Delaying reinforcement in an autoshaping task generates adjunctive and superstitious behaviors

Behavioural Processes, Elsevier

13 (1986) 327-338

DELAYING REINFORCEMENT SUPERSTITIOUS BEHAVIORS1

RITA 6. Department U.S.A. (Accepted

of

327

AN

IN

AUTOSHAPING

TASK

GENERATES

XLEVEN and MESSING, MARK S. Pharmacology, University of Minnesota,

10 July

ADJUNCTIVE

AND

SHELDON 6. SPARBER Minneapolis, Minnesota,

1986)

ABSTRACT Delaying Reinforcement in an Messing, R. B., Kleven, M. S. and Sparber, S. B. Autoshaping Task Generates Adjunctive and Superstitious Behaviors. Behav. Processes, 13: 327-338. Key Words:

adjunctive behavior - autoshaping supersitious behavior

- reinforcemental

delay

-

Rats were autoshaped to touch a lever upon its insertion into an operant chamber on a 45 s random time schedule. Occurrence of a reinforced touch on each of 12 lever insertions per session and nose-pokes at the retracted lever as was exploratory rearing activity. Delays of 2, 4 or 8 s were monitored, interposed between the retraction of the lever, which occurred either after 15 s or after a touch response, and delivery of the food pellet reward, resulted in progressively slower acquisition of the extended lever touch response. However, if rats had already acquired the response under immediate reinforcement the delays subsequently introduced did not cause a decline in conditions, Nose-pokes at the retracted lever occurred during autoshaped touch responding. intervals over the course of both intertrial and reinforcement delay frequency of these autoshaping. The appearance and (adjunctive or superstitious) behaviors depended upon the reinforcement delay and behavioral history. These interval behaviors offer measurements of learning not based on arbitrary criteria; they thus provide information about effects on endpoints, or a more global approach to learning. INTRODUCTION Studies

of reinforcement

demonstrated

learning

a lever press delay (1956)

and

showed

in rats with

response,

rate

of

delay using discrete

that

reinforcement

with the expected

acquisition delay

of

trials operant

(Harker, reward

delays

negative 1956;

does not

of up to

correlation

Perin,

procedures

1943).

affect

have

10 s following

between

length of

Further,

asymptotic

Harker response

f***************************************~~~~~~~*~~~~~~~~~~~~~~~~~~~~~ lThis research was supported in part by a USPHS Mid-Career Development Award-Environmental Toxicoloav 5K07ES00123 to RBM and Grant No. SMF-396-84 from the Minnesota Medical Foindation. We thank J. Bruce Overmier for critical reading of the manuscript. Request for reprints should be sent to Rita B. Messing, Department of Pharmacology, 3-260 Millard Hall, 435 Delaware Street S.E., University of Minnesota, Minneapolis, Minnesota 55455.

0376-6357/86/$03.50

0 1986 Elsevier

Science

Publishers

B.V. (Biomedical

Division)

328

and

latencies, short

to

a

manifested

as

by

performance

standard it

lever

(Brown

&

(Buzsaki, response

Additionally,

increases

(ITI’s),

& Gamzu,

(Messing

the course

retracted

of

are

lever)

opportunity

adventitiously The

1948).

than

effects

between

development those

under

development

and

convenient

means

global approach response. interval

based

which

of

these

of

analyses

to what

Thus, behaviors

the

behaviors

responding

of

or

operant

a

with

or more

& Sparber,

interim

during

IT1 nose-poke

have

(Falk,

1971;

experiment,

provides

an additional

during

behavior

measurements

which

tend

session

these

of

intervals

may

in endpoints,

on

learning ceiling

Differences

to the required

reward

(Skinner,

to introduce

length.

differences

of

the

class of nose poke behaviors,

in addition

delay

intervals

responses

behavior

In the present

in

lever touching

intertrial

superstitious

responses,

is being learned

than

In essence,

1981),

and food reward provided

of possible

influence

rather

either

Terrace,

and

autoshaping

procedure.

adjunctive

1982).

manageable

of

1974),

a

these

learning

1983; Messing

These or

touching,

on discrete

extends

on

forward

clearly

1977;

of what may be another

maintenance for

not

occurs

progresses.

lever

conditions

shaping

of autoshaping,

lever retraction

reinforced

trial,

& Sparber,

schedule-induced

for measurement

reward

from

decrement

behaviors.

