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Associative learning of likes and dislikes: Some
current controversies and possible ways forward
Jan De Houwer
Ghent University, Belgium
Frank Baeyens
University of Leuven, Belgium
Andy P. Field
University of Sussex, UK
Evaluative conditioning (EC) is one of the terms that is used to refer to associa-
tively induced changes in liking. Many controversies have arisen in the literature
on EC. Do associatively induced changes in liking actually exist? Does EC depend
on awareness of the fact that stimuli are associated? Is EC resistant to extinction?
Does attention help or hinder EC? As an introduction to this special issue, we will
discuss the extent to which the papers that are published in this issue help to
resolve some of the controversies that surround EC. We also speculate about
possible boundary conditions of EC and attempt to reconcile conflicting results on
the functional properties of EC.
Preferences are assumed to play a crucial role in many phenomena that are
studied in learning psychology (e.g., Martin & Levey, 1978), social psychology
(e.g., Zajonc, 1980; also see Walther, Nagengast, & Trasseli, this issue), con-
sumer science (e.g., Stuart, Shimp, & Engle, 1987), emotion research (e.g.,
Sherer, 1993), and clinical psychology (e.g., Hermans, 1998). Given the per-
vasive impact that preferences have on behaviour, it is important to know where
these likes and dislikes come from. Although some preferences are genetically
determined, most stem from learning that took place during the lifetime of the
individual (e.g., Rozin, 1982). In this special issue, we focus on one such type of
Correspondence concerning this article should be addressed to Jan De Houwer, Department of
Psychology, Ghent University, Henri Dunantlaan 2, B-9000 Ghent, Belgium;
e-mail: Jan.DeHouwer@UGent.be
We thank Paul Eelen and the Fund for Scientific Research (Flanders, Belgium) for making
possible the special interest meeting on which this special issue was based. We also thank Eva
Walther for her critical comments on an earlier draft of this paper.
#2005 Psychology Press Ltd
http://www.tandf.co.uk/journals/pp/02699931.html DOI:10.1080/02699930441000265
COGNITION AND EMOTION
2005, 19 (2), 161±174
learning: Associative learning of likes and dislikes, that is, changes in liking that
are due to the pairing of stimuli.
1
Various terms, such as evaluative conditioning, evaluative learning, and
affective learning, have been used to refer to an observed change in the liking of
astimulus that results from pairing this stimulus with another, liked or disliked
stimulus. Because the term ``evaluative conditioning'' (EC) is the only of these
terms that refers to the fact that the induced changes in liking are due to the
pairing of stimuli (rather than to other factors, such as the mere repeated pre-
sentation of a stimulus), we prefer to use this term. De Houwer, Thomas, and
Baeyens (2001; see also Field, in press) recently reviewed the literature on EC.
From this review, it became apparent that there are still many controversies
about the conditions under which the pairing of stimuli will lead to changes in
liking. In an attempt to stimulate the debate about these issues, we organised a
special interest meeting on EC which was attended by most researchers who
were at the time actively engaged in EC research. This meeting took place in
May of 2002 and was sponsored by the Fund for Scientific Research (Flanders,
Belgium) as part of the Scientific Research Network ``Acquisition, Repre-
sentation, and Activation of Evaluative Judgements and Emotions''. Because
many of the papers that were presented during the meeting indeed furthered our
knowledge about EC, we decided to put together this special issue on the basis
of these papers. As an introduction, we will describe some of the controversies
that surrounded research on EC at the time we held the meeting and will discuss
to which extent the papers in this special issue help to resolve these con-
troversies. We conclude by discussing possible solutions for the remaining
unresolved issues.
CURRENT CONTROVERSIES
Is EC a genuine phenomenon?
