Dement and Kleitman (sleep and dreams) found a positive correlation between REM duration and the number of words used to describe the dream.

Mark scheme

Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.

1. [1] 1 mark for 'both variables go up together' OWTTE
2. [1] 1 mark for idea that longer REM durations was linked to more words
3. Do not award each mark if the information suggests causality.
4. when one variable increases the other one does too = 1
5. longer REM phases had more words to describe the dream = 1
6. An increase in one variable makes the other one rise = 0
7. Having longer in REM gave the P more chance to describe the dream in more words = 0
8. [1] 1 mark for identifying a reason
9. [1] 1 mark for explaining the reason in comparison to other measure.
10. timing is a scientific measure / is more objective;
11. whereas the number of words used might be affected by vocabulary;
12. whereas the number of words used might be affected by how easily the individual wakes up;
13. Participants may lie about dream details (to please the experimenter / so use more words);