Hi,
This is a great question - also, it requires some understanding of advanced stats principles, namely those of interactions.
The concept tested here is a deeper understand of ANOVA and design of experiments. For the MCAT, this is probably beyond the scope but here's what you should take away:
When examining categorical variables (M and F in this case):
- parallel lines indicate there is NO DIFFERENCE between the two categories
- non-parallel lines indicate THERE IS AN interaction between the two categories
You do not need to know why this is the case as it delves into stats knowledge but from your Psych/Soc knowledge you should reasonably be able to say 'gender must play some role in the relationship being evaluated and therefore, I should expect to see an interaction between being M or F and recalled items. Since I expect to see an interaction, there the lines cannot be parallel.'
If you want to get into deeper reading, here's a great link:
https://medium.com/@hpsuresh12345/the-significance-of-interaction-plots-in-statistics-6f2d3a6f77a3
Hope this helps!