Psicológica (2005), 26, 281-292.
Outcome similarity modulates retroactive interference
between cues trained apart
Oskar Pineño*1 and Helena Matute**
*University of Seville, Sevilla, Spain
**University of Deusto, Bilbao, Spain
Retroactive interference between cues trained apart has been regarded as an
effect that occurs because the target and interfering associations share a
common outcome. Although this view is consistent with evidence in the
verbal learning tradition (Underwood, 1966) and, more recently, in predictive
learning with humans (Pineño & Matute, 2000), little research has been
conducted to ascertain whether the occurrence of this effect critically depends
on the target and interfering associations sharing an identical outcome. The
present experiment examined, in predictive learning with humans, retroactive
interference between cues trained apart as a function of the similarity of the
outcome paired with the cues. Interference was found to be stronger when the
cues were paired with the same outcome than when they were paired with
either similar or different outcomes.
Since Kamin’s (1968) original study on forward blocking it is well
known in the associative learning literature that responding to a target cue, X,
does not only depend on the number of pairings of this cue with the outcome,
but also on the number of pairings of the outcome with an alternative cue, A,
that has been presented in compound with X during training. The same is true
for the effect known as backward blocking (Shanks, 1985; Miller & Matute,
1996), in which the AX compound is paired with the outcome prior to training
with A. Forward and backward blocking, among other effects (e.g.,
overshadowing and relative validity), represent what is generally referred to as
cue competition effects, namely, that cues trained in compound with the same
1 Support for this research was provided by Grant PI-2000-12 from Departamento de
Educación, Universidades e Investigación of the Basque Government to Helena Matute.
Oskar Pineño was supported by a postdoctoral fellowship from the Spanish Ministry of
Education (Ref. EX2002-0739). We would like to thank Leyre Castro, Nuria Ortega,
Miguel Ángel Vadillo, and Sonia Vegas, for their assistance with the experiment, and
Jeffrey C. Amundson, Tom Beckers, Ralph R. Miller, Gonzalo Urcelay, Kouji Urushihara,
and Daniel Wheeler for their insightful comments on an earlier version of this manuscript.
Correspondence concerning this article should be addressed to Oskar Pineño, Departmento
de Psicología Experimental, Facultad de Psicología, c/ Camilo José Cela s/n,
41018-Sevilla, Spain. Email: email@example.com
O. Pineño and H. Matute
outcome compete for behavioral control. Cue competition effects have been
largely studied with both human and nonhuman animals and have encouraged
the development of a great variety of associative models of learning (e.g.,
Dickinson & Burke, 1996; Mackintosh, 1975; Miller & Matzel, 1988; Pearce
& Hall, 1980; Rescorla & Wagner, 1972; Van Hamme & Wasserman, 1994;
Wagner, 1981). Despite several differences, most models of learning assume
that, in order for cues to compete, they must be trained in compound (i.e.,
together) with the same outcome.
A few years ago, however, Matute and Pineño (1998b) observed that
cues can also compete even if they are never trained together. Their
experiments showed that responding to a cue, X, paired with the outcome (i.e.,
X-O) in an early stage of the experiment can be attenuated due to the
subsequent training of another cue, A, with the same outcome (i.e., A-O). In
other words, training of A with the outcome retroactively interfered with the
expression of the previously learned X-O association. Matute and Pineño’s
demonstration of retroactive interference between cues trained apart was not
novel, but it can be regarded as an application to predictive learning of the
well-known interference effects observed in the verbal learning tradition (e.g.,
Underwood, 1966). Specifically, the effect of retroactive interference between
cues trained apart can be regarded as analogous to the A-B, C-B paradigm in
the paired associates literature (e.g., Abra, 1967; Cheung & Goulet, 1968;
Johnston, 1968; Keppel, Bonge, Strand, & Parker, 1971; Schwartz, 1968).
