Running Before It Was Noticed

A page has been read to the bottom, and nothing of it is left. The eyes moved line by line. A thought was somewhere else the whole time, and it had been running for a while before anyone noticed. KTT counts that thought as a thought, noticed or not, even when it was never a sentence and only a hum. Researchers call this zoning out, and they have studied how often people catch it. The sources read for this article are abstracts and reference lists of the main papers, not the papers in full.

The page that was read and not read

In studies from Jonathan Schooler’s lab, people read text and were stopped at random moments to say whether their thoughts were on the page. Some were not, and many had not noticed. The researchers separate two things: a wandering thought, and the noticing that it has wandered. The first can run without the second.

What a 2011 review found

In 2011, Schooler and colleagues reviewed the evidence in Trends in Cognitive Sciences. They report that the noticing is only intermittent: people often fail to recognize that their thought has wandered. In studies where participants were both probed and asked to catch themselves, they showed lower noticing when probed in the middle of a wandering episode than when they reported catching themselves. The review also cites a study in which people who had been drinking alcohol caught themselves wandering less often than people who had not.

What the brain did

In 2009, Kalina Christoff and colleagues used experience sampling during brain scans. Participants were probed at random moments and reported where their attention had been. This was among the first studies to look at the brain at the moment of a wandering thought. They found activity in both the default network and an executive network, which had not been expected to work together.

What is not known

How long a wandering thought typically runs before someone notices it is not known from these sources. The papers describe patterns across probes, not a number.

Whether probes catch the thought or change it is open. The researchers themselves treat that as a methodological issue.

Whether what is called noticing is itself a thought, or a different kind of event, is also open. KTT counts it as a thought, and the studies read here do not settle the matter.