Appendix 2—table 3. Models of stone-tool selection duration across years, with AIC.

AIC values reported for models fitted by Maximum Likelihood. PAB is the encounter in which stone tool selection events occurred.

Model	Formula	df	AIC
REML = F
Individual Random Slope and Intercept for Year-Scaled.	Log(Time)~Year-Scaled+Stones Selected + Stones Previously Taken + (1+Year-Scaled||ID) + (1|PAB)	8	231
Dropped Year-Scaled	Log(Time)~Stones Selected + Stones Previously Taken + (1|ID) + (1|PAB)	6	234
Null for All Fixed Effects	Log(Time)~1 + (1|ID)+ (1|PAB)	4	234
REML = T
Random Slope & Intercept	Log(Time)~Year-Scaled+Stones Selected + Stones Previously Taken + (1+Year-Scaled||ID) + (1|PAB)	8	244
Fixed Slope & Random Slope	Log(Time)~Year-Scaled+Stones Selected + Stones Previously Taken + (1|ID) + (1|PAB)	7	246