New research published in journal i-Perception Our results suggest that the effect of striped clothing on body shape perception is highly dependent on the specific spacing and orientation of the lines. People often believe that vertical stripes always make you look taller and thinner, but this study shows evidence that horizontal pencil stripes can actually produce the most slimming effect. The results of this study provide practical insights into how simple geometric patterns change visual judgments of the human figure.
Scientist Tzu-Yu Chen, a doctoral candidate at the National Yunlin University of Science and Technology Graduate School of Design, and Li-Hsun Peng, a former associate professor at the university, conducted the research. They wanted to explore competing theories about visual perception and clothing patterns. A scientific concept known as the Helmholtz illusion suggests that horizontal lines can make spaces and people appear taller and smaller than vertical lines.
Previous studies testing this illusion in humans have yielded highly inconsistent results. Peng said the goal is to extend the basic theory of design. “In the field of design psychology, I wanted to move beyond the traditional dualism of ‘horizontal and vertical stripes,'” Penn explained.
“While most existing studies focus only on orientation, our study shows that the interaction between stripe type and stripe orientation significantly influences visual body recognition,” Peng said. “Interestingly, our study also revealed that women tend to be more sensitive to these stripes than men when assessing body image.”
Most people observe the whole body in the real world and rarely compare horizontal and vertical patterns side by side. Clothing style also influences body image, which is the subjective mental image of one’s appearance. People often buy striped clothing specifically to enhance this individual’s body image, making optical illusions a very practical topic for fashion design.
To address past discrepancies, scientists designed an experiment using images of real human models. They classified the patterns into two different types. The first category is equidistant stripes, where the dark lines and the light spaces between them are exactly the same width.
The second category was pencil stripes. In these patterns, the light background space is significantly larger than the dark lines. The researchers recruited 241 undergraduate students from a Taiwanese university to participate in a visual survey.
They photographed a female volunteer model wearing a slim-fitting, short-sleeved dress. This model has a body mass index of 20.8, which represents an average to slightly above average body type for a Taiwanese woman. The study looked at five specific measurements of a white dress with black stripes.
Three of these styles featured equidistant stripes with both line and gap widths of 1 cm, 2 cm, or 5 cm. The other two styles featured pencil stripes using 1cm black lines separated by 2cm or 5cm white gaps. Students viewed these images on a computer screen and answered questions about what the model looked like.
The study was divided into three different experiments to isolate the different visual effects. In the first experiment, students observed only a dress with horizontal stripes. The results showed that a horizontal pencil stripe with a 2cm white gap had the most slimming effect and was favored by more than half of the participants.
However, horizontal dresses with a 5 cm white gap had the least support for slimming effects. This suggests that horizontal pencil stripes only make a person look thinner if they are relatively closely spaced. In the second experiment, we repeated this process using only vertical stripes, resulting in highly inconsistent visual feedback across students.
In the third experiment, the scientists asked students to directly compare horizontal and vertical stripes. To mimic real-world observations, horizontal and vertical versions of the same dress were displayed on alternating screens. Therefore, students were forced to rely on their short-term memory for evaluation.
“While a horizontal ‘pencil stripe’ pattern (1×2 h) can produce a slimming effect, certain vertical configurations can also achieve similar or better results depending on the perspective,” Peng said. “For example, our findings suggest that in a standard 1×1 striped dress, vertical stripes appear slimmer than horizontal stripes when viewed from the back.” This highlights how simple changes in viewing angle can alter human perception.
Although these findings are detailed, this study has several limitations that should be considered. This experiment used only one female model with a specific body type. This means that the visual effect may be different for people of different body shapes, heights, and sizes.
“It’s important to remember that ‘1×2 pencil stripes’ may not be the best slimming option for all body types, especially larger ones,” Penn noted. “We used a specific model prototype for our initial experiments because we focused on comparing five stripe types and two orientations.” Also, the students in the study were all from the same demographic group, which may limit how these perceptions apply to different age groups.
“For people with fuller figures who want to take advantage of such illusions, our data suggest that 1×1 equidistant vertical stripes may be a more effective and reliable option than certain horizontal patterns,” Penn added. Future research could investigate how these spacing patterns interact with loose clothing and different types of fabrics. Scientists can also test these illusions using different colors.
The researchers also found unexpected potential in certain designs of maternity wear. “One of the most surprising discoveries was the potential of 2×2 horizontal stripes as a functional option for maternity wear,” Penn explained. “We have succeeded in flattering the pregnant silhouette while remaining visually striking, combining aesthetic appeal with a degree of ‘visual safety’ (visibility).”
“On a personal note, I also happened to be pregnant during this experiment, and I often wore this 2×2 horizontal striped dress,” Peng said. “Additionally, when we tested this particular pattern on eight different body types (ranges of height and weight), we observed a strong hysteresis phenomenon.” Hysteresis occurs when the current state of a system is highly dependent on its history. This means that visual perception tends to remain stable even when the underlying body shape changes.
“The results were not statistically significant for all eight body types in the 2×2 pattern,” Peng noted. “While we did not publish non-essential data, this ‘neutrality’ is appealing as it suggests versatile design options that remain visually consistent regardless of the wearer’s size.” This suggests that some patterns almost completely neutralize differences in body types.
The study, “Effect of striped clothing on visual body recognition: A study on pattern spacing design,” was authored by Tzu-Yu Chen and Li-Hsun Peng.
