Copyright 1987 by the American Psychological Association, Inc.
0735-7036/87/$00.75

Journal of Comparative PSychology
1987, Vol. IOI, No.2, 197-201

The Spontaneous Interconnection of Four Repertoiresof Behavior in a Pigeon (Columba livia)
Robert Epstein
Boston University andCambridge Center for Behavioral Studies
A pigeon was trained (a) to peck a small facsimile of a banana placed within its reach, (b) toclimb onto a box, (c) to open a door, and (d) to push a box toward targets. When confronted
with a new situation-the banana was placed out of reach, and the box was placed behind thedoor-the four repertoires came together rapidly to produce a humanlike solution to the problem.
A tentative account of the performance is offered in terms of empirically validated principles.

Epstein, Kirshnit, Lanza, and Rubin (1984) reported that
pigeons with appropriate training histories can solve the clas­
sic box-and-banana problem in an insightful, humanlike fash­ion. They assessed the contributions of different experiencesby varying the training histories of different birds. Three birds
had learned (a) to push a box toward a small green spot placedat random positions around the base of a large cylindricalchamber, (b) to climb onto a box and peck a small facsimileof a banana suspended overhead, and (c) not to jump or fly
toward the banana when it was suspended out of reach in theabsence of the box; all 3 solved the problem in what has
traditionally been called an "insightful" manner (Koflka,
1924; Kohler, 1925; Yerkes, 1929): Each bird first appeared
to be confused; it stretched toward the banana, motioned
toward the box, looked back at the banana, and so on. Then,in a continuous series ofmovements, it pushed the box toward
the banana, sighting the banana and realigning the box as it
pushed, stopped pushing when the box was near the banana,climbed, and pecked. The performances lasted roughly 1-2
mm.
Birds that had learned to peck but not to climb did not
successfully climb when the banana was suspended above thebox. Birds that had learned to climb and peck but not to push
did not push in the test situation. Birds that had learned topush but never to push toward targets pushed aimlessly during
the test; one bird managed to solve the problem after 14 minin a manner that one might call trial and error. Anotherprocedure produced behavior suggestive of the classic per­formance of Sultan, one of Kohler's (1925) chimpanzees: A
bird whose jumping and flying had not been eliminatedjumped and flew toward the banana for several minutes andthen, after a total of about 7 min, solved the problem in theinsightful manner described earlier.
Epstein et al. (1984) also offered a running account of thesuccessful performances in terms of relatively simple princi­
ples. The solution can be understood as the interconnectionof two repertoires of behavior which had been establishedseparately and which were controlled by separate stimuli. The
two repertoires were made to occur in close temporal prox­
imity by the new arrangement of box and banana, whichcontained approximations of the stimuli that controlled eachofthe repertoires separately. The period of apparent confusion
was probably the result of the competition between theserepertoires (Cumming & Eckerman, 1965; Epstein, 1985a;
Epstein et aI., 1984; Migler, 1964). The sequence that emerged
seems to have been determined by several processes, one ofwhich is automatic chaining: As the bird pushed the box
closer to the banana, it arranged for itself an increasingly close
approximation of the stimulus-box under banana-that
controlled climbing and pecking; hence it stopped pushing,climbed, and pecked.
Other investigations have also identified resurgence as aphenomenon that makes multiple repertoires available inproblem-solving situations (Epstein, 1985b; Epstein & Med­alie, 1983): When, in a given situation, recently successful
behavior is no longer successful, other behaviors that weresuccessful under similar conditions in the past tend to recur(Barker, Dembo, & Lewin, 1941; Epstein, 1983; Epstein &Skinner, 1980; Estes, 1955; Freud, 1920; Hull, 1934, 1952;
Leitenberg, Rawson, & Bath, 1970; Maltzman, 1955; Masser­man, 1943; Mowrer, 1940; Notterman, 1970; Pryor, Haag, &O'Reilly, 1969; Sears, 1943; Staddon & Simmelhag, 1971;
Yates, 1970). Resurgence seems to be the principal phenom­
enon that allowed pigeons to solve a problem by using a box
as a tool to extend their reach (Epstein & Medalie, 1983), andit also seems to have been involved in a more complicatedperformance in which a rapid, though not especially insight­
ful, solution to the box-and-banana problem was generated
by the spontaneous interconnection of three repertoires (Ep­stein, 1985a).
In this experiment, a pigeon was provided with four separate
repertoires appropriate to the solution of a still more compli­
cated problem.

