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LIT-1470: Motivational trade-offs and potential pain experience in hermit crabs

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StatusUnavailable — registered 2026-10-23 from Crossref, not read beyond the abstract: no lawful full text could be reached. OpenAlex lists it as closed; Queen's University Belfast's research portal has the record and abstract but no file; the Elsevier article is paywalled. Filed with its companion (LIT-1450) because it is the hermit-crab study that varies the cost: shock rising until the crab leaves its shell, in preferred and less preferred shells. That is the nearest published design to the test CLAIM-435 proposes. It stays Unavailable until a copy is supplied, not on merit.
Tagsemotion-and-affect, motivation, consciousness

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Mirjam Appel & Robert W. Elwood (2009), Applied Animal Behaviour Science 119(1–2):120–124 — DOI-10.1016/j.applanim.2009.03.013

Key takeaways

Registered, not read beyond the abstract.

  • Graded cost. Crabs in preferred or unpreferred shell species were tested “subjecting their abdomens to electric shocks of gradually increasing intensity.”
  • The threshold moves with the resource. “The first observable response was not affected by shell species but those in preferred shells evacuated at a higher shock level than those in poor quality shells.”
  • The authors’ reading. “Thus, they seem to trade-off the requirement to retain a high quality shell with that of avoidance of the noxious stimulus.” They take the findings as consistent with pain rather than a nociceptive reflex.

Standing in the record

Filed on 2026-10-23 for the test CLAIM-435 proposes. Do the data look continuous or thresholded? Each crab’s act is all-or-none: it stays until some shock and then leaves. But a continuous indifference curve, probed by raising the cost at a fixed resource, also gives an all-or-none switch, at the point where the curve is crossed. What tells the regimes apart is whether that switch point moves with the resource. Here it does: a better shell raises the shock at which the crab leaves. That is the compensatory pattern, and it is evidence against a level threshold at the shock levels tested. With two shell qualities, though, it is two points on a curve. ALARM’s override (THEORY-090) predicts that the switch point stops rising once the resource is good enough, a ceiling at c*. Showing whether that happens needs a range of resource qualities and shocks up to injury, which the design, as the abstract describes it, does not have. The unaffected “first observable response” could be a fixed reflex beneath the trade-off. That would be the two-layer picture CLAIM-435’s first defeater names: a currency and an override as separate mechanisms in one animal.

No instruction for machine-learning practice; nothing here belongs in the anthology.

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