I use psychophysical techniques to investigate human perception (mainly vision). Using well specified physical stimuli (e.g. amount of photons), and collecting observers responses during a well specified task (e.g. which of two stimuli appeared brighter), one can work out the relationship between physical and psychological variables. These Stimulus-Response relationships can help us deepens our understanding of the human mind, for example when they exhibit systematic characteristics (e.g. in the example above perceived brightness seemingly increases logarithmically with radiant energy, that's Weber's law). Here are examples of some tools we use for investigating perceptual systems:


Single cell recordings are used to monitor the activity of cells while a non-human primate is performing a task. We then study how the physical and psychological characteristics shape the neuronal activity. For example we studied the activity of cells in the intermediate layers of the Superior Colliculus while a macaque was making saccadic eye movements to target objects we knew strongly modulated response times. We then studied how the activity of motor and visuo-motor neurons changed depending on the stimulus. Currently we are studying the neural activity of freely-moving macaques performing a foraging task.


We also use mathematical models to try to predict animal behaviours (including human) in various tasks. Hewre are examples of models we used:


Binocular vision

My main interest is binocular vision, especially stereoscopic depth. Because the eyes are horizontally apart in the head, they see the visual scene from slightly different point of view. The visual system is able to exploit these minute differences between the relative position of points in the two retinae to reconstruct depth in the visual scene.

Multisensory perception

The brain is constantly receiving stimulation from different senses. When they originate from the same source, these stimulations can be combined to build a better representation of the world. We study both how the brain combine these cues, in particular in relationwith with an optimal bayesian model. We also study how the brain decides to combine or segregate these cues (causal inference).

Decision making and metacognition

Typical psychophysical techniques require the observer to make a decision, such as is it red or green? Usually only the answer in relation to the physical stimulus interests the psychophysicists, however the process of making the decision itself can be studied. In this case the stimulus becomes secondary and then decision-making process itself is studied. There are for example well known relationships between response times and accuracy. We are also interested in so-called metacognition such as confidence. Confidence is the ability to predict ones own performance.

Eye movements and perceptual stability

Our own motion causes changes in the inputs of the sensory systems. The brain must take that into account for computing what moved in the visual (or auditory) scene and what signal was caused by the observer's own motion. The most common type of movements are eye movements (about 2 a second), but similar questions can be asked about other types of movements.

History of science

All the paper I cited can be found in the library page. Here are my favourite searching places: