When discussing the paper "The Influence of Reading on Vocabulary Growth", the concept of a one-sided or two-sided Matthew Effect comes into play. The research study looks at this concept to see how the difference in reading skills that students have can affect later vocabulary growth.

• a two-sided Matthew Effect means that the difference in achievement or variable between two or more groups of students shows a significant difference for all groups, especially when compared to each other
• in this case, the difference in reading skills means that stronger readers show increasing rates of vocabulary growth compared to the average while weaker readers show decreasing rates of vocabulary growth when compared to the average and especially to strong readers