I have been puffing the good herb for nigh on 25 years, sonny, and my mind is the sharpest that I know.
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I hold degrees with distinctions in Psych, Phil, and Ling, I achieved the highest mark in Psych honours in the dept : 95%.
Short term memory problems only happen to beginners : MJ will not allow one to think about boring stuff; one loses concentration easily; but if it is interestesting stuff, then I can conentrate for 10 hours without a break. Puffing along merrily.
One has to be able to hop between the rational and the creative mind with mental agility. Like most things in life, if you are inexperienced, its not really going to work for you.