A post by Adam Morton.

Some acts of imagination are so ordinary that we hardly notice them. Some of them are never noticed because they are not conscious. Unconscious perceptual imagination is probably controversial (but see below). On the other hand imagining physical actions, of oneself or other people, seems to be both a very familiar part of life and not to fit a standard idea of what is conscious. Not conscious experience at any rate.

One form it takes when the imaginer imagines herself is rehearsal. You are preparing to do something, or anticipating having to do it, and you pause while the things you will have to do and their sequence get organized in your mind. You may have conscious images of yourself performing the acts, or of sensations in your muscles. But you may well not: you simply wait while something happens, and then you are ready to go. Think of a skier at the head of a slalom course; she is uncertain how to take the course and so she just looks at it and considers the poles, and when she feels ready, with no useful description of what that feeling is, she sets off down. I am sure that what conscious feeling there is consists mostly in the feeling of readiness, rather than in anticipation of what her body will do. But she is anticipating and rehearsing. When she gets to poles and slopes that she had seen and considered she acts automatically as if by plan, and when she gets to moguls and snowdrifts that were not salient from the start her reactions are less agile and immediate, as they are when she gets further down the course where it turns out of sight. (For remarks about how being able to imagine something helps make it possible to do it, though mixed with many other themes, see Epstein 2018. For a deep continuity between imagining action and performing it see Vyas 2017.) There is also evidence for incongruity between the "motor images" that accompany preparation for action and the familiar sensory images that accompany perception, including perception of action (Jeannerod 1994).

Why count this as imagination? Without getting onto the definitions and counterexamples treadmill, here are some considerations.

Rehearsal shares an exploratory quality with other kinds of imagination. When you imagine what somebody might do or how you might find your way to a destination you are not forming beliefs about the person or the place, though the imagining may play a role in subsequent belief formation. The nearest we can get is beliefs of a "just possibly if…" shape. Instead you are acquiring a very diffuse sense of the "lay of the land" (as my student Michael Lockhart has put it). Diffuse but invaluable. Similarly, in rehearsing how an action might be done in a particular situation you entertain in hypothetical form various components that could constitute the action in relation to the actual environment. You coordinate them and link them to what you know of the situation and to ways the environment is presented in imagination. This last is important because it means that we can adapt freely rehearsed actions to anticipated though not predicted developments. As the skier approaches the gate she finds a little patch of ice just where it would otherwise be best to dig in her edges, and so she straightens up and leans a moment later, falling into a sequence that had been rehearsed but not planned. An exploratory rehearsal like this facilitates a rapid intention, and is facilitated by environmental knowledge, much as the imaginative exploration of a possible situation facilitates later beliefs about it and is facilitated by knowledge of situations that may lead to it. This can be summed up by saying that rehearsal interfaces on both sides with other content-bearing states in a way that is parallel to that of other forms of imagination.

In particular, rehearsal interfaces with perception and perceptual imagination in a familiar way. When you run over a contemplated action you make it easier to imagine appearances and sensations that may accompany the action. As the skier contemplates a gate situated just downhill of two flanking moguls she prepares herself for a burst of muscular tension and discomfort as she suddenly leans to begin turning with very little time or space to spare. When in fact this is what she does the sensations may be comforting and confirming rather than disturbing. Things are developing as anticipated. When you rehearse coming out of your quiet and shaded building into the bright hubbub outside, and squinting while shielding your eyes with your hand so that you can see if the bus is just arriving at the stop, you make it easier to see the street and the bus in spite of all the distraction, because it is generally as you had imagined. (Conversely, if your imagination is faulty it may make it harder to perceive the actual scene.) An actors' trick is a famous example of this: in order to get the general manner and even the personality of a character consistent and plausible, actors will sometimes focus on imagining some small detail of their physical movement, a limp or a sore shoulder or whatever, and then find that the world of the imagined person is falling into place. Rehearsal in rehearsals! (One source of information about this is anecdotes about famous actors. See also acting advice sites on the web, listed in the bibliography.)

