Human communication is not restricted to words but also body language such as facial gestures, symbols etc. Semiotics is the study of signs and its related to several disciplines of education. We see it in art, psychology, linguistics etc. This tells signs that exists in every culture.

Reasons why signs or images work are:

  1. They’re easier to spot and legible than words. Perhaps one picks them faster over words. For example, ratings, traffic lights.
  2. To remember and recall images or drawings better than words.
  3. Ability to recognise patterns in representation better than sentences or paragraphs.

On the downside it's important to design signs and symbols to be comprehensible.