Psicológica (2018), 39, 25-40.

doi: 10.2478/psicolj-2018-0002

Extinction of the initial within-compound association

established in a blocked preexposure to two compound
flavours
Fernando Cabo*, José M. Caramés, Julián Almaraz & Alfredo Espinet

Universidad de Málaga (Spain)

Extinction of the A↔X association after blocked preexposure to AX-BX was

studied in two experiments. In Experiment 1, two groups of rats received long
(14 trials) or short (4 trials) blocked preexposure to AX-BX and subsequent
conditioning of X. The results showed that the AX association was equally
preserved after long and short preexposure. Experiment 2 studied the effect
of blocked preexposure to 0, 1 or 2 ruptures of the AX association on
extinction. In this experiment a "rupture" is produced when, in subsequent
blocks, one element of the original compound is presented in compound with
a different element. A significant extinction was observed only when the AX
association was broken twice

Perceptual learning improves discrimination between two confusable

stimuli AX and BX as a consequence of mere exposure to the stimuli. In the
field of animal learning, the ability to discriminate between AX and BX is
measured by means of generalization tests that require the use of
conditioning. For instance, when AX and BX are two compound flavours, an
aversion is conditioned to AX and the subsequent acceptance or reluctance to
drink BX indicates the level of discrimination of the animal: The greater the
acceptance of BX, the better the discrimination. In experiments on perceptual
learning with animal subjects it is usual to compare the performance of two
groups of subjects that receive the same amount of preexposure to AX and
BX “intermixed”, alternating presentations of the stimuli (AX, BX, AX, BX,
... AX, BX) or "blocked”, in which the stimuli are presented in blocks (AX,
AX, AX, ... BX, BX, BX). Subsequent conditioning of AX results in less
generalization to BX in the group that received intermixed preexposure (i.e.,

*
Acknowledgements: This research was supported by a grant from Junta de Andalucía
(P07HUM-03186). Corresponding author: Fernando Cabo. University of Málaga. Facultad
de Psicología, 29071, Málaga (Spain). Phone number: +34 952132980. E-mail:
fcabo@uma.es.

© 2018 (Cabo, Caramés, Almaraz & Espinet) This is an open access article licensed under the
Creative Commons Attribution-NonCommercial-NoDerivs License
(http://creativecommons.org/licenses/by-nc-nd/4.0/)
 26 F. Cabo, J.M. Caramés, J. Almaráz & A. Espinet

a perceptual learning effect). This phenomenon has come to be called the

"intermixed-blocked effect" (Honey, Bateson, & Horn, 1994).
In the last years, some experiments have provided evidence suggesting
that after blocked preexposure, the within-compound association stablished
in the first block would not be extinguished in the second block. In part, this
evidence comes from a group of experiments involving order effects, which
compare presentations of two blocks of stimuli in two possible orders. Hall
and Rodríguez (2009, Exp. 2) preexposed CX in a block before or after
intermixed preexposure to BX/X and found that the salience of C was reduced
in the subgroup of animals that received the CX trials after preexposure to
BX/X (i.e., BX/X-CX). This result was expected, given that associative
activation of a stimulus is the factor contributing to the preservation of its
salience (Hall, 2003) and when the CX trials come last, associative activation
of C is not possible. Most interesting was the finding that salience of C was
maintained in the subgroup given CX first during preexposure (CX-BX/X)
and this result was attributed to associative activation of C, via X, when X
was presented in the second block of preexposure. This mechanism could not
operate if the C↔X association established in the first block of preexposure
had been extinguished during the second block.
Espinet, Caramés and Chamizo (2011, Exp. 4) compared two groups
preexposed to AX-BX or to AX-BY. In the AX-BY group the A↔X
association could not be extinguished. Consumption of A after conditioning
of X was small and similar in both groups. This result led them to think that
the A↔X association was not fully extinguished in the AX-BX group after
preexposure. This conclusion does not fit with the salience mechanism
proposed by Hall (2003) to explain the differences between intermixed and
blocked preexposure to two compounds AX and BX. According to this
mechanism, repeated presentations of a stimulus produce a loss of its
salience. Associative activation of the stimuli can counteract this loss of
salience. This associative activation is possible when the stimuli are
preexposed in an intermixed schedule. Once the within-compound
associations A↔X and B↔X have been established in the first preexposure
trials, presentations of AX activate associatively, via X, the representation of
B and presentations of BX activate associatively, via X, the representation of
A and, hence, A and B both would maintain their salience. On the contrary,
in a blocked preexposure to AX-BX, the associative activation of B is not
possible and, following Hall (2003), the X↔A association should be
extinguished given that AX is not presented any more. The experimental
evidence supporting the basis for Hall's suggestion is unknown for us. Rather,
some experiments that compared the strength of the within-compound
 Extinction of within-compound flavour associations 27

