Spatial Learning and Memory in the Tortoise (Geochelone carbonaria)

Abstract

A single tortoise (Geochelone carbonaria) was trained in an eight-arm radial maze, with the apparatus and general procedures modeled on those used to demonstrate spatial learning in rats. The tortoise learned to perform reliably above chance, preferentially choosing baited arms, rather than returning to arms previously visited on a trial. Test sessions that examined control by olfactory cues revealed that they did not affect performance. No systematic, stereotyped response patterns were evident. In spite of differences in brain structure, the tortoise showed spatial learning abilities comparable to those observed in mammals.

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Wilkinson, A., Chan, H.M. and Hall, G. (2007) Spatial learning and memory in the tortoise
(Geochelone carbonaria). Journal of Comparative Psychology. pp. 412-418. ISSN
0735-7036
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Tortoise spatial learning 1
Spatial Learning and Memory in the Tortoise (Geochelone carbonaria)
Anna Wilkinson, Hui-Minn Chan, Geoffrey Hall
University of York
Short title: Tortoise spatial learning
Contact address:
Anna Wilkinson
Department of Psychology
University of York
York
YO10 5DD
UK
e-mail: a.wilkinson@psych.york.ac.uk

Tortoise spatial learning 2
Abstract
A single individual of the species Geochelone carbonaria was trained in an
eight-arm radial maze, with the apparatus and general procedures modelled
on those used to demonstrate spatial learning in rats. The tortoise learned to
perform reliably above chance, preferentially choosing baited arms, rather
than returning to arms previously visited on a trial. Test sessions that
examined control by olfactory cues revealed that these did not affect
performance. No systematic, stereotyped response patterns were evident. In
spite of differences in brain structure, the tortoise showed spatial learning
abilities comparable to those observed in mammals.
Key words: tortoise, Geochelone carbonaria, spatial learning, radial maze

Tortoise spatial learning 3
Spatial Learning and Memory in the Tortoise (Geochelone carbonaria)
Nonavian reptiles, birds, and mammals all evolved from a common
amniotic ancestor and it is therefore possible that these classes share
common behavioral traits and capabilities. Equally, since the putative
common ancestor lived as long as 280 million years ago, there is ample time
for evolutionary paths to have diverged and for quite different capacities and
mechanisms to have evolved in the different classes. Certainly, brain
structures appear to differ in important respects Ð for example the forebrain of
the reptile, with its thin cortical layer is very different from the multilayered
structure seen in mammals.
The study of spatial learning in chelonia (turtles, terrapins, and
tortoises) has a long history (for a review see Burghardt, 1977). It started early
with Yerkes (1901), who demonstrated that the speckled turtle (Clemmys
guttata) could learn a multiunit maze Òwith surprising quicknessÓ (quoted by
Macphail, 1982), a result confirmed for the common wood turtle (Clemmys
insculpta) by Tinklepaugh (1932). Acquisition and reversal of a T-maze task
by the terrapin Chrysemys picta picta was demonstrated by Kirk and
Bitterman (1963), and the ability of this species to show serial reversal
improvement in a (slightly different) spatial task was confirmed by Holmes and
Bitterman (1966). What these various studies do not reveal is whether
chelonians are capable of forms of spatial learning shown by mammals. In
mammals, some forms of spatial learning are thought to be dependent on the
hippocampus (a structure that reptiles lack). It is possible, then, that the
chelonians learned the mazes using a system (e.g., by learning to make a

Tortoise spatial learning 4
given turn or sequence of turns) different from some more advanced,
hippocampally dependent, navigational system used by mammals.
This issue has been addressed directly in a series of experiments by
L—pez and his colleagues. L—pez et al. (2000), working with the terrapin
Pseudemys scripta, showed that this species could learn, in a T-maze, to
approach a given location in space regardless of which of the other two arms
they started from. The animals maintained this performance even when the
entire maze was rotated, so that the starting point was some quite novel
location. The ability appeared to depend on navigation by means of
extramaze (room) cues, in that it was disrupted by the introduction of shielding
curtains around the maze. L—pez et al. suggested that the turtles were using a
Òcognitive mapÓ of the sort postulated for mammals. They went on to show
that lesions of a forebrain area, the medial cortex, taken on anatomical
grounds to be a parallel of the mammalian hippocampus, disrupted
performance on these tasks (L—pez, Vargas, Gomez, & Salas, 2003).
The results just described encourage the view that chelonians (with an
intact medial cortex) should be capable of coping successfully with other tasks
that have been used to demonstrate the spatial learning abilities of mammals.
To this end we have studied the performance of a red-footed tortoise
(Geochelone carbonaria) in an eight-arm radial maze (Figure 1).
This species is a land-dwelling chelonian, unlike the semi-aquatic
terrapins that were tested in the experiments just described. Previous work
with the desert tortoise (Gopherus agassizii) by Fink (1954, cited by Burghardt
1977) has shown that the performance of this species on a spatial reversal
task is comparable to that of terrapins. However, its behavioural ecology is

