Why do some people repeat the same stories over and over again?

My mother in law will repeat the same stories over and over again. And I don't mean old stories of reminiscing. She does that too, but to a normal degree. She'll tell recent stories or facts 5 times or more in the week they occurred. She doesn't show any signs that she knows she's already told me. I know sometimes people will forget if they'd told someone something once in a while, but usually they'll say something to that effect. But she'll say it like every time is the first time. I heard 3 times in two days that my nephew has jaundice. My husband says she's always been like this, but it has gotten worse lately. I don't feel like it's forgetfulness. I feel like she just has to constantly be talking. If there's a welcomed silence she'll find something to say to break the silence.

Is there a physiological reason behind this at all?