Mental Processes & Health

Abstract: In the study of violence severity, existing methodologies often encounter challenges in capturing the multi-attribute and context-dependent nature of violent acts (e.g. slapping, pushing etc.) (Harris et al., 2013). Previous research attempts to establish linear orderings have shown limitations, as they did not take into account the fact that violent acts are inherently complex and exhibit subjective nuances in perceived severity (Osman et al., 2017). Building on prior work, particularly that of Regenwetter et al. (2018), our approach deviates by utilizing pairwise choice questions to assess the instability in the ordering of violent acts and reject the transitivity assumption. The conventional reliance on linear regression for analyzing ordering or ordinal data has faced increasing scrutiny in recent years (Regenwetter & Cavagnaro, 2019; Liddell & Kruschke, 2018). Critics have raised valid concerns about the limitations of this method in capturing the nuanced and complex nature of ordering data. In response to these challenges, our study draws inspiration from methods, which facilitates the implementation of order constraint models. The pairwise methodology provides a nuanced lens through which to interpret violence severity data. By capturing the inherent instability in orderings, our research contributes to a more comprehensive understanding of violence severity perceptions at the population level. Furthermore, the application of order constraint models through pairwise comparisons offers enhanced inference capabilities, surpassing the limitations of traditional linear regression methods. Reference: Harris, S. T., Oakley, C., & Picchioni, M. (2013). Quantifying violence in mental health research. Aggression and Violent Behavior, 18(6), 695–701. https://doi.org/10.1016/j.avb.2013.07.022 Osman, M., Pupic, D., & Baigent, N. (2017). How many slaps is equivalent to one punch? New approaches to assessing the relative severity of violent acts. Psychology of Violence, 7(1), 69–81. https://doi.org/10.1037/vio0000079 Liddell, T. M., & Kruschke, J. K. (2018). Analyzing ordinal data with metric models: What could possibly go wrong? Journal of Experimental Social Psychology, 79, 328–348. https://doi.org/10.1016/j.jesp.2018.08.009 Regenwetter, M., & Cavagnaro, D. R. (2019). Tutorial on removing the shackles of regression analysis: How to stay true to your theory of binary response probabilities. Psychological Methods, 24(2), 135–152. https://doi.org/10.1037/met0000196 Regenwetter, M., Cavagnaro, D. R., Popova, A., Guo, Y., Zwilling, C., Lim, S. H., & Stevens, J. R. (2018). Heterogeneity and parsimony in intertemporal choice. Decision, 5(2), 63–94. https://doi.org/10.1037/dec0000069

This is an in-person presentation on July 22, 2024 (10:00 ~ 10:20 CEST).

Individuals with schizophrenia (SZ) and bipolar disorder (BD) show disruptions in self-referential gaze perception—a ubiquitous form of social perception that is related to symptoms and functioning. However, our current mechanistic understanding of these dysfunctions and relationships is non-specific, meaning various explanations could account for existing data. This study used mathematical modeling to identify cognitive processes driving gaze perception abnormalities in SZ and BD and how they relate to cognition, symptoms, and social functioning. We modeled behavior of 28 SZ, 38 BD, and 34 controls (HC) in a self-referential gaze perception task using drift diffusion models parameterized to index: drift rate (evidence accumulation efficiency), drift rate bias (perceptual bias), start point (expectation bias), threshold separation (response caution), and non-decision time (encoding/motor processes). Results revealed that aberrant gaze perception in SZ and BD was driven by less efficient evidence accumulation, drift rate biases predisposing self-referential responses, and greater caution (SZ only). Across SZ and HC, poorer social functioning was related to more self-referentially biased start points. Within SZ, drift rate biases and start point biases were associated with hallucination and delusion severity, respectively. These findings suggest that diminished evidence accumulation and perceptual biases may underlie altered gaze perception in patients and that SZ may engage in compensatory cautiousness, sacrificing RT to preserve accuracy. Moreover, biases at the belief and perceptual levels may relate to symptoms and functioning. This underscores the value of using computational cognitive modeling to achieve a more nuanced understanding of the mechanisms of social perceptual processes, like gaze perception, in the study of complex psychopathology.

This is an in-person presentation on July 22, 2024 (10:20 ~ 10:40 CEST).

In Parkinson’s disease (PD), degeneration of the dorsal striatal-substantia nigra pars compacta (SNc) pathways is associated with motor symptoms. However, to a lesser extent cell loss also occurs in the ventral striatal-ventral tegmental area (VTA) dopamine projections which are centrally involved in reward prediction error coding, thus affecting reinforcement learning (RL). Here we asked whether neurodegeneration in SNc and VTA differentially affects action value learning and stimulus value learning. We tested PD patients ON and OFF medication (N=22) as well as healthy age matched controls (N=24) on a novel probabilistic bandit task with a color and an action learning condition. In the color value learning condition, reward probabilities were tied to the color of handles (blue or yellow), irrespective of the action performed (pushing or pulling). Conversely, in the action value learning condition, reward probabilities were associated with the push or pull action, regardless of handle color. We developed an error-correction RL model with a new weighting parameter to assess the relative contributions of color and action values to the learning process. Hierarchical Bayesian inference was then employed to estimate latent parameters at both individual and group levels, allowing inference across medication states and participant groups. Using careful model comparison, we tested the hypothesis that action value learning is more impaired in PD patients OFF medication than color value learning, but restored ON medication.

This is an in-person presentation on July 22, 2024 (10:40 ~ 11:00 CEST).