Portions of this article were presented at the 26th annual meeting
ofthe Psychonomic Society, Boston, November 1985. The work was
supported in part by National Institutes of Health Grant MH32628
to the Foundation for Research on the Nervous System.
I am grateful to E. Scott for training the bird, to K. Greene, F.
Lopez, and J. Miller for technical support, to M. Marsted for help inmanuscript preparation, and to J. Cerella for suggestions.
Correspondence concerning this article should be addressed toRobert Epstein, Cambridge Center for Behavioral Studies, 11 Water­house Street, Cambridge, Massachusetts 02138.
197

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ROBERT EPSTEIN

MethodSubject and Apparatus
The subject was an adult, male, White Cameaux pigeon (289WP)
that had been previously used in a variety of laboratory experiments,
including a problem-solving experiment in which it had been trainedin directional pushing (see Procedure section). It was maintained atroughly 80% of the weight that it would normally attain if given freeaccess to food. Training sessions were conducted daily in a cylindrical,
wire-mesh chamber, 76 cm in diameter. A cardboard box, 8 em highand with a base 10 cm 2, was used in some conditions, as was a small,yellow, cloth-covered facsimile ofa banana, 7 cm in length. A portableenclosure, shaped like half a cylinder, was placed in the chamber
under some conditions. The enclosure was 12 cm deep at its center,and it had a wire-mesh back and, in front, a door that could be
opened. The door itself was made of clear Plexiglas and measured 18
em high by 27 cm wide; its outer edge was covered with opaque black
tape. It did not swing freely; its movement rotated a metal gear, theteeth of which caught a piece of metal that was fixed to the door
frame. Moving the door thus produced audible clicks. A standard
grain dispenser was attached to the base of the chamber.

Procedure
There were five parts to the training, which was accomplished intwenty-four sessions over a period of 9 weeks. The bird received a
total of about 16 hr of training during this period and had previously
received about 12 hr of training in directional pushing. I The major
steps in establishing directional pushing were as follows: At first,
aimless pushes were reinforced (with 3-s operations of the grain
dispenser); then pecks to a green spot (4 cm in diameter) were
reinforced; then the box was mounted on a thin wire that constrained
its movement, the spot was placed at one end, and sighting the spot
and then pushing the box toward it was reinforced; then the wire wasremoved, the box was placed close to the spot, and the sight-and­push sequence was reinforced; then the distance between the spot andthe box was gradually increased.
When directional pushing was well established, a few minutes werespent each day on one or more of each of the four other aspects oftraining: In the absence ofthe box, the banana, and the spot, opening
the enclosure door was shaped and maintained with intermittent foodpresentations. In the absence of the enclosure, the box, and the spot,
the banana was placed within reach of the bird, and pecking it wasshaped and maintained with intermittent food presentations. In theabsence ofthe banana, the enclosure, and the spot, the box was fixedin place on the floor ofthe chamber, and stepping onto it and standingin place was shaped (by means of a series of increasingly taller boxes)and maintained with intermittent food presentations. Finally, in theabsence of the other objects, the banana was placed out of the bird's
reach, and the bird was placed alone with it until the bird neither
flew nor jumped toward it. All of the objects were moved repeatedly
to different positions in the chamber during all phases of training.
The following test situation was arranged: The banana was sus­pended out of the pigeon's reach (41 cm from the floor) at a point(determined by a random number) 5 cm from an edge ofthe chamber.
The portable enclosure was placed opposite this point at the otherside of the chamber, the box was placed in the center rear of theenclosure, and the enclosure door was closed. A video camera re­corded the test session from a position about 1.5 m from the chamber.
The pigeon was placed in the chamber, and the chamber door was
immediately closed. The session was timed from the moment thechamber door was closed.