Although extensive research has been conducted on the effect of
retroactive interference between cues trained apart (e.g., Escobar, Arcediano, &
Miller, 2001; Escobar, Matute, & Miller, 2001; Escobar, Pineño, & Matute,
2002; Lipp & Dal Santo, 2002; Matute & Pineño, 1998b; Pineño, Ortega, &
Matute, 2000; Pineño & Matute, 2000), the most basic question remains to be
answered yet: Why does training of the A-O association interfere with the
expression of the X-O association? Several experiments have demonstrated
that this effect occurs only when the target and interfering associations share a
common outcome (e.g., Escobar, Arcediano, & Miller, 2001; Pineño &
Matute, 2000). Thus, the effect of retroactive interference between cues trained
apart has been regarded as symmetrical to those effects of retroactive
interference between outcomes trained apart (e.g., extinction and
counterconditioning), in which the target and interfering associations share the
cue as the common element (see Pineño & Matute, 2000). Moreover, the
observation that both of these effects, retroactive interference between cues
trained apart and retroactive interference between outcomes trained apart, are
determined by the target and interfering associations sharing a common
element led to the proposal that these effects could be caused by a common
mechanism (Matute & Pineño, 1998a). As proposed by Pineño and Matute
(1998b) and Miller and Escobar (2002), retroactive interference between cues
trained apart could be explained by a priming process akin to the one of
Bouton’s (1993) theory, which was developed to explain interference between
outcomes trained apart. In this framework, when the target and interfering
associations share a common element (i.e., the outcome in retroactive
interference between cues trained apart and the cue in retroactive interference
Interference between cues
between outcomes trained apart) and the interfering association is better
primed for retrieval than the target association (i.e., due to contextual and/or
punctuate cues or by the recency of its training), retrieval of the target
association is impaired. This impaired retrieval of the target association can be
viewed as akin to what in the memory literature is generally referred to as
retrieval inhibition (see Bjork, 1989) or retrieval-induced forgetting (see
Anderson, Bjork, & Bjork, 2000).
Due to the critical role attributed to the common element shared by the
target and interfering associations in the observation of interference, studying
its actual contribution to interference is of critical importance. One approach
that has been used to assess the role of the common element on proactive
interference consists of varying its similarity in the target and interfering
association. For example, some classic studies have shown that similarity
between the to-be-recalled and interfering items strongly determines proactive
interference in short-term memory (e.g., Delaney & Logan, 1979; Wickens,
Born, & Allen, 1963). To our knowledge, however, there are no studies
showing that the same is true for retroactive interference. Moreover, in the
predictive learning paradigm, the influence of the similarity between the
common elements has received little empirical attention. The only exception to
this was provided by Escobar and Miller (2003, Experiment 3), who showed
that retroactive interference between cues trained apart is stronger as the
temporal duration of the outcomes trained with the target and interfering cues
is more similar. Therefore, other manipulations of similarity, such as
manipulating the physical similarity of the outcomes, are critical to assess the
actual role played by the outcome in the occurrence of retroactive interference
between cues trained apart. This was the purpose of the present study.
In this experiment, three groups of participants were first given pairings
of the target cue, X, and an appetitive outcome (i.e., O1Ap). The critical
treatment was given in Phase 2. In this phase, group IO (i.e., identical
outcome) received pairings of cue A with the same outcome that was
previously paired with X (i.e., A-O1Ap trials). Group SO (i.e., similar
outcome) received pairings of A with an appetitive outcome that was slightly
different from the outcome previously paired with X (i.e., A-O2Ap trials).
Finally, group DO (i.e., different outcome) was given presentations of A
followed by a completely different outcome, specifically, a neutral outcome
that did not elicit responding (i.e., A-ONe trials).
If retroactive interference between cues trained apart is determined by
the target and interfering associations sharing an identical outcome, then
interference should only occur in group IO (i.e., as showed by weak
responding to X at test in comparison to group DO). Moreover, if outcome
similarity modulates retroactive interference between cues trained apart, then a
certain degree of interference should also be observed in group SO as
compared to group DO.
O. Pineño and H. Matute
Participants and Apparatus. The participants were one hundred and
fifty students from Deusto University, who volunteered for the study.
