Motivational trade-offs as evidence for sentience in bees: a critique

Establishing if insects feel pain can have far-reaching consequences for insect husbandry, commercial pollination and scientific research. Research in this field therefore requires careful experiments and strong evidence. One important criterion proposed for measuring insect sentience is the ability to show a motivational trade-off, in which "the negative value of a noxious or threatening stimulus is weighed (traded-off) against the positive value of an opportunity for reward". A recent paper investigated motivational trade-offs in bumblebees and concluded that bees can trade-off heat against high sugar rewards. In this paper, we develop a signal detection model to highlight which features would be key to supporting the argument that motivational trade-offs are evidence of the capacity for experiencing pain. We then re-analyse the data from the original paper and find several limitations. Our own re-analysis finds no support for the final conclusions made by the paper. We therefore provide recommendations for future studies investigating the ability of insects to feel pain.