Dr Georgie Powell

Research Associate

Research group:
Cognitive science
Developmental & health psychology
029 208 70573
Tower Building, Park Place

Research summary

Our brains make decisions all the time. Some of these are perceptual – is this car moving slower or faster than that car? Some are cognitive or motor– should I turn left or right at the junction? Most are a combination of the three. People differ greatly in the decisions they make and this leads to large individual differences in their perception of the world and their behaviour within it.   I’m interested in how studying these individual differences can inform our understanding of the processes underlying perceptual, cognitive and motor decision making.

One of the ways I’m exploring this is by studying how individuals with neuropsychological conditions, such as Autism, differ in their decision making processes. To do this, I’m using computational models to isolate the key processes that might contribute to differences in perception and behaviour.  I’m also interested in whether novel cognitive training paradigms can improve decision-making by targeting key areas of difficulty.

Another interest related to individual differences is how qualitative measures in psychology, for example personality or trait questionnaires, relate to experimental laboratory tasks that aim to measure the same trait. For example, how do questionnaire measures of impulsivity relate to experimental tasks that measure related constructs such as cognitive control and response inhibition? Also, how do questionnaire measures of sensory processing relate to psychophysical measurements of sensory detection and discrimination?

Selected publications (2014 onwards)


Full list of publications


Media activities

New Scientist TV: Friday Illusion – Colour an animation with your mind

Research topics and related papers

Individual differences in impulsivity and cognitive control

People differ greatly in their ability control their behaviour and impulses, and this is related to a wide range of general life outcomes such as heath and income. Psychologists have developed a number of tasks to measure response control, yet oddly, these aren’t related very strongly to personality measures of impulsivity.  Which raises the question – are they measuring the same thing?

We are currently exploring whether computational models of decision making can isolate the underlying factors that contribute to response control and provide more stable experimental measurements of impulsivity.

Drift-diffusion model (Ratcliff) – one of the computational models we are using to explore decision making and response control.

We are also investigating whether decision-making processes are different in individuals with Autism Spectrum Disorders (ASD), using the same computational models. In particular, we are trying to isolate factors related to speed/accuracy preference (e.g. caution) from task-related processing of information.

Sensory perception in Autism Spectrum Disorders

Individuals with ASD often have different sensory experiences of the world than individuals without ASD. This is apparent both from qualitative measures of sensory processing and from psychophysical measures of differences in detection and discrimination of sensory stimuli. I’m interested in why individuals with ASD have different sensory experiences of the world. One theory is that individuals with ASD do not use prior expectations about the statistics of the world to interpret incoming sensory information as much as individuals without ASD do (Pellicano & Burr, 2012). Prof Tom Freeman and I have recently tested this this theory in relation to visual motion processing.

This combination of incoming sensation and prior knowledge might be different in individuals with ASD.

In collaboration with Catherine Jones and Katy Unwin, I’m also interested in how multi-sensory environments (MSE) are used by children with ASD. MSEs are common in special educational needs settings, but relatively little research has explored what their potential benefits and limitations are. In particular, I’m interested in the relationship between sensory processing profiles (measured by questionnaires and psychophysics) and real life sensory behaviours and exploration.

An example of a multi-sensory environment.

Rehabilitation tools for Visual Vertigo

Visual Vertigo is a deliberating condition characterised by the experience of dizziness and nausea in response to certain visual environments.

Different types of environments that could trigger visual vertigo episodes.

One theory is that Visual Vertigo arises from an imbalance between vestibular and visual signals, perhaps as a result of a previous problem with the vestibular system. Rehabilitation from the condition can be poor and so there is a need to develop theory-driven and evidenced-based therapy tools. We are currently developing a battery of rehabilitation videos for visual vertigo that target visual and vestibular responses to moving images.

If you are a clinician who would like to access these resources, please visit the Cardiff Visual Vertigo Study webpage.

Visual attention control in individuals with neurodevelopmental disorders

Control of attention is vital for everyday functioning – choosing which objects to ignore and which to inspect, switching our attention between different objects, and sustaining attention on one stimulus over extended periods of time. Children with neurodevelopmental disorders may have difficulties with attention control and this could lead to knock-on effects on other areas of development.

In collaboration with Dr Sam Wass, we have recently been exploring whether a novel attention training paradigm, which uses eye tracking technology, can improve attention control in children with ASD and Rett Syndrome. Eye-tracking technology is becoming popular in special educational needs settings and so we piloted the attention training games in schools around South Wales.

Some screen shots from the attention training games.

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. These fascinating, robust illusions have long been demonstrated in laboratory studies and undergraduate perception lectures. Colour afterimages probably originate from an imbalance in the responding 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. We suggest that afterimage signals are inherently ambiguous and this means they are particularly influenced by cues that increase or decrease the likelihood that they represent a real object. We have explored several of these cues, including: boundaries and context, eye movements and attention.

Use full screen for best results: A colour afterimage illusion we created – called ‘afterimage jellies’.


ESRC Project grant

Research group

Cognitive Science
Developmental & Health Psychology
Wales Autism Research Centre

Research collaborators

Prof Petroc Sumner (impulsivity project, visual vertigo, colour afterimages)
Dr Craig Hedge (impulsivity project)
Prof Tom Freeman (Bayesian models of perception, smartphone map navigation)
Dr Catherine Jones (multi-sensory environments for Autism Spectrum Disorders, impulsivity project)
Prof. Sue Leekam (attention control training)
Prof Simon Rushton (visual vertigo)
Prof Chris Chambers (impulsivity project).
Mrs Solveiga Vivian-Griffiths (impulsivity project).
Dr Jon Erichson (attention control training)
Prof. Angus Clarke (Rett Syndrome and eye tracking)

Dr Sam Wass (MRC Cognition and Brain Sciences Unit, University of Cambridge)
Hannah Derry-Sumner (University Hospital of Wales)
Dr Deepak Rajenderkumar (University Hospital of Wales)
Mike Ayres (Mike Ayres Design)
Special Needs and Autism Project (London)

Current Students

Katy Unwin (co-supervised with Catherine Jones). Katy started her PhD in Oct 2015 and is exploring the use of multi-sensory environments for children with Autism Spectrum Disorders.

Undergraduate education

2009: BA Applied Psychology (Hons) 1st class, Cardiff University.

Postgraduate education

2013: PhD Psychology, Cardiff University.  Thesis: Conscious Perception of Illusory Colour. Supervised by P. Sumner and A. Bompas.

Awards/external committees

Hadyn Ellis prize for best PhD dissertation (2014), School of Psychology, Cardiff University.
Bristol Cardiff Young Vision Researchers Colloquium (2013, £50), 2nd Prize Oral Presentation Award.
Applied Vision Association (2012, £750), Richard Eagle Memorial Award.
European Conference of Visual Perception (2011, €500), student poster prize.
Speaking of Science, Cardiff University (2011, £50), 2nd Prize Oral Presentation Award.


Applied Vision Association (AVA).

External Committees

2009-present: Vice Chair, Innovate Trust.
2008-2009: Vice Chair, Student Volunteering Cardiff.  


October 2013 – present:  Research Associate at Cardiff University.

July – October 2012: Press Officer for Mental Health and Neuroscience, Science Media Centre.

2009-2013: Undergraduate teaching at Cardiff University.  Year 1 Practicals and Statistics Tutor, Year 2 Practical Assistant, and Year 3 Workshop Assistant.

2007-2008: Placement with Clinical Psychology team at Cardiff Adult Learning Disabilities Service.