Valence bias arises from both positive and negative responses to ambiguous stimuli.

Background: Individuals vary in their tendency to interpret emotionally ambiguous stimuli as relatively more positive or negative, a trait-like difference known as "valence bias." To date, research on valence bias has relied upon two-alternative forced-choice (2AFC) valence decisions that conflate the presence of positivity with the absence of negativity, and vice versa. This is problematic because more frequent negative judgments of ambiguous stimuli (i.e., a more negative valence bias) could represent true negative appraisals of those stimuli, or a difficulty in identifying a positive appraisal. Methods: In two preregistered studies, participants completed a standard 2AFC valence bias task ( Results: The 2AFC valence bias task captured independent effects of both positivity and negativity. Individuals with a more negative valence bias showed high endorsement of negativity Discussion: Despite individual differences as a function of valence bias, ambiguous stimuli were endorsed as both positive and negative on unipolar scales, refuting claims that they might be "valence-free." Collectively, these results demonstrated that multiple appraisals of ambiguity are recognized and weighted based on individual bias in valence processing during affective decision-making.