associations resulting from intermixed and blocked preexposure have

provided evidence that these associations are stronger after blocked than
intermixed preexposure (Rodríguez & Alonso 2014, 2015).
The possibility that the initial within-compound association is not
extinguished after blocked preexposure has been recently tested by Espinet,
Caramés and Cabo (2015) by comparing the strength of the A↔X and B↔X
associations after blocked preexposure to the two possible sequences of
presentation of two compound flavours: AX-BX or BX-AX. The logic of this
comparison is based in the obvious assumption that the within-compound
association established in the second block of preexposure is not
extinguished. Therefore, in case that the association established in the first
preexposure block were extinguished along the second block, the strength of
the A↔X association should be smaller after preexposure to AX-BX than
after preexposure to BX-AX. It does not matter whether the AX compound
was presented in the first or in the second preexposure block, the results did
not reveal significant differences in the strength of the A↔X association.
The above-mentioned results support the conclusion that preexposure
to AX-BX does not result in extinction of the A↔X association. An indirect
test of this idea may be found in Rescorla and Freberg (1978) which studied
different methods of extinguishing within-compound flavour associations
and found that, after preexposure to a compound flavour AX, presenting A
or X isolated or in compound with a new flavour resulted in attenuation of
the strength of the A↔X within-compound association. Since in a blocked
preexposure to AX-BX, X is separated of A and is presented in compound
with a new stimulus B, perhaps some extinction of the A↔X association
should be observed. But Espinet et al. (2015) found that the associations
remained preserved. The differences between blocked preexposure to AX-
BX and the exposure sequences used by Rescorla and Freberg in their
experiments as well as the difficulty to establish a comparison between their
procedures and those used in the more recent experiments have been
highlighted previously (Espinet, et al. 2015). Nevertheless, it is possible to
study the influence of some variables that could influence the level of
extinction of the A↔X association established during preexposure to AX-
BX. One of these variables is the amount of preexposure to the compounds.
For instance, Espinet et al., (2011, 2015) gave their subjects long preexposure
to AX (14 trials) while Rescorla and Freberg used a short preexposure (4
trials). The small extinction observed in the experiments by Espinet et al.
(2015) in comparison with those of Rescorla and Freberg could be perhaps
due to the different number of trials employed in the preexposure phase, to
the extent that 14 presentations of AX could contribute to establish the A↔X
 28 F. Cabo, J.M. Caramés, J. Almaráz & A. Espinet

association more firmly than only 4 presentations. Therefore, Experiment 1

explored this possibility. Subsequently, Experiment 2 explored whether the
number of ruptures of the A-X association (by presenting each of these
flavours in compound with another flavour, e.g., B-X and AY) could produce
a significant extinction.

EXPERIMENT 1
This experiment was designed to evaluate whether the amount of
preexposure to AX-BX influences the level of extinction of the A↔X
association established in the first block. Two groups received blocked
preexposure to AX-BX. One of them received long preexposure (14
presentations) while the second group received short preexposure (4
presentations). A third group received long preexposure to AX-BY. After
preexposure, flavour X was paired with nausea and subsequent tests
evaluated the aversion to flavours A and B when they were associated to X.
If long preexposure to AX contributed to make the A↔X association more
resistant to extinction, it should be observed that consumption of A in the test
should be less in the group that received 14 presentations of AX-BX than in
the group that received only 4 presentations. On the other hand, the test with
flavour B provides an indicator of the strength of the B↔X association after
14 or 4 presentations of the BX compound. Given that the BX compound is
presented in the second block of preexposure, the B↔X association cannot
be extinguished and no differences in consumption of B should be observed
between the two groups that received the BX compound. In the group
receiving extensive blocked preexposure to AX-BY, the A↔X association
should be firmly established and should be very strong after the preexposure
phase, given that the presentations of BY during the second block can hardly
contribute to the extinction of the A↔X association. Therefore, in this group
there is no chance for extinction of the A↔X association, and consumption
of A in the test should be lower than in the other two groups, in which the
presentations of BX during the second block (where X is separated of A)
could produce extinction of the A↔X association. Besides, in the group
preexposed to AX-BY, consumption of B in the test should be higher than in
the other two groups where flavour B was associated to the conditioned
flavour X.
 Extinction of within-compound flavour associations 29

