Mechanics of the animate.
Think of reinforcement as a gravity well: the closer and clearer the payoff, the faster behavior falls into it.
01Research in Context
What this study did
Lindsley (1992) wrote a theory paper. No kids, no rats, no data sheets.
He asked: what if we treat behavior like a marble rolling on a hilly surface? The hills are reinforcers. The marble’s path is the response.
What they found
The closer the reinforcer is in time and the stronger the contingency, the steeper the hill. A steep hill pulls the marble faster and deeper.
In plain words, tight, sure rewards grab behavior more strongly than loose, maybe rewards.
How this fits with other research
Killeen (1995) keeps the marble metaphor but adds hunger and satiation. Now the hills grow or shrink as the animal’s motivation changes.
Baum (2018) throws the marble away. He says behavior is not a tiny ball; it is a long rope of activity. The rope can’t be chopped into single responses, so the whole hill idea misses the point.
Cao et al. (2026) keep the physics love. They measure persistence like engineers measure stress on metal. They agree behavior can be quantified, but they use real mice and real numbers.
Why it matters
You can picture any reinforcement plan as a landscape. If you want a learner to move fast, make the hill steep: deliver the reward right after the target and keep the rule simple. If you want steadier, slower work, flatten the hill: use a leaner schedule. When motivation shifts, remember Killeen (1995) and adjust the hill height, not just the marble speed.
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02At a glance
03Original abstract
Behavior is treated as basic physics. Dimensions are identified and their transformations from physical specification to axes in behavioral space are suggested. Responses are treated as action patterns arrayed along a continuum of activation energy. Behavior is seen as movement along a trajectory through this behavior space. Incentives or reinforcers are attractors in behavior space, at the centers of basins of lowered potential. Trajectories impinging on such basins may be captured; repeated capture will warp the trajectory toward a geodesic, a process called conditioning. Conditioning is enhanced by contiguity, the proximity between the measured behavior and the incentive at the end of the trajectory, and by contingency, the depth of the trajectory below the average level of the potential energy landscape. Motivation is seen as the potential of an organism for motion under the forces impinging on it. Degree of motivation is characterized by the depth of the potential field, with low motivation corresponding to a flat field and a flat gradient of activation energy. Drives are the forces of incentives propagated through behavior space. Different laws for the attenuation of drive with behavioral distance are discussed, as is the dynamics of action. The basic postulate of behavior mechanics is incentive-tracking in behavior space, the energy for which is provided by decreases in potential. The relation of temporal gradients to response differentiation and temporal discrimination is analyzed. Various two-body problems are sketched to illustrate the application of these ideas to association, choice, scalar timing, self-control, and freedom.
Journal of the experimental analysis of behavior, 1992 · doi:10.1901/jeab.1992.57-429