percipient

adj

1. Having the ability to perceive, especially to perceive quickly.

   “Fasting, yet not of want Percipient, he on that mysterious steed Had reach’d his resting-place, For expectation kept his nature up.”

   “[...] he calls attention to the use of glasses […] The eye itself is no more percipient than the glass; is quite as much the instrument of the true self, and also as foreign to the true self, as the glass is.”

2. (dated)Perceiving events only in the moment, without reflection, like a very young child.

noun

1. One who perceives something.

   “As anatomy, physiology and, later, psychology have developed into more or less well-organized sciences, they have necessarily and rightly come to incorporate the study of, among other things, the structures, mechanisms, and functionings of animal and human bodies qua percipient.”

2. One who has perceived a paranormal event.

   “In the course of investigating the haunting, I interviewed several percipients.”