Separating the reinforcing and discriminative properties of brief-stimulus presentations in second-order schedules.
A brief stimulus can guide timing or carry value—decide which job you need and pair it with backup reinforcers only if you want it to keep working when it stands alone.
01Research in Context
What this study did
The team built a second-order schedule. Pigeons pecked for food. Brief lights flashed after every tenth peck. Some lights were paired with food. Some were not.
They then tested the same brief lights alone. No food ever came. They watched if the birds kept pecking.
What they found
During the main schedule, paired and unpaired lights controlled the same pattern of pecking. The birds paused, then burst, whether the light promised food or not.
When the lights ran alone, only the food-paired light kept the birds working. The unpaired light quickly lost power. One stimulus had two jobs: it guided timing and it carried value. Those jobs can be split.
How this fits with other research
Terrace (1969) showed that ICS shock as a reinforcer sharpens stimulus discrimination more than food does. L et al. now add that, once a brief stimulus is set up, its guiding role can be separated from its rewarding role.
Wetherington (1979) used the same second-order frame with cocaine or food. He found that schedule structure, not reinforcer type, shaped the response pattern. L et al. echo that result: patterning stayed the same whether the brief stimulus was paired with food or not.
Marcucella (1976) warned that partial signalling of reinforcers flips contrast to negative induction. L et al. give a tool: if you want only timing control, leave the stimulus unpaired; if you want it to keep strength, pair it every time.
Why it matters
When you add a brief praise, sticker, or beep in a token system, ask: do I want it to tell the learner when to respond, or do I want it to keep responding alive? If you need both, pair it with backup reinforcers. If you need only a cue, you can run it unpaired, but watch for rapid loss of power. Check which function is working by running a quick probe with the brief event alone.
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02At a glance
03Original abstract
Pigeons' responses were maintained under multiple schedules to study properties of briefly presented stimuli. Responses in one component produced food according to a second-order schedule with fixed-interval components in which food or a brief stimulus occurred with equal probability. In the second component responses produced only the brief stimulus under a fixed-ratio schedule. Under various conditions the brief stimulus in the first component was (a) paired with food, (b) not paired with food, (c) partially omitted, or (d) scheduled simultaneously with the second-order schedule under an independent variable-interval schedule. Paired and nonpaired brief stimuli maintained similar response patterning in the second-order schedule. However, only paired stimuli maintained responses in the second component. The data suggest that nonpaired brief stimuli engender response patterning in second-order schedules as a result of their discriminative properties. When the stimulus is paired with food, these discriminative properties sometime mask a reinforcement effect, and no change in response patterning is observed. When the discriminative properties of the brief stimulus are absent, the reinforcing effects of pairing the brief stimulus with food may be observed.
Journal of the experimental analysis of behavior, 1979 · doi:10.1901/jeab.1979.32-149