The Bin and the Prompt
Your 4-year-old client, Priya, is learning to mand. The program says: present a preferred item, wait 5 seconds, and if there is no response, deliver a full physical prompt to exchange the picture card, then provide the item. After four weeks, data show 96-100% correct responding with the physical prompt and 0 independent mands across 20 trials per session. You notice that when the item is visible on the table Priya reaches for it, and when the item is inside a closed cabinet she does not. Her mother reports that at home Priya "asks" only when the iPad is in sight and the television is off. Recently Priya has begun reaching for the card whenever she sees you take out the bin of preferred items, before any item has been presented.
1. Distinguish the roles of the motivating operation, the discriminative stimulus, and the prompt in this data set.
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- Motivating operation (establishing operation): deprivation from or restricted access to the item. That is what makes the item effective as a reinforcer and makes the mand more likely. Without it, the item is just a stimulus.
- Discriminative stimulus: the sight of the item - and, by extension, the bin - signals that the exchange will be reinforced. The evidence is the differential reaching: reaching when the item is visible, not reaching when it is in a closed cabinet.
- Prompt: the full physical guidance. Data showing 96-100% with the prompt and 0% without it mean the response is under prompt control, not under control of the MO plus the item.
The critical inference: high prompted accuracy is not evidence of a mand. A mand requires the response to occur in the presence of the MO without the prompt. What you have is a prompted motor chain with the therapist as the relevant SD.
2. What does the bin-reaching tell you, and what is the risk?
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It suggests the bin has become an SD for the reaching response - a precursor that has been absorbed into a learned sequence: bin appears → reach → therapist delivers physical prompt → exchange → item. The therapist's presence and the prompt delivery are part of the chain, so the response is coming under the control of your behavior rather than the child's state of deprivation.
Risks:
- The skill will not generalize to the mother or to school, because you are the SD.
- Reaching at the bin may be adventitiously reinforced by the item, building a response you did not plan to teach.
- Continued prompted trials can strengthen the prompt as a conditioned reinforcer, deepening prompt dependency while the graph looks excellent.
What the bin behavior does not tell you is that the mand is emerging. It tells you the chain has a new first link.
3. What would you recommend, and what is outside your role?
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Outside your role: changing the prompt procedure. You report and recommend; the BCBA revises.
Recommendations to bring to the BCBA:
- A measurement change that separates prompted from independent responses, so that independence is its own data path and can't hide inside 96% accuracy.
- A no-prompt probe condition: item visible, MO in place, therapist neutral, no prompt, defined response window - to test whether independence exists at all.
- A prompt-delay or least-to-most arrangement so the 5-second wait is preserved and the physical prompt is no longer delivered on every trial.
- Removing the therapist as an SD: vary who runs trials, vary the setting, and have the mother run probe trials at home with a simple yes/no record.
The conceptual point to raise: the target is a response under the control of the MO, not a response under the control of your hands.