Tortoise spatial learning 5
different from that of the red-footed tortoise; the latter species eats fallen fruit,
and flowers whereas the desert tortoise is largely a grass grazer. It is possible
that the differences in their foraging strategy may have more influence on their
performance than evolutionary proximity. The red-footed tortoise is a relatively
active species, and is capable of travelling up to 85 meters an hour
(Moskovits, 1985, cited by Strong & Fragoso 1987). This liveliness, in addition
to their foraging behavior makes this species an ideal subject for our study.
The radial arm maze was pioneered for use with rats by Olton and
Samuelson (1976) and consists of a central area from which eight arms
radiate. Food is available at the end of each arm. A well trained rat will visit
each arm to collect the food, and rarely return to arms that it has previously
visited, exhibiting an ability to discriminate among the various spatial
locations, and remember which places have been visited on a given trial. The
procedure provides an excellent test of an animalÕs spatial learning capacities
and its working memory. It can readily be adapted for use with many species
and provides a useful tool for making direct comparisons across species.
In the present experiment we examined the performance of a tortoise
in the radial maze asking, first, whether this animal could achieve efficient
performance. To anticipate, we found that he could. We then went on to
investigate the nature of the mechanisms responsible for its performance by
carrying out a series of tests designed to exclude the contribution of non-
spatial factors. We hoped to reveal the extent to which the tortoiseÕs behavior
is comparable to that of a mammal.

Tortoise spatial learning 6
Method
Subject
The subject (named Moses) was a male captive-bred red-footed
tortoise (Geochelone carbonaria). He was approximately 2 years old and his
plastron (the base of his shell) measured 7.5 x 6 cm at the start of the
experiment. He was experimentally na•ve. During the study Moses lived in a
tank in an office adjacent to the experimental room. The office was kept on a
daily 12L:12D cycle (light on: 0800-2000). The tank measured 61 x 30 x 30
cm and was maintained at 29oC (+/- 4oC); humidity within the tank was
maintained at 50%. The tortoise was given access to food (fruit and
vegetables) for 60 min each day, approximately 30 min after that dayÕs
experimental procedures had been completed.
Apparatus
The apparatus was an eight-arm radial maze made of opaque black
Perspex (see Figure 1). Each arm was 10 cm wide, 20 cm long, and the sides
and one end had walls 7 cm high. The arms radiated from a hexagonal central
platform, 24 cm across. Removable guillotine doors could be placed at the
junction between the arm and central platform. During the training and testing
phases a white plastic food cup, 3 cm in diameter and 1.5 cm high was placed
in a central position at the end of each arm. The maze was positioned on a
table in a small experimental room, that was lit by two 60-W ceiling lights and
maintained at approximately 27-29!C. External cues that were, in principle,
visible from within the maze, included shelving on which laboratory equipment
was stored (adjacent to arm 7 of the maze disposition shown on the left of
Figure 1), and a poster on the opposite wall (above arm 3). The wall adjacent

Tortoise spatial learning 7
to arm 1 contained a door, to the left of which (adjacent to arm 8), the
experimenter sat. The experimenter remained in the room for the entire
session. Two experimenters were involved in conducting experimental
sessions. Experimenter 1 observed the tortoise from the beginning of the
experiment up until midway through the training phase ÒAssessing the
influence of odor trailsÓ (see below). The second experimenter completed the
experiment.
Procedure
The experiment took approximately 5 months and was conducted from
25th January 2006 - 17th June 2006. Procedures took place in the afternoon,
as this was the time when Moses was most active. He was removed from his
tank and handled for approximately 5 min prior to experimentation. During this
time he was allowed to walk around the office space or the experimenterÕs
lap. This served to increase his activity level. He was then placed in a holding
cage and taken to the experimental room. On each day he received several
trials (detailed below), each separated from the next by an intertrial interval
(ITI), usually of 5 min, spent in the holding cage. The maze was wiped clean
at the end of each day but not between trials.
Familiarization to the maze. Extensive pretraining was needed in order
to ensure that the tortoise would locomote around, and eat readily in, the
maze. The procedures, which involved trial-and-error learning, as much on
the part of the experimenters as on the part of the tortoise, are detailed in
Table 1. By the end of this phase of pretraining the subject would, on most
occasions, visit all 8 arms within a 30-min trial, to obtain the reward (a small
piece of strawberry) that was visible at the end of each arm.

