addressed contradictory claims about causal reasoning in elephants. In
Experiment 1, 4 Asian elephants (Elephas maximus)
were pretrained to remove a lid from the top of a bucket and retrieve a food
reward. Subsequently, in the first 5 critical trials, when the lid was placed
alongside the bucket and no longer obstructed access to the reward, each
elephant continued to remove the lid before retrieving the reward. Experiment
2, which involved 11 additional elephants and variations of the original
design, yielded similarly counterintuitive observations. Although the results
are open to alternative interpretations, they appear more consistent with
associative learning than with causal reasoning. Future applications of Fabrean methodologies (J. H. Fabre, 1915) to animal cognition are proposed.
How do animals react to covarations between events? The causal model theory posits
that performance is, at times, based on the actor's belief and abstract
knowledge about a causal connection (Dickinson, 1994; Dickinson & Shanks, 1995). In contrast, the associative
model rejects the relevance of mental representation and belief about causality
and ascribes the performance solely to the reinforcement of a stimulus–response
(S-R) association (Cobos, López, Caño, Almaraz,
& Shanks, 2002).
Although the existence of
causal reasoning in animals has long received the attention of philosophers and
experimentalists, a clear-cut answer still eludes us. To date, perhaps the
least ambiguous evidence comes from Fabre's
(1915) classical 19th century experiments with wasps. Fabre's
straightforward interventionary procedures were later applied to bees (e.g., Gould & Gould, 1982), fruit flies (e.g., Nissani,
1975), and other insects, thus tending to support Fabre's
views that insects are incapable of causal reasoning (but see Griffin,
contemporary studies of causal reasoning often appear to lack the clarity and
seeming finality of Fabre's (1915)
and Thorndike's (1911) studies. For instance, whereas some
observations of cotton-top tamarins, capuchins, and chimpanzees are consistent
with causal reasoning, other observations offer ambiguous results and still
others argue against it (Fujita, Kuroshima,
& Asai, 2003; Hauser, 1997,
2003; Horner & Whiten, 2004; O'Connell
& Dunbar, 2005; Premack & Premack, 1988). As just one example of this ambiguity,
consider the trap-tube task. After presenting a similar task to the same
species, one research team concluded that some chimpanzees seemed to understand
the requirements of the task (reviewed in Visalberghi,
2002); another team concluded that the chimpanzees did not (reviewed in Povinelli, 2000).
In this article, I explore
the utility of a consciously Fabrean approach to the
perception of causality in elephants. In particular, this article raises the
possibility of a cognitive resemblance between elephants and Thorndike's cats.
This resemblance does not rule out—but still is not readily reconcilable
with—the attribution to elephants of ideation (Rensch, 1957), thinking (Gordon, 1966),
insight (Nissani, 2004; Williams, 1950),
grief (Spinage, 1994), suicide (Gale, 1974), deception (Morris, 1986), and
consciousness (Poole, 1997). The intent of this article is
also to expand the meager database of elephant behavior and cognition (for
recent claims and counterclaims about elephants' exceptional cognition, see Bradshaw, Schore, Brown, Poole, &
Moss, 2005; Hart, Hart, McCoy, & Sarath,
2001; McComb, Moss, Sayialel, & Baker, 2000; Nissani,
2004; Nissani, Hoefler-Nissani,
Lay, & Htun, 2005).
To determine whether
elephants learn about the consequences of their actions in such a way that they
can change their actions appropriately when circumstances change or,
alternatively, whether instrumental conditioning simply strengthens their S-R
habits, in Experiment 1 Burmese elephants were pretrained to remove food from a
coverless bucket. They were next pretrained to remove a lid from the top of
that bucket, insert their trunk into the bucket, and retrieve a food reward
from the bottom of the bucket. Once this behavioral sequence was established,
the lid was placed alongside the bucket so that it no longer obstructed access
to the reward. If elephants can change their actions appropriately (Dickinson & Balleine, 2000), they
might be expected to ignore the side lid in the first few trials and retrieve
the reward directly, as they did in the early stages of pretraining. On the
other hand, if instrumental conditioning merely strengthens an S-R habit, in
the first few trials the elephants might be expected to continue removing the
lid before retrieving the food. Experiment 2 tested the generalizability,
reliability, and robustness of the results.
