All Outputs (12)

Attractive and repulsive visual aftereffects depend on stimulus contrast (2025)
Journal Article
Gekas, N., & Mamassian, P. (2025). Attractive and repulsive visual aftereffects depend on stimulus contrast. Journal of Vision, 25(1), Article 10. https://doi.org/10.1167/jov.25.1.10

Visual perception has been described as a dynamic process where incoming visual information is combined with what has been seen before to form the current percept. Such a process can result in multiple visual aftereffects that can be attractive towar... Read More about Attractive and repulsive visual aftereffects depend on stimulus contrast.

Speed Estimation for Visual Tracking Emerges Dynamically from Nonlinear Frequency Interactions (2022)
Journal Article
Meso, A. I., Gekas, N., Mamassian, P., & Masson, G. S. (2022). Speed Estimation for Visual Tracking Emerges Dynamically from Nonlinear Frequency Interactions. eNeuro, 9(3), https://doi.org/10.1523/ENEURO.0511-21.2022

Sensing the movement of fast objects within our visual environments is essential for controlling actions. It requires online estimation of motion direction and speed. We probed human speed representation using ocular tracking of stimuli of different... Read More about Speed Estimation for Visual Tracking Emerges Dynamically from Nonlinear Frequency Interactions.

Adaptation to one perceived motion direction can generate multiple velocity aftereffects (2021)
Journal Article
Gekas, N., & Mamassian, P. (2021). Adaptation to one perceived motion direction can generate multiple velocity aftereffects. Journal of Vision, 21(5), Article 17. https://doi.org/10.1167/jov.21.5.17

Sensory adaptation is a useful tool to identify the links between perceptual effects and neural mechanisms. Even though motion adaptation is one of the earliest and most documented aftereffects, few studies have investigated the perception of directi... Read More about Adaptation to one perceived motion direction can generate multiple velocity aftereffects.

Disambiguating serial effects of multiple timescales (2019)
Journal Article
Gekas, N., McDermott, K. C., & Mamassian, P. (2019). Disambiguating serial effects of multiple timescales. Journal of Vision, 19(6), Article 24. https://doi.org/10.1167/19.6.24

What has been previously experienced can systematically affect human perception in the present. We designed a novel psychophysical experiment to measure the perceptual effects of adapting to dynamically changing stimulus statistics. Observers are pre... Read More about Disambiguating serial effects of multiple timescales.

History Effects on Perception of Noisy Stimuli (2019)
Presentation / Conference Contribution
Gekas, N., & Mamassian, P. History Effects on Perception of Noisy Stimuli. Presented at 41st European Conference on Visual Perception (ECVP), Trieste, Italy

Human perception is partially affected by what has been previously experienced. These history effects presumably help tackle current sensory uncertainty by tracking past stimulus statistics. However, there is no definitive framework on how stimulus h... Read More about History Effects on Perception of Noisy Stimuli.

Perceptual effects of adaptation over multiple timescales (2017)
Presentation / Conference Contribution
Gekas, N., McDermott, K., & Mamassian, P. Perceptual effects of adaptation over multiple timescales. Presented at VSS 2017

It is well known that adaptation to a visual stimulus leads to a negative correlation between the current percept and previous percepts. However, there are diverging views on how stimuli further in the past affect the current percept. We have argued... Read More about Perceptual effects of adaptation over multiple timescales.

A Normalization Mechanism for Estimating Visual Motion across Speeds and Scales (2017)
Journal Article
Gekas, N., Meso, A. I., Masson, G. S., & Mamassian, P. (2017). A Normalization Mechanism for Estimating Visual Motion across Speeds and Scales. Current Biology, 27(10), 1514-1520.e3. https://doi.org/10.1016/j.cub.2017.04.022

Interacting with the natural environment leads to complex stimulations of our senses. Here we focus on the estimation of visual speed, a critical source of information for the survival of many animal species as they monitor moving prey or approaching... Read More about A Normalization Mechanism for Estimating Visual Motion across Speeds and Scales.

Speed channel interactions in naturalistic motion stimuli (2016)
Presentation / Conference Contribution
Gekas, N., Meso, A., Masson, G., & Mamassian, P. Speed channel interactions in naturalistic motion stimuli. Presented at VSS 2016

Human observers are very sensitive to speeds of moving stimuli. However little is known about how such sensitivity arises independently upon the spatiotemporal properties of the stimulus. Here, we investigate the interactions between spatiotemporal f... Read More about Speed channel interactions in naturalistic motion stimuli.

Effect of orthogonal adaptation on the perceived velocity of multidirectional random dot stimuli at different speeds (2016)
Presentation / Conference Contribution
Gekas, N., & Mamassian, P. Effect of orthogonal adaptation on the perceived velocity of multidirectional random dot stimuli at different speeds. Presented at 39th European Conference on Visual Perception (ECVP) 2016, Barcelona

Motion adaptation generates strong aftereffects in the opposite direction. Here, we investigated the effect of orthogonal adaptation on perceived velocity across different speeds. Human observers adapted to a broadband grating, moving upwards at 6°/s... Read More about Effect of orthogonal adaptation on the perceived velocity of multidirectional random dot stimuli at different speeds.

Expectations developed over multiple timescales facilitate visual search performance (2015)
Journal Article
Gekas, N., Seitz, A. R., & Seriès, P. (2015). Expectations developed over multiple timescales facilitate visual search performance. Journal of Vision, 15(9), Article 10. https://doi.org/10.1167/15.9.10

Our perception of the world is strongly influenced by our expectations, and a question of key importance is how the visual system develops and updates its expectations through interaction with the environment. We used a visual search task to investig... Read More about Expectations developed over multiple timescales facilitate visual search performance.

Complexity and specificity of experimentally-induced expectations in motion perception (2013)
Journal Article
Gekas, N., Chalk, M., Seitz, A., & Series, P. (2013). Complexity and specificity of experimentally-induced expectations in motion perception. Journal of Vision, 13(4), Article 8. https://doi.org/10.1167/13.4.8

Abstract Our perceptions are fundamentally altered by our expectations, i.e., priors about the world. In previous statistical learning experiments (Chalk, Seitz, & Seriès, 2010), we investigated how such priors are formed by presenting subjects with... Read More about Complexity and specificity of experimentally-induced expectations in motion perception.

Investigating the specificity of experimentally induced expectations in motion perception (2012)
Presentation / Conference Contribution
Gekas, N., Seitz, A., & Seriès, P. Investigating the specificity of experimentally induced expectations in motion perception. Presented at VSS 2012

Our perceptions are fundamentally altered by our expectations, a.k.a. "priors" about the world. In previous statistical learning experiments (Chalk et al, 2010), we investigated how such priors are formed by presenting subjects with low contrast movi... Read More about Investigating the specificity of experimentally induced expectations in motion perception.