This study investigated whether the underlying structure of responses to facial expressions of emotion would emerge when the exposure time was increased. 25 participants judged facial photographs presented for varying durations of exposure, ranging from 4 msec. to 64 msec. in 4-msec. steps. A dual scaling method was carried out to analyze possible response differentiation as a function of exposure time. Two major components were extracted. Based on the configuration of variables they were interpreted as valence (hedonic tone) and activation. Results indicated that a positive emotion and a highly activated emotion such as surprise and fear were easily recognized under a relatively brief exposure to the stimuli.