Shanks and Dickinson (1990) and Field and Davey (1997, 1998, 1999) con-
vincingly argued and demonstrated that apparent EC effects can be due to an
artefact that is related to the stimulus assignment procedure. In several early EC
studies (e.g., Baeyens, Crombez, Van den Bergh, & Eelen, 1988), researchers
assigned neutral stimuli (conditioned stimuli or CSs) to liked or disliked stimuli
(unconditioned stimuli or USs) on the basis of perceptual similarity. If, for
1
Note that when we talk about ``associative learning'', ``conditioning'', or ``associatively
induced changes in behaviour'', we do not want to imply that observed changes in behaviour are due
to the formation of associative links between representations. We only want to indicate that the
changes in behaviour are due to fact that stimuli have been paired (i.e., presented together) in a
certain manner. That is, we use ``associative learning'' to refer to an effect (i.e., a change in
behaviour that is due to pairing stimuli) rather than to a theory (i.e., the formation of associations
between representations).
162 DE HOUWER, BAEYENS, FIELD
instance, a neutral stimulus was perceptually most similar to a liked picture, it
was repeatedly presented together with this liked picture during the learning
phase. If it was most similar to a disliked picture, it would be paired with that
disliked picture. Most often, neutral stimuli that were paired with liked stimuli
were afterwards liked more than neutral stimuli that were paired with disliked
stimuli. Field and Davey (1999), however, showed that a neutral stimulus that is
most similar to a liked stimulus will be liked more during a second rating phase
than a neutral stimulus that is most similar to a dislike picture even when the
stimuli were not paired or when the stimuli were never presented during the
learning phase!
Field and Davey (1997, 1998, 1999) therefore argued that to demonstrate that
changes in liking are due to associative learning, EC studies should include
between-subject control conditions in which stimuli are not paired. Given that
few if any studies included such controls, they raised doubts about the very
existence of EC as an associative learning phenomenon. Some have argued that
there are many within-subjects studies in which the construction of stimulus
pairs was counterbalanced across participants or randomised and that therefore
do provide strong evidence for the associative nature of EC (e.g., Baeyens, De
Houwer, Vansteenwegen, & Eelen, 1998; De Houwer, Baeyens, Vansteenwe-
gen, & Eelen, 2000; De Houwer et al., 2001). Nevertheless, it is good to see that
several of the EC experiments that are reported in this special issue did include a
between-subjects control condition and still found strong evidence for EC (DõÂaz,
Ruiz, & Baeyens, this issue; Field & Moore, this issue; Hammerl & Fulcher, this
issue). This should eliminate all doubts about whether genuine EC effects do
exist.
But as is noted by Field and Moore (this issue), EC is certainly not a robust
research finding. Field and Davey (1999) and Rozin, Wrzesniewski, and Byrnes
(1998) already reported several genuine failures to find EC, that is, failures that
were probably not due to a lack of statistical power or to obvious flaws in the
design. During our special interest meeting in Belgium, many more reports of
unpublished failures to find EC emerged (e.g., Field, Lascelles, & Davey, 2003).
Even researchers who were eventually successful in finding replicable EC (e.g.,
Olson & Fazio, 2001; Walther, 2002) spoke about their lengthy struggle to find
the parameters under which EC reliably emerged. It thus appears to be the case
that EC is subject to many as yet unidentified boundary conditions.
What are the functional properties of EC?
Given that preferences are such important determinants of behaviour, knowledge
about the processes that underlie the formation of preferences can help us
understand, control, and predict behavior. Researchers have therefore examined
the impact of a number of variables on EC in the hope of gaining insight in the
processes that underlie EC. Initial research suggested that, in comparison to
CURRENT CONTROVERSIES 163
other forms of Pavlovian associative learning, EC appeared to have several
unusual functional characteristics (see De Houwer et al., 2001, for a review; also
see Lipp & Purkis, this issue). For instance, EC does not seem to depend on
whether the participants are aware of which stimulus was paired with which
other stimulus (i.e., contingency awareness) and is not reduced when the CSs are
presented on their own after the learning phase (i.e., no extinction). However,
because some of the studies on which these conclusions were based used a
flawed (i.e., similarity-based) stimulus-assignment procedure (see above), there
was still strong disagreement about whether EC indeed has unique functional
properties and thus about the nature of the processes that underlie EC. Moreover,
some studies indicated that EC at least sometimes does show the same functional
properties as other forms of Pavlovian learning. This special issue includes
several papers that provide new important information about the role of
awareness, extinction, and attention in EC. We will thus focus on these three
functional properties.
