Do monkeys use sex toys? Evidence of stone tool‐assisted masturbation in free‐ranging long‐tailed macaques
Bibliographic record
Abstract
Abstract Recent reports on tool use in nonforaging contexts have led researchers to reconsider the proximate drivers of instrumental object manipulation. In this study, we explore the physiological and behavioral correlates of two stone‐directed and seemingly playful actions, the repetitive tapping and rubbing of stones onto the genital and inguinal area, respectively, that may have been co‐opted into self‐directed tool‐assisted masturbation in long‐tailed macaques (i.e., “Sex Toy” hypothesis). We predicted that genital and inguinal stone‐tapping and rubbing would be more closely temporally associated with physiological responses (e.g., estrus in females, penile erection in males) and behavior patterns (e.g., sexual mounts and other mating interactions) that are sexually motivated than other stone‐directed play. We also predicted that the stones selected to perform genital and inguinal stone‐tapping and rubbing actions would be less variable in number, size, and texture than the stones typically used during other stone‐directed playful actions. Overall, our data partly supported the “Sex Toy” hypothesis indicating that stone‐directed tapping and rubbing onto the genital and inguinal area are sexually motivated behaviors. Our research suggests that instrumental behaviors of questionably adaptive value may be maintained over evolutionary time through pleasurable/self‐rewarding mechanisms, such as those underlying playful and sexual activities.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.007 | 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 teacher head, 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".