Constraints on the Evolution of Reciprocity: An Experimental Test with Zebra Finches
Bibliographic record
Abstract
Reciprocity is apparently uncommon in animal societies because it requires, to evolve, specialized cognitive abilities that most species would not possess. In particular, memory would be important because cooperation can emerge and be maintained only if the same opponents interact repeatedly and adjust their decisions to their opponent’s previous move. To investigate how these constraints influence reciprocity, we first conducted a preliminary foraging experiment with zebra finches (Taeniapygia guttata) to insure that corticosterone elevations impaired the birds’ event memory capabilities. Then, we performed a reciprocity experiment with established pairs that were tested in a two-choice apparatus under two different conditions: once with an empty implant and once with an implant of corticosterone. We found that the birds were capable of sustained cooperation in the Prisoner’s Dilemma treatment but only when they had an empty implant. Thus, our results support the hypothesis that limitations in event memory constraint the frequency of reciprocity and hence would make this form of cooperation difficult for non-human animals. In addition, as levels of stress hormones can differ greatly among individuals, our findings might also contribute explaining individual variation in the propensity to cooperate.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.005 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.003 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.001 | 0.003 |
| Insufficient payload (model declined to judge) | 0.004 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".