Experiment 1: Side Placement of Lid
Four female Asian
elephants (Elephas maximus) served as subjects
(identified by their government registration numbers): No. 6389, age 7 years at
the time of the experiment; No. 5811, age 16; No. 5655, age 16; and No. 4800,
age 31. Prior to the initiation of the critical side-displacement trials, 2 of
these subjects took part in black+/white–visual discrimination and acuity tasks
and 2 took part in black–/white+ visual discrimination and acuity tasks
involving the same apparatus used in the present experiments (Nissani
et al., 2005). In an average of 161 trials, the 3 younger elephants
successfully met an overall learning criterion in that task; the older
31-year-old performed at the 50% level in 388 trials. Overall, just prior to
the beginning of the critical side-placement trials, the 4 elephants took part
in an average of 3.3 (range = 2–5) pretraining sessions, 16.4 (range = 7–22)
discrimination sessions, and 870.5 (range = 342–1,180) discrimination trials.
Owing to lack of
electricity and other conveniences, the present experiments relied on primitive
equipment and extensive controls. All lid-removal tasks involved the use of a
green plastic bucket. Each tapered bucket was 32 cm tall, had an internal top
diameter of 30 cm, and had an internal bottom diameter of 25 cm. On one side of
each bucket, about 10 cm from its bottom, there was a 10-cm hole—large enough
for an experimenter to insert one hand containing a food reward but too large
for an elephant to insert a trunk. The bucket was often secured to the ground
with bamboo stakes around its perimeter.
The bucket had a green,
black, or white, circular, 33-cm lid. A white, semicircular handle was attached
to each lid. The lid and the handle were made of the same hard plastic material
as that of the bucket.
The present experiments
were carried out in the forests of central Burma (Myanmar), in an open
clearing, in full daylight (for details, see Nissani et al., 2005).
Burmese logging elephants feed on their own in the forest on rest days or when
the day's work is done, and they are rarely given supplementary provisions.
Thus, they responded eagerly to the food rewards used in our experiments: (a) a
3- to 8-cm piece of sugarcane, (b) a 1- to 2-cm tamarind ball, and (c) a 3- to
6-cm rice paddy wrapped in banana leaves.
The crucial phase involved
the elephant's learning to remove a lid from the top of a bucket to obtain food
from the bottom of the bucket. The elephant typically stood on one side of a
heavy log, directly facing a single bucket on the other side of the log. The
bucket was about 1 m from the elephant's feet. A single trainer squatted or sat
behind the bucket, directly facing the subject, and gradually trained the
elephant to retrieve a reinforcer from a coverless bucket. Once the elephant learned
that task, a green, white, or black lid was introduced. At first, the lid
barely covered the bucket's opening when the food was placed into the bucket;
as the training proceeded, the lid covered an increasingly greater portion of
the opening. Once the elephant learned to remove the lid, the trainer held the
lid in place and allowed its removal only by the lid handle.
In the later pretraining
stages, the trainer simultaneously inserted the food into the bucket through
the bottom side hole with one hand and clicked the lid into place with the
other hand. The trainer then removed his hand from the handle while still
holding the food inside the bucket with the other hand. When the elephant
grabbed the handle with its trunk and tossed the lid away, the trainer released
the food and removed his hand from inside the bucket; the elephant then grabbed
the food with its trunk and placed the food into its mouth. The performance
criterion for this pretraining phase was defined as the point at which the
elephant grabbed the lid by the handle within 3 s of lid placement, tossed the
lid away, and removed the reward from the bottom of the bucket in 9 out of 10
Because the 4 elephants in
this group had already taken part in black–white discrimination tasks prior to
taking part in these side-placement trials, they were next trained to remove
one of two lids and retrieve food from one of two adjacent buckets (Nissani et al., 2005). Reward placement in one of the two
buckets followed a predetermined random sequence; the criterion was defined as
9 of 10 correct consecutive choices in two consecutive sessions.
The critical phase of the
experiment involved interspersing the base trials (lid on top of bucket) with
the experimental trials. In these experimental trials, the lid was placed a
short distance away from the edge of the bucket, onto the ground, randomly to
the right or left of the bucket, so that it no longer obstructed access to the
food inside the bucket—that is, during the last stages of pretraining and
during base trials of the experiment itself, the elephant had to remove the lid
to obtain the reward; during experimental trials, the elephant could ignore the
lid and retrieve the reward directly from the bucket.
independently recorded each subject's behavior. Interobserver reliability for
the first five trials, which entailed a judgment as to whether the elephant
approached or ignored the lid, was 100%. This interobserver
reliability was later confirmed by comparing the written records of one
experimenter to the video record, again yielding 100% (20 of 20) concordance of
this simple all-or-none behavior. When the elephant did not ignore the lid, the
interaction was classified into three categories: full toss, touch, and
approach (i.e., moving the trunk toward the lid but not touching it). Here, interobserver reliability was 95% (19 of 20), with the
single discrepancy involving a disagreement between a touch and an approach in
one of the three cases in which such an intermediate response was observed.
