They recorded students engaging in think-alouds as they completed three different types of writing assignments about social studies texts: taking notes, answering study questions, and writing an analytical essay.
System 1 engages in automatic (fast) thinking; among other things, this system helps us read and write words effortlessly, gauge the distance of objects, and answer simple math problems.
System 2 entails more effortful (slow) thinking, such as focusing on a conversation in a noisy room, comparing products when making a purchase, and determining the validity of a complex argument.
The researchers also found, however, that the writing assignments most benefited students who had stronger critical-thinking skills in the first place.
In other words, the analytical writing exercises seemed to have the same sort of Matthew effect that researchers have observed in reading—students who start with better skills increase their abilities at a faster rate than students who start with weaker skills (Stanovich, 1986). How writing shapes thinking: A study of teaching and learning.