& Sirenelhag, 1971; Wetherington,

delay interposed

operant

experiment

of

& Silberberg,

operant

(operant)

work

during

present delay

an

in a performance

a discrete

which

Schwartz

as learning

characteristics

Stadden

other

1982;

contingent

performing

result

of

Stiers

trials

behaviors,

previous

at the

using

1968;

are

not The

effects

or discrete

has shown that

which

does

latencies.

Jenkins,

respondent

the

in

autoshaped

poking

animals

reward

responding

free running

traditional

(nose

of

investigating

of

compares

press)

shifting

delay

increases

observations

procedure

that

long

development

in

provide

or a more lever touch of

these

was also examined.

METHODS Subjects The subjects were 21 male Long Evans rats obtained from Blue Spruce Farms Rats were gradually food weighing 440-515 g. (Altamont, N.Y.), initially deprived and maintained at 80-85% of initial body weights, in a temperature (22'C) and humidity (40-50%) controlled enviromment on a 12:12 hr light-dark schedule, with lights on at 0700 hr. Testing was done between 0900 and 1200 hr. Apparatus Rats were tested in 4 operant chambers (BRS/LVE Laurel, MD), 31 cm wide x 25 cm deep x 25 cm high, with floors of 0.5 cm diameter stainless steel bars spaced One 25 cm square panel in each chamber contained a food trough and 2 cm apart. a house lamp in the center, near floor and ceiling, respectively, and standard cue lamp configurations above slots for levers on the left and right sides. A retractable lever (BRS/LVE, Laurel, MD) was mounted in the left hand slot, while Chambers also contained speakers through which the right hand slot was covered. Each box was equipped with a metal strip a white masking noise was introduced.

329

(7.5 cm wide, 12 cm above the floor) on the two walls opposite the lever and opposite the door. Contacts with the strip, representing rearing activity along the walls, were monitored with a drinkometer circuit. Contacts with the lever either in an extended (touches) or retracted position (nose-poke responses) were likewise monitored with a drinkometer circuit. The drinkometer circuits were standardized against a 2 MU resistance to assure equal sensitivity between chambers and from day to day. Chambers were also cleaned with 70% (v/v) ethanol, and allowed to dry between subjects to prevent changes in sensitivity due to residual oils or salts. The experimental chambers were enclosed in custom made sound attenuating cubicles equipped with closed circuit video cameras, used to observe rats (Sparber, 1979). Control of the experimental chambers and collection of data were accomplished with microcomputers and cassette recorders (Tandy Corporation, Fort Worth, Texas) connected to the operant chambers by custom built interfaces. Procedure Three days before the first autoshaping session, rats were allowed to eat ten 45 mg food pellets (Bioserv, Frenchtown, NJ), placed in a food trough in wire mesh cages which were similar to the ones in which rats were housed. All This procedure was used instead of rats consumed the pellets within 25 min. magazine training, and insured that rats were familiar with the pellet reinforcers in the initial autoshaping session. They were not exposed to the experimental chambers prior to acquisition training. Rats were randomly assigned to one of four groups for autoshaping, the 8 s delay of reinforcement group having 6 subjects instead of 5. During the experimental sessions, a white cue light was illuminated above the lever. Extension of the lever into the chamber served as an exteroceptive stimulus and its retraction was followed, after various delays, with food pellet delivery. Lever insertions occurred according to a random time schedule, with an average 45 s (range 22-68 s) interval between food delivery and the next extension of The lever remained extended for 15 s, or until a lever touch was the lever. made, after which it was immediately retracted. The four groups were trained under different conditons of delay of food One group received reinforcement pellet delivery following lever retraction. simultaneously with lever retraction (0 s delay). Other groups were reinforced lever retractions. Rats were exposed to 12 lever 2, 4 or 8 s after presentations (trials) per day, five days per week. When all rats in a group reached the criterion of at least 11 extended lever touch responses in a 12 trial session in three of four consecutive sessions, the group was shifted to the next highest reinforcement delay interval, for the next three sessions. The delay intervals were then increased once every three sessions, regardless of animals' levels of performance (see Table 1).

