Choice Behavior One

Concurrent Schedules Concurrent Schedule – model of choice behavior Choice behavior such as changing TV stations, gambling on slot machines or many social interactions are common examples experimentally 2 response alternatives associated with reinforcement schedules Pigeon pecking at two key lights each with a schedule of reinforcement Figure 6.4 compare rate of responding on the two key lights Pigeon is free to switch from one response alternative to the other Allows researchers to determine which type of schedules animals prefer Example: VR 10 preferred over VR 100 Demonstration of choice behavior Choice behavior is very similar to foraging behavior it consists of successive visits to alternative sites where resources (food, water, shelter, mates) may be obtained accordingly, concurrent schedule performance consists of visits, now to one schedule, now to the other

Figure 6.4 – Diagram of a concurrent schedule for pigeons. The Principles of Learning and Behavior, 7e by Michael Domjan Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.

Measures of Choice Behavior Relative Rate of Responding Compare rate of responding on "left" to "right" side using ratio Ratio is "left side" behavior (BL) divided by behavior on both sides (BL + BR) when the ratio for the left side is 0.5 there is no preference for either side when the ratio for the left side is greater then 0.5 there is a preference for the left side when the ratio for the left side is less then 0.5 there is a preference for the right side Comparing two ratio schedules is not very interesting, VR 10 vs VR 100, because you get almost all the behavior on the VR100 Comparing VI schedules is interesting because you need to switch back and forth between the left and right side to maximize the number of reinforcers Relative Rate of Reinforcement Compare rate of reinforcement on "left" to "right" side Ratio is "left side" reinforcement (rL) divided by reinforcement on both sides (rL + rR)

The Matching Law Herrnstein (1961) compared VI schedules, see Figure 6.5 VI 6min vs VI 2min with maximum of 40 reinforcers per hour Pigeon could get 30 on VI 2min and 10 on VI 6min per hour Pigeon pecking behavior matched the VI distribution The relative rate of responding on a particular side equals the relative rate of reinforcement on that side If the left side produce lots of reinforcers there will be more responses on the left side behavior on the left matches the amount of reinforcement on the left If left side gives four times as much reinforcement as right side then make four times as many responses on the left side When an animal is "matching" the rate of responding on a particular side will be proportional to the rate of reinforcement

The Principles of Learning and Behavior, 7e by Michael Domjan Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.

Importance of matching law Simple schedules of reinforcement show contingency patterns Need to take into account other sources of reinforcement particularly important under natural conditions where there are a number of choices very important to understand human behavior because of the complex array of reinforcements that may be available For example Social Conversation Two-point vs three-point shots in basketball Unprotected sex among teenagers Individuals with other reinforcement options had less unprotected sex The Principles of Learning and Behavior, 7e by Michael Domjan Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.

Undermatching and Sensitivity The matching law provides an accurate description of choice behavior in many situations, but there are exceptions and problems. Undermatching Occurs when the subjects responds less than predicted on the advantageous schedule. For example with VI 6min and VI 2min the pigeon should make three times as many responses on VI 2min if it only makes twice as many on VI 2min then it is undermatching. According to the sensitivity concept the pigeon is being less sensitive to the relative difference between VI 2min and VI 6min Influenced by effort to switch between keys Varies across animal species

Overmatchng, and Response Bias Overmatching Higher rate of responding for the better of the two schedules than the matching law predicts. For example with Key A set at VI 6min and Key B set at VI 2min the pigeon should make three times as many responses on Key B put if it makes four times as many on Key B then it is overmatching. Overmatching occurs when it is costly for a subject to switch to the less preferred response alternative (e.g., when the two levers are far apart) So the pigeon is more sensitive to the relative difference between A and B. Bias Subject may have a special affinity or preference for one of the choices a pigeon may prefer a red key over a green key Difference in type of reward on for each choice; sweet vs plain food

Mechanisms of the Matching Law Subjects attempt to maximize the rate of reinforcement because animals have evolved to perform in a manner that yields the greatest rate of reinforcement. Can explain why subjects match with concurrent VI-VI schedules but not with concurrent ratio schedules VR-VR. Molar Maximizing according to molar theories animals distribute their choices to maximize reward over the long run animals distribute responses so as to maximize the reinforcers available in the long run developed to explain results from concurrent ratio schedules FR 20 - FR 10 has difficulty explaining concurrent VI - VI schedule has difficulty explaining concurrent VR - VI schedule Only occasional responses to VI needed for maximization Preference for VR not as strong as molar maximization predicts

Mechanisms of the Matching Law Subjects attempt to maximize the rate of reinforcement because animals have evolved to perform in a manner that yields the greatest rate of reinforcement. Can explain why subjects match with concurrent VI-VI schedules but not with concurrent ratio schedules VR-VR. Molecular Maximizing according to molecular theories animals choose whichever response alternative is most likely to be reinforced at that time animals distribute responses so as to maximize the reinforcers available in the short run (momentary maximizing) Switching occurs when the momentary probability of reinforcement on the alternative response key becomes greater than the momentary probability of reinforcement on the alternative response key With concurrent VI 6min vs VI 2min switch to the VI 6min occasionally Can be reinforced for switching

Melioration Theory “Meliorate” = to make better, improve Animals try to make the local rates of reinforcement equivalent Calculated just over the time devoted to that choice not the entire session Local rates of reinforcement are always higher then overall rates With a VI 6min there are 10 reinforcers possible in one hour If all of the behavior is on the VI 6min then it is 10 / hour However, continuously switching to the other choice Spend 15 minutes on VI 6min and spend 45 minutes on the VI 2 So local rate on VI 6min is 10/15 minute or 40 /hour switching to better their current chances of receiving reward Melioration mechanisms work on a time scale that is between molecular and molar. Responses are distributed between two choices “switching” so that the same local rate of reward is obtained on both alternatives