Participants were randomly assigned to groups IO (n = 54), SO (n = 51), and
DO (n = 45). The experiment was run in three replications, with the
participants being similarly distributed across groups in each replication. The
computers were located in a large room that allowed for simultaneous running
of about 70 participants. Participants were seated about 1.5 m apart, and each
subject was exposed to a different experimental condition (and
counterbalancing of stimuli) than the two adjacent subjects.
Design and Procedure. Table 1 summarizes the design of the
experiment. During Phase 1, all groups were given fifteen trials on which the
target cue, X, was paired with one of the appetitive outcomes (i.e., X-O1Ap
trials), interspersed with fifteen trials on which cue C was paired with an
aversive outcome (i.e., C-OAv trials). Presentations of C-OAv were filler
trials that were included in order to prevent cue generalization that would
result in strong responding appropriate to O1Ap to all cues. In Phase 2, all
groups were given fifteen trials with a third cue, A. In group IO, cue A was
paired with the same outcome previously paired with cue X during Phase 1
(i.e., O1Ap). In group SO, cue A was paired with the alternative appetitive
outcome (i.e., O2Ap). In group DO, cue A was paired with a neutral outcome
during Phase 2 (i.e., ONe). At test, all groups were given a single
presentation of cue X.
The preparation used in this experiment was the same as that previously
used by Pineño et al. (2000) for the study of associative learning with
humans. In this preparation, participants were instructed to imagine that they
were to rescue a group of refugees by helping them escape from a war zone in
trucks (see Pineño et al.; Pineño & Matute, 2000; for a detailed description of
the task, including the instructions1).
The cues were presented on a so-called spy-radio, which consisted of
six panels in which colored lights could be presented. Cues X, A and C were
blue, red, and yellow lights, counterbalanced. In this experiment, on each trial a
randomly chosen light position in the array was illuminated with the color of
that trial’s cue. Cue durations were 3 s. On each trial, the termination of the
cue coincided with the presentation of an outcome. The appetitive outcomes
(i.e., O1Ap and O2Ap) consisted of (a) the messages ‘[n] refugees safe at
home!!!’ or ‘[n] refugees safe at the embassy!!!’, counterbalanced (with [n]
being the number of refugees placed in the truck during the cue presentation)
1 A demonstration version of this preparation can be downloaded from
for a new adaptation of this preparation).
Interference between cues
and, (b) gaining one point for each refugee who was safe. The aversive
outcome (OAv) consisted of (a) the message ‘[n] refugees have died!!!’ and,
(b) losing one point for each refugee who died in the truck. The neutral
outcome (ONe) consisted of (a) the message ‘Road closed’ and, (b) no point
change. Outcome messages were presented for 3 s. During the intertrial
intervals, the lights were turned off (i.e., gray). The mean intertrial interval
duration was 5 s, ranging between 3 and 7 s.
Table 1. Design Summary of the Experiment.
15 X-O1Ap / 15 C-OAv
15 X-O1Ap / 15 C-OAv
15 X-O1Ap / 15 C-OAv
. A and X were the critical cues. C was included to prevent strong cue generalization.
These cues were blue, red, and yellow colors, counterbalanced. Presentations of X were
always followed by an appetitive outcome (O1Ap), whereas presentations of C were always
followed by the aversive outcome (OAv). Presentations of A were followed by O1Ap in group
IO, by a different appetitive outcome (O2Ap) in group SO, and by the neutral outcome (ONe)
in group DO. Trial types separated by a slash were interspersed. The numbers denote the
number of presentations of each trial type in each phase.
During each cue presentation, each response (i.e., pressing the space bar
once) placed one refugee in the truck, whereas holding the space bar down
placed up to 30 refugees per second in the truck. The number of refugees that
participants loaded in the truck on each trial (i.e., regardless of the number of
space bar presses) was our dependent variable, which can be viewed as
reflecting the participants’ expectation of the cue being followed by an
appetitive outcome (O1Ap or O2Ap). Presumably, the more certain the
participants were that the cue would be followed by an appetitive outcome, the
greater number of refugees they would load in the truck, whereas the more
certain participants were that the truck would explode (OAv) or that the road
would be closed (ONe), the fewer refugees they would place in the truck. The
number of refugees that participants loaded in the truck during each cue
presentation was shown in a box on the screen, this number being
immediately updated after each response. Although pressing the space bar
during the outcome message had no consequences, the number of refugees
loaded in the truck during the previous cue presentation remained visible
during the presentation of the outcome. Upon outcome termination, the score
O. Pineño and H. Matute
panel was initialized to 0. Responses that occurred during the intertrial
intervals had no consequence and were not reflected in the panel. The different
phases of the experiment were conducted without interruption.
