Affect measures (measures of affect or measures of emotion) are used in the study of human affect (including emotions and mood), and refer to measures obtained from self-report studies asking participants to quantify their current feelings or average feelings over a longer period of time. Even though some affect measures contain variations that allow assessment of basic predispositions to experience a certain emotion, tests for such stable traits are usually considered to be personality tests. Differentiating affect from other terms Scholarly work has noted the problematic nature of using the terms “emotion”, “affect” and “mood” interchangeably. A lack of thorough understanding of these concepts could influence the choice of measures used in assessing the emotional components of interest in a study, leading to a less optimal research result. The differentiation among these key concepts in affect research in the current era is becoming increasingly important, as consistent effort has been made to move out of the stage of using these constructs interchangeably. Affect Affect refers to the mental feeling from inside the body that underlies all emotional experience. It varies in valence (from unpleasant to pleasant) and arousal (from deactivated to activated). While affect is a general term, core affect is one of the fundamental components that constitute a basic emotional unit, what they termed as prototypical emotional episode, as proposed by Russell and Barrett in their seminal work. They suggest that besides core affect, other ingredients such as behavior facial emotional expression are also parts of one emotional unit. Emotion Emotion is a “complex set of interrelated subevents concerned with a specific object”. In other words, emotion is a physical compound constituted by a number of more basic ingredients. This view comes from the psychological constructionist tradition, a more recent and theoretically rich approach. Earlier tradition in the study of human emotion can be broadly divided into two, namely appraisal and basic emotion approach. The appraisal tradition views emotion as a short-lived experience that involves cognitive appraisal as its defining feature, while the basic emotion approach believes that there are exclusive categories in emotional states. Mood Mood distinguishes from emotion in duration and intensity. Generally, mood is viewed as more persistent and less intense than emotional state, and as a result more stable. It falls between the fleeting emotional states and more enduring trait. Overview of affect measures One categorization of affect measures is based on whether the measure