How does object play shape tool use emergence? Integrating observations and field experiments in longtailed macaques
Bibliographic record
Abstract
It has long been suggested that object play facilitates the development and evolution of tool use, through enhanced perception of an object's properties and potential for manipulation. However, ecologically relevant support for this claim is scant. We examined whether a form of culturally maintained object play, named stone handling, characterized by high interindividual variation in its behavioural expression, promotes the acquisition and further expression of stone-tool use in a nonhuman primate species. We conducted a series of field experiments in a free-ranging group of Balinese longtailed macaques, Macaca fascicularis , to test whether the stone-handling profiles of different individuals predicted their ability to solve a foraging task, whose solution required the functional and action-specific use of stones as tools. Frequentist network-based diffusion analysis, Bayesian multilevel regression modelling and descriptions of individuals' learning trajectories showed that the solutions to different foraging tasks required varying reliance on social and asocial learning strategies. Our results suggest that certain stone-handling profiles may increase an individual's likelihood of expressing stone-tool use. However, other trait- and state-dependent variables may also contribute to explaining individual differences in the development and expression of stone-tool use. The behavioural idiosyncrasies associated with stone handling in longtailed macaques may serve as an exaptive reservoir for the possible emergence of stone-tool use. To our knowledge, this is the first study to experimentally evaluate the role of stone-directed play in the acquisition of stone-tool use. • We examined whether object play influences the expression of tool use in macaques. • Stone handling in macaques promoted stone-tool use acquisition and expression. • Stone-handling profiles helped solve foraging tasks involving stones as tools. • Object play may serve as a potential precursor to tool use. • Social influences contributed to acquiring puzzle box solutions.
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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 | 0.000 | 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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".