentage of risky choice was inversely related to
fixed-ratio value. When only a single response was required but
the ITI was manipulated between 20 and 120 s (with maximum
session duration held constant), percentage of risky choice was
directly related to length of the ITI. The effects of the drugs
were investigated first at an ITI of 20 s, when risky choice was
low for most rats, and then at an ITI of 80 s, when risky choice
was higher for most rats. Ethanol usually decreased risky choice.
Phencyclidine did not usually affect risky choice when the ITI
was 20 s but decreased it in half the rats when the ITI was 80 s.
For d-amphetamine, the effects appeared to be related to
baseline probability of risky choice; that is, low probabilities
were increased and high probabilities were decreased. Although
increase in risky choice as a function of the ITI is at variance
with previous ITI data, it is consistent with foraging data
showing that risk aversion decreases as food availability
decreases. The pharmacological manipulations showed that drug
effects on risky choice may be influenced by the baseline
probability of risky choice, just as drug effects can be a
function of baseline response rate.
Key words: drug effects on risky choice, intertrial interval and
risky choice, fixed-ratio schedule and risky choice, foraging,
risk taking, lever press, rat