METHOD
Subjects and apparatus. Thirty experimentally naïve Wistar rats
provided by Harlan Ibérica with an average weight of 339 g at the beginning
of the experiment (range 281-432 g) were used for this experiment. A 2-week
adaptation period was carried out in this and the next experiment. During the
adaptation period the animals where housed in groups of four subjects in
makrolon cages (60 x 37 x 19 cm). Following the adaptation period, rats
were housed individually in 42 x 26 x 18 cm boxes with free access to food
and water. In this and the next experiment, rats were housed in a colony room
under constant temperature and humidity (22 ± 1 ºC and 60% respectively)
and a light-dark cycle (08:30-21:30).
Three flavoured stimuli were prepared with tap water and chemically
pure products provided by Probus or Merck laboratories: 0.3% (w/v) citric
acid; 0.15% (w/v) saccharin, and 0.5% (w/v) sodium chloride. A fourth
flavour was made from 9% of orange blossom essence (Vahiné-Ducros S. A).
Two compound solutions, saccharin-acid and salt-acid, were made with these
flavours maintaining the above-mentioned individual concentrations of each
substance. Citric acid served as flavour X and orange-blossom served as
flavour Y, while saccharin and salt were counterbalanced as flavours A and
B. The compounds were presented to animals in 100 ml plastic bottles fitted
with metal spouts. Consumption was measured by weighing the bottles
before and after each session. At the beginning of each session, each bottle
contained at least 70 ml of solution. Intraperitoneal injections of 0.3M LiCl
at 10 ml/kg of body weight were used for the conditioning trials and were
administered in an experimental room adjacent to the colony room.

Procedure. The day previous to the first session, water bottles were
removed at 9:00 pm. Throughout all the phases of this and the next
experiments the rats had access to fluid for 15 min in each of four daily
sessions starting at 9.00; 13.00; 17.00 and 21.00 hours.
The design of the experiment is shown in Table 1. The first 14 sessions
of preexposure constituted the first preexposure block. In these sessions 10
animals received the saccharin-acid compound and 10 received the salt-acid
compound. Once concluded the first block, these rats were assigned to group
14AX-BX and group 14AX-BY, matched on their consumption during the
first block, following the condition that for half of the subjects in each group
the compound AX was saccharin-acid and for the other half AX was salt-
acid. The following 14 sessions constituted the second block of preexposure.
Each subject in the 14AX-BX group received the compound that had not
received on the previous block, while subjects of the group 14AX-BY
 30 F. Cabo, J.M. Caramés, J. Almaráz & A. Espinet

received a compound made of orange blossom and the flavour (saccharin or

salt) that they had not received on the previous block. The remaining 10
animals were assigned to group 4AX-BX and received water during the first
20 sessions of preexposure. In sessions 21-24 half of the animals in the group
4AX-BX received the saccharin-acid compound and the other half received
the salt-acid compound. Subsequently, during sessions 25-28, each animal in
the group 4AX-BX received the compound that was not presented in the
previous sessions. After preexposure all the rats received the experimental
treatments at 09:00 and drank water in the three remaining daily sessions.
The four days after preexposure constituted the conditioning phase. On days
1 and 3 of this phase each rat received the flavour X (citric acid) followed by
an injection of LiCl. The days 2 and 4 of this phase were recovery days and
all the rats drank water in the four daily sessions. The last three days of the
experiment constituted the test phase. The first test day, half of the animals
in each group received flavour A and the other half received flavour B. The
second day, each animal had access to the flavour (A or B) that was not
presented the day before. The third day the animals received a test of
consumption of flavour X.

Table 1. Experimental Designs

Experiment Groups Preexposure Conditioning Test

1 AX-BX 14 AX-BX X+ A, B
AX-BY 14 AX-BY X+ A, B
AX-BX 4 AX-BX X+ A, B

2 AX-BX-AY 4 AX-BX-AY X+ A, B
AX-BX-Y 4 AX-BX-Y X+ A, B
AX-BY-Y 4 AX-BY-Y X+ A, B
Note. A, B, X, and Y, refer to different flavour stimuli. A and B were saccharin and sodium
chloride (counterbalanced in preexposure phase and tests), X and Y were citric acid and
orange blossom respectively. The numbers refer to the amount of preexposure trials. Stimuli
were presented in blocks, which appear separated by a dash (-). The + sign indicates
conditioning with LiCl injections.

