Editing Reinforcement (section)

===Concurrent schedules===

In [[operant conditioning]], concurrent schedules of reinforcement are schedules of reinforcement that are simultaneously available to an animal subject or human participant, so that the subject or participant can respond on either schedule. For example, in a [[two-alternative forced choice]] task, a [[pigeon]] in a [[Skinner box]] is faced with two pecking keys; pecking responses can be made on either, and food reinforcement might follow a peck on either. The schedules of reinforcement arranged for pecks on the two keys can be different. They may be independent, or they may be linked so that behavior on one key affects the likelihood of reinforcement on the other.

It is not necessary for responses on the two schedules to be physically distinct. In an alternate way of arranging concurrent schedules, introduced by Findley in 1958, both schedules are arranged on a single key or other response device, and the subject can respond on a second key to change between the schedules. In such a "Findley concurrent" procedure, a stimulus (e.g., the color of the main key) signals which schedule is in effect.

Concurrent schedules often induce rapid alternation between the keys. To prevent this, a "changeover delay" is commonly introduced: each schedule is inactivated for a brief period after the subject switches to it.

When both the concurrent schedules are [[variable interval schedule of reinforcement|variable intervals]], a quantitative relationship known as the [[matching law]] is found between relative response rates in the two schedules and the relative reinforcement rates they deliver; this was first observed by [[R.J. Herrnstein]] in 1961. Matching law is a rule for instrumental behavior which states that the relative rate of responding on a particular response alternative equals the relative rate of reinforcement for that response (rate of behavior = rate of reinforcement). Animals and humans have a tendency to prefer choice in schedules.<ref>{{cite journal | vauthors = Martin TL, Yu CT, Martin GL, Fazzio D | year = 2006 | title = On Choice, Preference, and Preference For Choice. | journal = The Behavior Analyst Today | volume = 7 | issue = 2 | pages = 234–48 | doi=10.1037/h0100083| pmid = 23372459 | pmc = 3558524 }}</ref>