Preanalysis Treatment of the Data. Prior to any analyses, as in our
previous studies using this task (e.g., Pineño & Matute, 2000; Pineño et al.,
2000), we used a data selection criterion in order to ensure that participants
were attending to the experiment and had learned to discriminate between cues
that signaled either the appetitive or the aversive outcome during Phase 1 (i.e.,
X and C, respectively). According to this criterion, the number of responses
given to cue X during the last trial in which it was presented during Phase 1
had to be higher than the number of responses given to cue C on its last
presentation during Phase 1. Following this criterion, two participants from
group SO were eliminated from the experiment.
Preliminary Analyses: Pooling data over replications
The critical results of the experiment (i.e., the results on Test of X) did
not differ among replications, as shown by a 3 (Replication) x 3 (Group)
analysis of variance (ANOVA) on the mean number of responses to X at test.
This ANOVA showed neither a main effect of replication, p > .12, nor a
Replication x Group interaction, p > .16. Therefore, the data from the three
replications were pooled in the subsequent analyses.
The top panel of Figure 1 depicts the mean number of responses during
training, averaged over blocks of five trials. As can be seen in the top-left
panel of this figure, during Phase 1 responding to each of the cues, X and C,
did not appreciably differ among groups. Also, during this phase responding
to cue X was seemingly stronger than responding to cue C in all groups
(something that is not surprising since the data selection criterion ensured that
all participants discriminated between X and C in this phase). These two
impressions were confirmed by a 3 (Group) x 2 (Cue) x 3 (Block of 5 Trials)
ANOVA on the mean number of responses, which yielded main effects of
cue, F(1, 145) = 3750.26, MSE = 168.46, p < .001, and block of 5 trials, F(2,
290) = 570.34, MSE = 32.67, p < .001. Also, this ANOVA revealed a Cue x
Block of 5 Trials interaction, F(2, 290) = 587.87, MSE = 39.55, p < .001.
Neither the main effect of group, nor any interaction involving group as a
factor proved significant, p > .15.
The results from Phase 2 can be seen in the top-right panel of Figure 1.
Responding to cue A was similar in groups IO and SO, and stronger than in
group DO. This impression was confirmed by a 3 (Group) x 3 (Block of 5
Trials) ANOVA on the mean number of responses to cue A during Phase 2,
Interference between cues
which yielded main effects of group, F(2, 145) = 473.21, MSE = 278.12, p <
.001, and of blocks of 5 trials, F(2, 290) = 180.72, MSE = 46.47, p < .001, as
well as a Group x Blocks of 5 Trials interaction, F(4, 290) = 21.96, MSE =
46.47, p < .001. Pairwise comparisons were performed using the error term of
the ANOVA and showed that responding to A did not differ between groups
IO and SO on any block of 5 trials, all ps > .16, and that responding to A was
stronger in these groups than in group DO on all blocks of 5 trials, all Fs(1,
145) ≥ 387.66, all ps < .001. This is not surprising since cue A was paired
with an appetitive outcome in groups IO and SO, and with a neutral outcome
in group DO. Therefore, responding to cue A was not differentially affected
by its being trained with the same outcome as cue X (i.e., O1Ap, group IO) or
with a similar outcome (i.e., O2Ap, group SO). Responding to cue A was
differently affected only by its being paired with an appetitive outcome (i.e.,
groups IO and SO) or a neutral outcome (i.e., group DO).
