Psychophysical methodology is used to evaluate the strength of the visual signals contained in facial expressions. Stimuli were black and white images of faces expressing a neutral, positive (happy) or negative affect (e.g. fear or anger). A range of signal strengths (0-100%) of expressions were created by morphing the neutral and expressive images. Stimuli were presented for 200ms in a temporal two-interval forced-choice paradigm. One interval contained the neutral face (0%) and the other the expressive face (varied from 0 – 100%). Observers indicated the interval that contained the image that was more expressive. This emotion detection task showed that observers were more sensitive to happy compared with fearful expressions. This indicates that the emotion signals conveyed by a happy face are more salient than those conveyed by a fearful face. Future research on emotion recognition should consider using psychophysical methodology to perceptually equate stimuli with different expressions. This will remove signal strength as a possible confound.