Thx for commenting and apologize for the late reply. I've been out in Australia (Sydney & Melbourne) all last week and have just return to SF.
FBM is a design model, not a quantitative model. As such, it is not suitable for accurate measurement purpose. For one thing you can't really measure the motivation factor accurately b/c we don't have a way to effectively and efficiently measure what's going on inside people's brain. One might argue that you can use response output as a proxy for people's motivation, but that is misleading, b/c response output is not affected by motivation alone. It could simply b/c you have an effective trigger or an simple task.
You can try to quantify simplicity by measuring how much resources is required to perform the task. But you won't really know how simple the behavior is, because you will also need to know how much resources do the subject have access to in order to answer that.
There is no rigorous way to measure any of the 3 factors effectively and accurately. A scientist can always poke holes in it. However, you can heuristically determine whethere there is motivation, is there a trigger, and comparatively how simple the behavior is compare to another reference behavior based on how much resources are needed to carry out the task. Keep in mind that these are not accurate measurements though. And trying to treat them as accurate measurements could be misleading.
For your example, the resource needed for #1 is just time to read the email. The resources needed for #2 is to read, but also to push a button. So it's less simple (more difficult). But how much more difficult? That is not easily quantifiable.
Finally, you can always survey people. For example, ask people to rank how difficult each task is. But I'm not sure you will get anything consistent out unless your sample is very very large.
Alright, not sure if this help, and sorry if this didn't help. But that is not what the FBM is designed to do.
See you around next time.
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