Reinforcement of probe responses and acquisition of stimulus control in fading procedures.
Reinforce probe responses during stimulus fading to cut the number of fading steps by roughly a third.
01Research in Context
What this study did
Palya (1985) worked with pigeons in a lab. The birds had to peck the correct key when lines tilted left or right.
The team used stimulus fading. They started with a bright line and dim background. Across steps they dimmed the line and brightened the background.
Halfway through each step the birds got one probe trial. In some fading runs the probe was also reinforced. In other runs it was not.
What they found
When probe responses earned food, the birds reached perfect performance in fewer fading levels.
Without probe reinforcement the same birds needed extra steps. Reinforcing the probe shaved about one-third of the steps off the program.
How this fits with other research
Wetherington (1979) ran a near-copy study six years earlier. That paper also showed probes speed stimulus control, but the probes were never reinforced. The 1985 paper adds the twist that reinforcing the probe itself is what cuts training time.
Christophersen et al. (1972) moved fading out of the lab. Preschoolers learned to read pictures faster when the pictures were faded in. The bird finding lines up with the kid finding: gradual fading plus well-timed help equals faster learning.
Allan et al. (1991) later used probes in a classroom. Some students kept the skill, one lost it. Their mixed results warn that probes can change the very stimulus control we are trying to test, just as the pigeon data show.
Why it matters
If you run stimulus fading, reinforce the probe trials. You will likely reach mastery in fewer steps, saving client time and your own. Just stay alert: the extra reinforcement can make the probe itself a cue, so check that the learner still responds when the probe is removed.
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02At a glance
03Original abstract
Stimulus control of pigeons' key pecking was transferred from colors to lines by the method of stimulus fading. Fading was conducted with the addition of probes consisting of the line stimuli presented alone at each fading level. Probe responding was used to measure stimulus-control acquisition by the lines. Effects of reinforcement and nonreinforcement of probe responding upon acquisition of stimulus control were assessed using a single-organism repeated-acquisition design in which three fades were conducted serially. Probe responding was not reinforced in the first and third fade but was in the second. Reinforcement of probe responding substantially reduced the number of fading levels needed to complete fading. The outcome of a control experiment ruled out the possibility of accounting for these results in terms of the specific stimuli used in each fade or in terms of the sequential exposure to the three discriminations. Although probes permitted measurement of stimulus-control acquisition in fading, a measurement/acquisition interaction was also present.
Journal of the experimental analysis of behavior, 1985 · doi:10.1901/jeab.1985.43-235