Othello likes going to the casino and playing the slot machine. He realizes that he will not win very often and that he never knows how many times he has to put money in and pull the level before he will win. Othello is being reinforced on a schedule of reinforcement.

variable ratio.

Explanation:

Operant conditioning theory describes a variable-ratio schedule as a situation where the response is repeated after an unforeseeable number of responses. It is given using a pre-determined average number of responses. Variable ratio schedules keep the desired behavior high and stable, and the behavior is very resilient to extinction. As per the question, Othello's realization of his unknown probability of wins reflects he has been reinforced by a variable ratio schedule of reinforcement.