In the first task, called the visual probe task (VPL), subjects were shown pictures of actor’s faces posing one specific emotion next to that of a neutral emotion. Data was gained from whether the subject initially gazed toward the emotional or the neutral face (called “initial attentional bias”) and the time looking at the emotional face versus the neutral face. Both were measured (resulting in “total attentional bias”) with electrooculography.

In the second task, called the dynamic emotion identification task (DEI), subjects were shown a procession of pictures of posed emotions and were asked to push a button when they had identified the emotion. During this timed task, the subjects’ facial responses in the zygomatic and corrugator muscles were measured by electromyography (EMG).

In the third task, called the talking task, subjects conversed with the research assistant about an important person in their life as the number of words spoken was measured.amphetamine did not affect initialor total attentional bias during the Vpl. The DEIT task showed that amphetamine 20 mg slightly, but significantly, lowered the intensity of emotions in the pictures required for identification of the emotion, with negative emotions (ie, fear, anger, sadness) requiring lower intensities than happiness. amphetamine also increased the subjects’ facial response to increasingly negative emotions, but not to happy ones. The talking task demonstrated amphetamine’s significant effect on increased talking.

The authors report that although amphetamine did not alter attention, identification, or reactivity to happy emotion, as they had predicted, the increased response to negative emotions was a key finding. They argue that the stimulant medication may increase one’s sensitivity to subtle cues of emotion, which positively effects talkativeness and thus improves social connectedness. They surmise that positive reinforcement from socialization then increases the desire to repeat drug use.