Stimulus duration as a measure of stimulus generalization.
Viewing time gives the same generalization hill as response rate, so you can measure stimulus control without counting pecks.
01Research in Context
What this study did
Pigeons learned to peck when the line on a screen tilted 45°. They got food for correct pecks.
Next the birds saw lines tilted 30°, 40°, 50°, 60°. No food. The birds could look as long as they wanted.
The team timed how long each bird stayed with each tilt. They also counted pecks per minute.
What they found
Viewing time made a smooth hill. The 45° peak matched the trained tilt. The slopes copied the peck-rate hill.
Letting the bird choose how long to look gave the same gradient as counting responses.
How this fits with other research
Okouchi (2003) got the same shaped hills with college students and line lengths. The 1976 duration trick works across species.
Terrace (1969) and Powell et al. (1968) showed that steady training sharpens gradients. Downing et al. (1976) adds a second ruler: viewing time.
HEARSKELLEHER et al. (1964) found that DRL and long VI schedules flatten hills. The 1976 study held schedule constant, proving the flattening is from schedule, not from the way we measure.
Why it matters
You can map stimulus control without counting every response. Let the client look as long as they want. The time they stay is your gradient. This helps when responses are hard to count, like eye gaze or quiet toy play. Try it next time you probe generalization of tacts or intraverbals.
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Join Free →During generalization probes let the learner control how long they look at each picture; time the looks instead of tallying responses.
02At a glance
03Original abstract
Four pigeons in the line-positive group were trained with a vertical line on a green background that signalled intermittent reinforcement while a plain green field signalled extinction. Four pigeons in the line-negative group were trained with the opposite discrimination. Response to a control key terminated any trial and initiated the next trial. The birds also used the control key during generalization tests to control the durations of trials in which various line orientations were presented. These durations were summed to provide generalization gradients of stimulus duration that were positive or negative in accordance with the trained discriminations. In Experiment 2, birds from the line-positive group were tested with a procedure in which the control key was not available on some trials. This provided an independent assessment of response rates to the test stimuli. These rates were used to predict the stimulus durations obtained when the control key was available. The findings supported a general model for the prediction of response distributions among concurrent stimuli from rates observed with single stimuli.
Journal of the experimental analysis of behavior, 1976 · doi:10.1901/jeab.1976.25-209