Although many people think PEARL is large, PEARL is not as large as the Large Hadron Collider at CERN, which is a circular tube about 27 km long, used to collide particles (hadrons) together so that scientists can explore the world of subatomic particles. But there is a sort of similarity. In order to study very tiny things we often need to create large pieces of equipment (think of the size of a Magnetic Resonance Imaging machine), and in a way, PEARL is large because it is studying tiny 'things'.
In order for us to study how people interact with the world around them, we need to see how their brain responds to different stimuli. If we don't create the kind of world people respond to, we cannot study the responses, and that means creating a world that is bigger than the person's imagination so that they imagine they are in a real world situation - street, station, park, supermarket - even though they are actually in the confines of a controlled laboratory environment. Yet the brain contains many very tiny particles - 86 billion neurons, 260 million photosensitive receptors in the eyes, 30,000 cilia (hairs) in the ears, and so on. To study how all these come together to create the perception that a person has of the world we need to study these in some detail. The difference between PEARL and other laboratories that study brain responses is that at PEARL we need to study them as a whole, so we need to study vision, and hearing and smell and touch, and more sensory information, all together.
What the brain receives is not what you see or hear: what it receives is a set of electrical signals. You then create a perception of what those signals add up to in terms of how you understand the world. When you walk down a street, you are responding to a massive amount of information, most of which you are unaware of, but it is all that 'unknown' information that is driving your perception - the bits you know about are very minimal. The electrical signals travel around the brain at extremely high speeds. They travel along the long axon, sort of tail, of each neuron. When they reach the end of the exon, there is a gap, called a 'synapse'. On the other side of this gap is a 'dendrite', which looks a bit like the branches of a tree. Under the right conditions, the signal will be able to cross the gap and thus connect different parts of the brain together. This is how we learn and create perceptions. The more often a particular axon-synapse-dendrite combination is used, the better they work together and the easier it is to repeat the process. If use of a particular combination reduces, then the dendrite becomes smaller and the connection with the axon becomes weaker.
So by creating a street in PEARL we can begin to understand what those 'unknown' information streams are and how they affect your perception. How do you 'see' a car coming towards you; how do you understand when it might be safe or unsafe to cross; to understand questions like these, and generate potential answers to them, we have to have enough of the real world there under our control so that we know what the reality of that environment is and can begin to understand some of the answers to our questions.
What does this mean for people who want to use PEARL? It means that in PEARL we can start to unpick the brain's preconscious responses to the design of the environment. Whether it is the way a street looks, how the seating plan of a bus forces people into uncomfortable proximity to each other, how the stress arises in a crowded metro train, when the difficulty of navigating a street when your vision is different from what has been assumed by the designer, or how the echoic reverberations of a particular space make it difficult to understand what someone is saying, we are dealing with the preconscious brain. If we want to know how to resolve these problems we need to understand how the brain creates our perceptions of the world before we are consciously aware of them, and then design to work with this process rather than just for the world we are consciously aware of. Understanding these tiny processes helps us to understand the world a bit better and to design better environments for people to enjoy.
We don't collide particles in PEARL to understand the world; we try to figure out what stimulates neurons to reinforce their axons and grow their dendrites so that communications around the brain become better at creating the perceptions that you need to make better sense of the world and thus lead to enabling you to have a better quality of life. So we try to understand how the synapses become less of an obstacle to the passage of the electrical signals around the brain. In this sense, PEARL is a place where we can test these connections and see how to make them easier by manipulating the design of the world. This is a question of understanding how neurons connect with each other and making that easier. Are synapses an obstacle to connectivity, or could they be a key to connecting across the brain? Is it a question of PEARL being a 'large neuron collider', or is it maybe a way of smoothing the gaps, or 'eliding the synapses', so that the connections are easier: a 'large synapse elider'?