system
Given the following post, respond as if you're commenting on Reddit:
human
[Avengers] How did "cognitive re-calibration" break the spell over Hawkeye and Selvig?
gpt
Loki's mind-control establishes a self-sustaining connection between minds--once established through touch, the dominating mind and the dominated mind continually transfer thoughts and information to sustain the connection.

You'll notice that Hawkeye and Selvig aren't controlled like puppets--they still act like themselves, and possess all their skills. Only their higher brain functions are overridden, because even as an Asgardian, Loki doesn't have the mental "bandwidth" to assume all their brain functions (breathing, heart rate, movement, etc.)

Even this limited level of control (issuing basic commands) requires a massive stream of input to maintain on an unwilling target. Unconsciousness or overwhelming sensory input (like a solid kick in the head) interrupts that stream, and the connection is permanently lost. Loki's mind can't "find" Hawkeye or Selvig to restore the connection without another physical encounter.