Primate Number Abilities Can Rhesus Monkeys Spontaneously Subtract? Gregory M. Sulkowski & Mark D. Hauser

Number Systems Object File Model –Instant recognition of small numbers

Number Systems Accumulator Model –Larger Number = harder to keep track Scalar Variability

Why Test Primate Number Abilities? Can counting exist without language? –Animal vs Human number learning fundamentally different Brute Memorization –1 = 1, 2 = > 1; 1 = 1, 2 = 2, 3 = > 2 … –The chimpanzee Ai VS Successor Function Successor Function –S(n) = n + 1 S(1)=1+1=2, S(S(1))=2+1=3,...

Why Rhesus Monkeys? Other animals have been tested…with training –Pigeons, Parrots Raccoons, Ferrets, Rats Why not other animals? –Rhesus can accomplish without training –Population ready to work with

Experiment 1 1 versus 1-1, Single Subtraction –Monkeys could be avoiding the side that was affected

Experiment 2 1 versus 3-1, Single Subtraction –Only action on one of the two sides

Experiment versus 2-1, Double Action –Monkeys could be avoiding the side associated with object removal

Experiment versus 1-1, Double Subtraction –Nothing but food on platforms, no identity to track

Experiment food versus 2-1 non-food, Double Subtraction and Object Identity –Removed different objects from each side, could make monkey think only metal on one side while food on the other

Experiment food versus 2-1 non food, double subtraction and object identity –Thus far, number of objects has been minimal

Experiment food versus 2-1 non-food, Double Subtraction and Object Identity –Might have avoided one side by ignoring non-food item

Experiment food versus 2-1 food, Double subtraction and Object Identity –Only tested one aspect of subtraction

Experiment versus 1+1, Subtraction and Addition Without Changing Initial Object Number –Equality has yet to be tested

Experiment versus 1+1, Subtraction and Addition Leading to Equality –Never represented zero in the presence of addition and subtraction

Experiment versus 1-1, Subtraction and Addition and the Representation of Zero

Conclusive Results Conclusive –Represent zero Something even human infants can not do –Identify object properties separately of computations Modifies what is known of object file model

Inconclusive Results Inconclusive –Numbering model utilized Data explainable by both models –How zero was represented Still uncertain how zero is represented in either model –Likely combination of both models