Final answer:
The claim that memory champions can memorize a deck of cards in under 20 seconds is false. Human memory is subject to the forgetting curve, and while mnemonic techniques can improve recall, they require extensive practice to master.
Step-by-step explanation:
The statement that it is possible to memorize a shuffled deck of cards in less than 20 seconds is false. Human memory, according to Ebbinghaus's research, has a tendency to fade following a pattern now known as the forgetting curve. Most people will lose half of newly memorized information after 20 minutes, with further decay happening over time. The brain's capacity for short-term memory is limited, and while memory champions use advanced mnemonic strategies to dramatically improve their recall abilities, memorizing a deck of cards in under 20 seconds far exceeds typical human capability. The highest level of memory performance involves techniques such as the memory palace, and even then, requires extensive training and practice beyond the capacity of average short-term memory.