An aside. There's benefit the other way, too: a sense of self-confidence also helps one concentrate despite distractions, and prevents urgent and desperate body

An aside. There's benefit the other way, too: a sense of self-confidence also helps one concentrate despite distractions, and prevents urgent and desperate body language. If you can concentrate, and not be overwhelmed with urgent or desperate feelings, you have more cognitive power available, and will perform closer to your potential. I agree with your points, especially about memory. Expert chess players have superior recall of chess positions - but only those that could occur in play. For other positions, their memory is comparable to ordinary people.