Weird results from a Bool value

Okay. I can work with this. But I'm really wanting to understand what is happening, because I've never had it happen this way before.

I created a standard two option field in Dynamics 2011.

When coding the plugin I'm getting the reverse value of what I'm expecting.

Here is the code:
            bool trigger = preImageEntity.GetAttributeValue<bool>("trigger");
When Yes is marked on the form, it comes back as False.
When No is marked on the form, it comes back as True.

I double checked the Options. Yes = 1 and No = 0.

Like I said, I can work with this, I'm just wondering why it's not returning the values I'm expecting.
I'm expecting Yes = True and No = False.

Thanks.