Awareness of the stimulus pairings. Just as there has been an intense debate
about the role of awareness in learning in general (e.g., Seger, 1994; Shanks &
St. John, 1994; Lovibond & Shanks, 2002), there has been a controversy about
whether participants need to be aware of the fact that a stimulus was paired with
apositive or negative stimulus to show an associatively induced change in the
evaluation of the first stimulus (e.g., Baeyens, De Houwer, & Eelen, 1994;
Baeyens, Eelen, & Van den Bergh, 1990; De Houwer, 2001; Field, 2000;
Fulcher & Hammerl, 2001; Lovibond & Shanks, 2002). This debate was
complicated by the fact that doubts were raised about whether EC is a genuine
associative phenomenon: If EC is an artefact of stimulus-assignments rather than
based on associative learning, it should come as no surprise that EC does not
depend on awareness of the presented associations (e.g., Davey, 1994). The
papers of Hammerl and Fulcher (this issue) and Field and Moore (this issue)
provide an important additional step toward resolving this controversy. Not only
do they provide new evidence for unaware EC, they also included between-
subject control conditions that allowed them to conclude that the observed EC
effects were based on associative learning.
Lipp and Purkis (this issue), on the other hand, describe one of their earlier
studies (Purkis & Lipp, 2001) in which they found EC only in participants who
could verbalise the crucial CS-US contingency and only after the moment at
which these participants could do so. The results of this study strongly suggest
that EC does depend on awareness of the stimulus pairings. Importantly, Purkis
and Lipp measured awareness during the learning phase rather than only at the
end of the experiment. Their awareness measure was thus probably more sen-
sitive than those that are used in most other studies. This raises doubts about the
conclusiveness of other studies in which EC did not appear to depend on con-
tingency awareness. Note, however, that the procedure that is used by Lipp and
164 DE HOUWER, BAEYENS, FIELD
Purkis is rather atypical in EC research in that only very few stimuli are pre-
sented. We will return to this topic later on.
Is EC sensitive to extinction? Another intriguing finding in the EC literature
is that EC appears to be resistant to extinction (e.g., Baeyens et al., 1988; De
Houwer et al., 2000). That is, once a stimulus has acquired a valence as the
result of being paired with a liked or disliked stimulus, this acquired valence
cannot be changed by repeatedly presenting the stimulus on its own. Although
there are other forms of learning that also appear to be resistant to extinction (see
Field, in press, for a discussion), typically, conditioned responses do decrease
rapidly when the CS is repeatedly presented on its own after the learning phase
(e.g., Hamm & Vaitl, 1996). If EC is indeed resistant to extinction, this would
have many implications (see Walther et al., this issue, for some of the
implications for phenomena in social psychology). But because most of the
evidence regarding the lack of extinction in EC came from studies that used a
similarity-based stimulus-assignment procedure (see above), doubts were raised
about this functional property of EC: If changes in liking are not based on
associative learning, then it is not surprising that a removal of the association
(i.e., presenting one stimulus on its own) has no effect on these changes (e.g.,
Davey, 1994; Field & Davey, 1997). The paper by DõÂazetal. (this issue) tackles
this potential problem by including between-subjects controls in extinction
studies. Their results confirm that evaluative conditioning is indeed resistant to
extinction.
Lipp and Purkis (this issue), however, describe the results of Lipp, Oughton,
and LeLievre (2003) who did find extinction in EC if they asked participants to
repeatedly rate the valence of the CS at the time it was presented on its own
during the extinction phase. Interestingly, they did not find extinction when they
looked only at the ratings that participants gave after the extinction phase. They
explained this result as an example of renewal, that is, recovery of a conditioned
response after removal of the extinction context. Previous failures to find
extinction in EC might therefore have been due to the fact that evaluative ratings
were only collected after the extinction phase. But as we will discuss later on,
there might be other reasons for the discrepancy between the results that were
obtained in the studies of Lipp and colleagues and the results that were obtained
at other labs.
Does attention help or hamper EC? In contrast to the many reported
experiments about the impact of contingency awareness and extinction on EC,
very little research has looked at the role of attention in EC. Field and Moore
(this issue) report two experiments that suggest that EC is reduced when
participants engage in an attention demanding secondary task during the
learning phase (i.e., counting backwards from 300). Although this finding is in
line with many theories of associative learning in general, other results suggest
CURRENT CONTROVERSIES 165
that secondary tasks do not always hamper EC. Field and Moore (this issue)
themselves point out that Hammerl and Grabitz (2000) did find significant EC
when participants solved arithmetical problems during the learning phase, but
argue that the divergent results could be due to differences in the nature of the
stimuli that were used. Walther (2002, Experiment 5; also see Walther et al., this
issue), however, did use stimuli similar to those of Field and Moore and found
that, if anything, the presence of a secondary task (remembering an 8 digit
number throughout the learning phase) strengthened the EC effect. But the
secondary task that Walther used was probably less demanding that the
secondary task of Field and Moore. Further studies in which the nature of the
secondary task is systematically manipulated could thus shed light on these
apparently conflicting results.
POSSIBLE WAYS FORWARD
Although the papers that are reported in this special issue will undoubtably help
to resolve some of the controversies surrounding EC, they also make clear that
many questions remain unanswered. When reading the special issue, one might,
for instance, be puzzled by the fact that Lipp and Purkis (this issue) conclude
that EC does depend on contingency awareness and does show extinction
whereas Hammerl and Fulcher (this issue) and Field and Moore (this issue)
present strong evidence that EC does not depend on awareness and DõÂaz et al.
(this issue) demonstrate that EC is resistant to extinction. Likewise, one might be
confused by the fact we highlighted that EC effects are not easy to obtain (also
see Field & Moore, this issue) whereas the papers in this special issue actually
contain several new and well-controlled demonstrations of EC. In the following
section, we will present some ideas that might help clarify these two incon-
sistencies and that could be helpful in guiding future research.
Possible boundary conditions for EC
In many ways, research on EC is still in its early stages. This is evidenced by the
fact that little is known about the conditions under which EC effects will emerge
and the fact that there are few if any detailed theories of the processes that
underlie EC (see De Houwer et al., 2001). Unfortunately, the one weakness
strengthens the other. Because it is not easy to find a paradigm that produces
reliable EC effects (see Olson & Fazio, 2001, and Walther, 2002, for some
promising exceptions), it is difficult to examine the functional properties of EC
and thus the processes that underlie EC. Likewise, because there are no detailed
theories of EC, it is difficult to make clear predictions about the conditions under
which reliable EC effects will be found. Hence, researchers often use a trial-and-
error strategy in their attempts to find EC. This also became apparent during the
meeting that led to this special issue. There were no reports of studies in which
possible boundary conditions were systematically investigated. But several
166 DE HOUWER, BAEYENS, FIELD
researchers commented on their failures to obtain EC and speculated about the
procedural parameters that need to be in place in order to find EC. The para-
meter that was mentioned most often was the manner in which participants
evaluate the stimuli. Various researchers mentioned that they found EC effects
only when participants were strongly encouraged to evaluate the stimuli on the
basis of their immediate, spontaneous feelings and were asked not to think too
much about their evaluation. In relation to this, it was mentioned that one needs
stimuli that participants feel they can evaluate in an intuitive, spontaneous
manner.
