Stimulus-reinforcer interactions in Pavlovian conditioning of pigeons: Implications for selective associations
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
Animal Learning & Behavior
1980, 8(4), 586-594
Stimulus-reinforcer interactions in Pavlovian
conditioning of pigeons: Implications
for selective associations
KIM RON L. SHAPIRO, W. J. JACOBS, and VINCENT M. LoLORDO
Dalhousie University, Halifax, Nova Scotia, Canada B3H 4]]
In a Pavlovian procedure, groups of pigeons were presented with a compound auditory-
visual stimulus that terminated with either response-independent electric shock or food. In
a subsequent test, the tone CS was dominant in aversive conditioning, reliably eliciting con-
ditioned head raising and prancing. The red light CS was dominant in appetitive conditioning,
reliably eliciting pecking. This result was replicated in a second experiment, in which trials
were widely spaced. Four additional groups of pigeons received pairings of the separate element
CSs with the USs. Red light, but not tone, was an effective CS in appetitive conditioning,
whereas tone, but not red light, was effective in aversive conditioning. There was no discrimi-
native responding in zero-contingency control groups. Several theoretical accounts of these
data are discussed.
Recently, there have been several demonstrations actions (LoLordo, 1979). In the single-cue design,
that an animal's performance in a conditioning ex- four groups of organisms receive the factorial com-
periment may be markedly affected by the experi- binations of two CSs and two USs. If acquisition of
menter's choice of particular combinations of con- a CR occurs more rapidly with CSI than with CS2
ditioned or discriminative stimuli and reinforcers. when USI is the reinforcer, but the reverse is true
Certain combinations of stimuli and reinforcers may when US2 is the reinforcer, then a stimulus-reinforcer
fail to produce changes in behavior, whereas other interaction has been observed. Such interactions can
combinations from the same set of elements result also be demonstrated in a compound-cue design, in
in marked changes in performance (e.g., Foree & which two groups of organisms receive a simultaneous
LoLordo, 1973; Garcia & Koelling, 1966; Jacobs & compound of the two CSs during conditioning, but
LoLordo, 1977, 1980). Such an outcome will be called the compound CS is paired with different USs in the
a stimulus-reinforcer interaction. Demonstrations of two groups. The response to the separate elements
stimulus-reinforcer interactions have aroused interest of the compound is assessed in a series of test trials
because they suggest that organisms' abilities to as- following conditioning. If there is more test respond-
sociate stimuli and reinforcers are somehow constrained ing to CSI than to CS2 when USI is the reinforcer,
and thus that there may be strong constraints on the but the reverse is true when US2 is the reinforcer,
generality of the laws of learning. A constraints- again a stimulus-reinforcer interaction has occurred.
on-learning account of stimulus-reinforcer inter- The occurrence of a stimulus-reinforcer interaction
actions suggests that there are selective associations cannot be attributed solely to a difference between
between stimuli and reinforcers, that is, that con- the CSs or solely to a difference between the USs,
nections between certain CSs and USs may be formed but must reflect some selective effect on learning or
very easily, whereas connections between other CSs performance (Schwartz, 1974).
and USs from the same set may not be formed at In one experiment using the compound-cue design,
all, or only with great difficulty. Foree and LoLordo (1973) trained groups of pigeons
Two basic experimental designs have been used in to press a treadle in the presence of an auditory-
demonstrations of such stimulus-reinforcer inter- visual compound stimulus to obtain grain or to avoid
electric shock. Responding in the absence of the com-
pound stimulus postponed its next occurrence. When
This research was supported by Grant A0283 from the Natural
Sciencesand Engineering Research Council to V.M.L. Some of the
the birds were responding on at least 751Tfo of the
research reported here was described by K.S. at the 1977 meeting compound trials, but responding infrequently between
of the Eastern Psychological Association. The authors are indebted trials, the degree to which the compound and each
to Jeffrey Willner for his comments on an earlier draft of this element controlled treadle pressing was determined.
report and to Nancy Beattie for typing the manuscript. Requests The compound stimulus exerted strong control over
for reprints should be sent to Kimron L. Shapiro, Department of
Man-Environment Relations, S-126 Henderson Human Develop- treadle pressing in both groups. In the appetitive
ment Building, Pennsylvania State University, University Park, group, there was strong visual dominance; red light
Pennsylvania 16802. strongly controlled treadle pressing, but few responses
Copyright 1981 Psychonomic Society, Inc. 586 0090-4996/80/040586-09$01.15/0STIMULUS-REINFORCER INTERACTIONS 587
occurred during the tone. On the other hand, in the presentations of a compound CS, consisting of on-
shock-avoidance group, the tone controlled more set of a tone and illumination of red houselights,
responding than did the red light; that is, there followed by response-independent grain, the US. Three
was auditory dominance. other birds received pairings of the same compound
Foree and LoLordo (1973) did not demonstrate CS and electric shock. Following conditioning,
that the stimulus-reinforcer interaction effect they responses to the compound and the separate elements
observed reflected selective associations rather than were assessed.