Results
The results are shown in Figure 1. At first the bird stretchedtoward the banana, then it oriented toward the enclosure doorand box. After about lOs, it approached the enclosure door
and pecked it open. Pecks on the door persisted even after it
was fully open. From 50 to 100 s into the session, the birdoriented and stretched toward the banana several times,
pecked the box briefly at 88 s (not shown), and again pecked
the open enclosure door. Finally, at 107 s, it began to push
the box out of the enclosure. It sighted the banana several
times as it pushed, stopped pushing about halfway across thechamber, climbed, and stretched toward the banana (142 s).
Then it dismounted, pecked weakly at the enclosure door
(150 s), climbed onto the box again, and stretched again
toward the banana (160 s), after which it dismounted andpushed the box along the path indicated in Figure 2 (164-230s). It oriented toward the banana at 221 s (not shown) andagain at 231 s, after which it immediately climbed and pecked
the banana (237 s).
The obvious competition of repertoires that occurred
throughout this session can be understood as the result ofmultiple controlling stimuli or stimulus matching (Cumming& Eckerman, 1965; Epstein, 1985a; Epstein et aI., 1984;
Migler, 1964). The bird was exposed to simultaneously pre­sented approximations of stimuli that controlled four separate
repertoires, and hence each of the behaviors appeared. The
sequence of their appearance and reappearance was.oon­strained by the changing arrangement of stimuli, die bird's
training history, and behavioral processes such as automatic
chaining and resurgence: The bird's first stretches toward thebanana disappeared rapidly, both because they were not rein­
forced and because of the bird's history of nonreinforcement
when the banana was alone and out of reach. Unsuccessful
stretches should have produced, among other things, a resurg­
ence of other behaviors that had been successful in the cham­ber; thus the bird oriented toward and then approached theenclosure door and box., but the physical setup at this point
prevented contact with the box. The bird pecked the enclosure
door open, and this behavior, too, went unreinforced, increas­
ing the probability of alternative behaviors. For nearly 1 min
pecking the enclosure door alternated with stretching toward
the banana until, finally, the bird approached and pushed thebox. With the box halfway across the chamber, other behavior
interfered (the spot-the usual target-was absent, and push­ing was also unreinforced): The bird climbed, faced the ba­nana, and immediately stretched toward it (the banana was
now more nearly in the orientation that had allowed the bird
to peck it during training sessions), but food was still withheld,
so the bird dismounted, again pecked weakly at the enclosure
door, which was immediately in front of the bird, and thenpushed the box closer to the banana. Previous experiments
I The bird had previously been a subject in a replication of the"tool use" experiment (Epstein & Medalie, 1983), for which it wastrained to push two types of boxes toward the green spot. It had had
no experience with the enclosure door or the banana in this experi­
ment and had not been taught to climb.

Figure 1,

Videotape frames showing the bird's performance at IO-s intervals. [Photos outlined in grey show the performance at other times.
The figure was constructed as follows: A dub of the original videotape was made, onto which a digital timer added running time to the lower
right of the picture, with a O.I-s resolution. Then a Tektronix 4632 raster-scan printer was used to print frames at the intervals shown. The
bird, box, banana, and enclosure door were outlined in black to make them easier to identify. During the first few seconds of the performance,
the bird stretched toward the banana. At about IO s into the performance (00100 in the figure), the bird began to open the enclosure door.
After it approached the banana again and pecked again at the open door, the bird pecked weakly at the box (88 s, not shown), stretched again
toward the banana, and then began to push the box out of the enclosure (107 s). It climbed and stretched toward the banana at 142 s and didso again at 160 s. Finally, it brought the box to rest near the banana, began to climb (233 s), and pecked the banana (237 s).]

