Time-Dependent Facilitation of Homologous Actions
Bibliographic record
Abstract
ABSTRACT Unimanual actions can interfere with or facilitate similar actions performed with the opposite hand, especially when in close temporal proximity. Across three sequential button-press experiments, we tested how effector homology – anatomical similarity between fingers – and temporal delays between actions shape these effects. Specifically, we examined whether a priming action altered the reaction time (RT) of a subsequent action. Compared with unimanual RTs, we indexed slowing of the second action’s RT as interference, and quickening as facilitation. Priming with homologous actions (e.g., index finger-index finger) produced interference at short intervals (≤200ms) but transitioned to facilitation at longer intervals (≥400ms). Priming with non-homologous actions (e.g., little finger-index finger) also produced interference at short intervals, but never resulted in facilitation. Critically, these patterns emerged whether the priming actions were performed with the opposite or the same hand, indicating that interference and facilitation do not depend on interhemispheric dynamics. Our results reveal a previously undocumented time-dependent shift from interference to facilitation that is specific to homologous actions, challenging models that explain the interference between parallel actions solely by competitive interhemispheric dynamics or central bottleneck processes. We propose that facilitation and interference flexibly coexist, and are shaped by effector homology and timing. These findings extend current models of bimanual coordination and highlight new opportunities for enhancing motor performance and neurorehabilitation. GRAPHICAL ABSTRACT A left-hand index finger press primed a subsequent right-hand index (homologous) or right-hand little finger (non-homologous) response at variable delays. For homologous actions (index–index), reaction times (RTs) quickened relative to unimanual single-press baseline for delays ≥400ms, whereas for non-homologous actions (index–little), RTs slowed and gradually returned to baseline by ~600ms. This dissociation indicates that effector homology and timing dictate whether a preceding action facilitates or interferes with the execution of a subsequent one.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.006 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".