THE POSITIVITY OFFSET THEORY OF ANHEDONIA IN SCHIZOPHRENIA

Abstract

Prior studies have concluded that schizophrenia patients are not anhedonic because they do not report reduced experience of positive emotion to pleasant stimuli. The current study challenged this view by applying quantitative methods validated in the Evaluative Space Model of emotional experience to test the hypothesis that schizophrenia patients evidence a reduction in the normative "positivity offset" (i.e., the tendency to experience higher levels of positive than negative emotional output when stimulus input is absent or weak). Participants included 76 schizophrenia patients and 60 healthy controls who completed an emotional experience task that required reporting the level of positive emotion, negative emotion, and arousal to photographs. Results indicated that although schizophrenia patients evidenced intact capacity to experience positive emotion at high levels of stimulus input, they displayed a diminished positivity offset. Reductions in the positivity offset may underlie volitional disturbance, limiting approach behaviors toward novel stimuli in neutral environments.

Keywords: Affective Ambivalence; Anhedonia; Emotion; Psychosis.

Figure 1. Standard Ratings of Positive Emotion, Negative Emotion, and Arousal

Note. A = How negative?; B = How positive?; C = Arousal. SZ = Schizophrenia; CN = Control. Values reflect means and error bars indicate standard error of the mean.

Figure 2. Positivity Offset, Negativity Bias, and Co-Activation

Note. CN = control; SZ = schizophrenia. A) The positivity offset and negativity bias as seen in regression lines predicting positivity and negativity ratings from mean arousal. The X axis represents affective input, whereas the Y axis represents affective output. The positivity offset is reflected in a higher intercept for positive than negative output, and negativity bias reflected in steeper slope for negative than positive output. B) Co-Activation: Bivariate representation of positivity and negativity ratings in evaluative space using a two-dimensional Cartesian coordinate system, with negativity ratings on the X-axis, positivity ratings on the Y-axis, and the hypotenuse reflecting vector magnitude.