The Conscious Phenotype

Consciousness is central to the human condition, furnishing us with phenomenal awareness of the external world and the ability to reflect upon our own thoughts and experiences.

It was with great anticipation that members of Perception Society welcomed Professor Geraint Rees to present this year’s very first Perception lecture.

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Professor Geraint Rees


Dean of the Faculty of Life Sciences and Professor of Cognitive Neurology at University College London, Professor Rees’s work has been internationally recognized by award of the Royal Society Francis Crick Medal, the Experimental Psychology Prize and the Young Investigator Medal for Human Brain Mapping. In addition to his research interests, he has a track record of personal and professional commitment to improving clinical academic training both at UCL Partners and throughout the UK.

In his talk ‘The Conscious Phenotype’, Professor Rees introduced us to the nature of individual differences in conscious perception and their neural basis, focusing on both the structure and function of the human brain. The audience was introduced to a variety of neuroimaging techniques used in his research, as well as to some of his several new approaches to analysing functional brain images; the lecture became wonderfully engaging, making for a completely hooked audience. Dr Rees made sure to use a mixture of scientific and interactive content to make the material accessible to everyone, whether they were completely new to neurology, or long-time enthusiasts.

“What is so special about humans? Why do we hold ourselves so highly?”

Professor Rees began by presenting us with seemingly simple questions. He continued: “Why study humans instead of mice? What makes us different?”. The answer, of course, lies in our distinctive ability to learn, teach, speak and to have a (human) awareness not found in any other species. Professor Rees called this our ‘consciousness’. Central to the human condition, consciousness furnishes us with a phenomenal awareness of the external world and the ability to reflect upon our own thoughts and experiences. Interestingly, there is substantial variability in how different people experience the same physical environment. It was this aspect that Professor Rees focused on for his lecture, having conducted significant research into the conscious perception of the world which aims to understand how our brain functions through retinotopy; that is, the mapping of visual input (what our eyes see) to neuronal activity inside the brain, specifically, in the visual cortex. The complexity of the human brain leaves scientists with a puzzling 100 trillion neural connections, and the subsequent challenge of understanding and decoding them.

It is establishing the specific features in brain structure and the effects these have on our perception, that Professor Rees really set out to achieve. Through various fascinating optical illusions, he beautifully conveyed these ideas by inviting the audience to study each image carefully.  The variety of interpretations from the Perception audience proved that what Professor Reese repeatedly called “these dumb nerve cells” lead to every one of us perceiving and understanding things in a slightly different manner, at different rates and with different reasoning. Not so dumb after all…

When presented with the following optical illusion, pupils learned that there’s more than meets the eye:


Even though the two spheres are identical in size, due to shading and the introduction of the side brick walls, it seems like the rear sphere appears much larger. This effect occurs when the visual system (your eyes and brain) attempts to interpret an image which evokes a perception different from reality, resulting in our brains displaying an image that makes most sense, but isn’t necessarily accurate. Even though both spheres occupy exactly the same size on the retina, the rear sphere activates an approximately 20 percent larger area in the primary visual cortex than the front sphere, all because of shadows and perspective.

Professor Rees helped us become aware of our own visual cortex and its weaknesses. The audience was exposed to illusions challenging their vision, something which quickly turned into a game similar to that of kids’ “Spot the Difference” puzzles.  The audience was exposed to two alternating images divided by a grey screen, and were asked to put their hand up once they saw the subtle alternation in the picture. As more and more people raised their hands, you could feel a growing tension in the room coming from those still focused on the screen, scrutinising every pixel. This was, after all, studying brain activity and response – live!

Professor Rees talked of the intellectual curiosity of children, something which seemingly fades as they grow older. Science not being able to answer the simplest of questions, especially in the case of neuroscientific research, is very much because of people lacking the boundless and shameless curiosity that allows a kid to ask his parent “But why?” millions of times until they grasp the entire concept, be it as trivial as why the sea is blue or as complex as why we feel emotion, why we have a consciousness, why we are different.  Ultimately, the audience was encouraged to consider the words of astronomer Carl Sagan: “Somewhere, something incredible is waiting to be known”. Why should it not be you, or me, to make the next big discovery?

Professor Rees’s lecture was as much inspiring as it was entertaining, a truly representative beginning to a fantastically exciting year of Perception lectures.

Cosima Graef, Adelina Dan and Cyprien Roche

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