These suggestions are in line with the idea that EC depends on automatic
(i.e., unconscious, unintentional, and/or effortless) processes that produce
intuitive, subjectively unjustifiable changes in liking. It is possible that these
processes can be immunised by controlled (i.e., conscious, intentional, and/or
effortful) processes. Alternatively, the output of the automatic processes might
only reveal itself in behavior (e.g., evaluative ratings) when that behavior is not
determined by other (controlled) processes. Similar suggestions about the
importance of intuitive judgements for measuring automatic processes have
been made in the context of implicit learning (e.g., Lewicki, Hill, & Czyzewska,
1997; but see Hendrickx, De Houwer, Baeyens, Eelen, & Van Avermaet, 1997)
and automatic affective processing (e.g., Fazio, 1986; Koole, Dijksterhuis, &
van Knippenberg, 2001). There is also some evidence that deliberative thought
is capable of inhibiting automatic affective responding (see Koole et al., 2001,
p. 673). It would thus be worthwhile to test whether EC effects are stronger and
more reliable when participants rely on intuition. Note, however, that some
researchers have failed to find EC even when participants were encouraged to
rely on their intuition and when stimuli were used that should allow for an
intuitive evaluation (e.g., Field et al., 2003). It is therefore likely that these
factors are not the only ones that determine whether EC will be found. There is
thus a clear need for studies that investigate possible boundary conditions of EC
in a systematic manner.
EC could be due to different processes
One of the most puzzling aspects of the literature on EC is that there are
diametrically opposed results about the functional properties of EC. Whereas
some researchers found that EC does not depend on contingency awareness and
is not resistant to extinction (see De Houwer et al., 2001, for a review, and Field
& Moore, this issue, Hammerl & Fulcher, this issue, and DõÂazetal., this issue,
for new evidence), Lipp and colleagues found strong evidence that EC does
depend on awareness and is resistant to extinction (see Lipp & Purkis, this
issue). In our opinion, these conflicting data suggest the EC effects that were
observed in the studies of Lipp and colleagues were due to processes different
from those that produced EC effects in other studies. If this is true, it should
CURRENT CONTROVERSIES 167
come as no surprise that the EC effects of Lipp and colleagues show different
functional properties that other EC effects. In this section, we will first give a
conceptual analysis of the term ``conditioning'' that clarifies that EC and other
forms of conditioning can indeed be based on a variety of processes. Next, we
will present an hypothesis about the processes that might have operated in the
studies of Lipp and colleagues.
For many psychologists, the term ``conditioning'' still has theoretical
implications. When someone says that a certain change in behaviour is due to
conditioning, most psychologists will infer that the associatively induced
changes in behaviour were due to simple, unconscious, automatic processes (see
Brewer, 1974). Research on human conditioning has clearly demonstrated,
however, that associatively induced changes in behaviour (i.e., conditioning) can
also be (and are perhaps even most often) due to or mediated by consciously
controlled processes (see Dawson & Shell, 1987; De Houwer, Vandorpe, &
Beckers, in press; Lovibond & Shanks, 2002, for reviews). Eelen (1980) pointed
out that rather than abandoning the term ``conditioning'' on the basis of these
findings, it should be used to refer to either a procedure or an effect of this
procedure and should be stripped from its theoretical connotations. The term
``classical conditioning'', for instance, should refer to the fact that stimuli are
paired in a certain manner (i.e., a procedure) or to the fact that the pairing of
stimuli leads to a change in the reaction toward the stimuli (i.e., an effect that is
due to the pairing of stimuli).
2
From this perspective, it becomes clear that
conditioning effects can result from a variety of processes, automatic or other-
wise. This clear separation between conditioning as a procedure, an effect, and a
theory allows one to avoid situations in which the term ``conditioning'' con-
strains theorising about the possible processes that could be responsible for the
observed conditioning effects. For instance, from this perspective, there is no
paradox in saying that conditioning effects are due to conscious, controlled
processes such as the deliberate generation and testing of hypotheses about CS-
US relations (see De Houwer et al., in press, for a discussion).
We believe that research on EC could also benefit from Eelen's (1980)
distinction between procedure, effect, and theory. As a procedure, evaluative
conditioning is similar to a classical conditioning procedure in that stimuli are
paired in a certain manner. The only unique procedural feature is that one
measures changes in liking. As an effect, evaluative conditioning refers to an
observed change in the liking of a stimulus that results from pairing that
stimulus with another, liked or disliked stimulus. There is no logical reason why
2
We want to emphasise that when a conditioning procedure results in changes in behaviour, one
needs to be sure that these changes are due to the pairing of the stimuli before one can refer to these
changes as a conditioning effect. That is, one always needs to control for nonassociative effects. This
definition of conditioning as an effect is, however, neutral with regard to the nature of the processes
that are responsible for the fact that the pairing of stimuli results in a change in behaviour.
