People who play slot machines in gambling casinos usually exhibit steady, rapid rates of responding because slot machines operate on a variable ratio schedule of reinforcement.

A variable ratio schedule of reinforcement is one where a reinforcer (in this case, a win or payout) is delivered after an unpredictable number of responses (pulling the lever or pressing the spin button). This schedule is very effective in maintaining and strengthening behavior because the reinforcement is delivered randomly, and the individual never knows when the next win will occur.

The key characteristics of a variable ratio schedule that make it so effective in sustaining behavior like playing slot machines are:

1. Unpredictability: Since the number of responses required for the next reinforcement is variable and unknown, the player is motivated to continue responding in the hopes of getting a win.
2. Resistance to extinction: Even when a player goes through a long period without a win (extinction), they are likely to continue playing because the reinforcement has been delivered on a variable ratio schedule in the past.
3. High response rate: The variable ratio schedule generates a high and steady rate of responding, as the player keeps pulling the lever or spinning rapidly in an attempt to get the next reinforcement.

The variable ratio schedule is widely used in many gambling games, such as slot machines, because it is highly effective in maintaining and reinforcing the gambling behavior, even in the face of frequent losses. This schedule of reinforcement is one of the reasons why gambling can be so addictive and difficult to stop once initiated.