Bias functions and operating characteristics of rats discriminating auditory stimuli.
Animals pick the option that delivers the highest payoff rate, even when penalties change.
01Research in Context
What this study did
Researchers put rats in a box with two levers. Pressing the correct lever after a tone gave a small zap to the pleasure center of the brain. Pressing the wrong lever started a short time-out.
The team varied how long the time-out lasted. They wanted to know if rats would still pick the lever that gave the most brain-zaps even when the penalty changed.
What they found
The rats always chose the lever that paid off with more brain stimulation. Longer or shorter time-outs did not sway them. They maximized the good stuff and ignored the penalty size.
In short, the animals acted like tiny economists: take the richest option, ignore the fine print.
How this fits with other research
Three years later, Kazdin (1977) showed rats also follow the matching law when they split time between running in a wheel and drinking sugar water. The 1974 study adds brain-stimulation proof that animals chase the best rate, not just match proportions.
Decades on, Lecavalier et al. (2006) built formal 'inverted-U' feedback curves and found rats again landed on the peak payoff. The 1974 maximization idea held up under tighter math.
Earlier work with pigeons (M et al., 1969) already showed time allocation matching reinforcement ratios. The rat data say the same rule applies even when the reinforcer is direct brain reward.
Why it matters
When you set up token boards, break schedules, or differential reinforcement, remember clients will work for the richest source, not the easiest one. If the payoff is strong, extra response cost or time delay rarely deters the response. Make the desired behavior the biggest 'brain-zap' in the room.
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02At a glance
03Original abstract
Rats were trained to discriminate between two bursts of random noise that differed in intensity. In a two-lever, discrete-trial procedure, correct responses were reinforced with brain stimulation, and incorrect responses produced timeout. Responding was studied as a function of the decibel difference between the stimuli, the probabilities of presenting the stimuli, the relative duration of timeout consequent upon the two types of incorrect responses, and the absolute duration of timeout consequent upon incorrect responses. The results showed that the distribution of responses between the two levers depended upon the stimulus probabilities, but were independent of either the absolute or relative durations of timeout. When the stimulus probabilities were varied, the response probabilities did not match the stimulus probabilities; when the relative durations of timeout were varied, the animals did not obtain the maximum rate of reinforcement per unit time. Instead, the animals distributed their responses so as to obtain the maximum number of reinforcements at each level of discrimination. In addition, the level of discrimination increased as a function of the decibel difference between the stimuli.
Journal of the experimental analysis of behavior, 1974 · doi:10.1901/jeab.1974.21-285