Our brains engage in two distinct cognitive modes: the attention-demanding “task-positive mode” and the go-with-the-flow task-negative mode, also known as the default mode. Observing thoughts is a cognitive task; the thoughts themselves arise while the brain is in default mode. Here’s the thing: these two modes reciprocally inhibit each other; that is, our brain can’t be in both modes at the same time. They alternate. Therefore, we can’t observe thoughts “as they unfold”, because their unfolding happens in the default mode and our observing happens in the task-positive mode. So observing thoughts is not simultaneous with their production but happens after they are produced: observing is remembering – even if a split-second later.
The converse of this is while we’re “observing” thoughts, we’re not producing them. We alternate modes. And if we’re doing a lot of observing, we’re also doing a lot of disrupting of what we’re observing. Hence, what we’re observing is not a natural unfolding of thoughts but a constantly disrupted stop-and-go of thoughts.
Jack A, Dawson AJ, Begany KL2, Leckie RL, Barry KP, Ciccia AH, Snyder AZfMRI reveals reciprocal inhibition between social and physical cognitive domainsNeuroimage. 2013 Feb 1;66:385-401. doi: 10.1016/j.neuroimage.2012.10.061. Epub 2012 Oct 27. . .