Tortoise spatial learning 8
Basic radial arm maze training. There were 12 daily sessions in the first
phase of training, each consisting of 4 trials. At the start of each trial Moses
was placed on the central platform, facing an arm selected at random. Each
arm of the maze contained a food cup baited with a piece of strawberry.
Choice of an arm was recorded whenever half of Moses had advanced into an
arm, so that half his shell was within the arm. This measure was used as
Moses rarely backed out of the maze once he had entered this far and we felt
that this measure was suitably conservative as to ensure all errors were
included in analysis. The trial ended when all eight rewards had been
consumed, or after 30 min. A record was kept of which arms were entered
and in what order.
Assessing the influence of food odor. This 2-day phase introduced test
trials designed to assess whether or not Moses was using odor cues from
food in the food cups to guide his behavior. Sessions were organised as
before, except that on trials 2 and 4, only four of the arms were baited. On trial
2 of the first test day and trial 4 of the second, these were arms 1, 3, 5, and 7;
on trial 4 of the first test day and trial 2 of the second they were arms 2, 4, 6,
and 8. If performance is guided by odor cues, we might expect Moses to show
a preference for the baited arms on these test trials.
Assessing the influence of odor trails: Training. During this phase,
which lasted 9 days, each trial was divided into two parts. In the first, four
arms (equally often the even- or odd-numbered arms) were blocked by the
guillotine doors, and Moses was allowed to take food from the food cups of all
four of the available arms. (A maximum of 30 min was allowed for this part of
the trial.) He was then removed from the maze and placed in the holding cage

Tortoise spatial learning 9
for 30 s. During this time the doors were removed, and the other four arms
were baited. Moses was then replaced in the maze and allowed to enter any
arm (although he only received reward when he entered an arm not visited
during the first part of the trial). The trial was terminated when all four rewards
had been eaten or after 60 min. The procedure of removing the tortoise and
then replacing him proved to be somewhat disruptive and on occasion Moses
failed to take all rewards in the time allowed. Over the course of the 9 days
Moses successfully obtained all the rewards on 17 of the 36 trials.
This procedure was introduced principally to provide a baseline against
which the effects of the test procedure, to be described next, could be
assessed. But it also allows the possibility of testing the animalÕs memory Ð
efficient performance in the second part of the test requires that information
acquired in the first part should survive the retention interval and the
disturbance it involved.
Assessing the influence of odor trails: Test. This test lasted 9 days and
consisted of four retraining days interspersed among which were 5 test days.
On retraining days the procedure was identical to that described above for the
odor trail training phase. Test trials were similar except that, when Moses was
removed from the maze having visited the four available arms, the maze was
rotated through 45 degrees (clockwise on half the trials, anticlockwise on the
rest) with the result that an arm not previously visited was now in the same
spatial location as one visited in the first part of the trial (see Figure 1). Food
was made available only in arms in spatial locations that had not previously
been visited (i.e., in order to perform efficiently Moses needed to return to
arms that he had traversed in the first part of the trial). This procedure allows

Tortoise spatial learning 10
us to test whether the tortoise had learned a strategy of avoiding arms that he
had previously visited, and had perhaps marked by means of some sort of
odor. (Such a strategy would result in poor performance in the rotated maze.)
This procedure also constitutes a test of the extent to which the animalÕs
behavior is controlled by extra-maze cues. We take up these matters in the
final Discussion.
Results
Basic radial arm maze behavior. In spite of the extensive
familiarization, the tortoiseÕs movement around the maze was often slow; on
15 of the 48 trials of the first training phase, the time limit was reached and
testing was terminated before the animal had made eight choices. Our
analysis will be confined to the remaining 33 trials, on each of which at least
eight choices were made. According to Olton (1978), the number of correct
responses in the first eight choices, to be expected on the basis of chance
performance, is 5.3. (A correct response is entering an arm that had not been
entered previously; chance performance is computed assuming that every
choice is made at random, without replacement). The mean number of correct
responses in the first eight choices of the 33 trials available for analysis was
5.88 (SEM = 0.16; range 4-8). A one-sample t test comparing this score
against chance expectation revealed a significant effect, t(32) = 3.59, p < .01.
To obtain a more detailed picture of MosesÕ performance we focused
our analysis on those trials on which he successfully visited all eight arms.
There were 18 such trials; the first occurred on day 2 of training and there was
at least one such trial on all succeeding days. Table 2 presents a full list of all
the choices made on these 18 trials. For each trial we calculated the