TABLE

1

Delay of Reinforcement

Designated (Original OS

2s 4s 8s

by Session

SESSION

Group Delay)

l-7

8

9

10

11

12

13

14

15

16-18

0 2 4 8

2 2 4 8

2 2 4 8

2 2 4 8

4 2 4 8

4 4 4 8

4 4 4 8

8 4 4 8

8 8 4 8

8 8 8 8

Touches of the extended lever, latency/l2 trials for each session (180s maximum), interval nose-pokes

to touch the extended lever of the retracted lever, and

330

unconditioned rearing (strip touch activity) were obtained for each twelve trial When a lever touch was not made before the lever was retracted, 15 s session. In addition, in 12 of was used for calculation of total extended touch latency. by trial printout of nose-pokes during each the 18 sessions, a trial permitting separate analyses of reinforcement delay and IT1 was obtained, These data were not retrievable for Sessions 2, responding during these times. 3, 6, 15, 17 and 18, because of malfunction of the data recording equipment (see Figures 3 and 4). Data Analyses Data for extended lever touches, touch latencies, interim nose pokes at the lever, and strip touches were analyzed in blocks of 12 trials (i.e. across experimental sessions) by two way (Group x Session) repeated measures analyses of variance (ANOVAs) (Winer, 1971). Strip touch and nose poke analyses were performed on square root transformed data to eliminate heterogeneity of variance. Since some groups were shifted to longer reinforcement delays at various times after the seventh session, separate ANOVAs were performed on data obtained in Sessions l-7 and Sessions 8-18 (see Table 1). A criterion of p < 0.05 was used for rejection of the null hypothesis. RESULTS

Extended

Lever Touching

As expected, was

inversely

delay

the

rate

related

of reward

to the delay

(0 s group)

delay of reinforcement groups

trained

responses Session

during

(E[18,

consistently the

first =

rats

The group means

an

8 s delay,

(evidence will

autoshape

Data are similar

scores,

The

for this group was

lo-12 touch

performed

An ANOVA

for mean to quanta1

by

responses

11-12 touches 16-18 ranged

this

(F_[17, 851

group

a significant

rats

8

in

the

during

Session

the

15, the

6.5; however,

s

1).

The

scores

effect x

in

of

Session

group

never

18 sessions

of

mean

of

number

4 of the 6 rats

in each of the last 3 sessions, one

no

lever touch

main

Group

between

and

of these

sessions.

7.8 and 8.5 correct

responses

for the group of rats trained with

did

= 2.03,

criterion

with

to a 2 s

1, Table

significant

in at least

on all sessions,

that

an 8 s delay,

shorter

example,

them

ANOVA on extended

as a group,

responses

revealed

with

Pc.01).

a

(Figure

attained

showed and

For

of learning)

with the,three

sessions

P<.OOl),

2.60,

for Sessions

out of 12 trials.

delays

response

The rats trained

session

shown).

lever touch

of these

seven

criterion

(not

in the 8 s group made all

=

12-trial

lever touch

for switching

The repeated measures

19.04,

1021

attained

experiment

extended

the 1021

extended

the criterion

reinforcement

(if at all).

(E[6,

interaction

longer

of the

of reinforcement.

reached

by the seventh

with

later sessions

of acquisition

indeed

PC.03).

but the process

show

an effect

It thus takes

many

of Session

appears more

that

rats

trials

than

delays. latency/l2

trials

data for extended

to touch

the extended

lever responding.

lever

(Figure

2)

If only the first

331

8

8

X-X

0 set

c+-o

2 set

8--8

4 set

t-a

8 set I

I

I

I

1

2

3

4

I

I

I

5

6

7

SESSION Acquisition of autoshaped lever touch responding. Each session Fig. 1. represents 12 lever presentations (trials) made on an 45 s random time schedule. Groups were trained with different delays between lever retraction and food pellet reward.

7 sessions delay

are considered,

Group

Session

(E[6,

interaction response to

an

(i.e.

there

collapsed

1021

(E[18,

=

19.6,

minimum;

group,

did show a significant

(![17,

851 = 3.08, Pc.001).

first

15 sessions,

evidence Sessions evident

for

change,

Pc.001).

decrease

as

a

a

173

for reinforcement 3.30,

P<.O5),

Session

and

x

Group

As was the case for the quanta1

touch

ANOVA

for the 8 s group did not fall

for

in latency

all

18 sessions

to respond

for

across

the

8 s

18 sessions

data of this group for the

Sessions

1-15

However,

response

the conclusion

=

significant

like the quanta1

for

group.

(E[3,

latencies

an

Again,

latencies

16-18, confirming

(see Figure

that response

2) show

latencies acquisition

fell

little during

was becoming

during the last 3 sessions.

