Adaptive Phototaxis in Response to Experience – Learning by Association in the Slime Mold Physarum polycephalum

Cognitive processes such as learning by association are traditionally considered exclusive to organisms with nervous systems. However, increasing evidence suggests that some aneural organisms, such as the slime mold Physarum polycephalum, exhibit behaviors indicative of basal cognition. In this study, we investigated whether P. polycephalum is capable of associative learning by combining light stimuli with food rewards. Using a controlled light gradient environment, we conducted three experiments: training plasmodia to move toward an aversive blue light, toward a neutral red light, and away from neutral red light. Following initial baseline tests, plasmodia underwent four training sessions with food cues, after which their phototactic behavior was reassessed without food. Results show that plasmodia significantly altered their behavior when trained toward both aversive and neutral stimuli, with the strongest effect observed in the aversive (blue light) condition. While these behavioral shifts suggest associative learning, the potential role of habituation could not be fully excluded. Our findings contribute to the growing body of evidence supporting cognitive-like capacities in aneural organisms and highlight the need for further investigation into the mechanisms underlying memory and learning in Physarum.