RESULTS AND DISCUSSION

In this and in the next experiment, a signification level of p < .05 was
adopted. Mean consumptions of the AX flavour in each session of the
 Extinction of within-compound flavour associations 31

preexposure phase were 5.06 g (SEM 0.56), 5.15 g (SEM 0.65) and 4.93 g
(SEM 0.48) for groups 14AX-BX, 14AX-BY and 4AX-BX, respectively. An
one-way ANOVA revealed that the differences among groups were not
statistically significant [F(2, 29) = 0.038, p > 0.05]. Mean consumption per
session of the BX flavour for groups 14AX-BX and 4AX-BX were 5.8 g
(SEM 0.29) and 5.21 g (SEM 0.24) while group 14AX-BY consumed 6.05 g
of the BY flavour (SEM 0.25). An one-way ANOVA did not reveal
statistically significant differences among-groups [F(2, 29) = 2.65, p > 0.05].
Conditioning successfully established an aversion to X in the three
groups. Throughout the conditioning phase the mean amount of flavour X
consumed by rats of groups 14AX-BX, 14AX-BY and 4AX-BX were,
respectively, 4.3 g (SEM = 0.66), 4.4 g (SEM = 0.71) and 3.9 g (SEM = 0.22)
in the first conditioning trial; 1.5 g (SEM = 0.49), 2.8 g (SEM = 0.65) and 1.8
g (SEM = 0.57) in the second conditioning trial; and 1.0 g (SEM = 0.43), 0.7
g (SEM = 0.08), and 0.5 g (SEM = 0.15) in the final test. A mixed 3 (Group)
x 3 (Trial) ANOVA found a significant main effect of trial, F(2, 54) = 49.2,
p = 0.000, η2p = 0.64. The main effect of group was not significant F(2, 27) =
1.2 , p = 0.29, η2p = 0.08, neither were significant the group x trial interaction
F(4, 54) = 2.1 , p = 0.09, η2p = 0.13.

10
14AX-BX
9
14AX-BY
8
Mean consumption (g)

4AX-BX
7
6
5
4
3
2
1
0
Test A Test B
Figure 1. Mean consumption of flavours A and B in the test phase of Experiment 1.
After the different types of blocked preexposure to the compounds represented in the
group names, flavour X was paired with nausea before this test. Vertical bars represent
standard error of the means.

Figure 1 shows the mean amounts of A (left) and B (right) consumed

by each group in the test phase. As it can be seen on the left part of the figure,
consumption of A was low and similar across groups. The right part of the
 32 F. Cabo, J.M. Caramés, J. Almaráz & A. Espinet

figure shows that the highest consumption of B corresponded to group 14AX-

BY and that the intake of B was similarly lower in groups 14AX-BX and
4AX-BX.
A mixed 3 (Group) x 2 (Test, A or B) ANOVA did not reveal
significant main effects of group or test (Fmax = 3.29) but the interaction of
group x test was statistically significant [F(2, 27) = 5.05, p < 0.05, η2p = 0.27].
Further analyses of this interaction by means of analysing the simple effect
of Group at each level of test found that the groups did not differ significantly
in their consumption of flavour A [F(2, 27) = 0.34, p = 0.71] but they did
differed significantly in their consumption of flavour B [F(2, 27) = 8.076, p
< 0.05]. Duncan’s post-hoc test confirmed that group 14AX-BY consumed
an amount of B significantly higher than that consumed by group 14AX-BX
(Cohen’s d = 1.1) and the group 4AX-BX (Cohen’s d = 1.8). These last two
groups did not differ significantly from each other (Cohen’s d = 0.7).
The results of this experiment are quite clear. The A↔X association
established in the first block remains equally preserved after long or short
preexposure to AX-BX. The comparison of the amounts of flavour A
consumed by these groups did not differ significantly from the amount of A
consumed by the group 14AX-BY where the initial A↔X association should
be very strong, given that presentations of BY could not contribute to the
extinction of this association. The lack of differences between the groups
14AX-BX and 4AX-BX not only in consumption of A but also in
consumption of B is not surprising given that the most of the experiments on
perceptual learning using rats and flavoured stimuli have found that four
presentations of the compound are enough to establish a strong within-
compound association. More interesting, these results show that presenting
BX 14 times in the second block was not enough to attenuate significantly
the strength of the initial A↔X association.
Perhaps this should not be surprising taking into account that Rescorla
and Freberg (Exp. 1) did not observe extinction of the initial A↔X
association after only four AX presentations followed by six presentations of
X or A isolated. In fact, Rescorla and Freberg (1978) only observed extinction
of the initial A↔X association when in their Experiment 2 a three-stage
preexposure sequence to AX-BX-AY was used. Note that with this sequence,
the A↔X association established in the first block is broken twice; in the
second block, when X is presented separated from A (in compound with B)
and in the third block, when A is presented separated from X (in compound
with Y). In a blocked preexposure to AX-BX the A↔X association
established in the first block is broken only once: when in the second block
X is presented separated from A (in compound with B). Given that, as
 Extinction of within-compound flavour associations 33

Rescorla and Freberg (1978) concluded, presentations of A or X isolated or

in compound with another flavour attenuated the initial A↔X association,
two ruptures of the A↔X association should produce more extinction of this
association than only one rupture.

