Author: Tiffany Ang, Class of 2025

Figure 1: A visual representation of how perception overload amplifies the complexities of cognitive processing.

Hallucinations are disruptions in perception that lead to incorrect interpretations of environmental stimuli. Dr. Larsen and colleagues from the Department of Psychology at Stony Brook University are exploring the relationship between hallucination-proneness and the weighting of information, particularly how a diminished responsivity to variations in information may play a role. In their study, they define “robust averaging” as the integration of multiple forms of stimuli while minimizing the influence of irrelevant stimuli. To model how sensory information is integrated across time and space, the researchers employed perceptual averaging, which refers to the mental process of averaging sensory information. 

Dr. Larsen’s team conducted a multielement perceptual averaging task in which participants were shown eight distinct colors, ranging from “very red” to “slightly red” and “slightly blue” to “very blue,” with variance manipulated at high, medium, or low levels. Participants were asked to make dichotomous judgments about the “average color” (red/blue). The data was analyzed using a log-posterior-ratio (LPR), which calculates the likelihood ratio of the probabilities for each response. According to the LPR, optimal decision-making involves down-weighting irrelevant information to avoid misleading conclusions. Dr. Larsen and colleagues hypothesized that individuals prone to hallucinations would demonstrate reduced adaptive down-weighting of irrelevant information and fail to engage in robust averaging. They also hypothesized that hallucination-prone individuals would exhibit diminished sensitivity to increasing variability in information. 

Results showed that, in the presence of irrelevant information, individuals tended to engage in robust averaging. In the low-variability group, the weight distribution displayed an inverted U-shape, suggesting that as variability increased, the down-weighting of information also increased. However, this effect was not observed in the high-variability group, where participants weighed relevant and irrelevant information equally. Dr. Larsen and colleagues concluded that hallucination-prone individuals have strong priors, meaning they are more likely to rely on past experiences of hallucinations in high-variance environments. In contrast, individuals not prone to hallucinations possess weaker priors, allowing them to engage in more effective down-weighting.

To date, perceptual processes related to psychosis have largely been studied utilizing signal-detection mechanisms, which provide limited insight because perceptual decision-making involves integrating sensory information over time or space rather than responding to a single, discrete stimulus. In future studies, Dr. Larsen and colleagues plan to investigate how reduced gray matter in the dorsal anterior cingulate cortex contributes to insensitivity to variance. They also aim to examine the role of the parietal cortex, which is involved in tracking the LPR for down-weighting irrelevant information. 

Works Cited:

[1] Larsen EM, Jin J, Zhang X, Donaldson KR, Liew M, Horga G, Luhmann C, Mohanty A. Hallucination-Proneness is Associated With a Decrease in Robust Averaging of Perceptual Evidence. Schizophr Bull. 2024 Jan 1;50(1):59-68. doi: 10.1093/schbul/sbad129. PMID: 37622401; PMCID: PMC10754164.

[2] Image retrieved from: https://pixabay.com/vectors/man-human-mental-health-mind-brain-7330159/