Against the older view that anxiety is an instinctive reaction to phylogenetically predetermined objects or situations, it is argued that anxiety is a learned response to conditioned stimuli that are premonitory of injury or pain situations. It is biologically useful in motivating organisms to adapt to harmful events in advance of their occurrence. But humans in particular develop irrational tendencies to have anxiety in situations that are not dangerous and vice versa. An analysis of the reasons for such "disproportionality of affect" throws light on superstition, social exploitation, and the psychoneuroses. If anxiety is a connecting link between well-being and organic discomfort, it accounts for day-to-day behavior in the absence of simultaneously active organic drives and for the action of the "law of effect" (learning through motivation-reduction). Anxiety may effectively motivate humans and reduction of anxiety may reinforce behavior that brings about a state of relief or security. This analysis suggests a number of experimental problems. (PsycINFO Database Record (c) 2016 APA, all rights reserved)