Their theory was devised as a result of a study in which participants were injected with either a stimulant (adrenaline) that causes elevated heart rate, sweaty palms and shaking, or a placebo. Participants were then either told what the effects of the drug were or were told nothing, and were then placed in a room with a person they did not know who, according to the research plan, would either play with a hula hoop and make paper airplanes (euphoric condition) or ask the participant intimate, personal questions (angry condition). What they found was that participants who knew what the effects of the drug were attributed their physical state to the effects of the drug; however, those who had no knowledge of the drug they received attributed their physical state to the situation with the other person in the room. These results led to the conclusion that physiological reactions contributed to emotional experience by facilitating a focused cognitive appraisal of a given physiologically arousing event and that this appraisal was what defined the subjective emotional experience. Emotions were thus a result of a two-stage process: first, physiological arousal in a response to an evoking stimulus, and second, cognitive elaboration of the context in which the stimulus occurred. Emotion perception is primarily a cognitive process driven by particular brain systems believed to specialize in identifying emotional information and subsequently allocating appropriate cognitive resources to prepare the body to respond. The relationship between various regions is still unclear, but a few key regions have been implicated in particular aspects of emotion perception and processing including areas suspected of being involved in the processing of faces and emotional information. The fusiform face area, part of the fusiform gyrus is an area some believe to specialize in the identification and processing of human faces, although others suspect it is responsible for distinguishing between well known objects such as cars and animals. Neuroimaging studies have found activation in this area in response to participants viewing images of prototypical faces, but not scrambled or inverted faces, suggesting that this region is specialized for processing human faces but not other material. This area has been an area of increasing debate and while some psychologists may approach the fusiform face area in a simplistic manner, in that it specializes in the processing of human faces, more likely this area is implicated in the visual processing of many objects, particularly those familiar and prevalent in the environment. Impairments in the ability to recognize subtle differences in faces would greatly inhibit emotion perception and processing and have significant implications involving social interactions and appropriate biological responses to emotional information. The hypothalamic-pituitary-adrenal (HPA) axis plays a role in emotion perception through its mediation of the physiological stress response.