Why do people see ghosts?

Ruling out psychosis, or the existence of actual ghosts, how do we explain ghostly sightings?

I saw one just after my son was born. To be exact, I ‘felt’ the ghost rather than saw him. ‘Feeling’ someone in the room is such a common occurrence in ghost sightings that it has a clinical name: “feeling of presence,” or FP.

In fact, survey data shows that while 18 percent of Americans say they’ve seen or been in the presence of a ghost, 29 percent say they have felt in touch with someone who has died.

A lightning storm lit up the sky while I sat bleary-eyed in Gabriel’s pitch-black bedroom, breastfeeding him in the armchair at some unknown hour. Then, the sensation descended – not as a possibility, but an absolute certainty, the way you know it’s raining because you are suddenly wet: there was a young man standing next to me.

My eyes scoured the contours of darkness for shapes, silhouettes. Petrified, I felt a maternal sixth sense alerting me to danger. It took every ounce of reason and self-reassurance to return Gabriel softly to bed and close the door, feeling all the while someone was watching us.

I tried to rationalize away the ghost as a manifestation of my anxiety as a new mom. My brain was uncomfortably awash with post-pregnancy neurochemicals responding in exaggeration to mundane stimuli: a baby’s face, a baby’s cry. I lay awake at night after putting Gabriel back to sleep thinking with genuine amazement that women everywhere do this all the time.