Explain "behavioral variables" in interaction design

We're studying the About Face book. We're reading in chapter two about "behavioral variables" as a part of developing persona hypotheses.

They give a very small example of behavioral variables:

• Frequency of shopping (from frequent to infrequent)
• Desire to shop (from loves to shop to hates to shop)
• Motivation to shop (from bargain hunting to searching for just the right item)

Can you give a deeper example of behavioral variables in relation to a role in a specific domain (ideally not the shopping domain)?

Here are a few questions that we are struggling with that may guide your example:

• Should we consider behavioral variables in the domain of the user (e.g. shopping) or behavioral variables in the domain of the product (e.g. shopping products) or both?
• How granular should our behavioral variables be? Should they be only high level (e.g. bargain hunting) or also low level (e.g. find the product in a particular category with the lowest price)?
• What's the difference between a persona goal (in interaction design) and a behavioral variable for a persona hypothesis? What are the similarities? We seem to be seeing some overlap.