Differences between Visual Paired Associate Subtests 1 and 2 of the "Wechsler Memory Scale-Revised"

I am reading a paper in which the Visual Paired Associate Subtests 1 and 2 of the "Wechsler Memory Scale-Revised" are used to assess cognitive function.

There is a significant difference in performance between control and test groups for subtest 1 but not subtest 2. Yet in the paper no background on the difference between these two tests is provided and I have been unable to find information on the subtests at this level of granularity through googling.

Any insight into the difference between these subtests would be much appreciated!

Thank you.