EXPERIMENT 2
Rescorla and Freberg (1978, Exp. 2) exposed their subjects to AX-BX-
AY. In this experiment, two "ruptures" of the A↔X association were
produced when in subsequent blocks, the flavours A or X were presented in
compound with a different flavour (for instance BX or AY). After these two
ruptures, the A↔X association was clearly extinguished.
To test if the number of ruptures of the initial A↔X association was a
factor influencing the level of extinction of this association, our second
experiment compared three groups of rats that received three blocks of
preexposure. In the first block, all the animals received AX presentations. In
the following blocks the A↔X association was broken twice (group AX-
BX-AY), only once (group AX-BX-Y) or never (group AX-BY-Y). After
preexposure, an aversion was conditioned to X and subsequent tests
measured the reluctance to drink flavours A or B. If the number of ruptures
of the initial A↔X association determines the amount of extinction,
consumption of A should be the lowest in the AX-BY-Y group where the
initial A↔X association was not broken, greater in the AX-BX-AY group
where the initial association was broken once, and should be the largest in the
AX-BX-AY group where the initial association was broken twice.

METHOD
Subjects and apparatus. Thirty experimentally naïve Wistar rats
provided by Harlan Ibérica were used for this experiment, with an average
weight of 271 g at the beginning of the experiment (range 224-330 g). The
individual flavours, compound solutions, and the concentration and doses of
LiCl were identical to those used in Experiment 1.
Procedure. The design of the experiment is shown in Table 1. The
adaptation period and the schedules for the drinking sessions were the same
as those described in the previous experiment. The solutions were presented
in three blocks of four sessions each. Preexposure lasted three days. Each
block consisted of four 15-min sessions and took place in one day. In the first
block half of the animals received the saccharin-acid compound and the other
half received the salt-acid compound. They were then orthogonally assigned
 34 F. Cabo, J.M. Caramés, J. Almaráz & A. Espinet

to three groups AX-BX-AY, AX-BX-Y and AX-BY-Y matched on the

amount of liquid consumed during the first block. Flavours A and B were
counterbalanced in such a way that half of the subjects in each group received
saccharin as flavour A and the other half received saccharin as flavour B.
During the second block each animal in the groups AX-BX-AY and AX-BX-
Y received the compound (saccharin-acid or salt-acid) that was not presented
in the previous block while half of the animals in group AX-BY-Y received
a compound of saccharin and orange blossom and the other half received a
compound of salt and orange blossom. During the third block animals in
groups AX-BX-Y and AX-BY-Y received the orange-blossom flavour while
half of the animals in group AX-BX-AY received the saccharin-orange
blossom compound and the other half received the salt-orange blossom
compound, following the condition that saccharin or salt had been presented
as A on the first block. Conditioning of X and the test phase followed the
same procedure described in the previous experiment.

RESULTS AND DISCUSSION

Mean consumptions per session of the AX flavour during the
preexposure phase were 5.4 g (SEM 0.40), 5.5 g (SEM 0.46) and 5.4 g (SEM
0.41) for groups AX-BX-AY, AX-BX-Y and AX-BY-Y, respectively. These
amounts did not differ significantly: F(2, 29) = 0.004 , p = 0.99. The mean
consumed amount of the BX compound during each session of the second
block by groups AX-BX-AY and AX-BX-Y was, respectively, 5.6 g (SEM =
0.43) and 5.0 g (SEM = 0.46) and did not differ significantly t(18) = 0.94 , p
= 0.36. The mean amounts per session of Y consumed by the groups AX-BX-
Y and AX-BY-Y during the third block of preexposure were 6.9 g (SEM =
0.56) and 7.3 g (SEM = 0.60) respectively. These differences were not
significant t(18) = 0.56 , p = 0.57.
Conditioning successfully established an aversion to X in the three
groups. Throughout the conditioning phase the mean amount of X consumed
by subjects in groups AX-BX-AY, AX-BX-Y and AX-BY-Y was,
respectively, 4.5 g (SEM = 0.82), 4.6 g (SEM = 0.58) and 4.9 g (SEM = 0.53)
in the first conditioning trial; 1.6 g (SEM = 0.34), 1.7 g (SEM = 0.42) and 2.3
g (SEM = 0.42) in the second conditioning trial; and 0.9 g (SEM = 0.20), 0.8
g (SEM = 0.10), and 1.1 g (SEM = 0.18) in the final test. A mixed 3 (Group)
x 3 (Trial) ANOVA revealed a significant main effect of trial, F(2, 54) = 62.2,
 Extinction of within-compound flavour associations 35

p = 0.000, η2p = 0.69. The main effect of group was not significant F(2, 27) =
0.81 , p = 0.45, η2p = 0.09, neither it was the group x trial interaction F(4, 54)
= 0.07 , p = 0.98, η2p = 0.05.
Figure 2. Mean consumption of flavours A and B in the test phase of

