UCL Psychology and Language Sciences


Dr John Greenwood

Dr John Greenwood


Experimental Psychology
26 Bedford Way


  • Senior Lecturer
    Experimental Psychology
    Div of Psychology & Lang Sciences

Joined UCL


My research examines human visual perception, primarily using techniques from behavioural psychophysics and computational modelling, as well as eye tracking and functional magnetic resonance imaging (fMRI). During my Ph.D., I examined the integrative processes required to perceive multiple directions of motion simultaneously. More recently, my research has focussed on peripheral vision and ‘crowding’ in both the ‘normal’ visual system and in children with amblyopia. Along the way I have also examined visual adaptation, saccadic eye movements, the perception of depth, position, and numerosity, as well as change-detection and attention.


A particular research focus is visual crowding, the deleterious effect of clutter on object recognition. Particularly in the peripheral visual field, objects can be highly visible when presented in isolation and extremely difficult to identify when surrounded by clutter, even when they are scaled to be just as visible (in isolation) as in the fovea. This effect, known as crowding, is of both applied and basic interest. From a clinical perspective, crowding limits the visual function of many patients with low vision, while elevated crowding is associated with common visual disorders such as strabismic amblyopia. It is also of basic theoretical interest because it is crowding, and not acuity or contrast sensitivity, that imposes the principle restriction on visual function in the peripheral visual field. My work examines the mechanisms underlying crowding, using simple stimuli to develop computational models that can be generalized to understand crowding with more complex letter-like stimuli and natural scenes.

Award year Qualification Institution
2008 PhD
Doctor of Philosophy
Australian National University

I completed my Ph.D. in 2007 at the School of Psychology of the Australian National University (Canberra, Australia), under the supervision of Dr. Mark Edwards. I then conducted postdoctoral research at the Institute of Ophthalmology at University College London (London, UK) with Prof. Steven Dakin and Dr. Peter Bex from 2008-2010, and at the Laboratoire Psychologie de la Perception of the Université Paris Descartes (Paris, France) with Patrick Cavanagh from 2011-2013. I joined the Department of Experimental Psychology in August 2013 to begin a Career Development Award from the Medical Research Council.


3D|*|Acuity|*|Amblyopia|*|Anisometropia|*|Contrast Sensitivity|*|Crowding|*|Density|*|Depth|*|Development|*|Numerosity|*|Peripheral Vision|*|Psychophysics|*|Saccadic Eye Movements|*|Stereopsis|*|Strabismus|*|Transparent Motion|*|Visual Perception