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2026-09-22 00:00 Papers Foundations & Methods Source language EN

New Ranking Method Moves Motor Imagery BCI's 'Golden Subject' From S5 to S1

Summary In cross-subject transfer learning for motor imagery BCIs, picking the right 'golden subject', the person whose EEG best serves as a training template for others, directly affects decoding accuracy for other users. An earlier study using the fuzzy decision method FDOSM named S5, but that method did not separate weighting from ranking. Researchers at Imam Ja'afar Al-Sadiq University in Iraq built a unified 9 x 18 golden-subject decision matrix covering nine subjects on 18 training- and evaluation-phase metrics, including accuracy, recall, F1 score, log loss and specificity. Using FWZIC for weighting and VIKOR for compromise ranking, they found the best candidate shifted to S1 (Q = 0.0000), which ranked first in three of four weighting scenarios in a sensitivity analysis. The work is an early methodological exploration involving only nine subjects and has not been validated on larger datasets.
Why it matters Cross-subject transfer in motor imagery BCIs leans heavily on the choice of golden subject, yet there has been no transparent framework that handles weighting and ranking separately. Switching methods reversed the result from S5 to S1, showing how much the decision method shapes the conclusion and suggesting earlier single-method findings need cross-checking. With only nine subjects, larger datasets are needed.

BCIwiki (bciwiki.com) — A researcher at Imam Ja'afar Al-Sadiq University in Baghdad has proposed a new multi-criteria decision framework for identifying the 'golden subject' in motor imagery brain-computer interface (MI-BCI) applications, as reported in the Mesopotamian Journal of Computer Science on September 22, 2026. In cross-subject transfer learning, the golden subject is the individual whose EEG patterns generalize best to other users. An earlier iteration of the same research line, the HAFL study, used the fuzzy decision by opinion score method (FDOSM) and selected Subject 5 (S5) as the top candidate. The new study separates criteria weighting from compromise ranking by building a unified 9 x 18 Golden Subject Decision Matrix (UGSDM) that evaluates nine subjects across 18 criteria spanning both training and evaluation phases, including classification accuracy, recall, F1-score, log loss, and specificity.

FWZIC was applied to compute criteria weights, and VIKOR was used to generate a compromise ranking. S1 emerged as the best compromise subject with Q = 0.0000, followed by S3 (Q = 0.1722) and S5 (Q = 0.3373) — a reversal from the earlier FDOSM result that had placed S5 first. Sensitivity analysis across four weighting scenarios confirmed the result: S1 ranked first in three scenarios and second only in the training-dominant scenario. The author argues that the ranking shift demonstrates how combining training and evaluation criteria in a single matrix, under different weighting logic, can surface different subject priorities. The study is limited to nine subjects and has not been validated on larger public datasets.

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doi.org 2026-09-22
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