some selective, nonassociative effect, for example,
selective sensitization (see LoLordo, 1979, for a dis- Method
cussion of this issue). The first step in demonstrating
Subjects
that selective associations were formed would be to Subjects were six experimentally naive male White Carneaux
demonstrate that the responses that the compound pigeons, housed in individual cages of a colony room. All pigeons
stimuli came to control were associative, that is, were maintained at 80070 of their free-feeding weights, had con-
depended upon the positive contingency between CS stant access to water, and were maintained on a l2-h light/l2-h
dark cycle. On the day prior to the first experimental session,
and US. This step is easier to take in a classical con- stainless steel wire electrodes were implanted around the pubis
ditioning experiment than in a discriminated operant bones of each bird. The electrodes were connected to a double
procedure like that used by Foree and LoLordo, banana plug, which was attached to a leather harness worn at
primarily because, in the former, the experimenter has all times (Azrin, 1959; Coughlin, 1970).
control over the number and temporal pattern of CSs Apparatus
and USs presented to the organism. Consequently, Sessions were conducted in a 42 em long X 29 em wide x 36 cm
groups that receive the same number of CSs and USs high chamber located in a darkened room. A 6 x 5 ern food
as the experimental groups, but with a zero-contingency magazine was centered on the black Plexiglas end wall, 7 em above
between CS and US, can be used as controls for the cardboard-backed wire grid floor. A darkened pigeon key
was located above the magazine. A speaker was mounted on the
nonassociative effects.
back wall, at the upper corner adjacent to the food magazine.
In the present context, the Pavlovian conditioning The tone stimulus was 440 Hz and raised the sound level from 53
procedure has the added advantage of allowing the to 71 dB (Scale C of a sound-level meter). The visual CSs came
experimenter to equate the shock density received by from light bulbs mounted above a translucent white Plexiglas
birds in an aversive conditioning procedure with the ceiling. Illumination of four red 120-VAC 7-W Christmas-tree
bulbs served as the red-light stimulus, and illumination of two
density of food reinforcement received by the pigeons similar white bulbs served as the white-light (intertrial) stimulus.
in an appetitive procedure. In contrast, in Foree and The front wall of the chamber, which was transparent Plexiglas,
LoLordo (1973) the probability of food increased as was hinged and allowed access to the chamber.
acquisition progressed, whereas the probability of Electric shock (60-Hz, IIO-V alternating current passed through
a variable transformer and a lO-kQ resistor) was transmitted via
shock decreased.
the cables attached to a swivel mounted in the ceiling of the box.
For these reasons, a Pavlovian conditioning pro- A double banana plug on the swivel cable was plugged into the
cedure was used in the present experiments. We were double banana socket on the bird's harness before each session.
able to determine whether the pattern of responses This arrangement allowed the birds to move freely.
that emerges when no response is required of the bird Masking noise was provided by the ventilation fan mounted
on the chamber and by white noise in the experimental room.
yields the same stimulus-reinforcer interaction observed A video camera stood outside the chamber, facing the transparent
by Foree and LoLordo, who analyzed only differences front wall. A video monitor, a video tape recorder, and all pro-
in the probability of occurrence of a single response, gramming equipment were located in an adjacent room. A
treadle pressing. In the present studies, birds were microphone mounted above the white Plexiglas chamber and con-
observed visually, so that any change in behavior nected through an amplifier to a speaker in the control room
allowed the observers to judge tone onset.
that occurred in the presence of the CS could be
analyzed. Procedure
The compound-cue design was used in Experiment 1; Conditioning. All pigeons received 30-min conditioning sessions
two groups of pigeons received pairings of the com- on 5 consecutive days. Each Pavlovian conditioning trial consisted
of a 5-sec presentation of the auditory-visual compound con-
pound CS and a US, either food or shock. In the ditioned stimulus followed by the US. The compound stimulus
second experiment, additional groups received un- consisted of the simultaneous onset of the red houselight and a
correlated presentations of the compound CS and a 44O-Hz tone. For three birds, the US was a brief, 52-msec, 45-V
US, and thus were controls for nonassociative effects electric shock; for the other three birds, it was 3 sec access to
of the procedure. Experiment 2 also included the mixed grain. The food magazine was illuminated whenever grain
was available. A 15-sec interval, during which the white house-
single-cue design; four groups received pairings-of light was illuminated, separated the termination of one CS from
the individual stimulus elements that constituted the the onset of the next. Thus, there were 90 conditioning trials
compound with a US. per session.
