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DISCRIMINATION OF QUANTITY IN CAPTIVE KILLER WHALES
Michael Noonan, Anne Janas,
Rebecca Jones & Georgia Bucci-Roach
Canisius College (Buffalo,
New York) and Marineland of Canada (Niagara Falls, Ontario)
Society for Marine
Mammalogy, Vancouver, British Columbia, November, 2001
Introduction
The processing of
arithmetical relationships is a hallmark of human cognition, and a number of
non-human animals have also been shown to possess a degree of numerical
competence. To assess an elemental level of numerical processing in the Orca,
we trained whales to choose which of two stimulus cards displayed a greater
number of dots. Thus, the paradigm/task employed here is an example of
“relative numerousness judgment”, and it is thought to reflect the most
rudimentary of numerical processes.
Methods and Results
Two captive born, juvenile
Killer Whales (of Icelandic stock) served as subjects of this investigation – an
eight-year-old female and a four-year-old male.
During training and
testing, the animal shuttled (across an 8 meter pool) between a stimulus station
and a feeding station where it was presented with fish reward for correct
responses. Each whale was tested separately and out of sight of the other.
Training Phase
(Sequential Comparisons)
Over successive trials, the
whales were presented underwater with two black stimulus cards, each of which
contained small white squares. The whales were rewarded for
touching their snouts to whichever of the two cards had the greater number of
squares. The size of the squares, the pattern of their placement on
the cards and the side of the correct card (left/right) were varied
pseudorandomly in counterbalanced fashion within and across days. The size of
the stimulus squares was varied so that the total white area on the correct card
was sometimes greater than, equal to, or less than that on the incorrect card.
Each whale was moved
through a series of progressively more difficult comparisons – staying at each
level until it reached a preset criterion of performance (18/20 & 12/14 in each
training phase respectively). The sequence of trials and each whales
performance during this training in summarized is Table One.
Table 1: Training Sequence and Performance
|
|
Training Phase (a) |
|
|
Subject F8 |
Subject M4 |
|
Comparison |
Trials |
Days |
Criterion
(18/20) |
Trials |
Days |
Criterion
(18/20) |
|
2-1 |
890 |
89 |
N |
614 |
55 |
Y |
|
3-1 |
20 |
2 |
Y |
60 |
6 |
Y |
|
3-2 |
60 |
6 |
Y |
250 |
25 |
Y |
|
4-1 |
20 |
2 |
Y |
20 |
2 |
Y |
|
4-2 |
20 |
2 |
Y |
30 |
3 |
Y |
|
4-3 |
180 |
18 |
N |
300 |
20 |
N |
|
5-1 |
20 |
2 |
Y |
20 |
2 |
Y |
|
5-2 |
20 |
2 |
Y |
20 |
2 |
Y |
|
5-3 |
115 |
12 |
Y |
30 |
3 |
Y |
|
5-4 |
110 |
0 |
Y |
200 |
20 |
N |
|
6-1 |
20 |
2 |
Y |
20 |
2 |
Y |
|
6-2 |
20 |
2 |
Y |
20 |
2 |
Y |
|
6-3 |
30 |
3 |
Y |
20 |
2 |
Y |
|
6-4 |
70 |
7 |
N |
20 |
2 |
Y |
|
6-5 |
|
|
|
60 |
6 |
N |
|
|
|
|
|
|
|
|
|
Training Phase (b) |
|
|
Subject F8 |
Subject M4 |
|
Comparison |
Trials |
Days |
Criterion
(12/14) |
Trials |
Days |
Criterion
(12/14) |
|
10-1 |
14 |
1 |
Y |
14 |
1 |
Y |
|
8-1 |
14 |
1 |
Y |
14 |
1 |
Y |
|
6-1 |
14 |
1 |
Y |
14 |
1 |
Y |
|
4-1 |
14 |
1 |
Y |
14 |
1 |
Y |
|
2-1 |
14 |
1 |
Y |
14 |
1 |
Y |
|
10-2 |
14 |
1 |
Y |
14 |
1 |
Y |
|
8-2 |
14 |
1 |
Y |
14 |
1 |
Y |
|
6-2 |
14 |
1 |
Y |
14 |
1 |
Y |
|
4-2 |
14 |
1 |
Y |
14 |
1 |
Y |
|
3-2 |
10 |
1 |
Y |
14 |
1 |
Y |
|
10-3 |
14 |
1 |
Y |
14 |
1 |
Y |
|
8-3 |
14 |
1 |
Y |
14 |
1 |
Y |
|
6-3 |
14 |
1 |
Y |
14 |
1 |
Y |
|
5-3 |
28 |
2 |
Y |
14 |
1 |
Y |
|
4-3 |
28 |
2 |
Y |
14 |
1 |
Y |
|
10-4 |
14 |
1 |
Y |
14 |
1 |
Y |
|
8-4 |
14 |
1 |
Y |
14 |
1 |
Y |
|
6-4 |
14 |
1 |
Y |
14 |
1 |
Y |
|
5-4 |
28 |
2 |
Y |
28 |
2 |
Y |
|
10-5 |
14 |
1 |
Y |
14 |
1 |
Y |
|
8-5 |
14 |
1 |
Y |
14 |
1 |
Y |
|
7-5 |
43 |
3 |
Y |
14 |
1 |
Y |
|
6-5 |
14 |
1 |
Y |
14 |
1 |
Y |
|
10-6 |
14 |
1 |
Y |
14 |
1 |
Y |
|
8-6 |
28 |
2 |
Y |
14 |
1 |
Y |
|
7-6 |
140 |
10 |
N |
56 |
4 |
Y |
|
10-7 |
14 |
1 |
Y |
14 |
1 |
Y |
|
9-7 |
30 |
3 |
N |
14 |
1 |
Y |
|
8-7 |
|
|
|
70 |
5 |
Y |
|
10-8 |
|
|
|
14 |
1 |
Y |
|
9-8 |
|
|
|
70 |
5 |
Y |
|
10-9 |
|
|
|
14 |
1 |
