Differentiating horizontal and vertical stripes in clothing: separating fact from fiction

Q: In the past, there was a belief that horizontal stripes give the illusion of width and vertical stripes of height. taller and thinner. But I keep seeing studies going back and forth whether this is true. Who do I believe?

A: Three decades or so of research on this question have yielded inconsistent results. A more recent study seems to show that this is because the answer is actually more complicated than we all would like.

BACKGROUND:

There’s a famous optical illusion called the Helmholtz Illusion, discovered by a man named Helmholtz in 1867.

• Which of these squares looks thinner and taller than the other? Most people would say the left square looks thinner and taller.

However, this contradicts the common belief that horizontal stripes give the appearance of weight or width. Shouldn’t it be the opposite?

• A number of studies have tested this effect and have found conflicting results. Why would fashion work differently than this famous optical illusion?

• Previous research conducted by three Japanese scholars revealed an intriguing pattern. The studies depicted models donning horizontal or vertical stripes, but there was a catch. using the same models: some were fat and some were thin. Additionally, they were all shaded differently. And finally, they were presented in various orders.
• These researchers decided there were multiple factors at play here and published a study testing their hypotheses in the journal i-Perception in 2013.
• The researchers did a number of studies testing the possibility that three factors were influencing all the previous research on this subject that has been conducted:

EXPERIMENT:

• The study involved 31 undergraduate participants, of which 63% were female.
• The students were placed in a chair and put their chin in a chin rest that ensured that their eyes were a certain distance from a computer screen.
• A number of computer images were flashed in the screens depicting people wearing clothing with either horizontal or vertical lines.
  • The size of the images was digitally altered to be either slim or wide.
• Participants were presented with two images side by side, one with horizontal stripes and the other with vertical stripes, for 1.8 seconds. They were then asked to determine which image appeared wider and indicate their answer by pressing a key.
• This method was done 20 times with slim figures and 20 times with fat figures, or with the fat figures first and then the slim figures.

RESULTS:

Do you believe that the traditional fashion belief is accurate, or is the Helmholtz illusion the primary factor?

• The conventional wisdom was not found to be true. Horizontal stripes don’t make people look fatter and vertical stripes don’t make people look slimmer and taller.
• BUT sometimes the stripes didn’t really make a difference at all.

What were the factors that influenced whether the figures exhibited the Helmholtz illusion or not?

• Size of the Model:

• • Indeed, according to the study, slim models appear even slimmer when wearing horizontal stripes, corroborating the Helmholtz illusion and contradicting conventional wisdom.
  • But this effect was not as strong for the wide models – for wide models, the type of stripe BY ITSELF actually didn’t have as much of an influence at all.

• Order of Presentation:

• • An intriguing finding was observed. When participants were shown slender models followed by wider ones, the Helmholtz illusion was most pronounced, making individuals appear taller and leaner when wearing horizontal stripes, regardless of their body size. This result contradicts conventional wisdom.
  • When the wide models were shown first, the type of stripe did NOT seem to matter for anyone.

• Variance Between Observers:

• • YES. Significantly, the researchers found that, even though there were noticeable results when they compared averages, there was a wide variety of results across all participants.

DISCUSSION:

What are the implications of the experiment’s findings? Here are some key conclusions that can be drawn from the results:

The traditional belief did not hold in any instance. Horizontal stripes did not make individuals look wider, and vertical stripes did not make them appear taller or slimmer, overall.

In fact, where there was an effect, it supported the opposite conclusion.

Horizontal stripes made slender people look taller and slenderer.

On the fatter models, the kinds of stripes made much less difference.

People’s judgments seemed to be more influenced by what models they had previously judged.

Interestingly, the Helmholtz illusion was particularly strong when participants evaluated a larger group of slim individuals first, for reasons that the authors did not fully comprehend.

What does this mean for laypeople?

It means that when we view a person, we are mentally comparing them to people we have already seen.

Here’s the (very strange but scientifically supported) bottom line:

• Wearing horizontal stripes to an event predominantly attended by slender individuals may have a slimming and elongating effect on a heavier person’s appearance.

Why? The researchers weren’t sure.

Finally, there was another big take-away:

The researchers determined that due to the considerable variability among participants in the study, stripes may not have a significant impact on one’s overall appearance.

This would explain why all the previous studies since the ‘80s were inconsistent.

It appears that unless one intends to make a deliberate and intricate choice based on the study’s findings, you might make your fashion selections based on other factors instead of whether the stripes are horizontal or vertical.

Whenever science doesn’t seem to go one way or the other, I say trust your own personal judgment.