Supplementary material for: Testing the peak-end rule in bumblebees: lack of preference for a higher-reward sequence when the final reward is disappointing

<h3>ABSTRACT</h3> <p>The peak-end rule describes the tendency to evaluate experiences by their most intense and final moments, rather than considering the entire experience as a whole. While this cognitive bias is well-established in humans, studies on nonhuman animals are very limited. Bumblebees make foraging decisions largely based on past experiences, but whether peak-end effects influence their subsequent flower choices is still unknown. Here, we trained individual <em>Bombus terrestris</em> workers on two artificial flower types, blue and yellow, over 12 consecutive foraging bouts. One flower type offered a sequence of three high-quality rewards (25 &mu;L drops of 50% w/w sucrose solution: &ldquo;consistent&rdquo; sequence), while the other provided the same sequence but ended with an additional, lower-quality reward (25 &mu;L drop of 20% w/w sucrose solution: &ldquo;poor end&rdquo; sequence). We then tested the bees' flower type preference in a final binary choice. Bees showed a strong preference for blue flowers, both in their initial and overall visits. Across all visits during a 1-minute period, they also favoured flowers associated with the &ldquo;consistent&rdquo; sequence, though this preference was significant only when these flowers were yellow. Interestingly, despite offering more sucrose per foraging bout, bees did not favour the &ldquo;poor end&rdquo; sequence flower. This study is, to our knowledge, the first to investigate peak-end effects in an insect. How bees evaluate sequential rewards when foraging remains largely unexplored, yet could provide valuable insights into nectar distribution and plant-pollinator co-evolution.</p>