Simple discrimination in stingless bees (Melipona quadrifasciata): Probing for select- and reject-stimulus control.

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.