My research

Audiovisual integration, timing and synaesthesia

I have been studying contextual interactions between different modalities, such as vision and hearing. For example, I have discovered that the pure timing of auditory events can influence the perceived direction of ambiguous visual apparent motion. I have also been involved in a collaboration examining interactions between the processing of time, number and space. My current projects are investigating individual differences in the ability to synchronise sight and sound, and also a little-known form of synaesthesia in which visual motion and flashes evoke faint auditory sensations.

Attention and task demands

In my early research I developed a paradigm for investigating how attention and task demands can influence visual contour integration, a fundamental process by which the visual brain integrates its fragmentary input into global forms. My theme has since broadened to studying how the brain resolves the interpretation of ambiguous stimuli, according to the context in which they are encountered. Such context interactions can be gated (effectively switched on or off) by voluntary goal-directed attention, sometimes with dramatic consequences for subjective awareness.

My methods are primarily behavioural (psychophysics), but I have also worked on projects involving fMRI, transcranial magnetic stimulation (TMS) transcranial electrical stimulation, and EEG. I am happy to supervise projects on attention, vision and crossmodal (e.g. audiovisual) integration.

 

I am currently investigating a little-known form of synaesthesia, whereby visual motion or flashes evoke faint auditory sensations. I have a personal interest in this, because I experience this phenomenon myself. 
When we talk to someone, we naturally expect to hear their voice at the same time as their lips move. But for some people, the experience is sometimes like a poorly dubbed movie. This research investigates individual differences in audiovisual synchronisation.
 
This research introduced an illusion whereby the timing of a sound influences the perceived apparent motion of flickering lines. 
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It is often assumed that when we attend to one part of an object, such as the handle of a mug, our attention spreads involuntarily to all other parts and features of it, even if irrelevant (e.g. the body of the mug, and the logo inscribed on it its colour). This fMRI research presents a challenge to this theory. 

 

When two drifting striped pattens are added together, they combine to form a ‘plan’, which moves in a different direction to the components. It can be very hard to separate them again. This research shows that when placed in the right context we can perceptually peel the plaid apart again. This provides insights into how our visual system assembles the basic elements of our visual world in a context-dependent way.

Ambiguous stimuli change their appearance while we look at them, even if they physically remain the same. This fMRI research has examined how brain activity changes when your perception flips. 

Two rotating cylinders are placed left and right, like wheels joined by an invisible axle. As you watch, you might notice they often appear to rotate together in the same direction, synchronously switching direction every few seconds, like wheels rolling towards and you then away. In this illusion one of these cylinders is physically rendered less ambiguous, and its current state influences the other fully ambiguous cylinder across a distance. This demonstrates how the visual system resolves local ambiguities by integrating across less ambiguous global contexts.

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Selective motion integration

In this demo there is an array of gratings each its own diagonal motion. Look at the centre of the figure on the right, and without moving your eyes, pay attention to the combination of centre, upper and lower patches. You might be able to see that they form a vertical zig-zag pattern moving…
 
This psychophysics research shows that the basic mechanisms by which the visual system assembles image fragments into perceptual wholes can be modulated by attention, depending on the specific perceptual groups that are currently relevant for a given task.