Tortoise spatial learning 11
probability that the task would be completed in the number of choices actually
made, on the assumption that choices were made at random and with
replacement. This probability is given in the far right column of the table. This
shows that, although accuracy of performance fluctuated substantially from
trial to trial, it was consistently at a level unlikely to be achieved on the basis
of chance. Particularly, good performance was as likely to be seen on early
trials as on later trials; that is, there was no indication of a gradual acquisition
process.
It is possible that Moses adopted stereotyped response patterns (e.g.,
a pattern of always turning into the next arm on the left would ensure perfect
performance). To examine this we scored each of the responses he made
after the first choice on each of the trials detailed in Table 3. There were 203
of these. Table 3 breaks these down into choices of arms that were 1, 2, or 3,
positions, either clockwise or anticlockwise, from the arm just left, and those
that were choices of the arm directly opposite. A strategy of a sort is
immediately apparent as on none of the trials did Moses reenter the arm that
he had just exited. Random choice among the remaining 7 possible turns
would result in 29 choices of each of these possibilities. Table 3 reveals a
tendency for choices of arms two positions away from that being exited to be
overrepresented, at the expense of choices of arms 3 positions away. A one-
sample chi-squared test on the scores presented in the table showed the
deviation from chance expectation to be significant, chi-squared = 18.96, df =
6, p > .01
Assessing the influence of food odor. This test was designed to assess
if MosesÕ performance was based on odor cues. If it were, we might expect

Tortoise spatial learning 12
him to choose preferentially those arms that were baited on the four test trials
of this phase on which four of the arms were left unbaited. Performance on
these test trials turned out to be very similar to that shown on the four
standard trials with which they were intermixed. Scoring a correct response as
choice of an arm not previously visited (whether it contained food or not)
showed that he made a mean of 6.25 (95% CI = +/-.49) correct responses in
the first eight choices on the standard trials, and a mean of 5.75 (95% CI = +/-
.49) on the test trials. Critically, correct choices on test trials were as likely to
be made by entering unbaited as by entering baited arms; of the total of 23
correct responses under consideration, 10 were to unbaited arms and 13 to
baited arms, chi-squared = 0.39, df = 1, p >.50.
Assessing the influence of odor trails: Training. In this phase of
training, the guillotine doors forced Moses to enter four of the arms before a
30-s interval; after this all eight arms were made available. Moses performed
rather poorly during the forced-choice trials of this procedure and on several
occasions failed to visit the four arms available during the 30 min allowed for
the first part of the trial. This seemed to be caused by the introduction of the
barriers which he spent a large amount time trying to push, a pattern of
behavior that became more pronounced as training proceeded. This behavior
is commonly observed in tortoises. If barriers either have visible gaps or move
when pushed, tortoises spend a great deal of time trying to get through.
These trials were abandoned and were excluded from the analysis. We
analyzed the 17 trials in this phase on which Moses succeeded in visiting all
eight arms. On these trials the first four baits were collected efficiently (the
mean number of choices required was 5.88). When returned to the maze after

Tortoise spatial learning 13
the interval he took a mean of 9.59 (range 5Ð15; see Table 4) choices to
collect the remaining four baits. For comparison we looked at the number of
trials taken to obtain the final four baits on the 18 trials of phase-1 training on
which this was achieved (see above). In this latter case the mean number of
trials required was 7.78. These scores differed significantly, t(33) = 2.07, p <
.05.
Evidently performance was rather poor on these trials, but despite
performance being disrupted, it did not decline to a level that might be
expected on the basis of random choice. Table 4 shows the number of
choices required to visit the remaining four arms on each trial of this stage
and, for each such trial, the probability that the task would be completed in the
number of choices actually made, on the assumption that choices were made
at random and with replacement.
Assessing the influence of odor trails: Testing. In this final test the
maze was rotated after the retention interval so that arms that had previously
been visited were now in spatial locations that had not previously been visited.
The score is the number of trials taken, after the retention interval, to visit the
four unvisited spatial locations. The scores were 11, 9, 7, and 15 trials, with a
mean of 10.50. This is not markedly worse than that (9.59) reported for the
second training phase. Had his performance in that phase been based on the
avoidance of the odor of a previously visited arm we would have expected a
total disruption in performance.
Discussion
Basic radial arm maze behavior. In spite of the extensive
familiarization, the tortoiseÕs movement around the maze was often slow.