That single discrepancy was resolved by consulting the video record.
The 4 elephants
successfully achieved pretraining discrimination criterion within 2–5 sessions.
Accurate records of the duration of each pretraining session were kept in just
one case and comprised 125 min.
traces the performance of the 4 subjects in the critical side-placement
configuration. In this figure, side-placement trials (top and bottom of y-axis) were interspersed with base trials in which
the lid blocked access to the reward (center of y-axis).
A trial that involved a full toss of the lid before food retrieval is shown at
the bottom of the y-axis; a trial that involved
the elephant merely approaching or touching the lid with its trunk is shown
midway between the center and bottom axes. The top of the y-axis depicts experimental trials in which the
elephant ignored the lid and directly inserted its trunk into the bucket.
Figure 1: Performance across trials of 4 elephants in lid–bucket side-placement task
For instance, in the first
6 trials of No. 5811's experimental session, a reward was placed inside the bucket
while a lid was simultaneously placed on top of the bucket. In all 6 base
trials, the elephant promptly tossed the lid, inserted its trunk into the
bucket, and secured the reward. In the next 10 trials (7–16), the lid was
placed onto the ground, to the right or left of the bucket, while the morsel
was simultaneously placed into the bucket. In Trials 7–14, the elephant tossed
the lid first and only then inserted its trunk into the bucket to retrieve the
morsel. In Trial 15, it merely touched the lid and then retrieved the food. In
Trial 16, it ignored the lid for the first time. Thereafter, before retrieving
the food in the remaining 17 experimental trials, it ignored the lid in 7 of
the trials, tossed the lid in 9 of the trials, and merely touched the lid in 1
The most relevant data
involved the first few trials, before the elephants could revert to the early
pretraining procedure (prior to the introduction of the lid) of retrieving the
food directly from the bucket. In the first 5 side-placement trials, none of
the 4 elephants ignored the lid, although their exact behavior varied somewhat.
Before retrieving the food, No. 6389, No. 5811, and No. 4800 applied the same
full toss to the lid on the ground as they had applied earlier to the lid on top
of the bucket. No. 5655 performed a full toss before retrieving the food in its
first two trials and merely touched the lid in its last three trials.
Similarly, in experimental Trial 4 of the first 5 trials (and in subsequent
Trials 7, 12, 13, and 17), the elephant searched for the food under the lid
before retrieving it from the bucket (for visual details, see Hoefler-Nissani & Nissani, 2004).
Although the limited
number of trials, the variable design, and the all-or-nothing nature of the
results do not lend themselves to meaningful statistical analyses, the behavior
of the elephants in the first 5 trials is consistent with earlier significant
observations (Nissani et al., 2005) of a marked age effect in
the learning ability of elephants. Thus, in its last 6 experimental trials, the
7-year-old elephant (No. 6389) ignored the lid and retrieved the food directly
from the bucket even though, in this case, trials were often interspersed with
base trials. The two 16-year-olds ignored the lid in an average of 1.5 trials
out of 6, while the 31-year-old elephant (No. 4800) fully tossed the lid in 21
As mentioned previously,
only No. 5655—in 5 of 17 experimental trials—searched for food under the lid
before removing food from the bucket. In its remaining trials, and in all
experimental trials of the other 3 elephants, interactions with the lid were
immediately followed by food retrieval from the bucket. Because elephants can
sense the presence of food at that distance only by sniffing and touching the
ground (Nissani et al., 2005), this observation suggests that
the 4 elephants did not form an alternative causal model, in which the lid is
perceived as an obstacle to food underneath it (not to food in the bucket).
Experiment 2: Procedural Variations
Eleven elephants from three geographically
isolated logging camps served as subjects (see Table 1). As
was the case with the 4 elephants of Experiment 1, the 8 older elephants of
Experiment 2 previously took part in an extensive series of discrimination
studies. Thus, just prior to commencement of the critical side-placement
trials, these 8 elephants took part in an average of 3.9 (range = 1–6)
pretraining sessions, 12.3 (range = 3–31) discrimination sessions, and 734
(range = 150–1,699) discrimination trials. In contrast, the 3 younger elephants
in this group were tested immediately following the completion of pretraining
with just a single bucket (2 subjects) or two buckets (1 subject).