AX-BX-Y
AX-BX-AY
10
AX-BY-Y
9
Mean consumption (g)

8
7
6
5
4
3
2
1
0
Test A Test B

Experiment 2. After the different types blocked preexposure to the

compounds represented in the group names, flavour X was paired with
nausea before the test. Vertical bars represent standard error of the
means.

Figure 2 shows the amount of A (left) and B (right) consumed by each

group of rats during the tests. As it can be appreciated, consumption of A was
high in group AX-BX-AY while the other groups consumed similar and low
amounts of this flavour. The highest consumption of B corresponded to the
group AX-BY-Y while the other groups consumed small and almost identical
amounts of this flavour. A mixed 3 (Group) x 2 (Test A or B) ANOVA
revealed a significant group x test interaction [F(2, 27) = 6.162, p < 0.01, η2𝑝
= 0.31]. No main effect was significant (Fmax = 1.227). Separate ANOVAs
explored the group x test interaction revealing that groups differed
significantly in their consumptions of A [F(2, 29) = 4.49, p < 0.05] and B [
F(2, 29) = 8.05, p < 0.01]. Duncan’s post-hoc tests revealed that consumption
 36 F. Cabo, J.M. Caramés, J. Almaráz & A. Espinet

of A was significantly higher in the AX-BX-AY group than in groups AX-

BX-Y (Cohen’s d = .94) and AX-BY-Y (Cohen’s d = 1.7) and that these last
two groups did not differ significantly from each other. Duncan’s post-hoc
test also confirmed that group AX-BY-Y consumed an amount of B
significantly higher than that consumed by groups AX-BX-AY (Cohen’s d =
1.4) and AX-BX-Y (Cohen’s d = 2.0) which did not differ significantly from
each other (Cohen’s d = 0.2).
These results show that only one rupture of the A↔X association does
not produce a significant extinction of the association while two ruptures did
produce the extinction of this association. The A↔X association was not
broken in the AX-BY-Y group and, hence, could not be extinguished. This
explains the low consumption of A in this group. Consumption of A was
slightly higher in the AX-BX-Y group where the A↔X association was
broken once. Nevertheless, the groups AX-BX-Y and AX-BY-Y did not
differ significantly in their consumptions of A and, hence, it must be
concluded that the A↔X association was not extinguished in the AX-BX-Y
group. Given that presentations of Y in the third block are unlikely to produce
extinction of the A↔X association, the lack of extinction found in group
AX-BX-Y can be considered comparable to that found by Espinet et al. after
blocked preexposure to AX-BX and, hence, is not surprising. The absence of
extinction in group AX-BX-Y is also supported by the fact that consumption
of A in this group does not significantly differ from consumption of B in the
groups that received BX in the second block. In these groups the B↔X
association was not extinguished and consumption of B in these groups may
be used as an indicator of the amount of fluid drank by the animals when the
association of this fluid with X was not extinguished. Consumption of A in
the AX-BX-AY group reveals an extinction of the A↔X association after
two ruptures. This affirmation is based in the fact that consumption of A in
group AX-BX-AY is almost identical to consumption of B in group AX-BY-
Y. Given that in this last group B was not associated to X, the large
consumption of B is not surprising and this consumption can be taken as an
indicator of the amount of fluid that the animals drank when they were not
reluctant to drink. The fact that the amount of B consumed by the AX-BY-Y
group was similar to the amount of A consumed by the AX-BX-AY group
indicates that animals in this last group were not reluctant to drink A and,
therefore, it can be concluded that the A↔X association was fully
extinguished in this group, as well as it happened in the AX-BX-AY group
of Rescorla and Freberg (1978).
 Extinction of within-compound flavour associations 37