No decreases rats were shifted no

the

and

lever touch however,

main effects

Sessions)

P<.OOl),

1021 = 2.89,

data, the extended

asymptotic

are significant

across

marked

in the

number

of extended

to longer delays

increases

in response

lever

after attaining latencies

responses criterion

were observed

were

observed

(not shown).

for the

trained

when Also, rats

332

x 3

180

0 set

x--x O--O

2 set

H

4 set

O---O

8 set

‘I

I

:

I

I

I

I

3

1

I

5

II,

I

7

9

I,,

I

I

I

11

13

I

I

15

17

SESSION

Total latency/l2 trials to touch the extended lever as a function of Fig. 2. experimental session and delay of reward during the acquisition phase. Each lever presentation lasted for 15 s, or until a correct lever touch response was made. The dashed vertical after Session 7 indicates that designated groups were shifted to longer reinforcement delays at various times after this Session (see Table 1).

when

they

although they

were naive

have been

to respond

switched rats

to

learn

successfully

at asymptotic,

longer

reinforcement

an 8 s delay autoshaped

short

of with

latencies

delays

reinforcement a shorter

(Figure task

delay

as the delay

2).

very

they will

is increased

Thus,

slowly,

if

continue

from 0 to 8

5. It

thus

appears

produce

varying

trained

with

that

response

values

2 or 4 s delays

than they do to rats trained a significant when

the

responses

change

number

of

sessions

spread between

reinforcement

between

The acquisition

(i.e.

to those trained

required

as an effect

for

is considered

groups

to

8 s,

with no delay is measured

of Session). achieve

as a criterion,

and an 8 session

0 and

rates for subjects

with an 8 s delay, when acquisition

0 and 2 s delay groups,

(Table 1).

of

rates.

appear more similar

in performance

for 3 of 4 sessions

delay groups

of delay

acquisition

there

spread

11-12

as

However, correct

is a 4 session

between

0 and 4 s

333

Interval

Nose-Poking

Increasing behavioral

the

reinforcement

consequences.

1, 4, 5 and 7, (Figure 51]=

4.16,

Pc.02).

ANOVA's

Pc.01). responding (E[3, not

511's

increase

reinforcement

for

response

of nose poking

3, left) shows a significant

a significant

for simple

changed

delay

An analysis

with

main

session

= 7.91 and 4.57, nose-poke

of session

3, right).

of Session

with

during

delays with

(E[3,

showed of

that

2 or 4 s

a 0 s delay did as the delay

ITI’s,

An analysis

other

(r[9, 511 = 3.30,

for each group

The rats trained

significantly

(Figure

interaction

in rats trained

P's c.01).

responding

was increased

x Group

effects

has

for Sessions

ITI’s

main effect

Session

only

acquisition

during

of nose-poking

of

data

Noncontingent lever responding during ITI’s as a function of Fig. 3. experimental session, and delay of reward during the acquisition phase. The dashed vertical after Session 7 indicates that designated groups were shifted to longer reinforcement delays at various times after this Session (see Table 1).

available Group

for Sessions

(5[3,

173

nose-poking

in

Session

despite

changed

7,

between

8-16 showed

= 4.27, ITI’s

P<.O2),

remained the

Sessions

fact

no effect and

no

essentially that

7 and 16.

of Session,

interaction. unchanged

reinforcement

a significant Thus, from

delays

levels were

effect of

it appears attained

that by

systematically

334

F

a

w’ 140 n 5 g 120

x--x

0 set

O--O

2 set

O-0

4 set

O--a 8 set

e g IL 100 Z ii 80

Z Z r

60

3; E B ’

40

i Z

I

I

I

1

I

I

I

I

5

I

t

I

I

10

I

1

15

SESSION Noncontingent lever responding during reinforcement delay intervals Fig. 4. as a function of experimental session and delay of reward during the acquisition phase. The dashed vertical after Session 7 indicates that designated groups this Session (see Table 1). shifted to longer reinforcement delays after were

An

analysis

variance

of

performed

reinforcement

delay

intervals

Sessions

since

no measurements

8-16

sessions. Session 2.97,

There

PC.01).

the extended appeared

were

main

(E[7, 1191 = 6.79,

lever touch

delay.

