It is important to have a variety of back-up reinforcers on a reinforcer menu or to change them up on a regular basis because

Explanation:

Variety is a basic human need and individuals will not respond at all if there are not enough choices

Not having a choice will send the message that working for tokens is not something that will pay off

Choices on the reinforcer menu are often the only positives many individuals receive on a regular basis

Only having the choice among the same items may cause individuals to become bored and stop earning tokens

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.        

well its is frequent rain

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