JOURNAL OF COSMETIC SCIENCE 168 METHOD PARTICIPANTS A total of 104 females (mean age 35.1 years, S.D. = 8.5) voluntarily participated in this experiment. They received a reward for their participation. All reported normal or corrected- to-normal visual acuity and normal color vision. All participants were unaware of the purpose of the experiment and were tested individually. STIMULI AND APPARATUS The experiment was conducted using a computer with custom software. The stimuli were presented on a 24.1-inch LCD screen (NANAO FlexScan SX2461W-BK, EIZO Corpo- ration, Ishikawa, Japan). Although we did not secure the observing position with an apparatus, the viewing distance remained constant at approximately 75 cm. The stimuli were photographs of six Japanese females with/without eye shadow. The ap- plied eye shadow was Maquillage True Eye Shadow® manufactured by Shiseido Co., Ltd. (Tokyo, Japan) This product is a multicolor palette eye shadow composed of fi ve carefully balanced shades including “line color” for the edge of eyelids and “main color” for broader area around the eyes, and so on. The general method of creating the stimuli was the same as that in Experiment 1. The dimensions of the stimuli were 744 pixels wide (16.3° in visual angle) and 1052 pixels high (22.9°). The mean dimensions (across the six models) of the face itself were approximately 479 (S.D. = 19.6) pixels wide (10.6°) at the cheek- bone level and approximately 807 (S.D. = 26.7) pixels high (17.7°) from the top of the head to the tip of the chin. The stimuli were color images with a gray background. The standard stimuli were facial images with/without eye shadow (Figure 5). Because the levels of eye shadow were binary (with or without) for the six models, the total number of standard stimuli was 12. The comparison stimuli were images of individual faces, without any eye makeup, whose eye size was sequentially changed from 90% to 110% of the original eye size (i.e., 100%) in steps of 2% both horizontally and vertically (Figure 6). These comparison stimuli were made for each model. Note that the original eye size of one model might differ from that of another model thus the percentage indicates the relative size within models. PROCEDURE The same procedure as that of Experiment 1 was used, except for the following. For coun- ter balancing, half of the participants were instructed to choose the stimulus whose eyes appeared smaller, and the other half were instructed to choose the stimulus whose eyes ap- peared larger. For each standard stimulus, there were two initially ascending staircases and two initially descending staircases hence, the experiment consisted of 48 concurrent staircases of trials, randomly interleaved. In all the trials, the model in the presented comparison stimulus was always the same person as in the standard stimulus. The eye size of the comparison stimulus for the fi rst trial of each staircase was selected from either 90% (ascending series) or 110% (descending series).

MEASUREMENT OF EYE SIZE ILLUSION 169 RESULTS AND DISCUSSION The PSE for each standard stimulus was calculated in the same way as that in Experiment 1 (Figure 7). The mean of the perceived eye size with eye shadow was 104.8 % (S.D. = 0.83 110% in area), whereas that without eye shadow was 100.1% (S.D. = 0.20). A two-way repeated-measures ANOVA with eye shadow and model as factors showed that the main effects of both factors were statistically signifi cant, F1, 103 = 471.98, p 0.001 and F5, 515 = 13.27, p 0.001. In addition, the interaction between the two factors was statistically signifi cant, F5, 515 = 10.46. The analysis of simple main Figure 5. Samples of the standard stimuli used in Experiment 2. Left: Without eye shadow. Right: With eye shadow. These images are Model E in Figure 7. Figure 6. Samples of the comparison stimuli used in Experiment 2. Left: 90% eye size. Center: 100% eye size. Right: 110% eye size.