Stimulus-response bindings in priming

Abstract

People can rapidly form arbitrary associations between stimuli and the responses they make in the presence of those stimuli. Such stimulus-response (S-R) bindings, when retrieved, affect the way that people respond to the same, or related, stimuli. Only recently, however, has the flexibility and ubiquity of these S-R bindings been appreciated, particularly in the context of priming paradigms. This is important for the many cognitive theories that appeal to evidence from priming. It is also important for the control of action generally. An S-R binding is more than a gradually learned association between a specific stimulus and a specific response; instead, it captures the full, context-dependent behavioral potential of a stimulus.

Keywords: S–R bindings; automaticity; masked priming; negative priming; repetition suppression; subliminal priming.

Figure 1

Schematic of component processes, stimulus–response (S–R) bindings, and priming paradigms. (A) When someone is asked to make a decision about a stimulus (e.g., whether the object depicted by an image is living or nonliving), several component processes are required to, for example, identify perceptually the object (here, a lion) and retrieve conceptual information about it (that a lion is a living entity) (top row). When that stimulus is presented a second time, the reaction time (RT) to make the same judgment is normally faster, a phenomenon called priming. This could reflect facilitation of one or more of the component processes engaged on initial presentation (second row) or it could reflect retrieval of an S–R binding that encodes the stimulus and response made on the initial presentation, without needing to re-engage the original component processes (third row). (B) The three main types of priming paradigm considered here are repetition priming (top row), negative priming (middle row), and masked priming (bottom row). The initial presentation is shown on the left and the repeat presentation on the right. In the case of negative priming, the red square indicates the target stimulus to which participants attend to determine their response (other concurrent stimuli are distractors). In the masked priming case, the prime is often presented for less than 50 ms and followed by a backward mask (illustrated by a square of pixel noise here) to render it subliminal. The broken lines indicate potential encoding or retrieval of an S–R binding.

Figure 2

Possible stimulus–response (S–R) binding. Schematic of a possible structured S–R binding formed by giving a response to a picture of a lion during a binary ‘bigger than shoebox?’ categorization task, where red lines indicate bindings. Stimulus representations include a visual image of the picture and a more abstract representation of the identity of that stimulus, such that if the word ‘lion’ is later presented, it can also cue responses via the bindings between the identity representation and response representations. Response representations include a specific motor action (e.g., right index finger depression), a binary decision (e.g., ‘yes’) and a particular classification (e.g., ‘bigger’ in the size task). This means that retrieval of an action or decision can influence responses even if the task is changed; for example, to an ‘is the object living?’ categorization instead (as shown). Similarly, retrieval of a decision can influence responses even if the effector (action) is changed and retrieval of a classification can influence responses even if the task (and hence decision and action) is reversed (e.g., to a ‘smaller than shoebox?’ task). Retrieval of the S–R binding may also be mediated by the spatial/temporal context (e.g., laboratory setting).

Figure 3

Neural correlates of stimulus–response (S–R) retrieval. (A,B) Data from the functional MRI (fMRI) study of Dobbins et al. in which simply reversing the task in a repetition priming paradigm reduced repetition suppression (RS). In the start phase, participants judged whether visual objects were bigger than a shoebox; in the switch phase, the same objects (together with new, unprimed objects) were judged as to whether they were smaller than a shoebox (in the return phase, the original ‘bigger’ task was reinstated). The red patches in the three views of a canonical brain in (A) indicate regions showing smaller responses to primed than unprimed trials in the start phase (i.e., RS). The plots in (B) show the average fMRI evoked response to unprimed (dark blue) and primed (light blue) trials from two representative such regions: the prefrontal cortex (PFC) and the ventrotemporal cortex (fusiform). Note that RS in the fusiform is abolished when the task is reversed. Dobbins et al. suggested that the RS in the start phase reflected bypassing of component processes when S–R bindings are retrieved, whereas the lack of RS in the switch phase arises when S–R bindings are no longer used. Reproduced, with permission, from . (C,D) Data from the event-related potential (ERP) study of Horner and Henson . Participants performed the same size-judgment task as in Dobbins et al., except that the referent object (e.g., a shoebox) was switched between prime and probe to render the previous response congruent or incongruent. (C) A time window (grey box) within a stimulus-locked ERP over parietal electrodes during which an effect of stimulus repetition was seen that was not modulated by whether the response was repeated or reversed between presentations (at least until later). (D) An effect over frontal electrodes showed a response congruency effect for primed (repeated) stimuli, but for not unprimed (novel) stimuli, a few hundred milliseconds before a key was pressed (i.e., response-locked). Whereas the stimulus-locked effect was hypothesized to reflect the facilitation of (perceptual) component processes, the response-locked effect was hypothesized to reflect decision processes that resolve the conflict when responses retrieved from S–R bindings and responses generated by component processes are incongruent. Reproduced, with permission, from .