199

200

ROBERT EPSTEIN(Epstein, 1985a; Epstein et al., 1984; Epstein & Medalie,1983) have shown that pigeons that have learned both to pusha box toward the training target and to peck the banana will
push the box toward the banana, a phenomenon suggestiveof what some call Junctional generalization (Bruner, Good­
now, & Austin, 1956; Stemmer, 1972). Because the bird had
never seen box-under-banana (cf. Epstein et al., 1984), it
pushcd somewhat beyond the banana but then, because thebanana was still the target, pushed back toward the banana:and so on, until pushing extinguished in roughly a damped
oscillatory pattern of pushes in the area of the banana (Figure2). With pushing and pecking the enclosure door greatly
weakened, the bird climbed and, orienting toward the banana,
immediately pecked.

Discussion
This test was my first and only attempt at obtaining theinterconnection of four repertoires of behavior in a pigeon,and I believe that a positive result is significant even if
attempts with other pigeons fail. Ifmy analysis ofthe perform­
ance is correct, however, additional attempts will succeed,
although individual differences among subjects should affectboth the rapidity and smoothness of the process of intercon­
nection. As noted earlier, when another pigeon was con­
fronted with a simpler problem, three repertoires came to­gether to produce a solution in less than I min (Epstein,
1985a).

289WP

A large number of repertoires can undoubtedly be made tocompete with each other in a novel situation, but that does
not guarantee that they will combine successfully to produce
adaptive behavior. Trivial factors can have profound effects:
A turn ofthe head radically changes the visual field and hence
may increase the probability of inappropriate behaviors; crit­
ical behaviors that persist too early in the performance may
weaken to such an extent that they are unavailable at appro­
priate points later in the performance; the problem may be
structured so that a slight variant of an appropriate behavior
leads to a cul-de-sac (the box could easily have becometrapped behind the open door of the enclosure, for example).
I have described elsewhere a general approach to under­
standing and predicting ongoing, novel performances in bothhuman and nonhuman animals (Epstein, 1985c, 1986V Pre­viously established behavior manifests itself in new situations
in orderly ways as a function of the genes and ontogenic
history of the individual, as well as of the current stimuli andthe manner in which they are changed over time by theorganism or other agents. Researchers will further an under­
standing of ongoing behavior by varying species and individ­
uals, by varying training histories, and by further elaborating
the principles that predict the transformation of previously
established behavior under new circumstances.
This approach to understanding ongoing behavior has been
helpful in two ways: It has allowed the engineering of increas­
ingly complex, novel performances in relatively simple orga­
nisms (Epstein, 1985a; Epstein et al., 1984; Epstein, Lanza,& Skinner, 1981; Epstein & Medalie, 1983; Epstein & Skinner,1981), and it has led to the development ofa formal theory,
called generativity theory, which has proved useful in predict­ing ongoing behavior in human subjects under laboratory
conditions (Epstein, 1985c). The approach might also prove
helpful in the design of problem-solving software for artificial
intelligence systems.
2 The interconnection of repertoires has often been suggested as asource of novelty in behavior. Consider Hull (1935), Koestler (1964),
Maier (1929), Maier and Schneirla (1935), Poincare (1946), andRothenberg (1971).

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Figure 2. floor diagram of the chamber. (The bird pushed the box
fairly directly toward the banana but did not stop pushing when thebox first approached the banana. Rather, it pushed somewhat beyond,pushed back toward the banana and then somewhat beyond, and soon, in roughly a damped oscillatory pattern. In so doing, the bird
kept the box within a few centimeters from the position on the floor
beneath the banana for more than 50 s before it finally climbed. The
open circle marks the position at which the bird twice climbed andstretched toward the banana before bringing the box to rest near thc
banana. Times are shown in minutes and seconds.)

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Received Apri12, 1986
Revision received December 31, 1986
Accepted December 31, 1986 •