Category: Projects

Using Candy Crush to study perceptual learning

This is a guest post by Gabriela Raleva, who did a summer project with me in between her first and second years of the undergraduate degree.

gabrielaVisual learning refers to the enhanced sensitivity to visually relevant stimuli. Affective value of stimuli (e.g. reward, punishment), has been proposed to enhance action selection via instrumental learning (Hickey et al., 2010, Wilbertz et al., 2014).  The majority of studies in perceptual learning adopt an artificial approach of training participants in the lab for many sessions before testing them (although, see (Bavelier et al., 2012)). We used Candy Crush game sets as it represents an ideal platform for natural visual learning and assessed the performance of experienced players that have willingly engaged in a lot of practice hours as well as non-players.

In a between-subject design participants completed a visual search task, searching for a uniquely-shaped Candy Crush target among a number of nonhomogeneous Candy Crush distractors. Targets were divided into 4 conditions: neutral value, reward-value, punishment value and control condition (Figure 1). Reaction time for detection of targets was assessed and compared for each condition.

Figure 1. Target-present sets in all 4 conditions: (a) Neutral condition showing a single green candy (circled) which is a target of neutral consequences in the game, (b) Reward-associated containing a single multi-coloured bomb candy (circled) which is of positive consequences in the game, (c) Punishment-associated condition containing a blue bomb (circled) of negative consequences in the game, and (d) Control condition
Figure 1. Target-present sets in all 4 conditions: (a) Neutral condition showing a single green candy (circled) which is a target of neutral consequences in the game, (b) Reward-associated containing a single multi-coloured bomb candy (circled) which is of positive consequences in the game, (c) Punishment-associated condition containing a blue bomb (circled) of negative consequences in the game, and (d) Control condition

The results suggest that players and non-players revealed largely comparable responses in their detection of control, neutral, negative and positive stimuli (Figure 2). This indicates that the results are not due to self-selection bias. However, players were 35% faster at detecting rewarding targets than neutral targets stimuli. In contrast, non-players were on average 5% slower in detecting rewarding compared to neutral targets. Our analyses indicate that players reveal a consistent pattern of greater rewarding/neutral reaction time ratios than those of non-players consistent with the idea that features of affective-associated stimuli facilitate their perception in visual processing. Furthermore, the only Candy Crush condition in which players showed significantly slower reaction times than non-players is the neutral condition. One possible explanation is that players have developed better visual templates in regards to the game (Bejjanki et al., 2014) and therefore exhibit a visually holistic mode of performance (Green & Bavelier, 2003). Players may have learnt to quickly recognize patterns beneficial for the game such as the rewarding bomb. The green neutral candies compose a beneficial pattern only when they can be combined (at least 3) so it is possible that players learnt to recognize a single neutral candy as a distractor and thus suppress it more effectively. Such holistic expert performance is characterized by “chunking” – a process during which individual constituents are processed as a single perceptual or cognitive entity.

Figure 2. Mean reaction time of players and non-players in all 4 conditions as obtained by the target detection task.
Figure 2. Mean reaction time of players and non-players in all 4 conditions as obtained by the target detection task.

Bavelier, D., Green, C. S., Pouget, A., & Schrater, P. (2012). Brain plasticity through the life span: learning to learn and action video games. Annual Reviews of Neuroscience, 35, 391–416.
Bejjanki, V. R., Zhang, R., Li, R., Pouget, A., Green, C. S., Lu, Z.-L., & Bavelier, D. (2014). Action video game play facilitates the development of better perceptual templates. Proceedings of the National Academy of Sciences, 111(47), 16961–6.
Green, C. S., & Bavelier, D. (2003). Action video game modifies visual selective attention. Nature, 423(6939), 534-537
Hickey, C., Chelazzi, L., & Theeuwes, J. (2010). Reward guides vision when it’s your thing: Trait reward-seeking in reward-mediated visual priming. PLoS ONE, 5(11), 1–5.
Wilbertz, G., Van Slooten, J., & Sterzer, P. (2014). Reinforcement of perceptual inference: Reward and punishment alter conscious visual perception during binocular rivalry. Frontiers in Psychology, 5, 1–9.


Postscript from Tom:

One of the great difficulties of studying learning is that true expertise only comes after many many hours of practice. Psychologists often study perceptual learning in the lab with participants engaging in training with specific stimuli that last a few hours. The results of this project demonstrate the potential for using people who have already given themselves hundreds of hours of training with the specific stimuli as a side effect of a game they’ve played. To illustrate how large the effect is I plotted each participant’s Candy Crush level (so 0 for non-players) against the ratio rewarding / punishing stimulus RT : neutral stimulus RT. Even with the small number of participants the effect is clear – Candy Crush players are faster for the value-relevant stimuli relative to neutral stimuli, non-players aren’t.

