"The human brain is not optimized for the abstract thinking and data memorization that that websites often demand.
Many usability guidelines are dictated by cognitive limitations.
People can't keep much information in their short-term memory.
This is especially true when they're bombarded with multiple abstract or unusual pieces of data in rapid succession.
Let's designers forget how easily users forget, let's review why our brains seem to be so weak.
Human beings are remarkably good at hunting the woolly mammoth...
Many of the skills needed to use computers aren't highly useful in slaying mammoths...
It's no surprise that people are no good at these skills, since they weren't important for survival in the ancestral environment...
"Designing Websites for Cavemen" for our new course on how psychology explains usability guidelines,
http://www.nngroup.com/events/tutorials/usability_mind.html
http://www.useit.com/alertbox/short-term-memory.html