Birds in the appetitive conditioning group did not receive
magazine training prior to the conditioning sessions, but at the
EXPERIMENT 1 start of the first conditioning session the illuminated grain magazine
was elevated, and the 30-min trial sequence started only after the
In Experiment 1, three pigeons received repeated birds bC~3n eat in!! from the grain magazine.588 SHAPIRO, JACOBS, AND LoLORDO
During conditioning, several experimenters observed the devel- APPETITIVE AVERSIVE
opment of various conditioned responses, in order to construct 100
a set of behavioral categories that could be used during the sub- 90
sequent test. 80
Testing, On the day following the last day of conditioning, the 70
pigeons received 20 presentations of the compound CS followed 60
by the US. and then received 7 test presentations each of red '0
light, tone, and no signal (blank trials) randomly interspersed 40
among 49 presentations of the compound CS. Reinforcement oc-
30
curred on all but the blank trials, which were included to assess
20
(he possibility of conditioning to temporal cues. Stimulus dura-
tions and the intertrial interval were like those used in condi-
tioning.
10
CTLB
l
CTLB
l CTLB
..,
CTLB CTLB CTLB
Three observers, including one who was not told about the 8626 886-4 872~ 8826 8969 8922
C COMPOUND T TONE L LIGHT e BLANK
purpose of the experiment, recorded whether certain predesig-
nated behaviors occurred on each trial. Performance during test Figure 1. Left panel i1ustrates, for each bird in the appetitive
sessions was also recorded on videotape. condition of Experiment 1, the percentage of trials on which a
peck CR occurred during each of the four test stimuli. Right
panel lIIustrltes, for each pigeon In the aversive condition, the
Results percentage of trills on which head raising occurred during each
of the four test stimuli.
Acquisition
All pigeons began responding to the CS in a
distinctive fashion by the fifth conditioning session. response on virtually all presentations of the com-
Conditioned behavior was highly stereotyped for all pound CS. They crouched, so that their bodies were
birds within a given reinforcement condition. In the lowered, with the horizontal axis parallel to the floor.
presence of the CS, all birds in the appetitive condi- This response was also judged reliably (>92.9%
tion typically pecked in or around the food hopper. On agreement). For Bird 8725, this response was perfectly
most of the trials, peckingwas initiated when the CS oc- correlated with pecking. For Bird 8628, the correla-
curred. Occasionally, pecking was already occurring tion between body lowering and pecking was broken
but increased in frequency when the CS was presented. only on presentations of the tone. This bird lowered
Pigeons in the aversive condition typically were its body on 62% of the tone trials, as opposed to 100%
facing the transparent front wall and then raised of compound and red-light trials and only 14% of
their heads and pranced vigorously in response to the blank trials.
CS. "Head raising," which typically occurred while.
the bird was otherwise motionless, refers to lifting Test: Aversive Condition
the head a few centimeters above its previous posi- All three birds in the aversive conditioning group
tion. "Prancing" refers to rapid side-to-side move- were observed to raise their heads and then prance on
ments, during which the pigeon lifts its feet higher most of the presentations of the compound CS. Ob-
than in normal walking. The CR was quite similar to servers' judgments of these behaviors were in agree-
some components of the response to shock, although ment on 89%-91 % of the trials. Whenever it raised
the latter tended to be more vigorous. Head raising its head, Bird 8826 then turned its head from side to
and prancing occurred infrequently, and with less side repeatedly. Bird 8922 made repeated up-and-down
vigor, between trials. head-bobbing motions after raising its head. The
right panel of Figure 1 illustrates for each bird the
Test: Appetitive Condition mean percentage of trials on which head raising oc-
In the test session, the three birds in the appetitive curred for each of the four types of test trials. All
condition were observed to peck in or around the birds raised their heads on a large proportion of the
food hopper on virtually all presentations of the compound trials. Moreover, they made this response
compound CS. The three observers' judgments of on many more tone than red-light trials. Little
the occurrence or nonoccurrence of this behavior head raising was observed on blank trials except in
were in agreement on 84010-96% of the trials. The left Bird 8969, which raised its head on roughly 50% of
panel of Figure 1 illustrates, for each bird, the the blank trials.
percentage of trials on which a peck CR occurred for Bird 8969 pranced after every head-raising CR,
each of the four types of test trials. The percentages whereas Birds 8826 and 8922 pranced on most of
shown are means for three observers. Each bird the trials on which they raised their heads (770/0 and
pecked on virtually all presentations of the visual CS, 89% of the compound trials, 37% and 52% of the
as well as on presentations of the compound. In con- tone trials, 14% and 2% of the red-light trials, and
trast, the birds rarely pecked during presentations of 3% and 7% of the blank trials for Birds 8826 and
the auditory CS or on "blank" trials. 8922, respectively).
