Here’s a quote from Kahneman’s Thinking, Fast and Slow:
The experimenters recruited 40 Princeton students to take the CRT (Cognitive Reflection Test).
Half of them saw the puzzles in a small font in washed-out gray print. The
puzzles were legible, but the font induced cognitive strain. The results tell a
clear story: 90% of the students who saw the CRT in normal font made at
least one mistake in the test, but the proportion dropped to 35% when the
font was barely legible. You read this correctly: performance was better
with the bad font. Cognitive strain, whatever its source, mobilizes System
2, which is more likely to reject the intuitive answer suggested by System 1.
Here’s a quote from Kahneman’s Thinking, Fast and Slow: