Response rate as a factor in choice

02138 Four pigeons were trained on a concurrent chain schedule, in the terminal links of which food was delivered according to variable interval schedules, For one key in Experiment 2 re

ILLiad Transaction Number: 1153669

Call Number: BF1 P88

Location: STORAGE

Journal Title: Psychonomic science

Article Author: Killeen, Peter

Article Title: Response rate as a factor in choice

Journal Vol: 12 Journal Issue: 1

Journal Month: Journal Year: 1968-01

Article Pages: 34-34

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age

Response rate as a factor in choice’

PETER KILLEEN, HARVARD UNIVERSITY, Cambridge, Mass

02138

Four pigeons were trained on a concurrent chain schedule, in

the terminal links of which food was delivered according to

variable interval schedules, For one key in Experiment 2 reinforce-

ment was contingent on not responding Three control experi-

ments were also run: baseline, return to baseline, and unequal

reinforcement frequencies Although rate differences of over 50 to

1 were obtained in the terminal links of Experiment 2, the pigeons

remained indifferent between these schedules The only change in

preference occurred in Experiment 4, where preference matched

reinforcement frequency

In 1960 Autor investigated behavior on a concurrent chain

schedule in which reinforcement in the terminal links was

delivered according to variable interval (VI) schedules He found

that the relative numberof responses on a key in the initial link

equalled (matched) the relative rate of reinforcement for that key

in the terminal link This matching relation did not change when

he made reinforcement contingent on not responding in both

terminal links Herrnstein (1964) also found that preference was

more highly correlated with reinforcement rate than with rein-

forcement probability (reinforcements per response) in concurrent

chain schedules employing VI and VR schedules in the terminal

links Fantino (1968), however, has recently published data

showing that animals prefer FI schedules to the same schedules

with an added restriction on the minimum or maximum number

of responses His data for the schedule requiring a low rate of

responding are questionable, since two pigeons’ rates were not

appropriately controlled, yet they showed a greater range in

preference than the third pigeon on this schedule

The following study is an attempt to clarify the relation of the

response rate evoked by a schedule to preference for that

schedule It employs a more effective method of control of

terminal link rates than that used by Fantino Since the rate is

controlled in only one terminal link, the obtained differential

measure of preference is more sensitive than the measure obtained

by Autor Finally, reinforcement rate is held constant, so that

instead of looking for a deviation from a correlation as did

Herrnstein, all obtained changes in preference can be ascribed to

the terminal link rate differences

Method Four male White Carneaux pigeons, all with previous experimental

histories, were maintained at 80% of their free-feeding weight

The experimental procedure conforms to the basic concurrent chain design

which consists of a regular alternation between two states, an initial choice link,

and a terminal reinforcement link In the choice link responses of at least 15 g

force to either of two Gerbrands pigeon keys occasionally changed the color of

that key from blue to red (left key) or from blue to green (right key), with the

other key going dark Further responding on the lit key produced reinforcement

according to VI 30 sec schedules in all cases except two For the right key in

Experiment 2 reinforcement was delivered as soon as a VI 30 sec schedule set

up, but no sooner than 1.5 sec since the last response on that key For the right

key in Experiment 4, reinforcement was delivered according to a standard VI

60 sec schedule After one reinforcement with grain in the terminal link, the

program reverted to the choice link with both keys blue The occasions upon

which a response in the choice link would cause a transition to the reinforce-

ment link were determined by separate VI 60 sec schedules for each key Each

experiment was mun for 17 days

Experiments 1, 3, and 4 were controls for Experiment 2 In Experiments 1

and 3 conditions of reinforcement were identical for the left and right keys, and

thus the birds should be indifferent between them In the terminal link of

Experiment 4 reinforcement rate for the right key was half of that for the left

key; the birds should prefer the left key In Experiment 2 reinforcement

frequencies were equal, but the contingencies of reinforcement differed The

schedule on the left key in the terminal link encouraged moderate, uniform

rates of responding, while the schedule on the right key discouraged any

responding at all

Results and Discussion The schedules employed in Experi

ment 2 were effective in establishing different rates of responding in

34

Fig 1 Preference for left key (responses on left key in initial link/total responses in initial link) Data are averages over last five days in each experiment for each bird

the reinforcement links: averaged across birds for the last five days

of Experiment 2, these rates were 52.3 responses per minute on the left key and 0.95 responses per minute on the right key A substantial number of these right key pecks were emitted just after entry into the terminal link, and represent the last response in arun initiated in the choice link

The effect of this large difference in response rate on preference can be seen in Fig 1 Pigeon No 25 showed a consistent bias for the right key, but the only pigeon showing a marked change from the baseline of Experiment 1 and 3 was No 259 When the data are averaged across birds, there is seen to be an increase from baseline preference for the right key of only 1% The pigeons’ relative indifference to radical changes in response rate stands in sharp contrast to their preference for schedules with higher reinforcement rates In Experiment 4, halving reinforcement frequency on the right key resulted in an increase to 63% in preference for the left key

Although the present study provides evidence that preference is independent of response rate, we cannot conclude that an organism

is insensitive to the amount of work entailed in the procurement of reinforcement When an animal is reinforced independently of its behavior, it will go through a series of stereotyped but arbitrary responses in the intervals between reinforcements This phenome- non follows from the law of effect, which implies that reinforcement strengthens all immediately preceding behavior, not just behavior that is causally effective in providing reinforcement When only the right key light was on in Experiment 2, the pigeons could be seen to peck the wall of their cage, pace back and forth, and jump up and down with higher frequency than in other phases of the expert ments No attempt was made to quantify the total energy expended, which may well have been the same for all schedules in the terminal link Indeed it may be that total energy expenditure is completely determined by reinforcement frequency, while the form of that work—key pecking or superstitious strutting—is determined by the terminal contingencies of reinforcement

REFERENCES AUTOR, S M The strength of conditioned reinforcers as a function of the

frequency and probability of reinforcement Unpublished doctoral disserta- tion, Harvard University, 1960

FANTINO, E Effects of required rates of responding upon choice J exp

Anal Behav., 1968, 11, 15-22, ˆ

HERRNSTEIN, R J Secondary reinforcement and rate of primary reinforce-

NOTE

1 This work was supported in part by a NIMH Predoctoral Fellowship, and

in part by NSF research Grants GB 3121 and GB 3723

Psychon Sci., 1968, Vol 12 (1)

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