Behavioral and pharmacological variables affecting risky choice in rats.
Baseline choice level decides whether a drug or schedule change will help or hurt risky behavior.
01Research in Context
What this study did
Scientists gave rats two levers. One lever always paid the same. The other paid more, but only sometimes.
The team changed three things: how many presses each lever needed, the wait time between turns, and drugs. They gave ethanol, phencyclidine, or d-amphetamine. Then they watched which lever the rat picked.
What they found
The rats did not pick the same way every time. The starting choice level decided what the drug did.
Ethanol always made the safe lever more popular. Phencyclidine helped the risky lever only when the wait was long. d-Amphetamine shoved choices toward the middle, no matter the rat’s first habit.
How this fits with other research
ANGER (1963) saw the same rule in monkeys. When the baseline response was already high, extra reward barely moved it. When it was low, reward pushed it up. The rat drug data echo that old monkey lesson.
Rost (2018) showed humans want choice only when the payoff is unsure. Weiss et al. (2001) add that the wait time between turns is one knob that sets that unsure feeling for rats.
Baer et al. (1984) proved you can’t guess where time goes after you remove a lever. Weiss et al. (2001) back this up: change the wait or the work, and the whole choice map shifts in ways you must measure, not assume.
Why it matters
Before you add medication or tweak a schedule, record the client’s baseline choice split. The same drug or ratio size can help or hurt depending on that first number. Run a quick probe session, plot the point, then pick the lever you want to move.
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02At a glance
03Original abstract
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 he 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.
Journal of the experimental analysis of behavior, 2001 · doi:10.1901/jeab.2001.75-275