Vehicle Braking is Slower under Dual-Task Conditions: Evidence for “Central” Interference
DOI: 10.1177/154193120404801923
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Summary
This study investigates whether the psychological refractory period (PRP) effect—a delay in responding to a second task when two tasks are presented in close temporal proximity—generalizes to real-world driving activities, specifically vehicle braking. While laboratory studies have established that central cognitive processing bottlenecks cause dual-task interference, it remained unclear whether these effects persist in highly practiced, naturalistic tasks like driving, where participants possess years of experience. The researchers aimed to determine if braking, often considered a "simple" reaction task, is subject to central interference when performed concurrently with another cognitive task. The experiment utilized a driving simulator with 40 participants who had at least two years of driving experience. Participants performed two tasks: a braking task, requiring them to depress the brake pedal when a lead car’s brake lights illuminated, and a choice task, requiring manual or vocal responses to indicate whether a visual or auditory stimulus occurred once or twice. The stimulus onset asynchrony (SOA) between the two tasks was varied at 0, 150, 350, and 1,200 ms. The design included single-task and dual-task trials, with dual-task trials comprising only 20% of the block to discourage prioritization strategies. A follow-up experiment without the driving component was also conducted to verify the findings. Results demonstrated that brake reaction times (RTs) significantly increased as SOA decreased, exhibiting the characteristic PRP curve. Brake RTs were slowest at 0 ms SOA and decreased monotonically at shorter intervals, indicating that the concurrent choice task interfered with braking performance. This interference was attributed to central processing delays rather than perceptual or motor conflicts, as evidenced by the lack of significant effects from the choice task’s stimulus or response modalities on brake RTs. Decomposition of brake RTs revealed that the delay occurred primarily during the "gas-off" phase (lifting the foot from the accelerator) rather than the movement phase (pressing the brake). The follow-up experiment replicated these findings, confirming that the interference was not unique to the simulator environment. The study concludes that vehicle braking is not automatic and is subject to central cognitive bottlenecks, even with extensive practice. The observed delay of approximately 174 ms at short SOAs translates to a significant increase in stopping distance (over 16 feet at 65 mph), highlighting substantial safety implications. These findings extend the central-bottleneck model to real-world activities and suggest that any concurrent task requiring central processing, regardless of sensory or motor modality overlap, can impair driving performance. This underscores the importance of understanding cognitive limitations in the design of in-vehicle systems and traffic safety measures.
Key finding
Vehicle braking reaction times are significantly delayed under dual-task conditions, confirming that the psychological refractory period effect extends to highly practiced real-world driving tasks.
Methodology
simulator
Sample size: 40
Provenance
The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via openalex_abstract on 2026-05-08.
| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | — | — | — | 1 | 2026-05-07 |
| archive | success | canonical_url | — | — | 7 | 2026-06-06 |
| extract | success | cached | — | — | 3 | 2026-06-10 |
| clean | success | clean | — | — | 1 | 2026-06-04 |
| chunk | success | chunk | — | — | 1 | 2026-06-04 |
| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 1 | 2026-06-04 |
| enrich | success | openalex | — | — | 2 | 2026-05-08 |
| promote | success | — | — | — | 1 | 2026-05-07 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 2 | 2026-06-10 |
| tag | success | vector_similarity | — | — | 15 | 2026-06-11 |
| verify | success | — | — | — | 2 | 2026-06-10 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.
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- Empirical Findings: behavioral performance data
- Theoretical Contribution: theory or model