Christina U. Pfeuffer

Perceiving by proxy: Effect-based action control with unperceivable effects

Anticipations of future sensory events have the potential of priming motor actions that would typically cause these events. Such effect anticipations are generally assumed to rely on previous physical experiences of the contingency of own actions and their ensuing effects. Here we propose that merely imagined action effects may influence behaviour similarly as physically experienced action effects do. Three experiments in the response-effect compatibility paradigm show that the mere knowledge of action-effect contingencies is indeed sufficient to incorporate these effects into action control even if the effects are never experienced as causally linked to own actions. The experiments further highlight constraints for this mechanism which seems to be rather effortful and to depend on explicit intentions.

The power of words: On item-specific stimulus–response associations formed in the absence of action.

Research on stimulus–response (S-R) associations as the basis of behavioral automaticity has a long history. Traditionally, it was assumed that S-R associations are formed as a consequence of the (repeated) co-occurrence of stimulus and response, that is, when participants act upon stimuli. Here, we demonstrate that S-R associations can also be established in the absence of action. In an item-specific priming paradigm, participants either classified everyday objects by performing a left or right key press (task-set execution) or they were verbally presented with information regarding an object’s class and associated action while they passively viewed the object (verbal coding). Both S-R associations created by task-set execution and by verbal coding led to the later retrieval of both the stimulus–action component and the stimulus–classification component of S-R associations. Furthermore, our data indicate that both associations created by execution and by verbal coding are temporally stable and rather resilient against overwriting. The automaticity of S-R associations formed in the absence of action reveals the striking adaptability of human action control.

Defining stimulus representation in stimulus–response associations formed on the basis of task execution and verbal codes

Responding to stimuli leads to the formation of stimulus–response (S–R) associations that allow stimuli to subsequently automatically trigger associated responses. A recent study has shown that S–R associations are established not only by active task execution, but also by the simultaneous presentation of stimuli and verbal codes denoting responses in the absence of own action [Pfeuffer et al. (Journal of Experimental Psychology: Human Perception and Performance 43:328–347, 2017)]. Here, we used an item-specific priming paradigm to investigate whether the stimulus part of S–R associations formed based on task execution and verbal codes is represented in abstract or specific format by examining whether S–R associations are retrieved for perceptually different forms of the same stimulus or not. Between the prime and probe instance of a stimulus, its format switched from image to word or vice versa. We found that, irrespective of whether stimuli were primed by task execution or verbal coding, performance was impaired when S–R mappings switched rather than repeated between the prime and probe instance of a stimulus. The finding that prime S–R mappings affected probe performance even when stimulus format switched indicates that stimuli were represented in abstract form in S–R association based on both task execution and verbal coding. Furthermore, we found no performance benefits for stimuli primed and probed in the same format rather than different formats, suggesting that stimuli were not additionally represented in specific format. Overall, our findings demonstrate the adaptability of automatized behaviors and indicate that abstract stimulus representations allow S–R associations to generalize across perceptually different stimulus formats.

Multiple priming instances increase the impact of practice-based but not verbal code-based stimulus-response associations

Stimulus-response (S-R) associations, the basis of learning and behavioral automaticity, are formed by the (repeated) co-occurrence of stimuli and responses and render stimuli able to automatically trigger associated responses. The strength and behavioral impact of these S-R associations increases with the number of priming instances (i.e., practice). Here we investigated whether multiple priming instances of a special form of instruction, verbal coding, also lead to the formation of stronger S-R associations in comparison to a single instance of priming. Participants either actively classified stimuli or passively attended to verbal codes denoting responses once or four times before S-R associations were probed. We found that whereas S-R associations formed on the basis of active task execution (i.e., practice) were strengthened by multiple priming instances, S-R associations formed on the basis of verbal codes (i.e., instruction) did not benefit from additional priming instances. These findings indicate difference in the mechanisms underlying the encoding and/or retrieval of previously executed and verbally coded S-R associations.

How long is long-term priming? Classification and action priming in the scale of days

Previous research has shown that stimulus–response associations comprise associations between the stimulus and the task (a classification task in particular) and the stimulus and the action performed as a response. These associations, contributing to the phenomenon of priming, affect behaviour after a delay of hundreds of trials and they are resistant against overwriting. Here, we investigate their longevity, testing their effects in short-term (seconds after priming) and long-term (24 hr and 1 week after priming) memory. Three experiments demonstrated that both stimulus–classification (S-C) and stimulus–action (S-A) associations show long-term memory effects. The results also show that retrieval of these associations can be modulated by the amount of engagement on the same task between encoding and retrieval, that is, how often participants performed this task between prime and probe sessions. Finally, results show that differences in processing time during encoding are linked to the amount of conflict caused during retrieval of S-C, but not S-A associations. These findings add new information to the existing model of priming as a memory system and pose questions about the interactions of priming and top-down control processes.