Option Adjusted Spread (OAS) higher, interest, following, understand

water2012

Please help me to understand the following statement


The higher the interest rate volatility assumed, the lower the OAS. In the case of a putable bond, the higher the interest rate volatility assumed, the higher the OAS.

(CFA Institute. Level 1 Volume 5 - Equity and Fixed Income, 5th Edition. Pearson Custom Publishing). page(477)

Regards/Manoj Badera