Are depressive symptoms related to differences in categorization?

As depressive symptoms are widespread in current society, continued research focusing on the involved emotional, interpersonal, and cognitive characteristics, is vital to improve both preventive and curative interventions. This dissertation focuses on possible cognitive characteristics of depressive symptoms. More specifically, we investigated whether depressive symptoms could be associated with distortions in the organization and categorization of perceptual material. In particular, all studies investigated analytical processing, with the first chapter focusing on analytical reasoning during category learning with non-emotional material and all other chapters focusing on analytical attention for different dimensions or aspects of emotional stimuli.

In Chapter 1, we performed a conceptual replication study, to test whether people with high depressive symptoms would show a deficit in flexible analytic processing during a category learning task involving non-emotional verbal material. No difference in flexible analytic processing was found between people with more versus less depressive symptoms.

In Chapter 2, using a prototype categorization task involving pictures of human faces showing varying emotional expressions, we investigated whether depressive symptoms could be associated with a stronger focus on sad emotional expressions, compared to happy expressions. A prototype categorization model was fitted to the data, which included an attentional weight (AW) parameter, reflecting selective attention for the emotional stimulus dimension. Depressive symptoms were not found to be associated with the AW for sad emotional expressions, nor for happy emotional expressions.

In Chapter 3, the same task and model was used as in chapter 2, to assess an attentional bias (AB) for sad emotional expressions in people with a major depressive disorder (MDD), borderline personality disorder (BPD), comorbid MDD and BPD, and healthy controls. There was no evidence for a difference between the different diagnostic groups and the heathy controls in their attentional preference for sad expressions, conceptualized as the AW parameter.

Chapter 4 did not involve a categorization task to assess selective attention for negative emotional expressions, instead a similarity rating task was used to investigate attentional processing. In a first study, again attention for sad versus happy expressions was investigated, and in a second study, attention for angry versus happy expressions was investigated. In this second study, the effect of rumination induction on attentional preferences was investigated as well. However, for both studies, no evidence was found for associations between depressive symptoms and selective attention for sad, angry, or happy expressions.

In Chapter 5, we assessed attentional encoding using the category confusion or “who said what” paradigm. The first question we addressed was whether people encoded other’s facial expressions when forming a first impression, and second whether depressive symptoms would be related to stronger encoding of angry, compared to happy expressions. We indeed found that people implicitly encoded angry and happy facial expressions, however there was no meaningful association between depressive symptoms and encoding of angry or happy expressions.

To conclude, using different paradigms, populations, and manipulations, we found no evidence for a difference in the organization and categorization of emotional and non-emotional material, related to depressive symptoms.