Sweetcorn Effect 

When someone is unable to extract anything meaningful out of information presented to them, either verbally from another person or through forms of media.
Parallel taken from the apparent lack of change to a sweetcorn kernel after it has passed through the human digestive system.

"You may as well not bother telling him, it's the sweetcorn effect with him"

Sweetcorn Effect by Solonist March 24, 2010