Lecture 4 - Show me the way to go home
Without a map or an intimate knowledge of the area, human beings are not very good at finding their way around. Our senses alone don't allow us to navigate and to explore with great efficiency. Other species, however , perform extraordinary feats of navigation, and they rely on a battery of remarkable sensory skills. The salmon searching for its home stream, the pigeon flying to its roost, migrating birds and fish, and even foraging insects have special sensory systems to enable them to guide themselves. The homing pigeon is a particularly good example: it can steer itself by the sun or the stars (but it needs an internal clock in its brain to do so), and it also has a built-in magnetic sense to act as a personal compass. And finally it uses the sight of familiar things on the ground to guide it precisely to its destination.
All animals, not just those that are especially good at migration, need to know where they are in relation to gravity and to the things around them in order to regulate their posture and their movements. Vision is often important but there are also special sensory systems in the inner ear of mammals and in the lateral line organs of fishes that detect the direction of gravity, angular rotation in any plane and movement of water around the body. Most animals, including human beings, use sensory information from a variety of sources to keep the head and eyes relatively stable in space when the body is being moved about or is actively moving through space.
Finally there is the fascinating question of how we know where all the bits of our body are and how they link together. Proprioception - the detection of the positions of joints, the lengths of muscles and the relationships of all the parts of the body - is a vital sense, but one that we are not normally vividly aware of.
About the 1982 CHRISTMAS LECTURES
Our sense organs are windows on the world. But just like windows, as well as giving us a view of the physical world, the senses also restrict our outlook on the things around us. Philosophers have worried for centuries about the reliability of the human senses and about the relationship between the real world and the world as we see, hear and feel it. Is the world only a creation of our minds?
I am no philosopher, so I am happy to accept that there is a real world out there and that our sense organs simply describe it to our brains. But this means that the world we know through our perceptions is created by processes in our brains and the validity of this imagined world depends crucially on the way that our sense organs and our brains work together to perform the magic of perception. My aim in these lectures is to describe the way that the sense organs act as biological instruments of detection, measurement and analysis. I shall try not to be a 'human chauvinist' but will show that our senses, perfect though they are for our needs, are only a small part of the repertoire of biological instruments of detection and measurement that evolution has invented.
It is hard to accept that our perception of things around us is incomplete, but the fact is that we are blind and deaf to much that is happening in the world. We sense what we need to sense. Every animal lives in its own perceptual world, a world of its own creation. Let us be proud of the incredible performance of our own sense organs and brains but let us not forget that other creatures have marvellous sense organs that we do not. They live in other worlds, in perceptual worlds created by their own particular sense organs, worlds that we can never experience directly but can only dream about.Join me in these lectures on a journey to the edges of your own perceptual world and into the sensory worlds of other animals. I shall give the members of the audience plenty of opportunities to test their own senses and to discover how they work, and we shall be joined, from time to time, by animals who will show us all how very clever their sense organs are!
About Colin Blakemore
Sir Colin Blakemore (1 June 1944 – 27 June 2022) was a British neurobiologist, specialising in vision and the development of the brain. His own research work was mainly concerned with the mechanisms in the brain for the interpretation of signals from the eyes, and especially in the early development of vision during the first few days and weeks of an animal's life. He was well known for his work in communicating science to the public and published many popular books.