Tortoise spatial learning 14
Accuracy of performance fluctuated substantially from trial to trial; it was,
however, consistently at a level unlikely to be achieved on the basis of
chance. There was no indication of a gradual acquisition process. This is
perhaps not surprising. Although the food was visible during the extensive
familiarization phase, the general procedures used in that phase matched
those used in the basic radial arm maze training. The results of the
familiarization phase revealed a sharp learning curve. It is possible then that,
during pretraining, Moses acquired strategies that he could then use in the
training phase. This would allow the immediate above-chance performance
that we observed, even when the food was hidden from view by the food
cups.
The rest of the study was intended to elucidate the nature of the
strategies involved in MosesÕ performance. One possibility was that Moses
adopted stereotyped response patterns (e.g., a pattern of always turning into
the next arm on the left would ensure perfect performance). As we have
noted, our analysis showed that on none of the trials did Moses reenter the
arm that he had just exited. The analysis also revealed a tendency for choice
of arms two positions away from that being exited; rats show a similar pattern
(Olton, Collison, & Wertz, 1977). The factors controlling this behavior in rats
were investigated by Yoerg & Kamil (1982), who manipulated the size of the
central platform of a radial arm maze. They found that this had no effect on
the accuracy of performance, but the use of adjacent arms significantly
increased with a larger platform. They suggested that this could be due to the
increased cost of choosing a nonadjacent arm. However, it is possible (as
they acknowledged) that the sharp angles of adjacent arms in a small maze

Tortoise spatial learning 15
make it hard to negotiate and make it easier to choose a non-adjacent arm in
such a maze. Both of these hypotheses could account for our tortoiseÕs arm
choice behavior. No other simple response patterns were discerned.
Assessing the influence of food odor. If MosesÕ performance was
based on odor cues from the food we might expect him to preferentially
choose those arms that were baited on the test trials over those that were left
unbaited. Performance on these test trials turned out to be similar to that
shown on the four standard trials with which they were intermixed. There is no
evidence, therefore, of control by food odor.
Assessing the influence of odor trails: Training. This phase of training
was conducted in preparation for testing whether Moses learned to avoid his
own odor trails. It also allowed examination of the extent to which information
acquired in the first part of the trial survived the interval (and the disruption
consequent on removal from and return to the maze). Performance on this
part of the task was compared with that of the last four arms of the basic
radial arm maze training. There was some disruption following the retention
interval, however it did not decline to a level that might be expected on the
basis of random choice. This suggests that performance in the second part of
the trial was controlled, to some extent, by memory of the first part of the trial.
Assessing the influence of odor trails: Testing. In this final test the
maze was rotated after the retention interval so that arms that had previously
been visited were now in spatial locations that had not previously been visited.
MosesÕ performance was not markedly worse than that reported for the
training phase. Had his performance in this phase been based on the
avoidance of the odor of a previously visited arm, rotation of the maze (which

Tortoise spatial learning 16
required the animal to return to a location previously visited) would have
produced a total disruption. We tentatively conclude, therefore, that his
performance is based, at least in part, on information about the spatial
location of the maze arms.
Conclusions. The study of a single individual cannot tell us what is
generally true of some larger grouping (such as reptiles, or chelonians, or
members of the species Geochelone carbonaria). It does, however, set some
limits on assertions about what that group is or is not capable of. Our study
allows the conclusion that a tortoise is capable of showing fairly efficient
performance in a radial maze. Its performance is less efficient than that of rats
(see Olton & Samuelson, 1976) (for whatever reason Ð this may reflect an
inadequacy in our procedure rather than a lack of capacity in the animal), but
it is, none the less, above the level to be expected on the basis of chance. As
is true for rats, the performance of the tortoise does not appear to depend on
the acquisition of stereotyped response strategies; nor is it controlled by odor
cues or the following (or avoidance) of odor trails. As for the rats, the evidence
points to an ability to learn about spatial locations, to remember which have
been visited, and to adopt a strategy of going to those that have not been
visited previously (or of avoiding those that have). Exactly what cues control
this ability remains to be determined. It is tempting to suppose that the tortoise
identifies spatial locations by the configuration of extramaze cues that define
them. Direct support for this proposal requires studies in which the
relationship of the maze arms to the extramaze cue is explicitly manipulated.
We can further conclude that hippocampal formation of the mammalian
brain is not essential for adequate performance on this sort of spatial task.

