Gauging

One of them was how someone would act if they were being followed or they believed they were being followed.

Their anxiety levels would grow steadily until they would reach a stage where they would turn to look back or they would try to escape while some others would choose to ignore it and pretend they do not realise anything.

If they were pretending then their anxiety levels would rise or fall depending on how they were able to confirm how the presence they had picked up on had stopped following them, had gotten further away or had started to get closer.

If they were anxious enough to turn back to check then there would be some early signs of the rising anxiety that would let Ash slow down or get to some cover.