Attractiveness versus stickiness: Behavioural preferences of Drosophila melanogaster with competing visual stimuli

In nature, animals often encounter various competing stimuli and must make choices among them. Although the behaviour under two identical stimuli has been extensively studied for fruit flies, Drosophila melanogaster, how the appeal of one stimulus for the animals is influenced by the appeal of the other is not fully understood. In the present study, we systematically investigated this equation using a modified Buridan's paradigm. We focused on the behaviour of fruit flies under asymmetric visual stimuli, i.e., two black stripes of different widths. We characterized two behaviour modes: (1) Attractiveness: moving toward a stripe in the inner area of the platform, and (2) Stickiness: staying around the edge near a stripe. Our results reveal that while Attractiveness of a stripe is primarily influenced by its own width and remains relatively independent of the opposite stripe, Stickiness is significantly affected by the width of the competing stripe. These findings suggest that the behavioural response of fruit flies to visual stimuli involves complex decision-making processes influenced by both intrinsic and extrinsic factors. This study provides new insights into the cognitive and sensory mechanisms underlying visual preference behaviour in Drosophila and highlights the importance of considering multiple stimuli in behavioural assays.