Simple discrimination in stingless bees (<i>Melipona quadrifasciata</i>): Probing for select‐ and reject‐stimulus control
Stingless bees learn to go to the S+ but do not learn to stay away from the S-, showing pure select-control.
01Research in Context
What this study did
Scienza et al. (2019) asked whether stingless bees learn to pick the good color, the bad color, or both. They set up a simple Y-maze. One arm showed the S+ color that led to sugar water. The other arm showed the S- color that led to plain water.
Each bee flew 40 trials. The researchers tracked how often the bee entered the S+ arm and how often it skipped the S- arm.
What they found
Every bee kept flying to the S+ side. That part was rock-solid. But most bees still visited the S- side about half the time. They got the sugar when they were right, yet they did not learn to stay away from the bad color.
The data say the bees live under select-control. They approach the good stimulus. They do not use reject-control to rule out the bad one.
How this fits with other research
Felipe de Souza et al. (2014) ran almost the same test with rats. Five of six rats picked the new picture by refusing the old S-. The rats showed clear reject-control. The bee data look like the opposite answer to the same question.
The two studies differ in species and visual task. Bees may lack the brain wiring for exclusion. Rats appear to have it. The clash is real but it is biological, not methodological.
Mann et al. (1971) showed tight stimulus control in humans. Skin resistance responses tracked the S+ and S- within just a few trials. People can use both select and reject cues. Bees, again, seem stuck on the positive cue only.
Why it matters
When you write a discrimination program, decide if the learner needs to approach the right choice, avoid the wrong choice, or both. If your client acts like the bee, load extra trials on the S+ and add strong reinforcement for correct approaches. Do not assume the S- will teach itself. Check data on S- responses separately from S+ hits. If reject-control never shows up, break the task into smaller positive-only steps before you add the 'no' cue.
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02At a glance
03Original abstract
Simple and conditional discrimination training may produce various types of controlling relations. Responses may be controlled primarily by the positive stimulus (select-control relation) or by the negative stimulus (reject-control relation; the subject excludes the negative stimulus and chooses the positive). Bees learn to respond in simple and conditional discriminations. However, no study has searched for reject-control responding in Melipona bees. We trained Melipona quadrifasciata on a simple discrimination task (S+ vs. S-; e.g., blue vs. yellow) and then probed for stimulus control with two types of probe trials, S+ versus a new stimulus (Select-control probes) and S- versus a new stimulus (Reject-control probes). For Group Different, a new-stimulus color (e.g., white) was used in one type of probe and another color (e.g., black) was used in the other type. For Group Same, a single new-stimulus color was used in both types of probes. On Select probes, the bees always preferred S+ to the new stimulus. On Reject probes, results were mixed. Depending on the colors used in training and probing, bees responded to both stimuli, and even preferred the S-. The data suggest no control by the negative function of the S- and support the select-stimulus control hypothesis of responding.
Journal of the Experimental Analysis of Behavior, 2019 · doi:10.1002/jeab.531