I’m giving a talk and leading an ‘experience treasure hunt’ in Berlin on July 11th (see here). The aim will be to show how our perception works, using examples from city life. Cities, like all environments, channel our attention. One of the things I’m planning on doing is to recreate a classic experiment which shows how much we don’t notice about the city around us.
The experiment is a demonstration of change blindness – a phenomenon where we don’t notice changes in something we’re supposed to be watching. Here’s Richard Wiseman with a short video showing off the effect: The Colour-changing Card Trick. In 1998 Simons & Levin took this research out of the lab, using the general public as their experiment participants. They got a confederate, who we’ll call Person A, to approach people with the pretence of asking directions. When the unwitting participant had got underway giving directions, Simons & Levin had another pair of confederates walk rudely between them and Person A carrying a door. Person A used the shield provided by the door to sneak off, and another experimental confederate, person B, took their place. The research measure is whether the person giving directions noticed that they were now giving them to a totally different person. Amazingly, slightly less than half of the people approached noticed the switch. Here’s a fun recreation of the experiment I found on YouTube.
As well as being a great example of the fun of taking Psychology experiments out of the lab, this research confirms how narrow our perception of the world around us is. As with our visual blindspots, we think we capture a full-spectrum high-resolution image of the world, but actually we only sample a very limited slice, and our perceptual machinery infers across the gaps.
With luck we’ll be recreating this experiment in Berlin on July 11th (if you’d like to help out, get in touch!). Like all good experiments, this one opens up as many questions as it answers. Will different kinds of people be more or less sensitive to the switch? Will people be more likely to notice switches that cross social categories (men switched with women, old with young, etc etc)? Join me in Berlin and we’ll make a start on finding out.
Reference: Simons, Daniel J.; Levin, Daniel T. (1998), “Failure to detect changes to people during a real-world interaction”, Psychonomic Bulletin and Review 5 (4): 644–649, DOI:10.3758/BF03208840
Mind Hacks 
Speaking of not noticing things you’re supposed to be aware of, is the word “Blindness” deliberately spelled wrong in the title?
I can probably help, it sounds interesting. I organise Treasure Hunts for corporate clients.
In case you’re interested, here’s a video from our 1998 study:
I have seen this in the BBC as well. They had students in the library replace another student while talking to a patron. The results showed that many patrons did not even notice the switch.