JOURNAL OF COSMETIC SCIENCE 164 STIMULI AND APPARATUS The experiment was conducted using a computer with custom software. The stimuli were presented on a 24.1-inch liquid-crystal-display (LCD) screen (NEC MultiSync LCDPA241W, NEC Corporation, Tokyo Japan). Although we did not secure the observing position with an apparatus, the viewing distance remained constant at approximately 70 cm. The stimuli were facial images of a Japanese female with/without eyeliner and/or eye- lash makeup (see below for details). Eye makeup was applied to the model’s face by professional makeup artists. We edited the photographs so that all stimuli had exactly the same face except for the eye areas each eye area with eye makeup was cut out as an elliptic area with blurred edges, and then pasted on the same facial image, using digital photo editing software. The dimensions of the stimuli were 744 pixels wide (16.0° in visual angle) and 1052 pixels high (22.1°). The dimensions of the face itself were approximately 471 pixels wide (10.3°) at the cheekbone level and approximately 771 pixels high (16.5°) from the top of the head to the tip of the chin. The stimuli were colored images. The standard stimuli were facial images whose eye makeup was systematically manipu- lated from light to moderate. We used four levels of eyelash makeup: (a) no eyelash makeup (Figure 1, Eyelash 1) (b) mascara on only the upper eyelashes (Figure 1, Eyelash 2) (c) mascara on the upper and lower eyelashes (Figure 1, Eyelash 3) and (d) mascara on the upper and lower eyelashes with false eyelashes applied only on the outer half of the eye (Figure 1, Eyelash 4). In addition, we used fi ve levels of eyeliner: (a) no eyeliner (Figure 1, Eyeliner 1) (b) brown eyeliner on the upper inner rim of the eye (Figure 1, Eyeliner 2) Figure 1. The eye areas of the standard stimuli used in Experiment 1. Eyeliner varies horizontally from light (left column) to moderate (right column). Eyelash makeup varies vertically from light (bottom row) to mod- erate (top row). See the text for the detailed descriptions of each condition. Note that these images show only the left eye but the actual standard stimuli showed the whole face.

MEASUREMENT OF EYE SIZE ILLUSION 165 (c) brown eyeliner on the upper eyelid (Figure 1, Eyeliner 3) (d) brown eyeliner on the upper and lower eyelids (Figure 1, Eyeliner 4) and (e) black eyeliner on the upper and lower eyelids (Figure 1, Eyeliner 5). Thus, the combination of four levels of eyelash makeup and fi ve levels of eyeliner yielded 20 standard stimuli. Another standard stimu- lus used was a combination of the thickest eyeliner (Eyeliner 4) and the thickest eyelash makeup (Eyelash 5, with mascara on upper and lower eyelashes and with false eyelashes applied on both the inner and outer halves of the eye). Hence, the total number of standard stimuli was 21. It was ensured that the levels of makeup were within the range of every- day makeup, not too heavy or unusually conspicuous. Thus, even the thickest level of eye makeup in this experiment was moderate. The comparison stimuli were facial images, without any eye makeup, whose eye size was sequentially changed from 88% to 112% of the original eye size (i.e., 100%) in steps of 2% both horizontally and vertically (Figure 2). Note that a horizontal and vertical change of 2% is approximately equal to a change of 4% in area. To implement these manipula- tions, each eye was cut out as an elliptic area with blurred edges, enlarged or reduced, and then pasted back on the base facial image, using digital photo editing software. Hence, the standard stimulus with Eyeliner 1 and Eyelash 1 was identical to the comparison stimulus of 100% eye size. PROCEDURE The two experiments were approved by the ethical board of the School of Human Sciences of Osaka University. After each participant signed the informed consent form and was given instructions, the experimental task started. Each trial began with the presentation of a blank gray screen for 1000 ms. Then, a standard stimulus and a comparison stimulus were displayed side by side (Figure 3). The background of the images was gray. After the presentation of the stimuli for 1500 ms, the screen changed to a blank gray. The task was to choose the stimulus whose eyes appeared larger compared to the other stimulus. We instructed participants not to focus on only a few specifi c points of the stimulus, but to pay attention to the whole area of the face. The blank screen was presented for at least 1500 ms or until the participants responded. Following the response, the next trial Figure 2. Samples of the comparison stimuli used in Experiment 1. Left: 88% eye size. Center: 100% eye size. Right: 112% eye size. Although the eyes shown here are those of the actual model used in the experi- ment, the rest of the face is replaced with another face to hide her identity because the model consented to have only her unaltered face published, not the manipulated ones.