Tortoise spatial learning 17
This may mean that some quite different brain structure is capable of carrying
out the same functions, but perhaps by way of quite a different mechanism.
Alternatively it may be taken to support the view that the reptilian medial
cortex is functionally equivalent, even analogous, to the mammalian
hippocampus. In the latter case, further studies could reveal the operation of
similar mechanisms in reptiles and mammals.
In summarising his study, Tinklepaugh (1932) wrote as follows: ÒThis
report on the maze running of a single turtle is made not because this lowly
subject learned the maze, but rather because of the nature of its behavior
during the processÉÓ (p. 201). The same holds for our report. Tinklepaugh
went on to say: ÒIn my estimation, the learning of the turtle equalled the
expected accomplishment of a rat in the same maze ÉÓ (p.206). We would
not want to make the same claim for our own subject; we have already noted
ways in which his performance fell short of what might be expected of a rat
trained in the same maze. But we would want to say that his performance was
not fundamentally different from that of the rat Ð that any difference appears to
be quantitative rather than qualitative. His movements around the maze may
have been slow, but satisfactory learning was ultimately achieved. To that
extent we can endorse the conclusion reached by Tinklepaugh, that ÒÉthe
physical sluggishness and awkwardness of the turtle may have earned him an
undeserved reputation for stupidityÓ (p. 206).

Tortoise spatial learning 18
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(2000). Place and cue learning in turtles. Animal Learning & Behavior, 28,
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Strong, J.N., & Fragoso, J.M.V. (2006). Seed dispersal by Geochelone
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Tortoise spatial learning 20
Author Note
Anna Wilkinson, Hui-Minn Chan, and Geoffrey Hall, Department of
Psychology, University of York, York, United Kingdom. We thank J. Thijssen,
R. Gillett, K. Kirkpatrick and S. Franklin for statistical advice and assistance,
and Tiffany Galtress for her help in caring for the tortoise.
Correspondence concerning this article should be addressed to Anna
Wilkinson, Department of Psychology, University of York, York, YO10 5DD,
UK. E-mail: a.wilkinson@psych.york.ac.uk.

Tortoise spatial learning 21
Table 1
Overview of the experimental procedure
Procedure
Description
Criteria
ITI
Total no.
days
Total no.
trials
No.
trials/day
Familiarization
1
1 arm open. Tortoise placed in the center;
needs to enter the arm to get food.*
5 min or
completion
1 min
4
52
4-16
Familiarization
1a
No arms open. Dandelion and strawberry
placed in central platform.
30 min or all
food eaten
5 min
3
28
2-14
Familiarization
1
1 arm open. Tortoise placed in the center;
needs to enter the arm to get food.
15 min or
completion
1 min
13
145
8-48
Familiarization
2
All arms open. Food visibly available at the
end of each arm.
30 min or
completion
5 min
15
60
4
Familiarization
3
All arms open. Food available, but hidden in
cups at the end of each arm. Tortoise
allowed to accustom himself to eating from
food cups.
30 min or
completion
5 min
1
4
4
Basic RAM
training
All arms open. Food available, but hidden in
cups at the end of each arm.
30 min or
completion
5 min
12
48
4
Food Odor Test
All arms open. Food available in four of the
arms. Intermixed with normal training trials.
30 min or
completion
5 min
2
4 test
4 retraining
4
Odor Trails
Training
a: 4 arms open, other 4 arms blocked.
b: 30-s retention interval.
c: All arms open, food only available in the
arms not previously visited.
a: 30 min or
completion
c: 60 min or
completion
5 min
9
23
1-4
Odor Trails Test
a: 4 arms open, other 4 arms blocked.
b: 30-s retention interval during which the
maze is rotated by 45o.
c: All arms open; food only available in
unvisited arms spatially.
a:30 min or
completion
c: 60 min of
completion
5 min
9
5 test
4 retraining
1
Note. *After four days of training on this procedure, Moses was not eating
readily. Phase 1a was include to encourage him to eat in the maze; RAM:
Radial arm maze; ITI: Intertrial interval.

