Schedules are of two main types, time-based and response-based. Time-based schedules usually contain the word interval, as in time interval. Response-based schedules usually contain the word ratio, referring to the ratio of responses over time.
Fixed interval (FI) schedules reinforce any response made during an unchanging interval. For example, an FI-5 schedule would deliver a reinforcer every five seconds if at least one response had been made during the five seconds. Note that the FI-5 schedule would deliver just one reinforcer if many responses had been made during the five seconds.
Variable interval (VI) schedules are similar to FI schedules, except that the interval varies randomly for each reinforcer. So, a VI-5 schedule would deliver a reinforcer over an average interval of 5 seconds, not every five seconds. Each interval would be different.
Fixed ratio (FR) schedules deliver a reinforcer based upon a constant number of responses. For example, a FR-15 schedule would deliver a reinforcer every 15th response.
Variable ratio (VR) schedules are similar to fixed ratio, except that the number of responses required for a reinforcer changes each time. So, a VR-15 schedule would deliver a reinforcer over an average of 15 responses, not on every 15th response.
Let's examine some everyday examples of reinforcement schedules and their effects. A paycheck is a good example of an FI schedule. Workers get a check once a week, for example, if they show up and work. They do not get rewarded for working harder, or penalized for working less. Workers who work by the piece or by the job, piecework, are paid more if they produce more, and are paid less if they produce less. Piecework is an example of an FR schedule. Workers typically work harder on FR schedules than they do on FI schedules.
Gambling is the classic example of a VR schedule. Part of the allure of gambling is its uncertain payoff. Imagine a slot machine that paid off every 10th time; only the 10th pull would be exciting. A real slot machine, on the other hand, pays off on a random basis, so each pull is exciting. VR schedules maintain behavior at very high rates.
About the best everyday example of a VI schedule that I can think of is working for a shady character. This person pays you, but you never know when payday is going to be. It could be a week, two weeks, a month. So, you don't work very hard. You would probably jump to another job if the pay were the same but given regularly.
- Vegas Showgirls Slots--interactive, basic, short, links, graphics, Shockwave
- From a commercial game site, slot machine that works on the Web, users may change their "wagers" and get "payoffs" while the program tallies the results. Good for demonstrating variable ratio schedules. http://www.sabroco.com/greetings/WEB97/games/vegagame.htm