The major theories of aversive control include two-factor theory, operant theory, cognitive theory, and biological theory. Among these four theories, it is generally accepted that the two-factor theory is the dominant theory within the group. This is largely because the theory views the avoidance and punishment aspects of aversive conditioning as belonging to both Pavlovian and operant influences, hence the two-factor nomenclature theory. In the case of a bright light presented before a shock, the shock then escapes, creating reinforcement: the shock is interrupted. As each shock is escaped, Pavlovian conditioning begins to form through the association of the light with the shock until a pairing is finally formed. At this point, the light represents fear for the subject, who will now seek to escape the CS associated with fear. However, escaping the CS is basically equivalent to avoiding the United States. As such, the two-factor theory of avoidance appears to show that, in reality, avoidance is not actually avoidance, but rather an escape from a CS associated with the initial shock. In other words, because escape is vital for successful avoidance behavior, the theory holds that Pavlovian elements, as well as operant elements, manage and support avoidance. In fact, two-factor theory will even account for a Pavlovian CS when no stimulus is presented. In this case it is time to represent the CS. If the US occurs at regular intervals, the simple passage of time will serve as the CS. Regarding punishment in the two-factor theory, this Pavlovian conditioning must arouse fear in the subject. When the punished response is emitted, the subject will experience fear, however, if they experience a response other than punishment,...... middle of paper ...... the theory resembles previous theories to well respects. The focus is on a set of defensive responses that Bolles argues every species possesses. He called these species-specific defense reactions, or SSDF. Although SSDFs can occur randomly, it is believed that they most likely follow a hierarchical scale. In biological theory, a response resembling SSDF would result in rapid learning, whereas a response that did not result in SSDF would result in the opposite. Between biological theory and cognitive theory, we can see that although similar in some ways, biological theory clearly stands out. In short, where cognitive theory leads to what happens after a response occurs, biological theory focuses on what determines the first occurrences of those responses..