168 DE HOUWER, BAEYENS, FIELD
evaluative conditioning as an effect could be due to simple automatic processes
only, nor is there any reason to believe that only associatively induced changes
in liking that are based on simple automatic processes should be regarded as
``true'' evaluative conditioning. This perspective is liberating in that it allows
one to appreciate the possibility that some of the EC effects that have been
reported in the literature could be due to conscious controlled processes rather
than simple automatic processes.
These considerations led us to some speculative ideas about the processes
that might have been involved in the studies of Lipp and colleagues (see Lipp &
Purkis, this issue, for a review). In these studies, typically one CS was followed
by an aversive US (CS+, where + stands for the presence of the US) whereas
another CS was not followed by the aversive US (CS7, where 7stands for the
absence of the US). Moreover, the CSs were typically abstract geometrical
forms that most participants probably found difficult to evaluate in an intuitive
manner. Nevertheless, results consistently showed that the CS+ was afterwards
liked less than the CS7. This finding corresponds to evaluative conditioning as
an effect. However, EC might have been based on the formation of conscious
propositional knowledge about the CS-US relation. Participants might have
evaluated the CS+ as being more negative than the CS7not because of an
intuitive, unjustifiable feeling, but because they had formed conscious know-
ledge about the fact that the CS+ and not the CS7always preceded the aversive
US. That is, they had the conscious propositional knowledge that the CS+ was
always followed by the aversive US, which they saw as sufficient justification
for disliking the CS+. In other words, they had a justifiable preference: They
justified their dislike for the CS+ by referring to the fact that it was a reliable
signal for the aversive US. The assumption that preferences can be based on
conscious propositional knowledge could seem implausible at first sight to
psychologists who are most often focused on introspectively undefined or
incorrectly defined sources of preferences. However, the fact that some (and
perhaps even most) preferences are unjustifiable (i.e., not based on conscious
propositional knowledge about contingencies or events that actually led to the
preference) does not exclude the possibility that at least some preferences are
justifiable (i.e., based on conscious propositional knowledge about the con-
tingencies or events that actually form the basis of the preference).
The assumption that the EC effects that were observed in the studies of Lipp
and colleagues were based on conscious propositional knowledge about the
CS-US relations is compatible with the fact that those EC effects depended on
contingency awareness and showed extinction. If EC is based on conscious
knowledge of the CS-US relation, contingency awareness is of course required.
In addition, during the extinction phase, participants can form the additional
proposition that the CS+ is no longer followed by the US. Formulating this
new proposition will reduce EC during extinction but EC can resurface when
participants no longer consider this additional knowledge as relevant for
CURRENT CONTROVERSIES 169
evaluating the CS (i.e., renewal). In fact, because human associative learning
most often depends on conscious propositional knowledge (see De Houwer et
al., in press, and Lovibond & Shanks, 2002, for reviews), one would expect
that in those cases where EC is based on conscious propositional knowledge, it
will show all the functional properties that are normally found in human asso-
ciative learning.
It is also important to realise that justifiable preferences might not only be
expressed in direct, explicit measures of valence, such as ratings, but also in
implicit measures, such as the affective priming task (e.g., Fazio, Sanbonmatsu,
Powell, & Kardess, 1986) and the Implicit Association Test (IAT; e.g.,
Greenwald, McGee, & Schwartz, 1998). Indeed, there is evidence to support this
suggestion. For example, asking people to memorise the (positive or negative)
meaning of so-called Turkish words is sufficient to observe affective priming
(De Houwer, Hermans, & Eelen, 1998) and IAT effects (Mitchell, Anderson, &
Lovibond, 2003) when the Turkish words are used as (prime) stimuli. Likewise,
Gregg, Banaji, and Seibt (2004) found that nonsense labels will function as
positive or negative concepts in an IAT after merely asking participants to
suppose that one label is the name of a group of aggressive people whereas the
other label is the name of a group of victims. These findings are reminiscent of
earlier findings which showed that merely informing participants that a CS will
be followed by a US is sufficient to induce autonomic conditioned responses
toward the CS (see Dawson & Shell, 1987, for a review). Although further
evidence is needed, it does at least seem plausible that justifiable preferences
might indeed be detected also when using implicit measures of valence. Note
that this in no way excludes the possibility that implicit measures most often
reflect unjustifiable preferences.
