The impact of MRI scanner environment on perceptual decision-making

Maanen, Leendert van; Forstmann, Birte U.; Keuken, Max C.; Wagenmakers, Eric‐Jan; Heathcote, Andrew · 2015 · Behavior Research Methods

DOI: 10.3758/s13428-015-0563-6

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Summary

This study investigates the impact of the MRI scanner environment on human perceptual decision-making, addressing a lack of consensus in prior literature regarding how scanner conditions affect behavioral performance. While functional magnetic resonance imaging (fMRI) is widely used to link brain activity to behavior, few studies have systematically examined how the scanner environment itself alters that behavior. Previous research yielded inconsistent results, with some studies reporting faster responses due to arousal, others reporting slower responses due to motor constraints or increased caution, and still others finding no effect. To resolve these discrepancies, the authors analyzed data from three experiments involving a random dot motion task, comparing performance in a traditional behavioral setting versus inside an MRI scanner. The researchers employed the Linear Ballistic Accumulator (LBA) model, a cognitive model that decomposes response times (RTs) and error rates into distinct psychological parameters: drift rates (evidence accumulation speed), threshold (response caution), and non-decision time (motor execution and sensory encoding). Experiment 1 manipulated response bias via cues, Experiment 2 manipulated speed-accuracy trade-offs, and Experiment 3 manipulated task difficulty and inter-trial intervals to control for order effects and timing differences. Bayesian ANOVAs were used to quantify the likelihood of effects, and LBA modeling was applied to identify the specific cognitive mechanisms driving behavioral changes. The results consistently demonstrated that response times increased inside the MRI scanner across all experiments, while error rates increased to a lesser extent or remained unaffected. LBA modeling revealed that these behavioral changes were driven by two primary mechanisms: an increase in non-decision time ($t_0$), indicating motor slowing likely due to unfamiliar response devices or orientation, and a decrease in the difference between drift rates for correct and incorrect responses ($v_c - v_e$), indicating reduced attentional focus on the task. The model did not support explanations based on increased response caution (which would predict lower error rates) or general arousal (which would predict faster responses). Instead, the data suggest that participants in the scanner environment exhibit slower motor execution and diverted attention. The significance of these findings lies in providing a unified explanation for previously inconsistent results by distinguishing between motor and cognitive components of performance. The study concludes that the MRI scanner environment induces motor slowing and reduces attentional focus, rather than altering decision thresholds or inducing beneficial arousal. These insights are crucial for interpreting fMRI data, as they highlight that observed neural differences may be confounded by environmental effects on behavior. Understanding these specific mechanisms allows researchers to better control for scanner-induced behavioral changes and more accurately map the relationship between brain activity and cognitive processes.

Key finding

Participants exhibited slower response times and reduced attentional focus when performing perceptual decision-making tasks inside an MRI scanner compared to a traditional behavioral setting.

Methodology

lab_experiment

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

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• signal detection theory