Finding your way back from the toilet in the dark, and other lessons…

The nation's psychology teachers had a noticeable spring in their step last week after cognitive neuroscientist and Mind Hacks author Dr Tom Stafford of the University of Sheffield showed them the power of interactive demonstration. The Research Digest was lucky enough to be in the audience.

Moments into the keynote talk, the teachers and I found ourselves blinded by darkness. As our eyes adjusted, we were told to cover one eye with our hands before the lights were raised again. A little wait for our open eyes to become light-adjusted and then the lights re-dimmed. What would happen to our vision this time? The answer depends on whether adaptation to light levels occurs centrally, in the brain, or locally in each eye. The audience tested this, looking through each eye one at a time and discovering the strange experience of having one eye adapted to the light and one to the dark, thus showing that light adaptation occurs locally. Both eyes open led to a strange, grey, grainy, effect. "Whoever said psychology isn't useful is wrong," Stafford said. "You now have the perfect strategy for visiting the toilet in the night and finding your way back to your bed in the dark."

Light adaptation may well occur locally, but what about adaptation to motion? A huge video of a waterfall filled the screen. After a minute staring at the cascading water, the video was stopped and the audience experienced the well-known illusion of the water appearing to flow upwards. But what if the flowing water was watched with just one eye (with the other covered), with the paused video then observed through the previously covered eye? The illusion was still experienced, thus showing that in this case, adaptation to motion had occurred centrally, in the brain.

Here we were, an audience of several hundred, asking questions and finding answers about the organisation of the human brain, all from the comfort of our seats. "The wisdom of psychology," Stafford said, "is as a way of finding things out and generating facts. Everyone can take part."

"I'm now going to rewire your brains," Stafford continued, "by fostering your expectations." Led Zeppelin's Stairway to Heaven began to fill the lecture room. Then a verse was played backwards (courtesy of Jeff Milner). Could we hear any words in the backward version? None. But then Stafford told us the hidden lyrics: "Oh here's to my Sweet Satan…". The backward track was played again, and there the words were, bold, impossible to ignore. Visit the site and see for yourself. "Hours of fun or moral panic, depending on your perspective," Stafford said.

Once the expectations for what to hear are in place, they can't be undone. You can't unhear the devilish lyrics once you know about them. This is a powerful demonstration of how our perceptual experiences are based not just on what is served up by our senses, but also on what our brains bring to the table.

"Examples like these teach us that we all have access to the raw materials of psychology," Stafford said, "but that we can't necessarily trust them. Yet with sceptical enquiry and careful investigation, we can find out how the brain works."