Percipient
noun
One who perceives something.
One who has perceived a paranormal event.
“In the course of investigating the haunting, I interviewed several percipients.”
adjective
Having the ability to perceive, especially to perceive quickly.
Perceiving events only in the moment, without reflection, as a very young child.
“Over time children advance from the percipient stage to the perceptive stage, in which they begin to reflect on the significance of events.”