2011 West TruthBiasModelJudgment
West and Kenny (2011) introduce the Truth‑and‑Bias (T&B) model as a unified, formal framework for studying the simultaneous processes of accuracy (truth force) and systematic distortion (bias force) in interpersonal perception and other judgment domains. The model distinguishes three core constructs—truth force (the effect of the objective criterion on the judgment), bias force (the effect of a cue or bias variable on the judgment), and directional bias (the overall shift of judgments relative to the mean truth). It formalizes how these forces combine, how they can be moderated by perceiver, target, or situational variables, and how they may be correlated within and across persons. Four empirical case studies (sexual orientation from gait, roommate hurt‑feelings, assumed similarity, and mother‑adult‑child judgments) illustrate estimation of the forces, the role of moderators, and the interpretation of positive, negative, or null relationships. The paper then explores theoretical extensions (e.g., judgment causing truth, negative accuracy), measurement issues (scale alignment, centering strategies, dichotomous outcomes, discrepancy scores), and design considerations (dyadic, crossed, and round‑robin social‑relations designs). The authors argue that the T&B model complements existing lenses (Gibsonian, Brunswikian, signal‑detection) and provides a flexible analytic template for future research on accuracy and bias across psychological subfields.
Topics
Core Architecture and Measurement Considerations of the Truth‑and‑Bias Model
Defines the three central constructs—truth force (objective criterion influence), bias force (cue‑driven systematic distortion), and directional bias (overall shift of judgments). Presents the formal equations linking truth (T), bias (B), and judgment (J), and clarifies the distinction between force magnitude and bias value. Discusses essential measurement issues such as using common units for T, B, and J, scale alignment, centering strategies (grand‑mean, group‑mean, person‑mean), and handling of dichotomous outcomes and discrepancy scores.
Moderator Variables and Their Influence on Truth and Bias Forces
Explores how perceiver‑target closeness, relationship satisfaction, and individual traits moderate the strength, direction, and interaction of truth and bias forces. Highlights within‑person variance and the role of situational factors in shaping the magnitude of each force.
Design Extensions, Theoretical Challenges, and Future Directions for the T&B Model
Discusses methodological extensions such as dyadic, crossed, and round‑robin social‑relations designs. Addresses unresolved theoretical issues including judgment‑caused truth, negative accuracy, and multi‑level truth/bias forces. Outlines avenues for future research and integration with other frameworks (Gibsonian, Brunswikian, signal‑detection).