But even the most widely understood symbols may require some level of sophistication to be understood. Simlinger believes it would be possible to standardize a maximum of 150 to 200 public information symbols. More and more symbols that relate to technical features can be standardized because they are reduced pictures of what you really experience in everyday life. Other symbols work because of their ingenuity. The use of the question mark is intended to remove any suggestion that the sign refers to an umbrella shop.
Notable gaps do exist in pictography, however.
Symbols for abstract reference, he argued, are only understandable if they have been learned. They are only able to find out what a human being associates in its head with a given reference. If it's concrete, you can depict it, render it and show it. Then it can be tested. Another consideration in signage is energy conservation.