The critical results in this experiment are those of the test phase, which
are depicted in the bottom panel of Figure 1. As can be seen in this panel,
responding to cue X was weaker in group IO than in both groups SO and
DO. Also, responding to X was apparently weaker in group SO than in group
DO. These impressions were supported by a one-way analysis of variance
(ANOVA) among groups, which yielded an overall effect of group, F(2, 145)
= 17.15, MSE = 512.58, p < .001. Pairwise comparisons performed using the
error term of the ANOVA showed that responding in group IO was weaker
than in both groups SO, F(1, 145) = 14.64, p < .001, and DO, F(1, 145) =
32.55, p < .001. However, despite the figure suggesting that responding in
group SO was weaker than in group DO, pairwise comparisons showed that
this difference was only marginally significant, F(1, 145) = 3.69, p = .056.
The mean number of responses during the 3-s period previous to the
presentation of X at test was 10.37 (SEM = 4.48), 7.14 (SEM = 3.88), and
0.20 (SEM = 0.20) for groups IO, SO, DO, respectively. This stronger
responding before the presentation of cue X at test in groups IO and SO than
in group DO might be due to participants in groups IO and SO anticipating
another reinforced presentation of cue A and participants in group DO
probably expecting another nonreinforced presentation of this cue. Although a
one-way ANOVA on the mean number of responses during the pre-cue
period at test of X yielded no effect of group, p > .13, pairwise comparisons
performed using the error term of the ANOVA showed that responding in the
pre-cue period was stronger in group IO than in group DO, F(1, 145) = 3.95,
p < .05. Despite this stronger response in group IO than in group DO being
conservative (i.e., we expected these two groups to differ in the opposite
direction during the cue presentation at testing), in order to minimize the
potential influence of the pre-cue number of responses on the number of
responses at test, we performed an additional analysis with the test results
including the pre-cue scores as a covariate.
O. Pineño and H. Matute
1 2 3 1 2 3
Blocks of 5 Trials
Mean Number of Responses
Phase 1 Phase 2
IO SO DO
Mean Number of Responses
Figure 1. Top panel: Mean number of responses to cues X, A and C
during training, averaged over blocks of 5 trials. Bottom panel: Mean
number of responses to X at test. Error bars depict standard error of
Interference between cues
An analysis of covariance (ANCOVA) among groups including the pre-
cue number of responses as a covariant revealed an overall effect of group,
F(2, 144) = 17.52, MSE = 513.33, p < .001. The ANCOVA adjusted means
for responding to X at test were 32.40, 49.71, and 59.15 in groups IO, SO,
and DO, respectively. Pairwise comparisons performed using the error term
of the ANCOVA confirmed the previous result, that is, that responding in
group IO was weaker than in both groups SO, F(1, 144) = 14.94, p < .001,
and DO, F(1, 144) = 33.29, p < .001. Also, contrary to what was observed in
the previous analyses that did not include the pre-cue scores as a covariant,
pairwise comparisons showed that responding was also weaker in group SO
than in group DO, F(1, 144) = 4.02, p < .05.
As in previous studies (e.g., Escobar, Arcediano, & Miller, 2001;
Escobar, Matute, & Miller, 2001; Escobar et al., 2002; Matute & Pineño,
1998b; Pineño et al., 2000; Pineño & Matute, 2000), the present experiment
found a strong effect of retroactive interference between cues trained apart in a
group in which both the target cue and the interfering cue were trained with
the same outcome (i.e., group IO). Also, retroactive interference between cues
trained apart was also found to occur (although weakly) in a group in which
the target and interfering cues were paired with different appetitive outcomes
or, in other words, with similar outcomes that were of the same valence and,
hence, produced the same response (i.e., group SO). This latter result must be
qualified because responding to the target cue at test was significantly weaker
in group SO than in group DO only when the analyses included the pre-cue
number of responses as a covariant (see Results section). Of critical
importance, interference was weaker in group SO than in group IO, a result
that was found regardless of whether the pre-cue number of responses was
included as a covariant in our analyses. Therefore, these results indicate that
retroactive interference between cues trained apart can take place as a function
of the similarity between the outcomes associated with the target and
These results in the area of predictive learning are consistent with
classic studies in the verbal learning tradition (e.g., Delaney & Logan, 1979;
Wickens et al., 1963), which showed that proactive interference is strongly
determined by the similarity of the to-be-recalled item and the interfering item
(see also Osgood, 1949; Robinson, 1927). They are also consistent with the
recent study of Escobar and Miller (2003), who found that temporal similarity
of the outcomes trained with the target and interfering cues also modulates
retroactive interference between cues trained apart. If, as proposed by Escobar
and Miller, stimuli are viewed as having multiple components (e.g., physical
characteristics, temporal duration, and motivational properties), the influence
of outcome similarity in retroactive interference can be understood from a
broader perspective. In this framework, as the representation of the outcome
that is physically present during interfering training better matches the
memory of the representation of the outcome previously paired with the target
cue, responding to the target cue will result more strongly interfered.
