Edward Tufte's 1 + 1 = 3 Effects Principles

What is the 1 + 1 = 3 Effect? Here are two definitions

1. Edward Tufte's Definition 
2. Jans Meiert's Definition

Examples of this principle (click the following bullets):

• The area between blocks of text
• The illusion between columns
• Between lines of black text
• Between different lines of colored text
• The illusion that is created by frame borders