The positive activation – negative activation (PANA) or "consensual" model of emotion, originally created by Watson and Tellegen in 1985,[14] suggests that positive affect and negative affect are two separate systems. Similar to the vector model, states of higher arousal tend to be defined by their valence, and states of lower arousal tend to be more neutral in terms of valence.[2] In the PANA model, the vertical axis represents low to high positive affect and the horizontal axis represents low to high negative affect.