Video S1: Procedure demonstrations and monkey response

The video shows the lottery machine task used in all three studies. The first clip shows the Fruit Preference Validation procedure from Study 1 from the monkey's perspective. Here, E1 uses a stick (out of the monkey's view) to rotate the lottery machine; in this study the population of fruit is occluded in this phase. E1 then releases a lemon from the machine to the clear cup below, and says “now” to mark the start of the trial. Each trial then lasts 10 s, and the looking time of the monkey is recorded. The second clip shows the Probability Inference procedure from Study 2. Here, E1 open the curtains and reveals a lemon machine containing a population with a probable likelihood distribution (3:1 distribution of lemons and apples). Then, after rotating the machine, she releases the expected outcome (a lemon). The third clip shows the Non-causal control procedure from Study 3. E1 opens the curtains and reveals again a lemon machine, but this time it contains a population with a possible likelihood distribution (only one type of fruit is present). After rotating the cube, E1 visibly pulls the impossible (unexpected) outcome (an apple) from her pocket and then places it into the container above the cube. The final clip shows an example of the monkey's looking response in the task.