Birds 8628 and 8725 made a second characteristic Two birds made at least one other response, inSTIMULUS-REINFORCER INTERACTIONS 589
addition to head movements and prancing, on most and LoLordo cannot be attributed to the gradual re-
of the compound trials. Birds 8826 and 8969 were ob- duction in the number of shocks per session coupled
served to flap their wings, generally after beginning with the increase in the number of food reinforce-
to prance, on 69070 and 74070 of the compound trials, ments per session that resulted from the response-
respectively. The observers' judgments of wing flap- dependent procedures they used.
ping were in agreement on 74070 and 86070 of the trials There was virtually no responding to the non-
for the two birds. Bird 8826 rarely flapped its wings dominant stimuli following compound conditioning
except on compound trials. In contrast, Bird 8969 in the present experiment. Thus, there was little
flapped its wings on 67070 of tone trials but on only 14070 evidence to suggest that these stimuli were associated
and 19070 of red-light and blank trials, respectively. with the USs.
Discussion EXPERIMENT 2
Analysis of responses to the test presentations of In Experiment 2, separate groups of pigeons received
the stimuli reveals that there was strong visual dom- repeated pairings of the compound, the red light, or
inance in the appetitive condition. Both body lowering the tone CS with food or electric shock. The use of
and pecking in or around the hopper revealed this the single-cue design in this experiment allows us to
visual dominance, and the effect was weak only in determine whether the stimulus-reinforcer interaction
the case of body lowering for Bird 8628. Except in observed in compound conditioning in Experiment I
this case, conditioned responses rarely occurred depends upon some process that arises only when a
during the auditory stimulus or on blank trials. On compound CS is used, for example, selective atten-
the other hand, there was clear auditory dominance tion (Sutherland & Mackintosh, 1971). If the same
in the aversive condition. Auditory dominance was stimulus-reinforcer interaction were observed in the
strong for raising and bobbing the head and prancing single-cue design, then any adequate account of this
for Bird 8922. It was also strong for head raising, interaction would have to be couched in terms of the
prancing, and wing flapping for Bird 8969, although relative effectiveness of the various CS-US combina-
that bird pranced on many blank trials,' suggesting tions in generating conditioning.
that its responding may have been controlled in part Additional groups of pigeons received random pre-
by temporal cues. For these two birds, there was no sentations of the compound, red light, or tone CS and
indication that any response had been conditioned to a US, either grain or electric shock. Inclusion of these
the red light, since responding to light never exceeded zero-contingency control groups enables us to ascertain
responding to blank trials. For Bird 8826, raising and whether the responses to the CS that developed in the
turning the head was the most probable response. experimental groups resulted from the positive con-
The auditory CS evoked more conditioned respond- tingency between CS and US that existed for those
ing than the visual CS, which in turn evoked more groups. That is, if the same stimulus-reinforcer inter-
responding than blank trials. Prancing, a less probable action were observed in the zero-contingency and
response, revealed only weak conditioning to the positive-contingency groups, then it could not be
tone, and no conditioning to the light. Finally, there concluded that the effect is associative.
was even less wing flapping, and no firm evidence
that this response was conditioned to either element. Method
The joint outcome of visual dominance in the ap-
Subjects
petitive procedure and auditory dominance in the Subjects were 36 experimentally naive male White Carneaux
aversive situation replicates the pattern of results ob- pigeons, which were housed and maintained as in Experiment I.
tained by Foree and LoLordo (1973), who compared Shock electrodes were implanted in each pigeon as in Experiment I.
stimulus control of treadle pressing for food with
control of treadle pressing to avoid shock. The highly Apparatus
A second, identical chamber was added to the one used in
similar outcomes of the two studies suggest that the Experiment I.
response-reinforcer contingencies used by Foree and
LoLordo are not a necessary condition of the ob- Procedure
served stimulus-reinforcer interaction. For example, Conditioning. Eighteen birds received a 52-msec, 45-V ac elec-
tric shock as the US, whereas the other 18 received 3 sec access
the present data suggest that the auditory dominance
to mixed grain. Within each US condition, nine birds received
observed in Foree and LoLordo's avoidance pro- repeated CS-US pairings: Three brids received the compound CS
cedure probably resulted from pairings of the com- of Experiment I, three received the red light CS, and three, the
pound stimulus and shock early in training, rather tone CS. In order to minimize the possibility of intertrial re-
than from the occurrence of avoidance responses in sponding and reduce the likelihood of habituation to the shock
US, conditioning trials were separated by an average interval of
the presence of the compound. Furthermore, the 150 sec (minimum interval = 18 sec). There were 12 conditioning
stimulus-reinforcer interaction observed by Foree trials per session. A variahie intertrial interval was used (0 minimize590 SHAPIRO, JACOBS, AND LoLORDO
the chance of temporal conditioning, even though temporal con- APPETITIVE
ditioning did not playa major role in the first experiment. Nine
additional pigeons in each US condition received random pre- PAIRED RANDOM
sentations of CS and US: Three received the compound CS, Z 15
COMPOUND
r-- .--- r---
three, the red light, and three, the tone. The number of CSs o
and USs per session was matched with the experimental groups, ffi 12
~
but there was no contingency between the two events; that is. they eru 9
were presented on independent variable-time 150-sec schedules.
