Ben's sister-in-law always has a smile on her face and a joke to tell. the moment she walks into the house he starts smiling, even before she says something funny. this is caused by:

The one that is causing Ben to smile even before she says something funny was because of the mood linkage. This causes a human to participate in the mood in which produces an individual to act or improve their mood depending on the instances that is given in a particular scenario.

its because Ben always thinks the jokes are funny

Explanation:

so when his sister walks in the house Ben is ready to hear another joke

well its is frequent rain

have a good day