'What does the brain do when we day dream, our mind wanders, our thoughts flit from one thing to another, or we seem to be mentally “idling”? Some evidence has accumulated during the past 30 years that implicates the involvement of an intrinsic default network in the brain: an anatomically defined network which includes the medial temporal lobe and medial prefrontal subsystems and posterior cingulate cortex. Functionally, this network supports a baseline, so-called default, mode of cortical activity that engages when externally directed thought is absent (stimulus-independent thought) and also possibly during watchfulness towards the external environment (stimulus-orientated thought). Brain activity in this default system seems to be inversely related to activity in another intrinsic network, the “attention system”, which is activated during goal-directed cognition. These networks have been explored mainly using brain imaging, but—though at first sight incongruous—could doodles, and the doodling that produces them, provide another way of probing the default network and the brain functions it supports? Although of enduring interest to the public and to teachers, psychologists, psychiatrists, and many in the humanities, doodles have received little attention from neuroscientists. Because of the circumstances in which they are often produced, however, doodles and doodling might reveal insights about how the brain functions, notably when in “idling” mode."