Sentence:  In B. M. Spinley 's portrayal of the underprivileged and undereducated youth of London , a salient finding was the inability to postpone gratification , a <WSD>need</WSD> to satisfy impulses immediately without the pleasure of anticipation or of savoring the experience . 
Meaning of the word marked with <WSD> tags:  the psychological feature that arouses an organism to action toward a desired goal; the reason for the action; that which gives purpose and direction to behavior