It is perceived wisdom that vertical stripes on clothing make a person look thinner and horizontal stripes make them look fatter.
Has any research been done into these optical illusions that support either of the claims?
The basis for this is the Helmholtz-Square Illusion:
The horizontal stripes make an object look "taller".
His experiment revealed that when two women were the same size, the one wearing the horizontal-striped dress appeared to be the thinner of the two. And to make the women appear to be the same size, the one wearing the horizontal stripes had to be 6% wider.
While it is uncertain when the idea that horizontal stripes are fattening took hold, the opposite - and now apparently correct - view was documented 150 years ago. German physiologist Hermann von Helmholtz noted in his 1867 Handbook of Physiological Optics that 'ladies' frocks with cross stripes on them make the figure look taller'.