Why 4x8 and 6x8 Are, Perhaps Surprisingly, Some of the Hardest Multiplication Facts for Students to Remember
There's a cognitive principle behind this: associative interference, the phenomenon that conceptually related pieces of knowledge can interfere with each other's recall.
Let’s do a little experiment. I want you to take a guess at the top 4 multiplication facts (within $10 \times 10$) that students have the most trouble remembering.
Most people know that higher-number facts are typically harder than lower-number facts, but the 10s are really easy and the 9s follow a pattern that makes them fairly easy as well.
So, we arrive at the following guess: $8 \times 8$ is probably the hardest, then $7 \times 8,$ then $7 \times 7,$ tied with $6 \times 8.$ Or something like that.
There’s actually a cognitive principle behind this: associative interference, the phenomenon that conceptually related pieces of knowledge can interfere with each other’s recall.
For instance, when recalling $4 \times 8,$ related facts like $\mathbf{4} \times 6 = \mathbf{24}$ and $3 \times \mathbf{8} = \mathbf{24}$ interfere with the spreading activation during the recall process and increase the likelihood of the error $4 \times 8 = 24.$