However,

response

without

a delay

lever during this portion

exist

for

only for

the

of Group

and a significant

groups

response,

considerably

of the experiment.

during

the

available for

(E[3, 173 = 10.88,

the

P<.OOl),

interaction

from

first

7

and of

(E[21, 1191 =

performance

scores

rates during the reinforcement

of reinforcement, during

poking data

0 s group

reached maximum

response

responding showed

that

nose

includes

effects

a 2-4 s delay

as with

4)

P<.OOl),

For all three

to peak with

(Figure

for

delay

and to fall with a 4-8 s

ITI's, the group less activity

that

toward

acquired

the

the retracted

335

Rats were

switched

nose-poking

were

experiment,

it appears

Sessions

l-7

behavior

to higher

attained.

had

before

effect

occured

on

either

asymptotic

within

that the reinforcement

a marked

which

delays

Nevertheless,

delay

emergence

during

the

levels of interim

limits

schedule

of

and

intertrial

of

the

subsequent

or

present

experienced

during

nose-poking

reinforcement

delay

intervals. Behaviors differently relatively delays

real,

0,

after

4).

An

tended

numbers

Fig.

contrast

delay

3 for the

Session

4.

during

of

responding

missing

data

extended shows

for

these

reinforcement other the

reinforcement for the

Session

animals

delays

groups),

but

reinforcement

Rearing

delays

may

influenced remained

reinforcement

acquired be more

the behavior apparent

reinforcement

delays

than

changed

for 0, 2 and 4 s groups,

time

lever

4 shows

Fig.

and

nose-poking

this

there

did

group

levels

of Figs.

4.

in

(Evaluation

because

of nose

of the

increase

poking

and basal

in

is always

during

levels

at low levels

responding

rate of nose-poking

lever

an increase

a marked

8 s group

remained between

increase

3 and 4 for the 0 s group

amounts

for the ITI’s

difference

showed

not

1 with

in extended

was

to

behaviors

of Fig.

problematical

considerable

during

the

increase

that

is more

as opposed

of these

in this group in Session

examination

poking

intertrial

Comparison

touching.

intertrial

delays

Also,

during

of development

there was a marked

exhibited

is that

responding

in which

6,

Another

in reinforcement

for

throughout

in

ITI's

and

apparently

much

delays.

Activity

No effects activity.

of the

present

procedure

The number of strip touches

between

groups.

Initial

the 2 s group to 4.5/min varied

during

been

responding

rates during

effect

increased

4 s group

(e.g. above nose

experiment.

higher

were

that

However,

lever touching.)

that

shows

5, even though

nose-poking interim

latter

is the

of extended

2 s group,

until after Session by

response

responses

between

intervals,

to development

touching

of

have

IT1

in all groups which

this

as delays

may

however.

to rise slightly.

interesting

relative

intervals

7, while

of delay,

However,

absolute

reinforcement

nor

Session

less than did rates,

actually

different experience,

as a function

2 and

since

these

subsequent

constant

changed

(Groups

much

during by

between

2.6/min

mean

were

varied

observed neither

rates of rearing

for the 4 s group.

on

exploratory

rearing

as a function .of sessions, ranged

between

3.2/min

At the end of the experiment,

for the 2 s group to 4.7/min

for

means

for the 0 s group.

DISCUSSION The

expected

acquisition

relationship

was found.

between

reinforcement

The data are in agreement

delay

and

speed

of

with those of Perin (1943) who

336

found s,

relatively

with

10

consistent with

s with

discrete

on

remained

high

longer

delay

pellet

variables.

three

studies

resemble

have

investigated

which

governing

depend

instrumental The

contingency

behavior

(Skinner,

1948).

the

will

lengthened,

since

readily

Staddon

autoshaping) behavior

importance of

and

phase

the

term

or

as a class

periods

of low

interval

relationships behaviors,

see

and behavior,

and

reinforcement during

during

or

delay

its

during

of

training,

reinforcement

directed

density,

then

by

"supertitious" for

behavior

variability,

cf.

this interval both

rats trained

with

if the delay

a 0

is later

with a 2 or 4 set of IT1 nose-poking

only.

If,

following

(and

by

extension

schedules,

at appropriate

and

reinforcement

as suggested

during

determinant

conditioning

delay IT1

or CS-US interval,

Thus,

behaviors

the major

the

from the other terminal

emphasizes

nose-poke

the

reinforced,

is used, behavior

classical

reinforcement

more

instrumental

using a classical

of

this behavior and

of reinforcement

as behavior

which

motoric

CS-US

"superstitious"

and later.

