Regret is related to Should. Should is a synonym of Want. Want is related to Desire. Desire is the opposite of Have. 
Person wants (to) Hug. Scientist is a type of Person. 
Regret <--RelatedTo--> Should <--Synonym--> Want <--RelatedTo--> Desire <--Antonym--> Have 
Hug <--Desires-- Person <--IsA-- Scientist 