Doctoral Defense in Psychology – Anton Lukashevich

On Tuesday, November 25, 2025, Anton Lukashevich will defend his doctoral thesis in psychology at the Faculty of Psychology, University of Iceland.

The thesis is titled: Is ensemble perception attention-dependent? Attention in the crowd: probing ensemble perception attentional dependencies.

Opponents are Dr. Tatiana Aloi Emmanouil, Associate Professor at Baruch College, New York, and Dr. Jonathan S. Cant, Associate Professor at the University of Toronto Scarborough.

Advisor and supervisor was Professor Heiða María Sigurðardóttir. Other members of the doctoral committee were Dr. Igor Utochkin and Dr. Sabrina Hansmann-Roth.

Ragnar Pétur Ólafsson, Professor and Vice Head of the Faculty of Psychology, will chair the ceremony, which will take place in the Ceremonial Hall of the University of Iceland and begin at 9:00 a.m.

Abstract

In a world where we constantly process visual information : from scanning a busy street to spotting patterns in data - how does our brain quickly summarize scenes without getting overwhelmed? Ensemble perception enables the rapid extraction of summary statistics from visual scenes, bypassing capacity limitations, but its dependence on attention remains debated. This thesis investigates whether ensemble processing operates automatically or requires attentional resources, focusing on low- and mid-level features like orientation and length, through three studies combining behavioural paradigms and electroencephalography (EEG). Study I examined automatic detection of ensemble mean orientation changes using visual mismatch negativity (vMMN) in oddball tasks. Attended changes elicited P3 component, but unattended changes produced no vMMN, indicating no pre-attentive processing. Study II tested automatic parsing of spatially intermixed objects into categories based on feature distributions. vMMN emerged for length-based segmentation but not orientation alone, suggesting feature-specific automaticity. Study III manipulated spatial attention via Posner cueing; ensemble orientation judgments dropped to chance on invalid cues, unlike single items, confirming attention's necessity. Overall, findings demonstrate that ensemble perception is not fully automatic, particularly for orientation, requiring spatial and selective attention for accurate extraction. Implications extend to visual cognition theories, emphasizing attention's gating role in summary statistics processing.

About the doctoral candidate

Anton Lukashevich was born in Minsk, Belarus, in 1992. He graduated from Sechenov University in Moscow in 2015 with a degree in general medicine. In 2017, he specialized in neurology at the Research Center for Neurology. Since 2018, Anton has taught at the Department of Normal Physiology at Sechenov University. In 2022, he began his doctoral studies at the University of Iceland under the supervision of Professor Heiða María Sigurðardóttir and Dr. Igor Utochkin of the University of Chicago, USA. During his studies, Anton taught courses at both the Faculty of Psychology and the Faculty of Medicine at the University of Iceland.