It's not distance but similarity of distance: changing stimulus relations affect the control of action sequences.

Interacting with our environment happens on different levels of complexity: While there are individual and simple actions like an isolated button press, most actions are more complex and involve sequences of simpler actions. The degree to which multiple simple actions are represented as one action sequence can be measured via so-called response-response binding effects. When two or more responses are executed consecutively, they are integrated into one representation so that repetition of one response can start retrieval of the other. Executing such an action sequence typically involves responding to multiple objects or stimuli. Here, we investigated whether the spatial relation of these stimuli affects action sequence execution. To that end, we varied the distance between stimuli in a response-response binding task. Stimulus distance might affect response-response binding effects in one of two ways: It might directly affect the representation of the response sequence, making integration and retrieval between responses more likely if the responses relate to close stimuli. Alternatively, the similarity of stimulus distribution during integration and retrieval might be decisive, leading to larger binding effects if stimulus distance is identical during integration and retrieval. We found stronger binding effects with constant than with changing stimulus distance, indicating that action integration and retrieval can easily affect performance also if responses refer to separated objects. However, this effect on performance is diminished by changing spatial distribution of stimuli at the times of integration and retrieval.

Separated hands further response-response binding effects.

Action control is hierarchically organized. Multiple consecutive responses can be integrated into an event representation of higher order and can retrieve each other upon repetition, resulting in so-called response-response binding effects. Previous research indicates that the spatial separation of responses can affect how easily they can be cognitively separated. In this study, we introduced a barrier between the responding hands to investigate whether the spatial separation of two responses also influences response-response binding effects. In line with previous research on stimulus-response binding, we expected an increased separability of responses to result in stronger response-response binding effects when responding hands were separated by a barrier. We indeed found stronger response-response binding effects with separated hands. Results indicate that a more distinct representation of individual actions through increased separability might benefit the control of hierarchical actions.

Instructed speed and accuracy affect binding.

In the past few decades, binding and retrieval mechanisms have gained increased interest in research on human action control. Recent studies show that these mechanisms also play a role in the control of multiple independent actions. Here, two or more successively executed responses seem to be bound to each other so that repeating one of them can retrieve the other, affecting performance in this second response and resulting in so-called response-response binding effects. Binding effects are typically found in the response time data and, somewhat less reliably, also in the error rates. Whether binding effects show in the response times, the error rates, or both, is likely influenced by the current speed-accuracy settings of the participants, with binding effects more likely showing in error rates under a speed setting, while more likely showing in RTs under an accuracy setting. Alternatively, different speed-accuracy settings might also entail changes in executive control, affecting the size of observed binding effects. In this study, we tested these assumptions by comparing binding effects under different speed-accuracy settings that were induced via instructions focusing on speed, accuracy, or both (ambivalent). Binding effects were observed in response times independent of instructions, while in error rates, they only showed under speed or ambivalent instructions. These findings indicate that binding effects can be affected by instructions regarding speed and accuracy.

Effect-less? Event-files are not terminated by distal action effects.

Event-files that bind features of stimuli, responses, and action effects figure prominently in contemporary views of action control. When a previous feature repeats, a previous event-file is retrieved and can influence current performance. It is unclear, however, what terminates an event-file. A tacit assumption is that registering the distal (e.g., visual or auditory) sensory consequences of an action (i.e., the "action effect") terminates the event-file, thereby making it available for retrieval. We tested three different action-effect conditions (no distal action effect, visual action effect, or auditory action effect) in the same stimulus-response (S-R) binding task and observed no modulation of S-R binding effects. Instead, there were comparably large binding effects in all conditions. This suggests that proximal (e.g., somatosensory, proprioceptive) action effects terminate event-files independent of distal (e.g., visual, auditory) action effects or that the role event-file termination plays for S-R binding effects needs to be corrected. We conclude that current views of action control require further specification.

Binding between Responses is not Modulated by Grouping of Response Effects.

Several action control theories postulate that individual responses to stimuli are represented by event files that include temporal bindings between stimulus, response, and effect features. Which stimulus features are bound into an event file can be influenced by stimulus grouping. Here, we investigate whether effect grouping moderates response feature binding. For this purpose, we used an adapted response-response binding paradigm introducing a visual effect after each response. These effects could either appear spatially grouped, i.e., close to each other, or non-grouped, thus far from each other. If effect grouping influences response representation, response-response binding effects should be larger for responses producing grouped effects than for responses producing non-grouped effects. In two experiments, we found no indication for a modulation of response-response binding by effect grouping. The role of effect grouping for binding and retrieval processes seems to differ from past evidence regarding stimulus grouping.