Tortoise spatial learning 22
Table 2
Sequence of choices in the 18 trials of the first phase of training on which all
arms were visited.
Day
Trial
Choices
No. choices to
completion
Probability
2
4
[2,5,4,7,1,2,1,8] 7,6,5,1,3
13
.139
3
3
[3,4,8,7,5,6,5,1] 7,5,8,2
12
.093
4
2
[1,6,8,6,8,6,8,7] 5,6,8,2,4,3
14
.192
5
2
[2,6,4,3,1,7,5,7] 8
9
.011
6
1
[2,4,5,8,3,7,1,2] 8,6
10
.028
6
2
[5,8,2,6,1,2,1,7] 4,5,8,7,6,3
14
.192
6
3
[4,5,2,8,6,3,7,1]
8
.002
6
4
[4,7,1,5,7,1,2,8] 6,3
10
.028
8
3
[5,1,8,2,8,6,7,3] 4
9
.011
8
4
[4,8,4,7,1,8,6,8] 2,1,8,5,6,1,3
15
.248
9
2
[7,8,6,7,1,2,8,3] 8,6,5,7,3,8,4
15
.248
9
3
[6,4,8,6,1,7,6,5] 1,2,6,8,6,3
14
.192
9
4
[6,5,3,7,6,8,7,8]1,8,7,8,4,1,7,5,2
17
.366
10
2
[3,1,3,8,2,6,7,1] 8,4,3,5
12
.093
10
3
[2,7,3,8,2,6,4,2] 4,5,3,8,1
13
.139
10
4
[4,8,3,5,7,6,4,2] 8,2,1
11
.056
11
4
[3,8,4,5,1,5,6,8] 2,5,6,8,7
13
.139
12
4
[4,7,6,7,8,2,1,3] 8,1,3,5
12
.093

Tortoise spatial learning 23
Note. The numbers in the Choices column refer to the arms of the radial
maze. The first eight choices made are enclosed in square brackets. Choices
in bold indicate errors (returning to an arm already visited). The probability
given for each trial is that associated with the number of choices to completion
assuming that every choice is made at random, with replacement of choices
already made.

Tortoise spatial learning 24
Table 3
Classification of type of turn for choices made in the 18 trials of the first phase
of training on which all arms were visited.
Type of turn
Number
Percentage of total
1 arm anticlockwise
30
14.8
2 arms anticlockwise
42
20.7
3 arms anticlockwise
15
7.4
1 arm clockwise
33
16.3
2 arms clockwise
37
18.2
3 arms clockwise
19
9.4
Opposite
27
13.3

Tortoise spatial learning 25
Table 4
Number of choices required to complete the task for the 17 trials of the
second phase of training on which this was achieved.
Day
Trial
No. choices to
completion
Probability
1
2
9
.192
1
3
7
.089
1
4
8
.137
2
2
9
.192
2
3
5
.022
2
4
10
.250
3
1
13
.429
3
2
15
.539
3
4
9
.192
4
1
11
.310
4
3
14
.485
4
4
13
.429
5
2
11
.310
6
1
10
.250
7
2
5
.022
8
1
11
.310
9
1
5
.022

Tortoise spatial learning 26
Note. In this phase of training the subject had received forced trials with four
of the maze arms; choices to completion refers to the number of choices
required to visit the remaining four arms when all eight were made available.
The probability given for each trial is that associated with the number of
choices to completion assuming that every choice is made at random, with
replacement of choices already made.

Tortoise spatial learning 27
Figure Caption
Figure 1. Layout of the maze in the two phases of a trial when testing the
influence of odor paths. Before the turn, guillotine doors blocked access to
four of the arms, allowing access to food only in the other four (those
numbered 1, 3, 5, and 7 in this example). After rotation of the maze the doors
were removed and food was available again only in arms 1, 3, 5, and 7. The
tortoise was therefore required to enter same arms as had been visited
before, these now being in different spatial locations.

Tortoise spatial learning 28
Figure 1
5
6
7
8
1
2
3
4
Before the turn
After the turn
4
5
6
7
8
1
2
3