The black line shows where participants’ reaction times should be if there are equally fast on the valuable Candy Crush stimuli as with neutral Candy Crush stimuli


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New grant: ‘Neuroimaging as a marker of Attention Deficit Hyperactivity Disorder (ADHD)’

We have been awarded ~£11k by the White Rose Collaboration Fund. This will allow us to carry out a small neuroimaging study investigating brain activity associated with higher levels of ADHD traits. The collaboration combines expertise and facilities across the Universities of Sheffield, Leeds and York. Paul Overton has previously proposed that the subcortical area known as the superior colliculus may be crucial in ADHD. This is the focus of Maria’s PhD thesis (co-supervised by Paul and me). Jaclyn Billington from Leeds has experience imaging the colliculus, and Tony Morland is the deputy director of York’s neuroimaging facility (as well as having a wealth of experience imaging the areas associated with visual function). Alex Wade and Jeff Delvenne provide additional expertise in visual attention. I lead the project.

Here is the blurb:

We will create a unique network of expertise, personnel and facilities from across the WR network in order to establish a novel biomarker of Attention Deficit Hyperactivity Disorder (ADHD).

Despite a high prevalence (up to 10% of children by some estimates), ADHD remains controversial in terms diagnosis and treatment. Using brain scanning, this network aims to establish a biological marker common to all ADHD suffers. Such a biomarker could revolutionise our response to ADHD, allowing us to better understand the condition, diagnose earlier, manage the symptoms and target pharmacological interventions. This could potentially alleviate suffering and improve function for millions.

Theoretical direction for this proposal arises from Overton’s recent proposal that a core dysfunction in ADHD is hypersensitivity of the Superior Colliculus (SC), a key subcortical brain region known to play a critical role in attention, spatial orientation and saccadic eye movements. The development of this ‘collicular hypersensitivity’ hypothesis was possible because of the tradition of research into the fundamental neuroscience of subcortical structures at Sheffield.

This hypothesis has been taken forward by Stafford (Sheffield) who, with Panagiotidi, has been developing behavioural tests of collicular sensitivity. Early results show that healthy adults who are high and low on ADHD traits differ in these behavioural measures. However, behavioural tests are limited in that they cannot provide definitive insight into the neural basis of function. Teams in York and Leeds provide expertise in functional brain imaging and the neural basis of attention which would allow the direct translation of the Sheffield research programme into a test of a biomarker for ADHD.

Our primary objective will be to test two groups, high and low in ADHD traits for collicular responsiveness, using fMRI brain imaging. This testing will use behavioural measures which have been shown to discriminate the two groups, and analytic and imaging expertise from the Leeds and York based applicants in order to determine collicular responsiveness

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New grant: Reduced habitual intrusions : an early marker for Parkinson’s Disease?

SurprisalDensityPlotFor4CharacterWindowI have very pleased to announce that the Michael J Fox Foundation have funded a project I lead titled ‘Reduced habitual intrusions : an early marker for Parkinson’s Disease?’. The project is for 1 year, and is a collaboration between a psychologist (myself), a neuroscientist (Pete Redgrave), a clinician specialising in Parkinson’s (Jose Obeso, in Spain) and a computational linguist (Colin Bannard, in Liverpool). Mariana Leriche will be joining us a post-doc.

The idea of the project stems from hypothesis that Parkinson’s Disease will be specifically characterised by a loss of habitual control in the motor system. This was proposed by Pete, Jose and others in 2010. Since my PhD I’ve been interested automatic processes in behaviour. One phenomenon which seems to offer particular promise for exploring the interaction between habits and deliberate control is the ‘action slip’. This is an error where a habit intrudes into the normal stream of intentional action – for example, such as when you put the cereal in to the fridge, or when someone greets you by asking “Isn’t it a nice day?” and you say “I’m fine thank you”. An interesting prediction of the Redgrave et al theory is people with Parkinson’s should make fewer action slips (in contrast to all other types of movement errors, which you would expect to increase as the disease progresses).

The domain we’re going to look at this in is typing, which I’ve worked with before, and which – I’ve argued – is a great domain for looking at how skill, intention and habit combine in an everyday task which generates lots of easily coded data.

I feel the project reflects exactly the kind of work I aspire to do – cognitive science which uses precise behavioural measurement, informed by both neuroscientific and computational perspectives, and in the service of am ambitious but valuable goal. Now, of course, we actually have to get on and do it.

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New project: “Bias and Blame: Do Moral Interactions Modulate the Expression of Implicit Bias?”

The Leverhulme Trust has awarded a 36 month grant to the University of Nottingham, for a project led by my collaborator Dr Jules Holroyd, with support from myself. The project title is “Bias and Blame: Do Moral Interactions Modulate the Expression of Implicit Bias?” (abstract below). The aim is to conduct experiments to advance our understanding of how implicit biases are regulated by ‘moral interactions’ (these are things such as being blamed, or being held responsible). The grant will pay for a post-doc (Robin Scaife) in Sheffield and a PhD student (as yet unknown, let us know if you’re interested!) in Nottingham.

Obviously, this is something of a departure for myself, at least as far as the topic goes (which is why Jules leads). I’m hoping my background in decision making and training in experimental design will help me navigate the new conceptual waters of implicit bias. Some credit for inspiring the project should go to Jenny Saul and her Bias Project, and before that, Alec Patton and his faith in interdisciplinary dialogue that helped get Jules and myself talking about how experiments and philosophical analysis could help each other out.