DISCUSSION
The results of the two experiments presented here show that blocked
preexposure to AX-BX, does not produce a significant extinction of the initial
A↔X association, regardless of the length of the exposure (Exp. 1), and also
that the two ruptures of this association produced by the addition of a third
block of exposure (i.e., AX-BX-AY) result in extinction of the A↔X
association (Exp.2).
In spite of some procedural differences, the latest result coincides with
those obtained by Rescorla and Freberg (1978, Exp. 2). The absence of a
significant extinction of the A↔X association observed after preexposure to
AX-BX in the two experiments presented here does not fit with the salience
modulation account proposed by Hall (2003) which predicts that, in a blocked
preexposure to AX-BX, the absence of presentations of the AX compound
during the second block will produce the extinction of the A↔X association.
Whatever the basis for this proposal, one might wonder if the results of
Rescorla and Freberg (1978) constitute a basis for expecting the extinction of
the A↔X association when blocked preexposure is limited to two blocks
(i.e., AX-BX). We suggest that the answer to this question is no. Rather, the
evidence provided by some recent experiments and the experiments reported
here, leads to two conclusions: First, that preexposure to AX-X or to AX-A
does not produce a significant extinction of the A↔X association and,
second, that blocked preexposure to AX-BX does not result in a extinction of
the A↔X association.
The first conclusion is based on the results obtained by Rescorla and
Freberg (1978) and, those recently reported by Rodríguez and Alonso (2014,
2015). Rescorla and Freberg (1978, Exp. 1) found that isolated presentations
of A or X in the second block of preexposure (i.e., preexposure to AX-A or
AX-X) produced only a certain amount of extinction after the addition of an
extra-phase of X or A alone presentations. Therefore, preexposure to AX-A
or to AX-X (i.e., only one rupture of the A↔X association) does not seem
to be enough as to produce extinction. This statement receives recent support
from the experiments of Rodríguez and Alonso (2014) who preexposed AX
and X intermixed (AX/X) or in the two possible orders of blocked exposure
(AX-X or X-AX). The results showed that the A↔X association was better
preserved in the blocked than in the intermixed group and, what is more
important, the strength of the A↔X association in the AX-X group did not
differ significantly from that corresponding to the X-AX group, in which the
A↔X association could not be extinguished, given that AX presentations
took place in the last preexposure block.
 38 F. Cabo, J.M. Caramés, J. Almaráz & A. Espinet

The second conclusion, that there is no significant extinction of the

A↔X association after blocked preexposure to AX-BX comes from
Rodríguez and Alonso (2015, Exp. 1). They preexposed two groups of rats to
AX, BX, and X. One of the groups received first intermixed presentations of
AX and X, followed by a block of presentations of BX (i.e., AX/X-BX). The
second group received first the presentations of BX and later the
presentations of AX and X (i.e., BX-AX/X). X was highly concentrated
sucrose solution, and the tests consisted of consumption of A and B under a
hunger state. The greater the consumption of A or B, stronger should be the
association of A or B with X. The results suggested that the BX association
was better maintained than the AX association in both groups. The B↔X
association could not be extinguished in the A/X-BX group, where the BX
compound was presented in the last block. Some extinction of the B↔X
association should be observed after preexposure to BX-AX/X given that
preexposure in this group combines preexposure to BX-AX and preexposure
to BX-X, and these are precisely the two ways used by Rescorla and Freberg
(1978) to produce extinction of the within-compound associations. However,
contrarily to what it might be expected, the results showed that consumption
of B, although lower in the BX-AX/X group, did not differ significantly from
that of the AX/A-BX group in which there is no reason to expect the
extinction of the B↔X association. It can be argued that in Rescorla and
Freberg (1978, Exp. 1) the isolated presentations of A or X in the second
block (i.e., AX-A or AX-X) produced some amount of extinction of the
A↔X association. The question, then, is whether presentations of AX-X and
presentations of AX-BX produce comparable amounts of extinction of such
association. It is not possible to answer this question with our data, but
evidence proceeding from Rodríguez and Alonso (2015, Exp. 1) suggests that
the presentations of AX-X undermine the strength of the A↔X association
more than presentations of AX-BX do. As the authors noted, their results
contradict Hall's proposal and, concerning the question we presented above,
these results support the idea that extinction of the A↔X association should
not be expected after blocked preexposure to AX-BX.
The results of the experiments reported here give new support to this
suggestion. They are particularly clear in showing this by comparing the
groups AX-BY-Y, AX-BX-Y and AX-BX-AY. Given that there are no
reasons to expect the extinction of the A↔X association in the AX-BY-Y
group, the amount of A consumed by this group in the test, after conditioning
of X, can be used as a reference to evaluate the level of extinction of the other
groups. Inasmuch as the AX-BY-Y and the AX-BX-Y groups drank similar
amounts of A in the test it seems necessary to conclude that blocked
 Extinction of within-compound flavour associations 39