Each bird received conditioning sessions until it made at least ~
(f) 6
751Tfo CRsontwo consecutive sessionsor until 15 sessions had elapsed. Z
o
During conditioning, an observer recorded the development of Vi 3
various conditioned responses on a trial-by-trial basis, using the (f)
w
0 '--''--........._.L-L._'-
hehavioral categories developed during Experiment I. Birds in (f)
2447 2411 2438 2440 2416 2401
all groups were observed on every trial.
Testing, On the 2 days following the last day of conditioning,
TONE
Z 15 r-- r-- - r-- r-- -
o
pigeons that had received pairing of the compound CS and a US erw 12
were tested, as their counterparts had been in Experiment I. In I-
each test session there were four presentations of the compound er
u 9
CS, four of the red light, and four of the tone. No more than
two trials of a given type could occur consecutively. Reinforcement ~
(f) 6
occurred on all trials, and the stimulus durations and the intertrial Z
interval were like those used in conditioning. ~
(f)
3
w
(f) 0 L....--''--~'----'-'_...L-
2394 2406 3114
Results 2437 2419 2385
RED LIGHT r--
~ 15 .--- r---
Appetitive Condition ex:
~ 12
Acquisition. The three birds that received pairings er
of compound CS and food quickly began to peck in u 9
or around the hopper during the CS, as did their ~
(f) 6
counterparts in the first experiment. The top panel of Z
Figure 2 illustrates, for each bird, the number of ~
(f)
3
w
sessions (including the criterial sessions) to a criterion (f) 0 '--'--~'----'-'_...L-
2422 2409 2425
of two consecutive sessions with at least 75f1Jo CRs.
None of the birds that received a zero-contingency Figure 2. Top panel illustrates, for each bird in the appetitive,
between the compound CS and food reached this compound stimulus condition of Experiment 2, tbe number of
criterion. Moreover, percent CRs showed no trend sessions (including the criterial sessions) to a criterion of two
consecutive sessions with at least 751Tfo CRs. The middle and bottom
across the 15 sessions, and the highest percent CRs panels lIIustrate comparable data for tbe groups that received tone
for any bird in any session was 25f1Jo. and red-light CSs, respectively.
The three birds that received pairings of the red-
light CS and food also began to peck in or around contingency groups. None reached criterion, and
the hopper during the CS. One of the birds, 2417, none ever pecked on more than a third of the trials
pecked the hopper at a low rate during the pre-CS in a session. There was no difference between birds
period, and the CR for this bird was a marked in- that received tone-food pairings and those that re-
crease in the rate of pecking when the CS came on. ceived a zero-contingency between the two events.
The bottom panel of Figure 2 illustrates the number Thus, there was no evidence that repeated pairings of
of sessions to criterion for these birds. As in the case tone and food resulted in the formation of an as-
of the compound-food group, conditioning occurred sociation.
rapidly. None of the birds that received a zero- Testing. The left-hand panel of Figure 3 shows
contingency between the red-light CS and food that, during the two test sessions following con-
reached criterion. Again, percent CRs showed no ditioning, the three birds that had received pairings
trend across sessions, and no pigeon made more than of the compound CS and food responded on virtually
25f1Jo CRs in any session. all compound and red-light trials, but responded in-
In contrast with birds that received pairings of red- frequently on tone trials. The CR topographies during
light or compound CS with food, birds that received testing were the same as those observed during
tone-food pairings did not acquire a conditioned re- acquisition.
sponse (see the middle panel of Figure 2). Moreover,
only of the three birds responded at all; it pecked Aversive Condition
during the CS on roughly a third of the trials on Acquisition. The three birds that received pairings
Sessions 2-4, but then this behavior ceased. Generally, of the compound CS and shock generally behaved
birds that received a zero-contingency between tone like their counterparts in Experiment 1, All three
and food responded like birds in the other zero- birds began to raise their heads during the CS, and,STIMULUS-REINFORCER INTERACTIONS 591
APPETITIVE AVERSIVE or prancing CRs in a session, and they never responded
100
o between trials.
~ 90
a::
In contrast with the birds that received compound-
~ 80 shock or tone-shock pairings, none of the birds that
u
o 70
a::
received red light-shock pairings reached the acquisi-
U592 SHAPIRO, JACOBS, AND LoLORDO
and pranced on an average of 12% of the trials, and 60-trial session, pecking at or near the food hopper
there was no trend in the data. was reliably elicited by the CS. On the other hand,
Testing. The right-hand panel of Figure 3 illustrates Leyland and Mackintosh (1978) observed no pecking
responding during the two test sessions that followed during illumination of a blue houselight when that
conditioning by birds that had received compound- CS repeatedly preceded access to grain. Perhaps the
shock pairings. Each bird responded on virtually all more extensive magazine training used by Leyland
compound trials and on somewhat fewer tone trials. and Mackintosh was responsible for the failure of
Conditioned response topographies were like those pecking to develop in their experiment (see Tomie,
observed during acquisition. Two birds failed to 1980, for a discussion of this issue), but such a US-
respond on red-light trials, and the third responded preexposure effect cannot be construed as a failure
infrequently. of a blue light-food association, because Leyland and
Mackintosh found that blue light subsequently blocked
Discussion conditioning to an added keylight stimulus.
