Sometimes, people say that they are "running on autopilot", meaning that they are doing the things that they normally do, without any real conscious involvement. I have read that it is not uncommon for people to drive routes that they regularly drive without any conscious memory of it - I have occasionally done this myself, and it is very unnerving.

But how do we do this? How can we achieve the level of co-ordination and reaction that is required to drive a vehicle for a significant period without involving our conscious mind? I realise that we do a lot of things sub-consciously, but it seems that learned tasks like driving should require at least a minimal conscious engagement.

Incidentally, I am not suggesting that this is dangerous in any sense. I don't think it is. I am just surprised as the level of functioning we are capable of achieving sub-consciously.


4 Answers 4


What you describe is the textbook definition of a habit: routines of behavior that are repeated regularly and tend to occur subconsciously. These are triggered by some external (say, being behind the driver's well of a car) or internal (say, being upset) stimuli. This activates chunks of procedural memory, which attempts to carry out a task that was usually associated with the stimuli (keeping the car on the road; eating a cake).

Although chunking is best understood for factual memories, a similar procedure is believed to apply for how procedural memories become a habit. Obviously, this is a highly researched topic, mostly because of the connection to addiction.

A final minor point is to be careful with terminology. Subconscious is a vague term that should typically be replaced by unconscious or preconscious.

Annotated references

Wood, W., & Neal, D.T. (2007) "A new look at habits and the habit-goal interface." Psychological Review, 114(4): 843-863. [pdf]

  • A relatively well know article that shows a model of how habits are shaped and interfere with or aid conscious goals.

Barnes, T.D., Kubota, Y., Hu, D., Jin, D.Z., & Graybiel, A.M. (2005) "Activity of striatal neurons reflects dynamic encoding and recoding of procedural memories." Nature 437, 1158-1161 [pdf]

  • A look at the neurobiology of chunking of procedural memory and habit formation in rats. Stresses how easy it is to reactivate old habits.

Graybiel, A.M. (2008) "Habits, Rituals, and the Evaluative Brain." Annual Review of Neuroscience 31: 359-387 [pdf]

  • Reviews evidence for the involvement of basal ganglia–based circuits in procedural chunking and habit formation. Show that habits form for both overt behaviors (say, backing your car out of the driveway) and cognitive behavior (say, general route planning).

Dehaenea, S., Changeux, J.-P., Naccachea, L., Sackura, J., and Sergent, C. (2006) "Conscious, preconscious, and subliminal processing: a testable taxonomy" Trends in Cognitive Sciences 10(5): 204-211. [pdf]

  • Explains the difference between unconscious, preconscious, and subliminal and how to test for them.

A more computational explanation can be found in the expectation-based reasoning literature. The theory suggests that people are always generating expectations of what they expect to sense (see/hear/smell/feel etc) in the near future. These expectations are matched against observations. If expectations and observations match, then all is good. When they don't match, cognition is alerted. In this view, predictions flow top-down and errors (discrepancies between the prediction and the observation) flow bottom-up.

Lee, T.S., Mumford, D. (2003) Hierarchical Bayesian inference in the visual cortex. Journal of Optical Society of America, A. . 20(7): 1434-1448.

Hohwy, J., Roepstorff, A., & Friston, K. (2008). Predictive coding explains binocular rivalry: an epistemological review. Cognition, 108(3), 687-701. ELSEVIER SCIENCE BV. Retrieved from http://discovery.ucl.ac.uk/136548/


This phenomenon is called highway hypnosis (also called driving without attention mode or white line fever) and is an example of procedural memory (or automaticity). Procedural memory is the ability to perform certain tasks without conscious awareness.


There is nothing surprising or unusual in this. It is a straightforward application of skilled learning (the driving or whatever), habit formation (route following), and having your conscious attention on something else. Back in the 1990s, when I was doing landscaping, I used to make good use of this effect by consciously reviewing things I had recently read while doing routine work. It can be a problem when you slip into a habitual behavior without realizing it and you end up following an old route and find yourself at the wrong location.

Another reason for not remembering the particular, most recent, trip is that it tends to merge into all the almost identical trips you have made. Several times when this has happened to me, I have been able to reconstruct (how accurately is another question) the most recent trip by trying to remember extremely specific details that often change from trip to trip.

The only specific references I have right now are for habit learning, which I was reading a couple weeks ago, these two are the best general articles on habit learning that I found:

David T Neal, Wendy Wood, and Jeffrey M. Quinn (2006). Habits—A Repeat Performance. Current Directions in Psychological Science Volume 15—Number 4.

Wendy Wood and David T Neal (2007). A New Look at Habits and the Habit–Goal Interface. Psychological Review Vol. 114, No. 4, 843–863.

  • $\begingroup$ I can accept that some actions can be done on autopilot - like playing guitar, or the process of driving, but it is the route finding that I struggle with. And even when I follow a habitual route, it is done consciously, even if without concentrating, which I can accept. $\endgroup$ Mar 4, 2012 at 14:59
  • $\begingroup$ At the moment, I am favouring this simply because I think the memory aspect is probably important. If there is nothing odd about the journey, then it probably doesn't get separately logged into memory, so we have no specific recollection of it. I will be checking through the references and selecting an answer this weekend. $\endgroup$ Mar 7, 2012 at 19:24

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