DOCUMENTS

Raes, A. K., De Houwer, J., De Schryver, M., Brass, M., & Kalisch, R. (2014). Do CS-US pairings actually matter? A within-subject comparison of instructed fear conditioning with and without actual CS-US pairings. PLoS ONE 9(1): e84888. doi:10.1371/journal.pone.0084888

Previous research showed that instructions about CS-US pairings can lead to fear of the CS even when the pairings are never presented.In the present study, we examined whether the experience of CS-US pairings adds to the effect of instructions by comparing instructed conditioning with and without actual CS-US pairings in a within-subject design. Thirty-two participants saw three fractals as CSs (CS+1, CS+2, CS-) and received electric shocks as USs. Before the start of a so-called training phase, participants were instructed that both CS+1 and CS+2 would be followed by the US, but only CS+1 was actually paired with the US. The absence of the US after CS+2 was explained in such a way that participants would not doubt the instructions about the CS+2-US relation. After the training phase, a test phase was carried out. In this phase, participants expected the US after both CS+s but none of the CS+s was actually paired with the US. During test, self-reported fear was initially higher for CS+1 than for CS+2, which indicates that the experience of actual CS-US pairings adds to instructions about these pairings. On the other hand, the CS+s elicited similar skin conductance responses and US expectancies. Theoretical and clinical implications are discussed.

Bardi, L., Bundt, C., Notebaert, W. & Brass, M. (2015). Eliminating mirror responses via instructions. Cortex, 70, 128-136.

The observation of an action leads to the activation of the corresponding motor plan in the observer. This phenomenon of motor resonance has an important role in social interaction, promoting imitation, learning and action understanding. However, mirror responses not always have a positive impact on our behavior. An automatic tendency to imitate others can introduce interference in action execution and non-imitative or opposite responses have an advantage in some contexts. Previous studies suggest that mirror tendencies can be suppressed after extensive practice or in complementary joint action situations revealing that mirror responses are more flexible than previously thought. The aim of the present study was to gain insight into the mechanisms that allow response flexibility of motor mirroring. Here we show that the mere instruction of a counter-imitative mapping changes mirror responses as indexed by motor evoked potentials (MEPs) enhancement induced by transcranial magnetic stimulation (TMS). Importantly, mirror activation was measured while participants were passively watching finger movements, without having the opportunity to execute the task. This result suggests that the implementation of task instructions activates stimulus-response association that can overwrite the mirror representations. Our outcome reveals one of the crucial mechanisms that might allow flexible adjustments of mirror responses in different contexts. The implications of this outcome are discussed.

Van Dessel, P. , De Houwer, J., Roets, A., & Gast, A. (2016). Failures to change stimulus evaluations by means of subliminal approach and avoidance training. Journal of Social and Personality Psychology, 110, e1-e15.

Previous research suggests that the repeated performance of approach and avoidance (AA) actions in response to a stimulus causes changes in stimulus evaluations. Kawakami, Phills, Steele, and Dovidio (2007) and Jones, Vilensky, Vasey, and Fazio (2013) provided evidence that these AA training effects occur even when stimuli are presented only subliminally. We also examined whether reliable AA training effects can be observed with subliminal stimulus presentations but added more sensitive checks of perceptual stimulus discriminability. Three experiments, including a direct replication of the study by Kawakami et al. (2007), failed to provide any evidence for effects of subliminal AA training on implicit or explicit evaluations. Bayesian analyses indicated that our data provide robust evidence that subliminal AA training does not cause changes in evaluations. In contrast, we observed changes in evaluations when participants were provided with (either correct or incorrect) information about the stimulus-action contingencies in the subliminal AA training task and when participants performed a supraliminal AA training task that allowed participants to detect these contingencies. These findings support the idea that contingency awareness is necessary for the occurrence of AA training effects.

Mertens, G., Kuhn, M., Raes, A. K., Kalisch, R., De Houwer, J., & Lonsdorf, T. B. (In press). Fear expression and the return of fear following threat instruction with or without direct contingency experience. Cognition and Emotion.

Prior research showed that mere instructions about the contingency between a Conditioned Stimulus (CS) and an Unconditioned Stimulus (US) can generate fear reactions to the CS. Little is known, however, about the extent to which actual CS-US contingency experience adds anything beyond the effect of contingency instructions. Our results extend previous studies on this topic in that it included fear potentiated startle as an additional dependent variable and examined return of fear following reinstatement. We observed that CS-US pairings can enhance fear reactions beyond the effect of contingency instructions. Moreover, for all measures of fear, instructions elicited immediate fear reactions that could not be completely overridden by subsequent situational safety information. Finally, return of fear following reinstatement for instructed CS+s was unaffected by actual experience. In sum, our results demonstrate the power of contingency instructions and reveal the additional impact of actual experience of CS-US pairings.

