Anxiety	A specific emotional state often characterized by apprehension, worry, and physiological arousal. In the context of the SUDS, it is one of the primary constructs the scale was intended to measure (e.g., Wolpe’s “worst anxiety”), though the manuscript argues that its measurement by the SUDS is often confounded with other states.
Construct Irrelevance	A threat to construct validity that occurs when a test or measure includes aspects or captures variances that are not part of the intended construct. In the manuscript’s analysis of the SUDS, this refers to the scale potentially reflecting factors like frustration, hopelessness, or other emotions rather than solely the intended construct of distress or anxiety.
Construct Underrepresentation	A threat to construct validity where a test or measure fails to capture important aspects of the construct it is intended to assess. For the SUDS, this could mean that the scale does not fully encompass the multifaceted nature of subjective distress or anxiety, as it attempts to distill complex experiences into a single number.
Construct Validation	The overarching, integrative, and evaluative process of gathering evidence to determine whether a measure accurately assesses the specific psychological construct it claims to measure, and whether inferences made from its scores are appropriate and meaningful. The manuscript employs this process, particularly the Strong Program, to investigate the SUDS.
Distress	A general term for a state of negative affective intensity, suffering, or unease. Within the manuscript, it is the focal construct that the SUDS (Subjective Units of Distress Scale) purports to measure, but its lack of a clear, consistent operational definition is identified as a key psychometric weakness, leading to ambiguity in what SUDS scores actually represent.
Disturbance	A term originally used by Wolpe in relation to the SUDS (e.g., “subjective unit of disturbance”), often used interchangeably with “distress” or “anxiety.” The manuscript highlights that this broad term contributed to the scale’s early ambiguity regarding the specific construct being measured.
External Component (of Strong Program)	The third component of the Strong Program of Construct Validation, which examines how a measure relates to other established measures and variables (convergent and discriminant validity), and how it performs across different groups or conditions, to build a nomological network. The manuscript suggests that robust evidence in this stage for the SUDS is difficult to interpret due to weaknesses in earlier validation stages.
Negative Affect	A broad dimension of emotional experience encompassing various unpleasant feelings and states, such as anxiety, distress, fear, and sadness. The manuscript considers the SUDS as an attempt to measure “state negative affective intensity.”
Strong Program of Construct Validation	A theory-driven, multi-stage framework for evaluating the construct validity of a measure, integrating various forms of validity evidence. It includes three core components: Substantive, Structural, and External. The manuscript utilizes this program as its primary theoretical lens for critiquing the psychometric properties of the SUDS.
Structural Component (of Strong Program)	The second component of the Strong Program of Construct Validation, focusing on the internal structure of a measure and how well it reflects the structure of the intended construct. For single-item measures like the SUDS, this includes assessing its sensitivity to within-person, longitudinal variability and the consistency of its measurement properties.
Subjective Units of Distress (SUDS)	A self-report rating scale, typically ranging from 0 to 100, intended to quantify an individual’s current level of subjective distress, anxiety, or disturbance. The manuscript critically examines its validity and clinical utility.
Substantive Component (of Strong Program)	The foundational first component of the Strong Program of Construct Validation, concerned with defining the theoretical basis of the construct being measured and ensuring the measure (including its items, format, and scoring) adequately represents this theoretical domain, while avoiding construct underrepresentation and irrelevance. The manuscript argues that the SUDS has significant weaknesses in this component.