The road less traveled: low spatial frequency signals not prioritized in emotion-related decision making

Humans possess a remarkable ability to perceive emotional stimuli, particularly those evoking fear. However, the underlying cognitive and computational mechanisms that facilitate this perceptual process remain unclear. The classic “low road” hypothesis postulates that a subcortical neural pathway sensitive to low spatial frequency (LSF) visual signals is responsible for the rapid detection of fearful stimuli. However, the extent of its influence on behavioral perception is still debated. Furthermore, considering that threats frequently manifest within familiar contexts, where our attention is attuned to their presence and absence, it is imperative to explore whether signals supposedly from the low road plays a crucial role in fear perception under emotion-guided attention. Across four experiments (N = 199), we systematically investigated perceptual decision making when emotional faces were presented in low (LSF), high (HSF), and broad (BSF) spatial frequency (SF) under emotion and non-emotion guided attention. Our findings revealed a remarkable decrease in performance in detecting LSF emotional targets under emotion-guided attention, while HSF emotional targets remained unaffected. Drift Diffusion Modeling (DDM) further uncovered that emotion-guided attention suppressed the accumulation of evidence for LSF emotional information. These results unambiguously contradict the hypothesis that perceptual decision-making of emotional stimuli under top-down emotion-guided attention relies on the low road. Our findings shed new light on the intricate interplay between bottom-up and top-down factors involved in emotion perception, provide novel insights into the dual-pathway model of emotion processing, and bear significant implications for emotion theorization and its potential clinical applications.