"Kelly and Maria's study habits" or "Kelly's and Maria's study habits"?

[Mori]

Kelly and Maria have different study habits.

Judging from Kelly and Maria's study habits, the best way to study is the way that works for you.

Source: Interchange fifth edition level 3, page 55

Shouldn't it be Kelly's and Maria's study habits?

 

[5jj]

No.

It's correct as it is.

 

[Mori]

It's correct as it is.

Isn't it individual ownership?

 

[jutfrank]

Yes, but still it's only necessary to use the 's in the latter of the two people mentioned.

 

[Mori]

Yes, but still it's only necessary to use the 's in the latter of the two people mentioned.

That's different from what I've always taught about joint vs. individual ownership.

Note the difference between, for example:
Joe and Anna’s children (one lot of children: Joe and Anna are their parents)
Joe's and Anna's children (two separate lots of children: Joe’s and Anna’s)

Practical English Usage fourth edition, entry 123.1

What am I missing?

 

[jutfrank]

What do I miss?

Only the context.

If you say Joe and Anna's children, without any other context, it's hard not to interpret that Joe and Anna are the mum and dad of the children. In the context we have in post #1, there's no difficulty in interpreting what the writer means.

 

[Mori]

Only the context.

If you say Joe and Anna's children, without any other context, it's hard not to interpret that Joe and Anna are the mum and dad of the children. In the context we have in post #1, there's no difficulty in interpreting what the writer means.

You guys are amazing! I really appreciate the time you spend helping both English teachers and their students.