“The Phenomena of Inner Experience”, Christopher L. Heavey, Russell T. Hurlburt2008-09 ()⁠:

This study provides a survey of phenomena that present themselves during moments of naturally occurring inner experience. In our previous studies using Descriptive Experience Sampling (DES) we have discovered 5 frequently occurring phenomena—inner speech, inner seeing, unsymbolized thinking, feelings, and sensory awareness.

Here we quantify the relative frequency of these phenomena. We used DES to describe 10 randomly identified moments of inner experience from each of 30 participants selected from a stratified sample of college students.

We found that each of the 5 phenomena occurred in ~1quarter of sampled moments, that the frequency of these phenomena varied widely across individuals, that there were no statistically-significant gender differences in the relative frequencies of these phenomena, and that higher frequencies of inner speech were associated with lower levels of psychological distress.

[Keywords: Descriptive Experience Sampling, consciousness, awareness, inner experience, individual differences, inner speech, inner seeing, unsymbolized thinking, feelings, sensory awareness]