If both direct evaluative ratings and implicit measures of valence can reflect
either justifiable or unjustifiable preferences, how is one to determine whether a
conditioned preference is justifiable? At present, the best option seems to just
ask the participant to report the reasons behind his/her evaluation of a particular
stimulus. If the participant confidently reports propositional knowledge about
the actual CS-US contingency as the reason for his/her preference, one can
conclude that the conditioned preference is justified. Note that participants need
to be aware of the CS-US contingency before they can use the knowledge of the
CS-US contingency as a justification for their preference. However, participants
will not necessarily use their conscious knowledge of the contingencies to form
an opinion of the CSs. It is thus useful to both examine whether participants are
aware of the contingencies and whether participants attribute their preferences to
this conscious knowledge. Such an approach will be particularly useful in
studies in which contingency awareness is good (e.g., because only few CS-US
pairs are presented).
Although we realise that there are problems associated with verbal reports
(e.g., Nisbett & Wilson, 1977), one should realise that verbal reports can at least
170 DE HOUWER, BAEYENS, FIELD
sometimes provide valuable insights (see Smith & Miller, 1978, for an insightful
critique of Nisbett & Wilson, 1977). Also note that researchers do already rely
heavily on verbal reports when studying the role of contingency awareness in
EC. We believe that research on EC could benefit greatly if participants were
asked to justify their preferences. It would, for instance, be interesting to see
whether participants in studies, such as those of Lipp and colleagues, will report
that their evaluation of the CS+ is based on the CS-US contingency. It would
also be interesting to examine whether the functional properties of EC are
related to whether participants can justify their preferences in an accurate
manner. As Meersmans et al. (this issue) point out, one could also manipulate
instructions (e.g., about the nature of the CSs and USs) in such a way that they
inhibit or promote the use of conscious knowledge of CS-US contingencies as a
basis for ratings. Meersmans et al. also found the distinction between justified
and unjustified beliefs helpful to interpret their finding that associative transfer
of nonevaluative stimulus properties seems to depend on awareness of the
contingencies.
Regardless of the merits of our ideas about the processes that were involved
in the studies of Lipp and colleagues, it is important to realise that not all EC
effects might be based on the same types of processes. Which processes are
involved could depend on procedural parameters, such as the number and nature
of the stimuli, the number of times that the CS-US pairs are presented, the
intensity of the USs, and instructions. From this perspective, it is interesting to
note that researchers use many different paradigms for studying EC. In fact,
almost every researcher seems to have his or her own paradigm. Given this state
of affairs, it is perhaps not surprising that findings from different labs do not
always converge. In any case, an important challenge for future research is to
clarify which type of processes can produce EC effects and to identify the
procedural elements that determine the nature of the processes that are
responsible for the observed effects.
CONCLUSION
Despite the many controversies that have plagued research on EC, it remains a
fascinating research topic. Research on EC not only has the potential to lead to
important new theoretical insights in the processes that underlie learning and
memory, it also has immediate implications for our understanding of numerous
phenomena in social psychology, consumer science, emotion theory, and clinical
psychology (see Walther et al., this issue, for an inspiring discussion of the
possible implications of existing EC research for many topics in social psy-
chology, consumer science, and clinical psychology). Moreover, there is the
exciting prospect of many intriguing questions that await an answer. We
therefore hope that more researchers will join our battle to gain a better
understanding of this important phenomenon.
CURRENT CONTROVERSIES 171
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