Conceptual question on simple harmonic motion

[xregina12]

1. a. Jim and Gina are swinging on adjacent swings of equal length. Jim weighs about twice as much as Gina. Who takes less time to swing back and force.
I got this answer, which is that they take the same time since mass doesn't affect the period in simple harmonic motion. However, I don't get part b below.

b. What, if anything, will change if Jim swings while standing on the seat of his swing?
I. Jim's period will decrease.
II. Gina's period will decrease.
III. No change in the period.

I put no change, however, the answer is wrong, does anyone know why?

 

[Redbelly98]

What things does the period depend on? Think about whether standing vs. sitting in the swing will change any of those things.

 

[xregina12]

Well I know the equation for period is T=2pi(L/g)^(1/2) however, 2pi and the length are constants, and g, acceleration due to gravity, I believe won't really remotely change to any notable degree so I don't see why the period changes.

 

[Redbelly98]

What distance does the length L actually refer to?