Dr Mauro Manassi

Biography

I obtained my Bachelor's degree in Psychology of Personality and Interpersonal Relationships from Padua University (Padua, Italy). Right before earning my Master's degree in Clinical Psychology and beginning a career as a clinical psychologist, I fell in love with Perception and Visual Neuroscience. Since then, this has been my passion and profession.

After completing my master’s thesis on motion priming under the supervision of Prof. Gianluca Campana, I joined Prof. Michael Herzog's Psychophysics laboratory at École Polytechnique Fédérale de Lausanne (Lausanne, Switzerland) for a PhD in Neuroscience (2009-2014). My PhD focused on how our visual system organizes the cluttered environment around us in a coherent manner (go here for more information about my work on visual organization).

At the end of my PhD, I was awarded the Early Postdoc.Mobility fellowship by the Swiss National Science Foundation for an 18-month postdoc in Prof. David Whitney's laboratory of Perception and Action at UC Berkeley (California, USA). Here, I became interested in how our visual system stabilizes our visual interpretations of the world, turning discontinuous and chaotic retinal images into coherent visual percepts (go here for more information about my work on visual stabilization).

In August 2019, I was appointed Lecturer (equivalent to Assistant Professor) in Psychology at the University of Aberdeen (UK). In 2022, I was awarded a prize for Best Research Article of the Year by the British Psychological Society. In August 2024, I will co-host the 46th European Conference on Visual Perception in Aberdeen with Dr. Constanze Hesse.

Prizes and Awards

British Psychology Society Cognitive Psychology Section Award: Best Research Article of the Year (2022)

Research Overview

Object recognition seems an effortless task. We just open our eyes and the objects are there. However, it is such a complex task that - after more than a century of research - even the fundamental principles of object recognition are not yet fully understood. As if this were not problematic enough, our visual world is constantly dynamic and cluttered. We have frequent eye movements, and scenes are congested with visual features and objects that are often themselves changing. The enormous amount of information should easily overwhelm our visual system’s limited capacity. Fortunately, the visual system has evolved sophisticated mechanisms that organize and stabilize our visual interpretations of world, turning discontinuous and chaotic retinal images into coherent visual percepts. The Manassi lab investigates two important principles of visual processing that let us achieve a coherent visual world: Organization and Stabilization. 

Current Research

Our visual world is constantly dynamic and cluttered. The enormous amount of information should easily overwhelm our visual system’s limited capacity. My research focuses on two important mechanisms of visual processing that let us achieve a seemingly coherent visual world: Organization and Stabilization (see www.manassilab.com/research/).

Organization (https://www.manassilab.com/crowding):
Using visual crowding (Whitney & Levi, 2011) and ensemble perception (Yamanashi et al. 2018) as a tool to investigate object recognition, my research focuses on understanding the fundamental aspects of how the visual system organizes the visual input coming from cluttered scenes into more global, organized representations. For example, can we extract trustworthiness from a crowd? When dealing with a crowd, how fast can we tell whether it is a trustworthy one or not?

Stabilization (see this recent article https://theconversation.com/everything-we-see-is-a-mash-up-of-the-brains-last-15-seconds-of-visual-information-175577):
Recently a novel mechanism of object stabilization was proposed, suggesting that perception occurs through serial dependencies in visual perception. By biasing our current percept towards the past, serial dependencies make similar (but distinct) objects appear more similar than what they really are, thus promoting the perception of object stability (see an illusion of stability here: https://www.manassilab.com/stability-illusion).
This research areas aims at investigating underlying mechanism of visual stabilization.

Medical Image Perception
Cancer diagnosis in medical images is crucial for the health of millions of people, but it is still far from perfect. One critical reason for misdiagnoses is the misperception of radiographs by clinicians (see Manassi et al. 2021). Radiographs can contain various kinds of structures, from actual masses, to microcalcifications, and other morphologies. It is thus crucial for radiologists to correctly recognize lesions in cluttered radiographs, discarding non-relevant masses. The research area aims at investigating visual biases in radiological screening.

Past Research

Organization
Our visual system is continuously confronted with an enormous amount of visual information: objects, faces, letters and simple features are constantly present in our visual field. This presents a fundamental limitation to object recognition throughout most of the visual field most of the time, known as visual crowding: objects that can be easily identified in isolation seem jumbled and indistinct in clutter (Whitney & Levi, 2011). Still, despite such a cluttered environment, our visual system is able to organize the world around us into a coherent percept. How do we achieve this? The Manassi lab, using crowding as a tool to investigate object perception, investigates how our visual system organizes all the visual input coming from cluttered scenes into a more global, organized representations.
Crowding was traditionally thought to be characterized by target-flanker interactions, which are (a) deleterious (e.g., pooling and substitution), (b) locally confined, (c) feature-specific and (d) restricted to low-level representations. We showed that none of these assumptions hold true. These results show that the spatial configuration across the entire visual field determines crowding, challenging most current models of crowding and object recognition (Bornet el at. 2021). Importantly, they highlight how crowding on a single element is determined by the perceptual organization in a scene, thus, making grouping a necessary component for any proposed crowding mechanism (Herzog et al. 2015a, 2015b). ​In cluttered scenes crowding happens at multiple levels of visual processing, from low level representations, like orientation and lines to high-level ones, like objects and faces. Importantly, crowding impairs the access we have to visual information at many levels, but it does not impair the representation of that information (Manassi & Whitney, 2018; Xia et al. 2020).
More info at https://www.manassilab.com/crowding