O. Pineño and H. Matute
La semejanza de las consecuencias modula la interferencia
retroactiva entre claves entrenadas separadamente. La
interferencia retroactiva entre claves entrenadas separadamente ha sido
considerada como un efecto que ocurre debido a que las asociaciones “diana” e
interfiriente comparten una consecuencia común. Aunque este punto de vista
es consistente con la evidencia en la tradición del aprendizaje verbal
(Underwood, 1966) y, más recientemente, en el aprendizaje predictivo con
humanos (Pineño y Matute, 2000), se ha llevado a cabo escasa investigación
para averiguar si la ocurrencia de este efecto depende críticamente de que las
asociaciones “diana” e interfiriente compartan una consecuencia idéntica. El
presente experimento estudió, en aprendizaje predictivo con humanos, la
interferencia retroactiva entre claves entrenadas separadamente en función de
la semejanza de las consecuencias emparejadas con las claves. Se encontró
una interferencia más fuerte cuando las claves fueron emparejadas con la
misma consecuencia que cuando fueron emparejadas con consecuencias
similares o diferentes.
Abra, J. C. (1967). Time changes in the strength of forward and backward associations.
Journal of Verbal Learning and Verbal Behavior, 6, 640-645.
Anderson, M. C., Bjork, E. L., & Bjork, R. A. (2000). Retrieval-induced forgetting:
Evidence for a recall-specific mechanism. Psychonomic Bulletin & Review, 7, 522-
Bjork, R. A. (1989). Retrieval inhibition as an adaptive mechanism in human memory. In
Roediger, H. L. III, Craik, F. I. M. (Eds.), Varieties of Memory and Consciousness:
Essays in Honour of Endel Tulving. Lawrence Erlbaum, Hillsdale, NJ, pp.
Bouton, M. E. (1993). Context, time, and memory retrieval in the interference paradigms
of Pavlovian learning. Psychological Bulletin, 114, 80-99.
Cheung, C. G., & Goulet, L. R. (1968). Retroactive inhibition of R-S associations in the
A-B, B-C, C-B paradigms. Journal of Experimental Psychology, 76, 327-328.
Delaney, H. D., & Logan, F. A. (1979). Item similarity and proactive interference in short-
term memory. Bulletin of the Psychonomic Society, 14, 288-290.
Dickinson, A., & Burke, J. (1996). Within-compound associations mediate the
retrospective revaluation of causality judgements. Quarterly Journal of Experimental
Psychology, 49B, 60-80.
Escobar, M., Arcediano, F., & Miller, R. R. (2001). Conditions favoring retroactive
interference between antecedent events (cue competition) and between subsequent
events (outcome competition). Psychonomic Bulletin & Review, 8, 691-697.
Escobar, M., Matute, H., & Miller, R. R. (2001). Cues trained apart compete for
behavioral control in rats: Convergence with the associative interference literature.
Journal of Experimental
Psychology: General, 130, 97-115.
Escobar, M., & Miller, R. R. (2003). Timing in retroactive interference. Learning &
Behavior, 31, 257-272.
Escobar, M., Pineño, O., & Matute, H. (2002). A comparison between elemental and
compound training of cues in retrospective revaluation. Animal Learning &
Behavior, 30, 228-238.
Interference between cues
Johnston, W. A. (1968). Bidirectional interference in an A-B, C-B paradigm. Journal of
Verbal Learning and Verbal Behavior, 7, 305-311.
