Speed judgments during smooth pursuit reflect low gain efference copy

In 29 participants performing smooth pursuit with brief target speed perturbations, perceptual reports show systematic under-compensation: faster eye movements predict lower perceived speed changes.

• Why it matters: The brain must discount self-generated retinal motion during pursuit using efference copy, but prior trial-by-trial links between eye signals and perception have been inconsistent.
• What they did: Participants tracked a moving target that underwent brief speed changes while eye velocity, perceived sign (faster/slower), and confidence were recorded; logistic regression tested efference copy gain using stimulus speed and eye speed.
• The result: Perceptual and oculomotor sensitivity correlated across participants (r =0.53), yet trial-by-trial perceptual and oculomotor responses were independent; confidence was well-calibrated and negatively related to eye speed.

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