Joanna looks out for good bargains for all her purchases. She once bought a T-shirt that was being sold for $50 and perceived it to be a good deal as everything else was priced higher. However, on her next shopping trip, she dismissed the same t-shirt as expensive as the other apparels were being sold at prices much lower than $50. Joanna's varying interpretation of the value and meaning for the same product is an example of _____.