Fig 2. Absolute color conditioning and memory retrieval in workers.

Acquisition curves (proportion of bees that responded to the tested color stimulus by extending the proboscis [% PER]) of workers during absolute conditioning of four different color stimuli (A: 435 nm, B: 455 nm, C: 488 nm and D: 528 nm). Workers were trained either with a paired (filled circles) or an unpaired (empty circles) presentation of CS and US. Memory retrieval was tested by presenting the CS (colored bar) and a novel color stimulus (NCol: gray bar) to the bees 2h after conditioning. *** P < 0.001; ** P < 0.01.