“Time” is something that both philosophers and physicists have been wondering for about, well, a long time. And now, the neuroscientists have joined in. They have found a man who, when he looks at you, hears what you are saying to him before your lips move.
The man is known only by the letters PH. He is a retired pilot, and a highly intelligent man. There’s nothing special about his medical history. In November 2007 he had surgery for pericarditis — an infection of the covering of the heart. In 2008 he developed generalised myaesthenia gravis. This is an autoimmune disease that leaves you both easily tired and with variable and fluctuating muscle weakness.
About two to three months after the onset of the myaesthenia gravis, Mr PH noticed something strange about his daughter’s TV sets. He was hearing people on the TV speak before he saw the lips move and he said to his daughter, “Hey, you’ve got two TVs that need sorting!” But the TVs were fine. Instead, something odd was happening to the timing circuits inside his brain.
Now you might not realise this, but in terms of vision you are always living 0.3 second (or 300 milliseconds) behind reality. That’s how long it takes between when the incoming light lands on the cells in your retina, and you get that full magnificent wraparound 3D colour sensation that we call vision.
There’s a lot that has to happen inside your head.
First, the rods or the cones in your retina turn the incoming light into electricity. Then the remaining nine layers of cells in the retina compress and process that electricity. By this time, your retina ‘knows’ the difference between a horizontal bar in your field of view and a vertical bar. Furthermore, your retina ‘knows’ if it’s a white bar on a black background or vice versa. Then the compressed signal gets sent along the optic nerves to some sections of your brain right at the back of your skull called the Brodmann areas 17, 18 and 19. These then decompress and deconvolute the electrical information to give you this thing we call ‘vision’. This all takes a significant amount of time — 300 milliseconds.
We don’t notice this delay in reality because we have evolved to be able to deal with this. We can anticipate actions or patterns through experience.
Now it turns out that it also takes time for the incoming audio signals from our ears to be processed. If you’ve ever dealt with audio and video computer files, you would know that the audio files are much much smaller than the video files. So in the case of the human brain, when the Brodmann areas associated with hearing, areas 41 and 42, start processing the incoming audio information, they can do so quite quickly, because the amount of data is rather small. Normally, we process this audio information in just 100 milliseconds.
So how come we normally see the lips moving at the same time as we hear the voice? Almost certainly, it’s because our brain deliberately inserts a delay of about 200 milliseconds on the audio circuit.
Now sure, there would be an advantage in being able to hear dangerous things, such as the killer kangaroo bearing down upon you that extra 200 milliseconds earlier. But all of us are a product of an evolutionary pathway that decided it was more important for us to be able to easily communicate with our fellow humans, than to hear the killer kangaroo that 200 milliseconds sooner.
After all, we humans are quite pathetic as a hunting animal. We can’t run very quickly, our eyes are not very sharp, and neither is our sense of smell. Our claws are silly little fingernails, and our teeth are not very good at ripping and tearing. But thanks to our amazing brain, we can organise ourselves into groups and so we have become masters of the planet.
So, getting back to Mr PH, if the sound of the outside world was deliberately electronically delayed by 200 milliseconds, suddenly audio and vision were in sync for him again. And when the neuroscientists did an MRI scan on his brain, they found damage in areas that were “well-placed to disrupt audition and/or timing”.
I wonder if Mr PH has an advantage over the rest of us with the quick one-line reply …