With 8 elephants, the
lid–bucket combination used in Experiment 1 was used here, as well. In addition
to the elephants being consistently tested with either black or white lids, 1
elephant was consistently tested with a green lid.
To rule out the
possibility that the observed behavior was traceable to some particular feature
of the apparatus, 3 elephants were presented with a variation that involved a
circular depression in the ground and black or white teak boxes. The depression
was 10 cm deep and 19–23 cm wide. All boxes used were of similar height (7–8
cm), but their surface areas ranged from 245 cm2 to 1,681 cm2
(for details, see Nissani et al., 2005).
The basic design of
Experiment 1 was used, with the following variations (see also Table
1). Experimenter bias was unlikely to account for the observations with the
first elephant of Experiment 1 (No. 6389) because its behavior was surprising.
However, by the time observations of the second elephant were conducted, it was
clear that experimenter bias could influence the results. To rule out such a
bias more methodically, more than five different experimenters carried out
Experiment 2 in 3 different logging camps, with 11 new elephants. In
particular, two experimenters—each working with the first elephant of each of
the two additional camps—were deliberately not informed about the goals of the
experiment and about the expectations of the senior experimenter, who recorded
the observations from a distance and did not interact with the elephants during
those critical trials.
As evidenced in the
previous experiments, after mastering the lid-removal task, the 4 elephants of
Experiment 1 and the 8 oldest elephants of Experiment 2 (see Table
1) took part in an average of 14.8 discrimination sessions and 840.7
discrimination trials before being faced with the lid-placement task. Thus, the
possibility was raised that by then, the elephants' behavior had become
ingrained, resembling functional fixedness (Luchins,
1959) and belief perseverance (Nisbett
& Ross, 1980; Nissani & Hoefler-Nissani,
1992) in humans. Similarly, it could be argued that this overtraining
preferentially strengthened the elephants' S-R habits over their action–outcome
associations. To mitigate such potential problems, the experimenters
implemented several additional controls with the 3 younger elephants of
Experiment 2. First, these 3 elephants were presented with the
side-displacement task as soon as they had achieved the pretraining criterion
with a single bucket (see Table 1), thereby minimizing the
probability that the behavior had become ingrained. Second, in each session
involving 2 of these 3 youngest elephants, pretraining and critical trials were
preceded by 20–64 control trials, in which a piece of sugarcane was noisily
tossed into one of two open buckets. In these control trials, if the elephant
inserted its trunk into the correct bucket, it was able to retrieve the
sugarcane. Thus, throughout the training and just before the critical
side-placement trials, these 2 elephants were engaged in a control variation
that relied on their ability to retrieve food directly from an open bucket.
As in Experiment 1 and in
the bucket–lid variation of Experiment 2, the box–hole variation involved the
elephants learning to displace the box to retrieve a reward from a circular
depression below the box. Again, in critical trials, the box was placed
alongside the circular depression while the reward was simultaneously placed
inside it. Additional minor procedural variations involving only 1 or 2
elephants are briefly described in the Results
for the first five trials, which entailed a judgment of whether the elephant
interacted with or ignored the lid or box, was 98% (54 of 55), with the single
discrepancy being resolved by the video record. When the elephant interacted
with the lid or box, the behavior was classified into three categories: full
toss (lid) or displacement (box), touch, and approach (moving the trunk toward
the lid or box but not touching it). Two discrepancies occurred. One was
resolved by consulting the video record; the other was arbitrarily classified
as a touch (as opposed to a toss).
summarizes the first 5 side-placement trials. In 3 of 55 trials, 3 different
elephants (ages 12–17) ignored the lid and proceeded directly to the bucket or
hole. In the remaining 52 trials, 2 food retrievals were preceded by trunk
movement toward the box without coming into contact with it, 9 retrievals were
preceded by touching (but not moving) the lid or box, and 41 retrievals were
preceded by a full toss (of the lid) or displacement (of the box). None of the
procedural variations seemed to affect the results, thus rendering unlikely the
competing interpretations of experimenter bias and peculiarities of the
Observations of the 2
youngest elephants in this group are of particular interest here, for they seem
to argue against the functional fixedness (or rigidity-of-behavior)
interpretation. These 2 elephants were confronted with the side-placement task
as soon as they had mastered the removal of a single lid. Moreover, every
pretraining and experimental session with these 2 elephants was preceded by at
least 20 control trials in which a piece of sugarcane was tossed into one or
another bucket, followed in all cases by trunk insertion into one of the
buckets. Despite these two additional controls, and despite the 2 elephants'
comparative youth, they tossed or touched the side lid first in 9 of 10 trials.