Maes, E., De Filippo, G., Inkster, A., Lea, S.E.G., De Houwer, J., D'Hooge, R., Beckers, T., Wills, A.J. (2015). Animal Cognition

Humans can spontaneously create rules that allow them to efficiently generalize what they have learned to novel situations. An enduring question is whether rule-based generalization is uniquely human or whether other animals can also abstract rules and apply them to novel situations. In recent years, there have been a number of high-profile claims that animals such as rats can learn rules. Most of those claims are quite weak because it is possible to demonstrate that simple associative systems (which do not learn rules) can account for the behavior in those tasks. Using a procedure that allows us to clearly distinguish feature-based from rule-based generalization (the Shanks-Darby procedure), we demonstrate that adult humans show rule-based generalization in this task, while generalization in rats and pigeons was based on featural overlap between stimuli. In brief, when learning that a stimulus made of two components (“AB”) predicts a different outcome than its elements (“A” and “B”), people spontaneously abstract an opposites rule and apply it to new stimuli (e.g. knowing that “C” and “D” predict one outcome, they will predict that “CD” predicts the opposite outcome). Rats and pigeons show the reverse behavior – they generalize what they have learned, but on the basis of similarity (e.g. “CD” is similar to “C” and “D”, so the same outcome is predicted for the compound stimulus as for the components). Genuinely rule-based behavior is observed in humans, but not in rats and pigeons, in the current procedure.

Unpronounceable strings of 4 consonants (conditioned stimuli: CSs) were consistently
followed by familiar words belonging to one of two opposed semantic categories
(unconditioned stimuli: USs). Conditioning, in the form of greater accuracy in rapidly
classifying USs into their categories, was found when visually imperceptible (to most
subjects) CSs occupied ≥ 58 ms of a 75-ms CS–US interval. When clearly visible CSs
were presented in a 375 ms CS–US interval, conditioning was strongly correlated with
measures of contingency awareness, and did not occur in the absence of that awareness.
These experiments delineated two forms of conditioning: Unconscious conditioning
occurred with a brief CS–US interval, with an effectively masked CS, and with no
reportable knowledge of the contingent CS–US relation. Conscious conditioning
occurred with a substantially longer CS–US interval, a perceptible CS, and with subjects’
reportable knowledge of the contingent CS–US relation.

We investigated whether instructions have the potential to generate memory-independent
attitude acquisition as indexed by a stochastic model of evaluative conditioning that distinguishes
between memory-dependent and memory-independent learning. For that purpose, we instructed
participants about pairings of conditioned and unconditioned stimuli without having participants
experience them. We obtained a significant contribution of memory-independent learning that
depended on whether instructions emphasized the importance of memorization at learning or the
importance of feelings at either learning or retrieval. Our findings call for caution when
interpreting the memory-independent contribution as an indicator of association formation on the
one hand and unaware learning on the other hand. Our research demonstrates the need to clearly
distinguish between processes operating at encoding and processes operating at retrieval in
empirical and theoretical research on evaluative conditioning.

Teuchies, M., Demanet, J., Sidarus, N., Haggard, P., Stevens, M. A., & Brass, M. (2016). Influences of Unconscious Priming on Voluntary actions: role of the Rostral Cingulate Zone. Neuroimage, 135, 243–252.


The ability to make voluntary, free choices is fundamental to what it means to be human. A key brain region that is involved in free choices is the rostral cingulate zone (RCZ), which is part of the medial frontal cortex. Previous research has shown that activity in this brain region can be modulated by bottom-up information while making free choices. The current study extends those findings, and shows, for the first time, that activation in the RCZ can also be modulated by subliminal information. We used a subliminal response priming paradigm to bias free and cued choices. We observed more activation in the RCZ when participants made a choice that went against the prime’s suggestion, compared to when they chose according to the prime. This shows that the RCZ plays an important role in overcoming externally-triggered conflict between different response options, even when the stimuli triggering this conflict are not consciously perceived. Our results suggest that an important mechanism of endogenous action in the RCZ may therefore involve exerting an internally-generated action choice against conflicting influences, such as external sensory evidence. We further found that subliminal information also modulated activity in the anterior insula and the supramarginal gyrus.