In contrast,

is defined

is defined

changes

or

response,"

adventitiously

terminology

(1971),

and

Harker(1956)

temporal

behaviors

behaviors

touch,

Simmelhag

on the

antecedent

increase

classical

conditioned

of a "terminal

as

these

or

a

throughout.

precise

of the reinforcement

exhibit

effect

retraction

schedule

but to a lesser extent than rats that were trained

to be the delay &

the

it delineates

acquisition

with

of the two).

prefer

lever

as a function

of reinforcement.

appears

(We

extended

response

or

lever

of the apparatus

maintenance

to be part

by starting

(and of interval

is nominally

Nose-poke

(1971),

1966.) Whichever,

varies

set delay

during

the

response

demonstrates and

also were

reinforcement

the

no

as delays

(1943)

other

of

topography

interval.

interval, -

Herrnstein,

during

delay

Simmelhag

this

clearly

also

be considered

component

delay

(or a mixture

acquisition

reinforcement

and

of the

of

of

had

responding

generally

Perin

be that

of a specified

not

delay

delay

ITI

motivational

unchanged

of

results

or not the response

for

may

those

therefore

on details

experiment

schedule

delay

It may

acquisition

not on whether

during

remained

resemble

1961).

do

also

4 s delays

of introducing

behaviors

are

conditioning

of an adverse

on

of up to 5

with

to a longer

emission,

effect

the consequences

operant

not differ

produced

the result

an

behaviors

2 or

response

of

results

(Kimble,

Staddon

than

nose-poke

since rearing

procedures

delay

rather

likely

results

experiment,

with

performance

between

delays

The

using

did

a short

present

poorer

is most

found,

from

trained

present

all

below)

the

who

rats

with

acquisition.

latencies

In the rats

association(s)

maintain

behaviors,

than

in

Furthermore,

or

The

switching

of reward,

of

(1956)

asymptotic

latency.

of an operant

slower

Harker

that

Thus,

delivery,

induce

of

rates

increased.

formation

on learning

markedly

and that

response at

further

those

trials,

reinforcement, effect

small effects producing

stimuli

nose-poking

and adjunctive (goal objects) directed

at the

337

retracted

lever

during

ITI's

may

be

viewed

as

schedule-induced

adjunctive

behavior. The

results

response (i.e.

with

rates

of

rates

interval

history

of

of the

of animals

determinant

administration,

which

clinical

to

effectiveness

summary,

In

results

experiments

perform

at

of drugs

response

without

asymptotic

the course

is strongly reaching

is 2-4 s.

the conditions its

several

conditioned

convenient (e.g.

and

drugs,

rapid

The and

apparent

task

is

with

switched

brain

which

occurred)

amendable

lesions,

use

learning

delay

to

of

the

acquired

will

long

(8

continue s)

and history

of

reinforcement (i.e.

determinant

difficulty

be measured, of

of

develop

of an organism

in

to

of the delay of

training

influence

etc.) on learning

delays

behaviors

is the

and the appearance

variations may

repeated potential

acquisition

may be an important

behaviors

in

may not

deficits.

delays,

to

repeated

Such

have already

the

be a

or memory

extinction,

superstitious

when

might

in predicting

a short

or

behavioral

tasks

subjects.

rats which

by the

(e.g. drug or toxicant

on

naive

interposed

studies

that

learning

shows that the history

unconditioned for

to expect

with cognitive

maximum

acquisition

method

toxicants,

with

influenced

the rate of autoshaped

being

adjunctive

the study

under which

performance.

conditions.

utility

related to the magnitude

an

Finally,

or

after

of autoshaping

reinforcement,

of

a delay

levels

in different

have experienced with

in patients

Additionally,

engaging

experiments

differential

of reinforcement,

these behaviors

delay

experiments have

touch

optimally,

environmental

or other

manipulations

it was found that although

reinforcement. during

such

lever

response

to be greatly

reasonable

to learn and/or of

slower with longer delays contingent

appear

Therefore,

of

may

even while

of other manipulations

lesions).

extended

this

external

to autoshaping

effects

the

perform

latency)

is thus

It

acquired

will

similar

effects

have learned

comparable

acquisition

study

have

responding

animal.

brain

to

under

subjected

of performance

acquisition

which

conditions

in response

behaviors

past

be

rats

delay

no decrement

is,

subjects

that

interval

That

history

show

under different

making

diverse

and it a

factors

and memory.

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