. Leyland and Mackintosh also administered repeated
The test performances of the pigeons that had re- pairings of an auditory CS and food to pigeons. They
ceived pairings of the compound CS and a US were observed no pecking during the auditory CS. Similar
generally like the performances of the birds in Ex- results were obtained by Rashotte, Griffin, and Sisk
periment 1 in all important respects. The visual (1977) and by Winokur and Boe (Note 1). Apparently,
stimulus was dominant when the US was food, but the failure to peck observed by Leyland and Mackintosh
the auditory stimulus was dominant when electric and by Rashotte et aI. did not reflect a failure of as-
shock was the US. sociation, since the former found that the tone sub-
The single-cue design was included in this exper- sequently blocked conditioning to an added keylight,
iment to assess the possibility that the dominance ef- and the latter found that the tone subsequently was
fects observed following compound conditioning are an effective first-order stimulus in a second-order
the result of some process that emerges in compound conditioning procedure.
conditioning procedures and do not simply reflect the Other investigators have observed conditioned re-
relative conditionability of the various cues. The re- sponses during auditory signals for food. Wasserman
sults of the single-element conditioning treatments (1972) observed head turning and bobbing in response
suggest that the dominance effects observed with elec- to a train of clicks that had been paired with access
tric shock and food do reflect the relative condition- to grain. Farthing (1971) observed orientation toward,
ability of tone and red light. and some pecking at, the grain hopper during an
Consider the groups that received food reinforce- auditory CS+, and a smaller amount of orientation
ment. The three birds that received pairings of red toward the speaker itself. Newlin (1974) observed
light and food acquired a CR, pecking, in five to consistent pecking at or around the hopper during an
eight sessions, whereas none of the three birds that auditory CS+ in all seven birds that received tone-
received pairings of tone and food responded dis- food pairings, although pecking developed more
criminatively to tone in 15 sessions. These data are slowly than in the case of a red light paired with
consonant with the test data from birds that had food. The basis of these discrepant outcomes is un-
received compound conditioning in Experiments 1 clear; however, the last two studies employed a longer
and 2, and are in accord with the suggestion that the CS-US interval (and CS duration) than the studies
tone was not associated with food. in which there was no pecking. Perhaps there
Now consider the groups that received the electric was an initial startle response to the tone in these
shock US. The three birds that received tone-shock studies, and a longer CS-US interval permitted this
pairings during conditioning acquired a CR, head startle to dissipate and pecking to emerge.
raising and prancing, in 5-11 sessions, whereas the Thus far, the discussion has assumed that test re-
three birds that received red light-shock pairings failed sponding to the CS was conditioned, that is, reflected
to acquire a CR in 15 sessions. These data, too, are an association between CS and US that depended on
consonant with test data from birds that had received the positive contingency between CS and US. The
compound conditioning, and are in accord with the data from the zero-contingency groups of Experi-
suggestion that the red light was not associated with ment 2 bear on this assumption. Pigeons that received
shock. random and independent presentations of a CS and
Single-cue experiments in which auditory or diffuse a US failed to acquire a conditioned response. This
visual CSs have been paired with food have been con- finding indicates that the positive contingency between
ducted in several other laboratories. In an unpublished CS and US in the experimental groups is a necessary
PhD thesis, Newlin (1974) presented pigeons with re- condition for the development of discriminative
peated pairings of 100sec illumination of red houselights responding to the CS, that is, that the effects ob-
followed by access to grain. By the end of the first served in the experimental groups were associative.STIMULUS-REINFORCER INTERACTIONS 593
GENERAL DISCUSSION shock should cause auditory cues to be more readily
associated with any US than are visual cues. This
Demonstrations of stimulus-reinforcer interactions attentional account does not require the postulation
in classical and instrumental conditioning have aroused of specific learning-rate parameters for particular
interest largely because they suggest that selective as- CS-US combinations. This account and a selective
sociations between stimuli and reinforcers sometimes association account make differential predictions in
occur. Selective association implies that connections an experiment in which one group of pigeons receives
between certain antecedent and consequent events pairings of the compound and food, with electric
(CS1-US1, CS2-US2) within a set of events (CSI, shocks occurring between trials, whereas a second
CS2, US1, US2) may be formed very easily, whereas group receives pairings of the same compound and
connections between other antecedents and conse- electric shock, with food being presented between
quents (CS1-US2, CS2-US1) within the set may not be trials-but such an experiment has not been con-
formed at all, or only with great difficulty (LoLordo, ducted (see Rescorla & Furrow, 1977, for a formally
1979). In Rescorla and Wagner's (1972) model of similar experiment using this design).
