Dear Dr. Mo: Sometimes, when a professor calls out my name to answer a question, I just block and can’t answer even though I know that I knew the answer just moments ago. Why is that?
Dear reader: To block when you want to speak can happen when you are suddenly put on the spot and it’s called the Cortisol effect – there’s a hormone called Cortisol and it is associated with stress among other things. Whenever you get nervous, even the smallest, tiniest amount of Cortisol that comes out into your blood in that fraction of a second can block the long term memory. All of a sudden, you start to stutter, mind is blank and you can’t remember what you knew a second ago. Familiar?
This effect can be desensitised by repeated practice and the more you’re being called out the better you’ll be able to cope with it but for some, no amount of practice will ever entirely defeat the underlying physiology. People who are terrified of public speaking know this all too well.