Low coupon isues vs Higher coupon on Mortgage Passthrough because, interest, completely

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Q19 from Reading 29 in CFAi states that on Mortgage Passthrough Securities, low coupon isses exhibit less negative convexity than higher coupon issues and will outperform during falling interest rate periods.

Can someone elaborate on why this is?

My thinking is that its because lower coupon issues have less prepayment risk due to less refinancing but not completely confident as to that being why.