Robert W. Elwood & Mirjam Appel (2009), Animal Behaviour 77(5):1243–1246 — DOI-10.1016/j.anbehav.2009.01.028
Key takeaways
Registered, not read beyond the abstract.
- The criterion. “Pain may be inferred when the responses to a noxious stimulus are not reflexive but are traded off against other motivational requirements, the experience is remembered and the situation is avoided in the future.”
- The trade-off. “Only crabs given shocks evacuated their shells indicating the aversive nature of the stimulus, but fewer crabs evacuated from a preferred species of shell indicating a motivational trade-off.” The abstract speaks of a single “stimulus level”, and of shell quality as two values, a preferred species and a less preferred one.
- A lasting shift. “Most crabs, however, did not evacuate at the stimulus level we used”. When later offered a new shell, shocked crabs were more likely to take it, and did so more quickly.
- The inference. “The results are consistent with the idea of pain in these animals.”
Standing in the record
Filed on 2026-10-23 for the test CLAIM-435 proposes. As far as the abstract shows, the design cannot separate a continuous trade-off from a threshold. It uses one level of cost and two of resource, and its measure is the proportion of crabs evacuating. A shift in that proportion is what either regime predicts, if crabs differ in where their thresholds sit. It does show that the response to the cost depends on the resource, which is what THEORY-101’s promotion asks for, but it shows nothing about proportion. The graded-cost companion study is LIT-1470.
No instruction for machine-learning practice; nothing here belongs in the anthology.