Project Abstract:

This project will investigate whether moral interactions are useful tool for regulating implicit bias. Studies have shown that implicit biases – automatic associations which operate without reflective control – can lead to unintentionally differential or unfair treatment of stigmatised individuals. Such biases are widespread, resistant to deliberate moderation, and have a significant role in influencing judgement and action. Strategies for regulating implicit bias have been developed, tested and evaluated by psychologists and philosophers. But neither have explored whether holding individuals responsible for implicit biases may help or hinder their regulation. This is what we propose to do.

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The Department’s first Director of Public Engagement

I am now the department’s first Director of Public Engagement. It’s a position which encompasses my previous admin roles of media liaison, website coordinator, faculty external relations and marketing contact, outreach and widening participation champion and academic organiser* of the internal and external seminar series and of our inaugural lectures for new Professors.

The creation of the Public Engagement role brings no particular new powers or benefits (apart from I get to be Director of something, which flatters me). What I hope it does do is signal that the department takes its duties for public service seriously, and give me remit to promote the kind of activities I believe the department should do more of. At this point, I wanted to write something about what, for me, the principles of public engagement are.

First, public engagement signifies a kind of public service which is wider than the ‘Impact’ agenda. At the moment the government funding model for Universities has prioritised measurable economic benefits which arise from specific research outputs (i.e. from academic papers). This means that if you publish a research paper on widget manufacture, and a local business consequently is able to up its Widget production from £100k of widgets per year, to £200k of widgets you have had impact. If you spend thirty years synthesising the values and methods of a domain of enquiry and write a textbook (or appear on television like Brian Cox) talking about your discipline you have had no impact (what you are doing is not based on a specific unit of research, the outcomes are unclear and hard to measure). For me public engagement captures many of the range of nonspecific, hard to measure benefits of Universities. We are in an immensely privileged position within the University to be able to specialise, to dedicate ourselves to thoroughness, scholarship, discussion and fairness. There is a societal benefit to having spaces committed to these values, it would be a shame if those were eroded because the benefits were hard to measure. So I’m pleased that the University of Sheffield is working hard to celebrate the cultural and intellectual value of Universities, reflected in the good work of our Public Engagement with Research team and things like the Civic University project.

Second, ‘public engagement’ is not ‘public understanding’, nor is it science communication. These two are both wonderful things, in a limited sense, but we’re not here to bludgeon the public with things we think they should understand. Public engagement means talking with people outside of the department, not just telling them things.

Third and finally, there are many publics, rather than one public. Public, for the Psychology Department, means everyone who isn’t a student or colleague. Within that group there will be many different interests – specialists and generalists, bystanders and activists. If we cater our engagement for a ‘general public’ we’re going to miss out on the opportunities to engage with specific individuals and groups in ways that mean our unique strengths as a department can be fully taken advantage of.

That’s probably enough of the theory. In the immediate future I’m going to concentrate on finding out more about what people in our department already do in terms of Public Engagement, and pursue a few specific plans: making sure the department supports the Civic University project, growing our new schools programme, organising a set of Inaugural lectures for our new professors and hopefully some events for the upcoming Off The Shelf festival in Sheffield. Watch this space, as they say.

* ‘academic organiser’ of course means that all the real organising is done by our wonderful support staff (for the seminars that’s Liz Carl specifically – thanks Liz!)

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3 PhD studentships in decision making

“Decision making under uncertainty: brains, swarms and markets”

The cross-disciplinary neuroeconomics network at the University of Sheffield is seeking applications for PhD studentships as part of the project: “Decision making under uncertainty: brains, swarms and markets”

– Tutition fees at UK/EU rate, annual maintenance at the standard RCUK rate (£13,726 for 2013-14), and a contribution towards research and travel expenses of £1,000 p.a.
– World-leading research environment
– Deadline for applications 15 February, to start between August 1st and December 1st 2013
– Initial enquiries via

Project overview:

How do we make decisions in uncertain situations? And what is the right thing to learn from the outcome of such decisions? Most of our decisions involve insufficient knowledge and a certain degree of risk. To study such decisions comprehensively is the goal of ‘neuroeconomics’, which brings to bear the insights of computational theory, neuroscientific evidence and behavioural experiment. We have assembled a local team of internationally renowned experts in a diversity of disciplines (Computer Science, Automatic Control and Systems Engineering, Psychology and Management). Together we will combine theoretical insights with tests in practical domains to advance the field.
Continue reading

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Project LongArm: Drawing Machines

Sheffield Artist Mattias Jones and team built a drawing machine which implemented a solution to a mathematical algorithm, in the form of a set of straight lines connecting many tens of thousands of points (which in turn were placed based on photographs of the Peak District). The whole installation took about two weeks to draw, and happened as part of the Festival of the Mind at the end of september.

I had a small part in the project because the robot control was based on an algorithm I wrote – basically only the part which told the motors how much to move and when to stop so as to get from point to point while drawing a straight line. You might think this is a funny place for a psychologist to be involved in an art project, but the fundamentals of movement control apply to robots just as they apply to people (that’s why they are fundamentals!).

You can see come great photos of the project by photographer Andy Brown here, and a video of the project here. Interview with Matt here

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