Figure 3. Effect of Age of the Observers on the Perceptual Threshold of the Lips.

Group 1 consisted of younger observers between the ages of 17 and 40 years (mean age, 33 years; n = 49). The dashed blue line indicates observers in group 1 who considered the lips in the images to be treated; the solid blue line indicates observers in group 1 who considered the lips in the images to be artificial. The threshold differential between perception of treated and artificial lips for 50% of participants (dTA₅₀) in group 1 was 0.89 mm. Group 2 consisted of older observers between the ages of 41 and 73 years (mean age, 52 years; n = 49) The dashed orange line indicates observers in group 2 who considered lips in the images to be treated; the solid orange line indicates observers in group 2 who considered the lips in the images to be artificial. The dTA₅₀ in group 2 was 1.15 mm.