'Tis true - it works for any visual thing (gardeners are recommended to plant groupings in odd numbers, and when decorating your home, odd numbered groupings are more visually pleasing (three vases on a shelf vs. four, etc).
Strange how the human brain perceives things. My theory is that perfect symmetry is impossible, so when we see even numbers our brain tries to force the symmetry, and it makes us uncomfortable. Odd numbered groups are inherently assymmetrical so we don't even try to make it work, making it more pleasant visually.