Ms Georgie Powell
Overview
Research Group:
Perception & Action
Supervisor(s):
Petroc SumnerAline Bompas
Location: 58 Park Place
Email: PowellG7@cardiff.ac.uk
Telephone: +44(0)29 208 75271
Research Summary
Our perception of colour is based on the brain’s best interpretation of the incoming signal, rather than the physical wavelengths of light reaching the retina. This means we are often not conscious of what our eyes are really telling us. Our visual systems use many different cues to paint a sensible impression of the world around us. My research explores these cues in an attempt to piece together the jigsaw of colour perception.
Teaching Summary
2009-present: Level 1 Psychology practical marking and tutorials
2009-present: Assisting with Level 2 Psychology practicals.
Publications
Full List of Publications
Conference Presentations
Powell, G., Bompas, A., & Sumner, P. (2011). Hues being framed and the nulling of the afterimage. Perception 40, European Conference of Visual Perception Abstract Supplement.
Bompas, A., Powell, G., & Sumner, P. (2011). Colour perception across the visual field: no mastery of sensorimotor contingencies. Perception 40, European Conference of Visual Perception Abstract Supplement.
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Research
Research Topics and Related Papers
Colour variation across the retina
Colour appearance in laboratory studies varies across retinal eccentricities. This is probably due to the density variation of yellow macular pigment, which filters short wavelength (blueish) light at the fovea (Fig. 1). Three interesting questions arise from this. Firstly, why do we not perceive this variation in the real world? Secondly, to what extent, and how, has our visual system compensated for it? Thirdly, is this difference still observed when we view natural rather than computer generated stimuli?
Fig 1. Effect of macular pigment filter between fovea and periphery.
Colour afterimages
Franz (1899) ‘In the history of after images we seem to have an epitome of the interrelation of physics, physiology and psychology; and probably no other single phenomenon is so good an example of the growth of experiment and measurement in psychology’
Fixating a coloured stimulus before transferring gaze to a uniform field results in the perception of a ghostly afterimage, complementary in hue to the original stimulus (Fig. 2). These fascinating, robust illusions have long been demonstrated in laboratory studies and undergraduate perception lectures. Colour afterimages probably originate from fatigued responses of specific classes of retinal cells, yet our rare experience of them in the real world suggests they are influenced by factors beyond the retina. I am currently exploring several of these factors, including: boundaries and context, eye movements and attention.
Fig.2. Stare at the fixation cross. When the coloured squares are replaced by black outlines, you should perceive four ghostly afterimages in their place.
Funding
School of Psychology and BBSRC
Research Group
Supervisors
Biography
Undergraduate Education
2004 - 2005: Diploma in Film Making, New York Film Academy.
2005-2009: B.A. Applied Psychology, 1st Class honours, Cardiff University
2007: The Undergraduate Research Opportunities Programme, Cardiff University
Postgraduate Education
2009 – present: PhD Psychology, Cardiff University
Awards
Applied Vision Association Richard Eagle Memorial Award (2012, £750)
European Conference of Visual Perception (2011) student poster prize (€500)
Speaking of Science (2011) 2nd Prize Oral Presentation Award (£50).
Cardiff Graduate School Postgraduate Researcher Initiatives 2009-2010 (£1000)
Cardiff Graduate College Postgraduate Researcher Initiatives 2010-2011 (£1000)
Memberships
Applied Vision Association
Other Duties
Organiser of the External Sensational Seminar Series