Stablization
We perceive the world around us as stable over space and time, even though our visual experience is often discontinuous and distorted due to eye movements, masking, occlusion, camouflage, or noise. How are we able to easily and quickly achieve stable perception in spite of this constantly changing visual input? Recently, a novel mechanism of object stabilization was proposed, suggesting that perception occurs through serial dependencies in visual perception (Fischer & Whitney, 2014). By biasing our current percept towards the past, serial dependencies make similar (but distinct) object appear more similar than what they are, and thus promote the perception of object stability. The Manassi Lab investigates how serial dependencies contribute to stabilize our percept across time, with different kinds of features and under various modalities.
In the complex environment we experience every day, stable scene perception is achieved through global serial dependencies: a special of global serial dependence between ensemble representations. Serial dependence occurs also in position perception, contributing to the stable perception of objects in space from moment to moment. Serial dependence occurs also in facial expression and identity (Liberman et al. 2014), but it is highly selective for gender. Serial dependence occurs within same genders whereas it does not occur within different genders. 
Taken together, these results show that serial dependencies are a global and selective mechanism which stabilize perception at many stages of visual processing, from initial position assignment to ensemble representations to emotional expression. Crucially, we found that serial dependence can generate an online illusion of stability: a single physically changing object can be misperceived as unchanging (Manassi et al. 2022).
In the autocorrelated world we live in, it is useful for our visual system to trade accuracy for increased perceptual stability. In artificially uncorrelated situations, however, serial dependencies can be detrimental for object recognition.  We found that radiologists’ perceptual decisions on any given current radiograph are biased towards the previous images they have seen (Manassi et al. 2019; 2021).
More info at https://www.manassilab.com/serialdependence

Knowledge Exchange

• Philosophy Café: Active member of a programme of discussion evenings which gives lecturers the opportunity to share their research. Talk title: How do we perceive a coherent visual world? (2022)

• Media Engagement: In 2022, 103 news stories on my research (Manassi et al. 2022) were reported by 85 international media outlets with 25 interviews (UK, Italy, Mexico, US, France, Israel, Saudi Arabia, Spain, China, India, New Zealand, Japan, etc.). In 2024, my laboratory got further media attention when our article from Marini et al. (2023) was reported on 36 media outlets with 26 broadcasted interviews. Marini (PhD student in my lab) won an award for public engagement with research at the Principal’s Excellence Awards (2024).

• Media Outreach: I have created a novel visual illusion based on my research which has gone viral on the internet with more than 259’000 views (YouTube link).

• Science Journalism: I have written a popular science article on The Conversation with more than 259’000 views (Everything we see is a mash-up of the brain’s last 15 seconds of visual information).

• Perception Science Internship: Organizer and teacher in a High School students program on neuroscience, coding, statistical analysis and scientific writing/presentation skills (4 weeks duration; 2015-2019).

• Science Outreach Program: Presentations and demos on vision and perception science for local schools in socially and economically disadvantages areas (2015-2019).

Collaborations

Merav Ahissar (Hebrew University, Jerusalem, Israel)
Aaron Clarke (Bilkent University, Ankara, Turkey)
Gianluca Campana (University of Padua, Italy)
Karin Pilz (University of Groningen, Netherlands )​
Greg Francis (Purdue University, West Lafayette, USA)
Michael H Herzog (École Polytechnique Fédérale de Lausanne, CH)
Meike Ramon (University of Fribourg, CH)
Clare Sutherland (University of Aberdeen, UK)
Frouke Hermens (University of Lincoln, Lincoln, UK)
Árni Kristjánsson (University of Iceland, Reykjavik, Iceland)
Andrea Pavan (University of Lincoln, Lincoln, UK)
Bill Prinzmetal (University of California, Berkeley, USA)
Bilge Sayim (University of Bern, CH)
David Whitney (University of California, Berkeley, USA)
Julia Föcker (University of Lincoln, UK)

Funding and Grants

Carnegie Research Incentive Grant RG15781 (2021-2022). (£ 12’002 awarded)

Assisted to writing of NIH R01 grant 1R01CA236793-01, in collaboration with prof. David Whitney, Berkeley (2019). ($ 1'704'638 awarded)

“Early Postdoc.Mobility” fellowship from Swiss National Science Foundation P2ELP3-158876 (2015-2016). (CHF 72'650 awarded)