Which is our dominant sense?
If we get conflicting signals from different senses, which one do we tend to believe? Students investigate the answers to these questions in the following activity.
Can you touch your finger to your chin with your eyes closed? Our brain has an internal "map" of our entire body that allows us to do things like this. Even without the visual guidance of our sense of sight, our fingers still know where to go. Our sense of the relative positioning of the different parts of our body is referred to as proprioception.
This internal map is so ingrained in us, that people who have lost limbs due to accident or amputation will often report still being able to feel sensations from their (missing) limb–a phenomenon known as the Phantom Limb Syndrome. Many people will continue to experience this sensation for months after their accident, until their brain develops a new map of their body.
Our proprioception can also be manipulated the other way around, such that we come to think that something that looks similar to one of our body parts actually IS one of our body parts.
When we receive conflicting inputs from different senses, we tend to believe what our eyes are telling us above all else, as vision is the dominant sense in humans. In this activity, when we see a fake hand being stroked while also feeling our real-but-hidden hand being stroked, we can be induced into believing that our real hand has somehow been transposed into the fake one.
Teacher's Tip: This activity is best performed as a station so that all of the students get a chance to give it a try.
Fun Fact: Anecdotal evidence from Science World testing seems to indicate that males are more susceptible to this illusion than females.