A final similarity between rehearsal and other forms of imagination is that the contemplated act has (approximately) the same temporal shape and is resisted by (some of) the same factors as its physical versions. A shorter action will take less time to rehearse, in part because it has fewer parts, but also because coordination with sequential events in the imagined environment is simpler. And rehearsing an action that has to negotiate difficulties is likely to be halting and incomplete in ways that parallel the difficulties that its enacted counterpart would face. If you are sight-reading music the imagined half notes will take longer than the imagined eighth notes, and tricky chromatic passages are likely to be hesitant and inaccurate in imagination. (For me, any rate.) I might conjecture, in fact, that the similarity is based on a two-way influence. Imagining actions needs input from imagining perception, which is well known to exhibit a similar sensitivity to actual physical arrangements. Though the explanation is controversial the phenomenon is rarely denied (Thomas 2018). In fact, the classic evidence consists in imagined actions, mental rotation of shapes and volumes. And in the other direction imagining perception (or imagining perceptible aspects of the environment) needs input from imagining actions, from going to a suitable looking or hearing position through moving the head, focusing, and scanning with one's eyes, and ultimately to saccades and other thoroughly unconscious motor acts. Moreover it might be natural to speculate that there is a connection with the phenomenon that a couple of The Junkyard posts have mentioned, that limitations of physical capacity induce restrictions on imagination (Jansen 2018, Jones and Schoonen, Morton 2018).

I do not think it is really controversial that actions are imagined just as scenes are, and that imagining them is often preparation for performing them. The unity of imagination is a tricky issue, so a suggestion might be that when we understand these things better the same pattern of deeply similar and only superficially similar processes will emerge. (The not very controversial methodological principle is to count as imagination processes that interact functionally with the same other processes as central cases of imagination, in the same ways.) If I am on the right track, though, there is a lot more imagination of action than anyone is likely to write in their diary. For ubiquitous though it surely is, much of it is unconscious, so that even when people know that it has occurred they can nearly always describe it only at the crudest level of detail. The imagination of action would in fact be central to all imagining if an "enactive" account of it were adopted, according to which to imagine something is to explore, search through, a situation in which it would appear. As the Stanford Encyclopedia of Philosophy article on mental imagery (Thomas 2018) describes this position:

The perceiving organism is not merely registering but exploring and asking questions of its environment ... actively and intentionally ... seeking out the answers in the sensory stimuli that surround it. Imagery is then experienced when someone persists in acting out the seeking of some particular information even though they cannot reasonably expect it to be there. We have imagery of, say, a cat, when we go through (some of) the motions of looking at something and determining that it is a cat, even though there is no cat...  there to be seen. Visually imagining a cat is seeing nothing-in-particular as a cat.

The point is that searching is something one does, and roaming through a possible venue preparing to capture information of a predetermined kind is something that one can rehearse doing. Typically when one does this it both builds on and supports many other kinds of imagination. 

References

Acting advice: http://www.michaelchekhov.net/gesture.html https://www.theatrefolk.com/blog/developing-your-characters-physicality-from-head-to-toe/

Brogaard, Berit and Dimitria Electra Gatzia (2017) Unconscious Imagination and the Mental Imagery Debate. Frontiers in Psychology (www.frontiersin.org) 8, Article 799: 1-14.

Epstein, David (2018) Are athletes really getting better, faster, stronger? TedTalks.

Jansen, Julia (2018) Situated models of-imagination and some political implications  The Junkyard Blog.

Jeannerod, M. (1994). The Representing Brain: Neural Correlates of Motor Intention and Imagery. Behavioral and Brain Sciences 17:187-245.

Jones, Max and Tom Schoonen (2018) Embodied Constraints on Imagination?  The Junkyard Blog.

Morton, Adam (2018) Comment The Junkyard Blog.

Thomas, Nigel J.T., (2018) "Mental Imagery", The Stanford Encyclopedia of Philosophy (Spring 2018 Edition), Edward N. Zalta (ed.).

Vyas, Saurabh and others (2018) Neural Population Dynamics Underlying Motor Learning Transfer Neuron 97: 1177–1186