Projects

Biases in memory and perception

In many tasks across the cognitive hierarchy, seemingly irrelevant context biases decision-making. This line of studies asks a simple question: Why can’t people be accurate? Why can’t they ignore information that should not affect their decisions? Using computational modeling, we show that biases can be understood as a consequence of optimal inference under uncertainty. In particular, the “demixing model” suggests that biases arise as we try to disentangle the mixed signals from two (or more) items, and it predicts both attraction and repulsion effects.

Background and reviews | Nature Human Behaviour 2026 | bioRxiv 2023

Demixing model: A normative explanation for inter-item biases in memory and perception

This paper formalizes the demixing model: when multiple similar items produce mixed evidence, the most probable estimate is often biased even under optimal inference. The model predicts both attraction and repulsion as a function of similarity and noise, and reframes these effects as unavoidable consequences of the inference problem rather than heuristic failures.

Noise in Competing Representations Determines the Direction of Memory Biases

This study tests a novel prediction of the demixing model, namely, that bias direction depends on relative noise between target and non-target representations, not only on absolute noise levels. Across four color-memory experiments, the same target noise level could produce more attraction or repulsion depending on how noisy the competing item was.

Feature distribution learning

One of the driving questions in vision science is how internal models of the world relate to the world itself. Quite often, answers to this question are pursued by studying single stimuli (e.g., a green circle) or sets of similar stimuli (a set of green circles). In contrast, this research line studies how people encode perceptual ensembles (such as fields of grass or differently colored marbles). It uses an experimental paradigm based on priming of pop-out in visual search to study ensembles with different probability density functions and to analyze the internal representations corresponding to these functions.

Background and reviews | Neurons, Behavior, Data analysis, and Theory 2022 | Cognition 2021 | Elements in Perception 2024 | Neuromethods 2020 | Progress in Brain Research 2017

Probabilistic representations as building blocks for higher-level vision

This article asks whether probabilistic representations are rich enough for higher-level vision, beyond simple “summary-statistics” accounts. Using Bayesian modeling and visual-search data, it shows that observers encode uncertainty jointly with feature conjunctions and spatial structure.

Extracting statistical information about shapes in the visual environment

This paper extends ensemble-statistics work from basic features to shape structure and tests whether people can extract distributional information from more complex stimuli. The results indicate robust statistical extraction for shape ensembles, supporting distribution-level representations outside classic color/orientation tasks.

Affect-as-feedback for predictions

Most cognitive acts can be treated as prediction or inference processes. This line asks what role affect plays in these processes and why positive or negative experience is needed. The central hypothesis, tested across multiple studies, is that affect provides feedback on prediction accuracy weighted by prior probability. One corollary is that errors should yield negative affect proportional to the evidence in favor of the correct response. Crucially, this is not about complex choices (“Should I buy this car?”), but about errors in simple and largely automatic processing (“Did I see this face before?”).

Background and reviews | Acta Psychologica 2016

Other papers

This section includes additional work from across methods and domains, ranging from tests of RT measurement accuracy in online experiments to simulations for transcranial ultrasound neuromodulation to perception of #TheDress. Note: the list here includes only selected papers; see the Google Scholar page for the full list.
  • Probabilistic coding and representation of uncertainty. A central line of work asks how uncertainty is represented in neural and behavioral data. For example, Chetverikov & Jehee (2023) shows bimodal probabilistic coding of motion direction, while Chetverikov & Kristjánsson (2024) reviews how visual variability is represented across tasks.
  • Transcranial Ultrasound Stimulation (TUS). In collaboration with Verhagen lab at Donders Institute, Andrey worked on brain stimulation to test causal roles of oculomotor/frontal circuits in decision-making. A key study in Nature Communications demonstrates rapid modulation of choice behavior by ultrasound targeting human frontal eye fields.
  • Bots in online studies. Are LLM-driven bots already taking part in online behavioral experiments? In a reply to Van der Stigchel et al. (2026), Andrey argued that unusual response times are not evidence of bots. Together with the authors of the original commentary, Özüdoğru et al. (2026) then showed that a general-purpose agent, built entirely through natural-language prompting, can complete 26 online experiments across seven hosting platforms, mostly with human-like performance.
  • Methods and open resources. Methodological work includes benchmarking online response-time measurement in Chetverikov & Upravitelev (2016) and large shared metacognitive resources in Rahnev et al. (2020).