Y |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
During this training
phase, Subject F8 successfully mastered 6 vs 5 and failed at 7 vs 6. Subject M4
successfully reached criterion up to 10 vs 9, the highest comparison used.
A consistent pattern of
errors appeared in the early stages of training. Both whales made many more
errors when the correct (greater number) squares were smaller in size (surface
area) than the incorrect (lesser number) of squares. That is, at the outset the
whales appeared to have difficulty separating “how much” from “how many”. This
pattern of errors may be called “Piagetian” in that it corresponds to the type
of errors that human children make during cognitive development. Errors of this
type gradually became less frequent and disappeared by the final Testing Phase
of our study.
There was a decrease in
the number of trials taken to reach criterion over successive comparisons (see
Table 1) – evidence that is compatible with the notion of learning set
formation.
Testing
Phase (Intermixed Comparisons)
Over a period of 20 days,
we presented each whale with a varied sequence of adjacent numerical comparisons
(18 trials per day). That is, in this testing phase the trials presented an
intermixed sequence of comparisons such as 7 vs 6, 3 vs 4, 1 vs 2, 9 vs 8, and
so on. The trial sequences were presented pseudorandomly – meaning without
discernable pattern, but counterbalanced by size, side and number.
Subject F8 reliably discriminated comparisons up to 8 vs 7.
Although, by contrast, Subject M4 did less well at 8 vs 7, he reliably
discriminated 9 vs 8 and 10 vs 9.
Logistically, it was
impossible for us to conduct all training and testing trials with de novo
stimuli and in “blind” fashion. However, in this phase we included probe trials
which presented entirely novel stimulus cards and in which all control signals,
stimulus presentations and fish rewards were given by individuals unable to see
the stimuli or know the correct responses. The performances by both subjects on
these probe trials did not differ significantly from that on our ordinary
trials.
Discussion
The large brainedness
(cephalization) of cetaceans may be expected to be associated with a refined
perceptual and cognitive processing of information. In this regard, it is
noteworthy that the performance in our study by our two Killer Whales (reaching
8 vs 7 and 10 vs 9) meets or exceeds the abilities of other non-human species
tested on this paradigm.
Ecologically, it can be
argued that the perception of quantity might be important to non-human animals
within cost/benefit analyses during predator-prey and/or social interactions.
Nevertheless, the very large number of trials needed during initial training
suggests that Killer Whales are not predisposed to readily attend to number as a
stimulus dimension.
In evolution, the
cephalization of cetaceans can be taken as parallel to (and independent of) the
same trend in primates. It might therefore be anticipated that cetaceans could
possess a “different” kind of intelligence from that of primates. However, the
fact that our subjects initially showed the same “Piagetian” pattern of errors
that are shown by human children and non-human primates when presented with the
same task is more compatible with a common form of processing in the two taxons.
To further explore this
dimension of Orca cognition and fully determine the limits of their abilities
and the extent to which their processing corresponds to primates, it will now be
interesting to test their abilities (a) to make “absolute” discriminations of
quantity (e.g., find the “5” regardless of its comparator), (b) to place stimuli
with quantitative content into ordinal relationships, and (c) to process
combinations (additions) or separations (subtractions) of stimulus quantities.
Acknowledgements
The authors wish to thank
and praise Joshua Russell, Keryn Priset, Rebecca Russo and Jennifer Snekser who
served very ably as research assistants on this project. We also gratefully
acknowledge the hospitality and support of Marineland of Canada, particularly
that of John Holer and David Elliott.
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