Kamin, L. J. (1968). "Attention-like" processes in classical conditioning. In M. R. Jones
(Ed.), Miami symposium on the prediction of behavior: Aversive stimulation (pp 9-
31). Miami, FL: University of Miami Press.
Keppel, G., Bonge, D., Strand, B. Z., & Parker, J. (1971). Direct and indirect interference
in the recall of paired associates. Journal of Experimental Psychology, 88, 414-422.
Lipp, O. V., & Dal Santo, L. (2002). Cue competition between elementally trained
stimuli: US miscuing, interference, and US omission. Learning and Motivation, 33,
Mackintosh, N. J. (1975). A theory of attention: Variations in the associability of stimuli
with reinforcement. Psychological Review, 82, 276-298.
Matute, H., & Pineño, O. (1998a). Cue Competition in the absence of compound training:
Its relation to paradigms of interference between outcomes. In D. L. Medin (Ed.),
The Psychology of Learning and Motivation, Vol. 38 (pp. 45-81). San Diego, CA:
Matute, H., & Pineño, O. (1998b). Stimulus competition in the absence of compound
conditioning. Animal Learning & Behavior, 26, 3-14.
Miller, R. R., & Escobar, M. (2002). Associative interference between cues and between
outcomes presented together and presented apart: An integration. Behavioural
Processes, 57, 163-185.
Miller, R. R., & Matute, H. (1996). Biological significance in forward and backward
blocking: Resolution of a discrepancy between animal conditioning and human
Journal of Experimental Psychology: General, 125, 370-386.
Miller, R. R., & Matzel, L. D. (1988). The comparator hypothesis: A response rule for the
expression of associations. In G.H. Bower (Ed.), The Psychology of Learning and
Motivation, Vol. 22 (pp.51-92). San Diego, CA: Academic Press.
Osgood, C. E. (1949). The similarity paradox in human learning: A resolution.
Psychological Review, 56, 132-143.
Pearce, J. M., & Hall, G. (1980). A model for Pavlovian learning: Variations in the
effectiveness of conditioned but not of unconditioned stimuli. Psychological
Review, 87, 532-552.
Pineño, O., & Matute, H. (2000). Interference in human predictive learning when
associations share a common element. International Journal of Comparative
Psychology, 13, 16-33.
Pineño, O., Ortega, N., & Matute, H. (2000). The relative activation of the associations
modulates interference between elementally-trained cues. Learning and Motivation,
Rescorla, R. A., & Wagner, A. R. (1972). A theory of Pavlovian conditioning: Variations
in the effectiveness of reinforcement and nonreinforcement. In A. H. Black & W. F.
Prokasy (Eds.), Classical conditioning II: Current research and theory (pp. 64-99).
New York: Appleton-Century-Crofts.
Robinson, E. S. (1927). The “similarity” factor in retroaction. American Journal of
Psychology, 39, 297-312.
Schwartz, M. (1968). Effect of stimulus class on transfer and RI in the A-B, A-C paradigm.
Journal of Verbal Learning and Verbal Behavior, 7, 189-195.
Shanks, D. R. (1985). Forward and backward blocking in human contingency judgment.
Quarterly Journal of Experimental Psychology, 37B, 1-21.
Underwood, B. J. (1966). Experimental psychology (2nd edition). New York: Appleton-
O. Pineño and H. Matute
Van Hamme, L. J., & Wasserman, E. A. (1994). Cue competition in causality judgments:
The role of nonpresentation of compound stimulus elements. Learning and
Motivation, 25, 127-151.
Wagner, A. R. (1981). SOP: A model of automatic memory processing in animal
behavior. In N. E. Spear & R. R. Miller (Eds.), Information processing in animals:
Memory mechanisms (pp. 5-47). Hillsdale, NJ: Erlbaum.
Wickens, D. D., Born, D. G., & Allen, C. K. (1963). Proactive inhibition and item
similarity in short-term memory. Journal of Verbal Learning and Verbal Behavior,
(Manuscript received: 1 September 2004; accepted: 9 December 2004)