The galvanic skin response (galvanic skin response, GSR) emerged as a robust index of sympathetic arousal, guiding conditioning research and multi-channel emotion mapping. Researchers advanced a multi-channel framework that integrated skin conductance with heart rate, respiration, and facial muscle activity to distinguish state-specific affective patterns rather than a single generalized arousal signal. The era also emphasized autonomic discrimination without awareness in subception, highlighting nonconscious processing as shaping physiological responses and informing early emotion theory. Historical Significance: These studies established core methodological and conceptual foundations that endured in psychophysiology, including the primacy of autonomic indices and the shift toward multi-modal measurement. The notion of autonomic response specificity, along with systematic cross-channel comparisons, influenced later emotion theories and multimodal research. Early demonstrations of nonconscious autonomic discrimination broadened the scope of subliminal psychophysiology and refined interpretations of emotional expression via facial electromyography.