Study Finds Serial Dependence in Time Perception Follows Precision-Weighted Updating Model
A preprint study using time reproduction experiments found that serial dependence — the tendency for perceptual judgments to be biased toward recent experiences — is stronger when sensory signals are less reliable and when the perceptual context remains stable. Researchers modeled this behavior using a three-state Kalman filter, suggesting the brain continuously updates how much weight to give recent history based on the precision of incoming sensory information. The findings support a unified 'precision-weighted updating' account of serial dependence, with implications for understanding how the brain balances stability and flexibility in perception.
Researchers conducted two time reproduction experiments with 44 participants to investigate how sensory uncertainty and contextual transitions shape serial dependence — the well-documented bias in which current perceptual estimates are pulled toward recent ones. In Experiment 1, participants showed stronger serial dependence under low motion coherence (higher uncertainty) than high coherence, suggesting the brain leans more heavily on prior history when current signals are noisy. In Experiment 2, introducing salient contextual boundaries via coherence category transitions revealed that serial dependence was markedly stronger when the context remained the same versus when it switched, indicating that perceived environmental stability also modulates history weighting. A three-state Kalman filter model — incorporating fast (serial dependence), slow (central tendency), and bias (decision carryover) components — successfully captured both patterns through coherence-dependent adjustments to process noise and Kalman gain. Crucially, the model did not require an explicit state reset at contextual boundaries, suggesting the brain smoothly recalibrates rather than abruptly discarding prior information. The authors argue these results unify previously debated mechanisms under a single precision-weighted updating framework.
What's missing
As a preprint, this study has not yet undergone peer review. The sample size (N=44) is modest, and generalizability across different sensory modalities or populations remains untested. The Kalman filter model was selected within a limited model space, so alternative computational accounts outside that space were not evaluated. The study also does not address the neural substrates underlying the proposed precision-weighting mechanism.
What different sources said
- bioRxivCenter
Precision-Weighted Updating Explains Serial Dependence Across Sensory and Contextual Transitions
Related
Gut Bacteria Enzyme Found to Break Down Heat-Processed Food Compounds, Producing Novel Biogenic Amines
Researchers have discovered that an enzyme in common gut bacteria can degrade N-epsilon-carboxymethyllysine (CML), a compound formed during thermal food processing, producing previously unknown biogenic amines. The enzyme, ornithine decarboxylase SpeC from enterobacteria, acts on CML and related modified lysine derivatives through a low-level 'underground' catalytic activity. This finding suggests a previously unrecognized communication axis between thermally processed dietary compounds and gut microbial physiology, with potential implications for host health.
Full-Length Gene Sequencing Reveals Two Distinct Bacterial Communities in Black-Legged Ticks Expanding Into Canada
Researchers used Oxford Nanopore full-length 16S rRNA gene sequencing to characterize the microbiome of Ixodes scapularis black-legged ticks collected in Nova Scotia, Canada, distinguishing between tick-adapted bacteria and environmentally acquired bacteria. The study comes as I. scapularis — the primary vector of Lyme disease — is rapidly expanding northward into Canada due to climate change. The findings suggest that environmentally derived bacteria in tick microbiomes are not mere contamination, which has implications for how tick microbiome data is collected and interpreted across surveillance studies.
Study Identifies Metabolic Link Between Cell Envelope Stress and Biofilm Formation in Bacteria
Researchers have discovered that the metabolite acetyl-CoA directly inhibits enzymes that degrade the bacterial signaling molecule c-di-GMP, connecting cell envelope biosynthesis stress to biofilm formation in Pseudomonas aeruginosa. The study found that sub-inhibitory concentrations of antibiotics targeting early peptidoglycan biosynthesis — but not other antibiotic classes — elevate c-di-GMP levels by reducing phosphodiesterase activity, with acetyl-CoA competing for the enzyme active site. Because the relevant enzyme domain is broadly conserved across bacterial species, this checkpoint mechanism may be widespread and could have implications for understanding antibiotic-induced biofilm responses.