Pavlovian conditioning, two separate learning-rate Another associative account of the present stimulus-
parameters, a and ~, describe the contributions of reinforcer interaction that does not postulate selective
the CS and US, respectively, to the growth of the associations is based on differential initial responses
association between the CS and US. In the terms of to the various CSs (see Jacobs & LoLordo, 1977,
this model, selective associations would be said to 1980; LoLordo, 1979, for a discussion of this issue).
occur whenever the rate of growth of a CS-US as- Suppose that the tone is initially aversive and the red
sociation can only be characterized by a single light is neutral. When the compound is paired with
parameter, unique to the CS-US combination, that electric shock, the auditory element very quickly at-
cannot be reduced to separate parameters for CS and tains considerable strength, whereas the visual element
US. acquires relatively little associative strength. Accord-
The present data demonstrate a stimulus-reinforcer ing to the Rescorla-Wagner model (1972), once the
interaction. Strong visual dominance was observed in sum of the associative strengths of the two elements
appetitive Pavlovian conditioning in both the reaches asymptote, there will be no further con-
compound-cue and single-cue designs, whereas ditioning to either element. Thus, there would be
strong auditory dominance was observed in aversive much more conditioning to the auditory than to the
conditioning in both designs. visual element, given our assumption. Mackintosh's
The low level of responding in the six groups of (1975) model of overshadowing makes the same
Experiment 2 that received independent presentations prediction. The same assumption predicts visual
of a CS and a US (i.e., the zero-contingency control dominance when the compound is paired with food,
groups) indicates that responding in the experimental if we also assume that an aversive (auditory) stimulus
groups was conditioned (i.e., reflects associations). functions like an inhibitor of appetitive conditioning,
Foree and LoLordo (1973,1975; LoLordo & Furrow, that is, initially falls below the neutral visual stimulus
1976) used an instrumental procedure in their exper- on a continuum of appetitive associative strength
iment and did not include groups analogous to the (Dickinson & Dearing, 1979). This account can ex-
zero-contingency groups of the present experiment. plain the data of the compound-cue groups, but in-
Thus, the present experiment contains the first correctly predicts that conditioning will occur when a
demonstration that responses to red light paired with red light is repeatedly paired with electric shock, or
food, and to tone paired with electric shock, are a tone with food.
associative. Although they rely on different mechanisms, all
The results of the present experimentsare compatible the accounts suggested thus far have in common the
with a selective association account. They are also assertion that the stimulus-reinforcer interaction ob-
compatible with several alternative accounts that are served in these experiments is the result of the forma-
associative, but not selective, as the word is used here. tion of strong associations between tone and electric
Rescorla and Holland (1976) proposed one alternative shock and between red light and food, and of weaker
to selective associative accounts of stimulus-reinforcer (or no) associations between red light and electric
interactions like that observed in the present exper- shock and between tone and food. Such an assertion
iments. Applied to the present case, this account as- is not required by the data. Perhaps the stimulus-
serts that the presentation of food increases attention reinforcer interaction we have observed results not
to visual cues, whereas the presentation of electric from associative differences, but from the relative
shock increases attention to auditory cues. Conse- failure of some associations to be manifested in
quently, the presentation of food should cause visual performance (see, e.g., Holland, 1977). In the present
cues to be more readily associated with any US than case, birds were observed during conditioning; hence,
are auditory cues. Conversely, the presentation of failure to observe a conditioned response in the594 SHAPIRO, JACOBS, AND LoLORDO
groups that receive tone-food and red light-shock perimental Psychology: Animal Behavior Processes, 1977, 3,
pairings was not due to the failure of a single, desig- 77-104.
nated response to reveal conditioning. Nonetheless, J ACOHS, W. J., & LoLoRDO, V. M. The sensory basis of avoidance
responding in the rat. Learning and Motivation, 1977,8,448-466.
the absence of a conditioned response in this situa- J ACORS, W. J., & LoLoRDO, V. M. Constraints on Pavlovian
tion may reflect a failure of performance, rather than aversive conditioning: Implications for avoidance learning in the
a failure of association formation. rat. Learning and Motivation, 1980, 11,427-455.
Holland (1977) has suggested several indirect pro- LEYLANO, C. M.. & MACKINTOSH, N. J. Blocking of first- and
second-order autoshaping in pigeons. Animal Learning &
cedures for assessing associations that are not reflected Behavior, 1978,6,391-394.
by performance changes during acquisition (see also LoLoRIlO, V. M. Selective associations. In A. Dickinson & R. A.
