Characterizing the Dark Category: Psychophysical Thresholds and Semantic Associations

ABSTRACT Dark colors constitute a perceptually and semantically rich domain, yet their category boundaries remain operationally underspecified. Blackness‐scaling studies and lightness‐stratified category mappings have established that perceived blackness varies with hue and chroma and that category structure reorganizes at low lightness levels, but these findings yield continuous scales or relative rankings rather than per‐hue decision boundaries suitable for color specification. This study characterizes dark as a probabilistic category shaped by the convergence of perceptual and semantic dimensions. A sequential mixed‐methods design combined expert interviews ( N = 9) with a psychophysical experiment and post‐task elicitation ( N = 29), first to ground the construct in professional Color, Material, and Finish (CMF) practice and then to derive a multi‐cue characterization. Logistic psychometric fits revealed that the 50% membership boundary ( L * 50 ) forms an orderly cool‐to‐warm hierarchy, shifting by approximately 11 L * units—from Purple‐Blue (≈30.1) to Yellow (≈41.5). Chroma acted as a hue‐contingent modulator: it suppressed category inclusion for most hues (e.g., odds ratio [OR] = 0.70 for Blue‐Green) yet enhanced it for Yellow (OR = 1.17), a reversal consistent with a chromatic‐weight interpretation. Post‐task verbal protocols showed that borderline decisions co‐occur with semantic associations—impressions of elegance, seriousness, or material density—that participants report as accompanying membership judgments despite ambiguous photometric cues. These findings demonstrate that dark is jointly conditioned by lightness, chroma, hue, and affective meaning. The resulting hue‐specific parameters ( L * 50 , Δ L *, chroma ORs) provide perceptually aligned targets and tolerances for industrial color specification and cross‐material matching.