preexposure to AX-BX-Y did not produce a significant extinction of the

A↔X association in these experiments. On the contrary, in consonance with
the results obtained by Rescorla and Freberg (1978, Exp. 2), the extinction of
this association was observed in the AX-BX-AY group. Having into account
the precedent considerations, a simple explanation for the results presented
here is that in a blocked preexposure, one rupture of the A↔X association is
insufficient to produce significant extinction but two ruptures are enough to
produce extinction.
It is clear that the significant extinction of the initial A↔X association
observed in the present Experiment 2 is dependent of the third block, but there
is no clear whether extinction is produced by presentations of A alone or in
compound with Y. Following Rescorla and Freberg (1978) any presentation
of A outside the AX compound should produce extinction of this initial
association. Therefore, it could be thought that presentations of A (alone or
in compound with Y) in the third block effectively produce a second rupture,
which causes the extinction of the A↔X association. Moreover, one might
expect that comparing the results of a test with A after preexposure to AX-
BX-AY and AX-BX-A could resolve this answer. These two preexposure
sequences include two ruptures of the initial A↔X association but differ in
important aspects. Clearly, extensive research is needed to address these
issues. Their resolution will contribute to a deeper understanding of the
processes involved in blocked preexposure.

RESUMEN
Extinción de la asociación intracompuesto inicial establecida en
una preexposición por bloques a dos compuestos de sabores. Se estudió
la extinción de la asociación A↔X después de una preexposición por
bloques a AX-BX en dos experimentos. En el Experimento 1, dos grupos de
ratas recibieron una preexposición en bloques larga (14 ensayos) o corta (4
ensayos) a AX-BX y posteriormente se condicionó X. Los resultados
mostraron que la asociación AX se preservó igualmente tanto después de la
preexposición larga como de la corta. En el Experimento 2 se estudió el efecto
de la preexposición por bloques a 0, 1 o 2 rupturas en la extinción de la
asociación AX. En este experimento una “ruptura” se produce cuando, en los
posteriores bloques, uno de los sabores que forman el compuesto inicial es
presentado formando un compuesto con otro sabor diferente. Solo se observó
una extinción significativa cuando la asociación AX se rompió dos veces.
 40 F. Cabo, J.M. Caramés, J. Almaráz & A. Espinet

REFERENCES
Anderson, N. H. (1981). Foundations of information integration theory. New York:
Academic Press. doi: 10.1016/j.beproc.2011.08.001
Espinet, A., Caramés, J. M., & Chamizo, V. D. (2011). Order effects after blocked
preexposure to two compound flavors. Behavioural Processes. 88, 94–100. doi:
10.1016/j.beproc.2011.08.001
Espinet, A., Caramés, J. M., & Cabo, F. (2015). Preservation of within-compound
associations after blocked preexposure to two compound flavors. Behavioural
Processes, 120, 94-100. doi: 10.1016/j.beproc.2015.09.003
Hall, G., & Rodríguez, G., (2009). Factors determining the effects of associative activation
on habituation. Journal of Experimental Psychology: Animal Behavioural Processes.
35, 266–270. doi: 10.1037/a0013292
Honey, R. C., Bateson, P., & Horn, G. (1994). The role of stimulus comparison in perceptual
learning: an investigation with the domestic chick. Quarterly Journal of Experimental
Psychology, 47B, 83–103. doi: 10.1080/14640749408401349
Lubow, R. E. (1973). Latent inhibition. Psychological Bulletin, 79, 398-407. doi:
10.1037/h0034425
Mondragón, E., & Hall, G. (2002). Analysis of the perceptual learning effect in flavor
aversion learning: evidence for stimulus differentiation. Quarterly Journal of
Experimental Psychology, 55B, 153–169. doi: 10.1080/02724990143000225
Rescorla, R.A. (2003). Protection from extinction. Learning & Behavior, 31:124–132. doi:
10.3758/BF03195975
Rescorla, R.A., & Freberg, L. (1978). The extinction of within-compound flavor
associations. Learning and Motivation, 4, 411–427. doi: 10.1016/0023-
9690(78)90003-6
Rodríguez, G., & Alonso, G. (2014). Differential effect of the intermixed and blocked
preexposure schedules on the strength of the within-compound associations. Journal
of Experimental Psychology: Animal Learning and Cognition, 40, 327–334. doi:
10.1037/xan0000026
Rodríguez, G., & Alonso, G. (2015). Within-subjects assessment of the within-compound
associations resulting from intermixed and blocked preexposure schedules. Learning
& Behavior, 43,12–19. doi: : 10.3758/s13420-014-0157-7

(Manuscript received: 20 November 2016; accepted: 16 May 2017)