Weisman & Dodd, 1979). Such procedures include Boakes (Eds.), Mechanisms of learningand motivation. Hillsdale,
transfer of training procedures such as blocking, N.J: Erlbaum, 1979.
second-order conditioning, and the demonstration of LoLoRIlO, V. M., & FURROW, D. R. Control by the auditory or
the visual element of a compound discriminative stimulus:
conditioned reinforcement. In the case of blocking, Effects of feedback. Journal of the Experimental Analysis of
the relative ability of tone and red light separately Behavior, 1976,25,251-256.
paired with food to block conditioning to an added, MACKINTOSH, N. J. A theory of attention: Variations in the
third stimulus could be assessed. If our stimulus- associability of stimuli with reinforcement. Psychological Review,
1975,82,276-298.
reinforcer interaction reflects selective associative ef- NEWLIN. R. The relation of Pavlovian and autoshaping outcomes.
fects, then, when food is the US, red light should be Unpublished doctoral dissertation, University of North Carolina,
a more effective blocking stimulus than tone. The Chapel Hill, 1974.
converse should be true when electric shock is the US. RASHOTTE, M. E., GRIFFIN, R. W., & SISK, C. L. Second-
order conditioning of the pigeon's keypeck. Animal Learning
& Behavior, 1977,5,25-38.
REFERENCE NOTE RESCORLA, R. A., & FURROW, D. R. Stimulus similarity as a
determinant of Pavlovian conditioning. Journal of Experimental
I. Winokur, S., & Boe, R. Effects of on auditory CS in auto- Psychology: Animal Behavior Processes, 1977,3, 203-215.
maintenance training with pigeons. Paper presented at the Psycho- RESCORLA. R. A.. & HOLLAND, P. C. Some behavioral approaches
nomic Society meeting, Denver, 1975. to the study of learning. In M. R. Rosenzweig & E. L. Bennett
(Eds.), Neural mechanisms of learning and memory. Cambridge,
REFERENCES Mass: M.I.T. Press, 1976.
RESCORLA, R. A., & WAnNER, A. R. A theory of Pavlovian
AZRIN. N. H. A technique for delivering shock 10 pigeons. Journal conditioning: Variations in the effectiveness of reinforcement
of the Experimental Analysis of Behavior, 1959, 2, 161-163. and non-reinforcement. In A. H. Black & W. F. Prokasy (Eds.),
CounHLIN. R. C., JR. Inexpensive pubis electrodes for delivery Classical conditioning ll: Current research and theory. New
of shock to pigeons. Journal of the Experimental Analysis of York: Appleton-Century-Crofts, 1972.
Behavior, 1970, 13,368-369. SCHWARTZ, B. On going back to nature: A review of Seligman
DICKINSON, A., & DEARtNG, M. F. Appetitive-aversive inter- and Hager's Biological boundaries of learning. Journal of the
actions and inhibitory processes. In A. Dickinson & R. A. Experimental Analysis of Behavior, 1974,21,183-198.
Boakes (Eds.), Mechanisms of learningand motivation. Hillsdale, SUTHERLAND, N. S., & MACKINTOSH, N. J. Mechanisms of
N.J: Erlbaum, 1979. animal discrimination learning. New York: Academic Press, 1971.
FARTIlINn, G. W. Effect of a signal previously paired with free TOMIE, A. Effects of unpredictable food upon the subsequent
food on operant response rate in pigeons. Psychonomic Science, acquisition of autoshaping: Analysis of the context blocking
1971,23,343-344. hypothesis. In C. M. Locurto, H. S. Terrace, & J. Gibbon
FOREE. D. D., & LoLoRDO, V. M. Attention in the pigeon: The (Eds.), Autoshaping and conditioning theory. New York:
differential effects of food-getting vs. shock avoidance pro- Academic Press, 1980.
cedures. Journal of Comparative and Physiological Psychology, WASSERMAN, E. A. Auto-shaping: The selection and direction of
1973, 85, 551-558. behavior by predictive stimuli. Unpublished doctoral dissertation,
FOR~;E, D. D., & LoLoRDO, V. M. Stimulus-reinforcer inter- Indiana University, 1972.
actions in the pigeon: The role of electric shock and the avoidance WEISMAN, R. G., & DODD, P. W. D. The study of association:
contingency. Journal of Experimental Psychology: Animal Methodology and basic phenomena. In A. Dickinson & R. A.
Behavior Processes, 1975, I, 39-46. Boakes (Eds.), Mechanisms of learningand motivation. Hillsdale,
GARCIA, J., & KOELLINn, R. A. Relation of cue to consequence N.J: Erlbaum, 1979.
in avoidance learning. Psychonomic Science, 1966,4, 123-124.
HOLLAND, P. C. Conditioned stimulus as a determinant of the (Received for publication February 25, 1980;
form of the Pavlovian conditioned response. Journal of Ex- revision accepted June 20, 1980.)You can also read
