what's the difference between "my mind fastened on" vs "I (was) fastened on"

Question

My mind fastened on his admission that he was an agent.

vs.

I was fastened on his admission that he was an agent.

Given that I can only say I was paying attention to or I was focused on not my mind was paying attention to or my mind was focused on, I don't know what the difference is and even after looking for it I couldn't find it.

I just want to know how fasten on works because I know how "pay attention" and "focused on" work. I just used those to make a point of why I don't know what the difference between my mind fastened on and I was fastened on

Answer 1

I think this may as well depend on the situation in which you say this.

When you are recounting to investigators the minute details of an aircraft accident that you recently survived, you may very well use the more precise "my mind fastened on" expression.

When however drifting on the waves of a fast-paced gossiping session at the tiny curbside table of a French café, you are all set using "I was fastened on his admission": in this context, choosing percievedly overly pedantic language may interfere with the engagement of your companions, and the development of a lighthearted atmosphere...

Answer 2

1

My mind fastened on his admission that he was an agent.

vs.

2

I was fastened on his admission that he was an agent.

Cambridge Dictionary defines the phrasal verb fasten on as

to give attention to something, because it is of special interest or often because you think it is the cause of a problem:

The politician has fastened on the problems of the working poor.

As shown in the politician example, we could use a person as the subject. We could hence say

I fastened on his admission that he was an agent.

This means I gave attention to his admission.

In your example (2), the passive voice I was fastened on means I was given attention. This would not work.