Only 3 elephants were
tested beyond the first five trials. In 2 elephants, with a mean of 6.4
additional experimental trials (beyond the first five), no change took
place—they continued to remove the lid or box as they did in the first trial.
The performance of the other elephant, however, improved over time (the lid was
ignored in three of four additional trials).
Only 1 elephant
consistently searched for food under the displaced box before retrieving food
from the hole; the other 10 elephants ignored the ground under the box or lid
and moved directly to the hole or bucket. This observation again seems to rule
out the notion that the elephants entertained a causal theory, but one of a
different kind (that the lid or box hindered access to food underneath).
These results are perhaps
more readily reconcilable with the associationist
model of elephant learning than with a causal learning model. The following
qualitative observations likewise do not prove, but appear more consistent
with, the associationist model.
- In its first side-displacement trial, No. 5654's trunk was
inside the bucket when the lid was placed onto the ground and when the
food was placed at the bottom of the bucket. The elephant removed its
trunk from the bucket, tossed the lid, and only then reinserted its
trunk into the bucket.
- On its fifth trial, No. 5746 hesitated for 14 s (appearing,
to human observers, to be “weighing its options”), then it approached
the ground lid, tossed it, inserted its trunk into the bucket, and
secured the food.
- After No. 5751 tossed the ground lid in 10 consecutive
trials with undiminished vigor, the lid was hidden from view and food
was placed into the bucket in 2 trials; in both trials, the elephant
directly retrieved the food from the bucket. These 2 trials were
followed by 3 additional base trials (in which the elephant had to
remove the lid to access the food) and 3 additional experimental trials
(in which experimenters placed the lid onto the ground). Yet, in these
last 3 trials, the elephant fully tossed the lid and only then
retrieved the food.
- The first five side-placement trials of No. 6437 and No.
3431 involved noisily dropping the food (a piece of sugarcane) into the
bucket (and loudly inserting it, instead of the usually silent manner
of inserting it, through the bottom side hole). The extra sounds had no
effect: The 2 elephants either tossed the lid (in nine trials) or
touched it (in one trial).
- In one trial, No. 5904 moved a box toward the hole and
covered it; then the elephant kept moving the box to uncover the hole
- With No. 6158, the lid was suspended in the air alongside
the bucket (and not placed onto the ground), but the elephant still
consistently tossed it.
The most parsimonious account would perhaps posit that
when acquiring the obstacle-removal task, elephants respond to the temporal
contiguity of the two events, not to their causal relationship. To my
knowledge, there are no comparable experiments or observations with elephants
that shed light on this interpretation. However, chimpanzees in somewhat
analogous situations confirm the suspicion that the obstacle concept is not an
easy one for nonhuman animals to grasp (Köhler, 1925).
The results of this study
could be ascribed to a variety of causes besides the failure to form a causal
connection between an obstacle and a reward. One cause could be that captive
elephants in Myanmar, at times, undergo harsh training (Himmelsbach, 2002) starting at about age 5—a
biographical detail that could impair their emotional and intellectual
development (Harlow & Harlow, 1965). Another cause could
be captivity itself. Still another cause involves the visual nature of the
task; it is conceivable that elephants would have grasped the concept of
obstacle removal in an equivalent task that relied on olfaction or hearing.
Likewise, although this experiment devised two control variations to minimize
the effects of functional fixedness and behavioral rigidity, we cannot
altogether rule out the possibility that the results speak more to the rigidity
of elephants' learned behavior than to their lack of causal reasoning. Finally,
although elephants in the wild are known to spontaneously engage in
obstacle-removal operations—for example, both African (Gordon,
1966) and Asian (U Tin Lay, personal communication, December 24, 2002)
elephants remove sand to gain access to water in a dry riverbed—tasks with
human-made artifacts may lack ecological validity.
It may be instructive to
suitably modify and apply the side-placement design to great apes and corvids—vertebrates whose visual acuity is sharper than
that of macrosmatic elephants but whose cognitive exceptionality is similarly
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intelligence; causal model theory; stimulus–response association; reasoning;
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