Van Dessel, P., De Houwer, J., Gast, A., Smith, C. T., & De Schryver, M. (2016). Instructing implicit processes: When instructions to approach or avoid influence implicit but not explicit evaluation. Journal of Experimental Social Psychology, 63, 1-9.

Previous research has shown that linking approach or avoidance actions to novel stimuli through
mere instructions causes changes in the implicit evaluation of these stimuli even when the actions
are never performed. In two high-powered experiments (total N = 1147), we examined whether
effects of approach-avoidance instructions on implicit evaluations are mediated by changes in
explicit evaluations. Participants first received information about the evaluative properties of two
fictitious social groups (e.g., Niffites are good; Luupites are bad) and then received instructions to
approach one group and avoid the other group. We observed an effect of approach-avoidance
instructions on implicit but not explicit evaluations of the groups, even when these instructions
were incompatible with the previously obtained evaluative information. These results indicate
that approach-avoidance instructions allow for unintentional changes in implicit evaluations. We
discuss implications for current theories of implicit evaluation.

Van Dessel, P., De Houwer, J., Gast, A., & Smith, C.T. (2015). Instruction-based approach-avoidance effects: Changing stimulus evaluation via the mere instruction to approach or avoid stimuli. Experimental Psychology, 62, 161-169.

Prior research suggests that repeatedly approaching or avoiding a certain stimulus changes the
liking of this stimulus. We investigated whether these effects of approach and avoidance training occur also when participants do not perform these actions but are merely instructed about the stimulus–action contingencies. Stimulus evaluations were registered using both implicit (Implicit Association Test and evaluative priming) and explicit measures (valence ratings). Instruction- based approach-avoidance effects were observed for relatively neutral fictitious social groups (i.e., Niffites and Luupites), but not for clearly valenced well-known social groups (i.e., Blacks and Whites). We conclude that instructions to approach or avoid stimuli can provide sufficient bases for establishing both implicit and explicit evaluations of novel stimuli and discuss several possible reasons for why similar instruction-based approach-avoidance effects were not found for valenced well-known stimuli.

Bundt, C., Bardi, L., Abrahamse, E. L., Brass, M., & Notebaert, W. (2015). It wasn’t me! Motor activation from irrelevant spatial information in the absence of a response. Frontiers in Human Neuroscience, 9, (539).

Embodied cognition postulates that perceptual and motor processes serve higher-order cognitive faculties like language. A major challenge for embodied cognition concerns the grounding of abstract concepts. Here we zoom in on abstract spatial concepts and ask the question to what extent the sensorimotor system is involved in processing these. Most of the empirical support in favor of an embodied perspective on (abstract) spatial information has derived from so-called compatibility effects in which a task-irrelevant feature either facilitates (for compatible trials) or hinders (in incompatible trials) responding to the task-relevant feature. This type of effect has been interpreted in terms of (task-irrelevant) feature-induced response activation. The problem with such approach is that incompatible features generate an array of task-relevant and -irrelevant activations [e.g., in primary motor cortex (M1)], and lateral hemispheric interactions render it difficult to assign credit to the task-irrelevant feature per se in driving these activations. Here, we aim to obtain a cleaner indication of response activation on the basis of abstract spatial information. We employed transcranial magnetic stimulation (TMS) to probe response activation of effectors in response to semantic, task-irrelevant stimuli (i.e., the words left and right) that did not require an overt response. Results revealed larger motor evoked potentials (MEPs) for the right (left) index finger when the word right (left) was presented. Our findings provide support for the grounding of abstract spatial concepts in the sensorimotor system.

With the discovery of the blocking effect, learning theory took a huge leap forward, because
blocking provided a crucial clue that surprise is what drives learning. This in turn stimulated the
development of novel association-formation theories of learning. Eventually, the ability to explain
blocking became nothing short of a touchstone for the validity of any theory of learning, including
propositional and other non-associative theories. The abundance of publications reporting a
blocking effect and the importance attributed to it suggest that it is a robust phenomenon. Yet, in
the current paper we report fifteen failures to observe a blocking effect despite the use of
procedures that are highly similar or identical to those used in published studies. Those failures raise
doubts regarding the canonical nature of the blocking effect and call for a reevaluation of the central
status of blocking in theories of learning. They may also illustrate how publication bias influences
our perspective towards the robustness and reliablilty of seemingly established effects in the
psychological literature.