Mental Imagery: Greasing the Mind's Gears

1. Introduction

Mental imagery is the kind of psychological state you are in when you picture or envisage an object, event or situation. This paper introduces and motivates a novel conception of mental imagery; namely, that it is grease for the mind’s gears. By “gears” I mean various psychological faculties: perception, belief and judgment, desire, intention, memory, etc. By saying that mental imagery “greases” these, I mean that it has the higher-older functional role of aiding the aforementioned faculties (“gears”) in discharging their functional roles. So this conception of mental imagery has two glosses. First, there is the imagery/grease analogy, then there is the more literal Mental Grease Thesis, or MGT for short.

Mental Grease Thesis (MGT):

Mental imagery aids psychological faculties in discharging their functional roles.

MGT is a naturalized thesis about mental imagery, one that draws inspiration from a wide array of research in clinical, experimental and social psychology. MGT is neither a definition of mental imagery, nor a piece of folk wisdom. The thesis does attempt to capture a truth about mental imagery, but one that is pitched at a high level of abstraction. For instance, MGT makes no mention of, and so is compatible with different views about, mental imagery’s content, format, phenomenal character and relation to the will. These topics have traditionally dominated philosophical discussions about imagery. However, overly narrow attention to them has obscured two important facts about imagery, ones that take central focus in the psychological literature and which MGT is intended to shed light on. The first of these is imagery’s architectural promiscuity.

Architectural Promiscuity:

Mental imagery is architecturally promiscuous insofar as it interacts with a variety of psychological faculties, including, for example, perception, belief and desire, among others.

For instance, in conditions of poor visibility, projecting mental imagery into the scene that one faces can help perception better “light the way” in terms of guiding action. Or, when working out the answer to a crossword clue, imagery may help one form beliefs about the right answer. Imagery can also bolster desire’s motivational force, keeping one on the straight-and-narrow when faced with competing impulses. These claims, which I unpack below, are backed by evidence from clinical, experimental and social psychology (Sects. 2 and 3).

The second feature of mental imagery that I discuss here is its psychopathological relevance.

Psychopathological Relevance:

Mental imagery is psychopathologically relevant insofar as abnormalities of mental imagery actively contribute to a range of psychological disorders.

For instance, variously “problematic” patterns of imagery are causally relevant for the onset, maintenance and even partial constitution, of psychological conditions as diverse as post-traumatic stress disorder, bipolar disorder and depression (Sects. 4 and 5).

Architectural promiscuity and psychopathological relevance deserve consideration in their own right, as two significant but under-theorized features of mental imagery. Once we do acknowledge them, two puzzles come into view. First, imagery’s architectural promiscuity raises the following question: How should we think about a state of mind that interacts with so many distinct psychological faculties and their associated processes, and seems to perform very different functions when doing so? Is there a way of thinking about imagery that might unify these heterogenous interactions? Second, imagery’s psychopathological relevance illustrates how harmful imagery can be to the human mind. This is in direct contrast with its architectural promiscuity. How should we characterize a psychological state that plays these opposing roles in human psychology, helping and hindering to such extreme degrees? MGT provides a solution to both puzzles, providing a unified account of imagery’s multifarious interactions with different psychological faculties and its apparently contradictory contributions to human cognition (confirming that the level of abstraction at which MGT characterizes mental imagery is not so elevated as to be vacuous).

Some qualifications: first, this is a paper about mental imagery and not the imagination. For those who equate the two, this paper might be read as one concerning the imagination. But some caution may be called for in making this equivalence (Gregory 2016; Arcangeli 2020). A second, and very much related, point is that, although the imagination is sometimes said to be functionally heterogeneous (Kind 2013; Kind and Kung 2016; Langland-Hassan 2020), that is not the driving concern here: my primary focus is restricted to architectural promiscuity, along with the question of how to square that feature of mental imagery with its psychopathological relevance. Third, since MGT is not a definition of imagery, everything I say is compatible with other mental states and processes being characterized in an identical way. This does not rob MGT of theoretical interest, however, insofar as MGT highlights harmony among imagery’s operations where we might otherwise have a discordant muddle.¹ Fourth, although other accounts of architectural promiscuity and its relation to psychopathological relevance are possible, a cost–benefit comparison with potential rivals is left for another time. Having said that, one reason for interest in MGT is that it represents an alternative to the currently dominant philosophical conception of mental imagery — that is, as a perceptual (or quasi-perceptual) state of mind. I shall have some things to say about that matter in closing.

2. Architectural Promiscuity I: Imagery-Assisted Perception

Mental imagery can be instantiated in a variety of ways. Sometimes mental imagery is tokened intentionally, via a deliberate act of will. On other occasions imagery is tokened intrusively, against one’s will. My focus here will be on the following distinction: imagery tokened in the mind’s eye versus imagery tokened in perceptual experience, or what I shall call “imagery-assisted perception.” Compare visualizing a bouquet of flowers “in one’s head,” and so in no space in particular, versus visualizing that same bouquet to be located in the empty vase currently before you. The latter is what I have in mind with the term “imagery-assisted perception.”²

Imagery-assisted perception has been put to several explanatory uses. Neil Van Leeuwen (2011, 57) claims that it shows how imagination is “central to producing action” and not decoupled from one’s motor system. Alan Thomas (2009), Bence Nanay (2010) and Amy Kind (2018) all claim that imagery-assisted perception explains amodal perception, i.e. how one represents the occluded parts of environmental objects and thus experiences objects as 3-D, despite being unable to see all of their sides simultaneously. Gregory Currie and Ian Ravenscroft (2002, 29) claim that what they effectively term the “invasion” of perception by imagery in these situations explains the visual character of the imaginings one undergoes when watching a film: one sees the screen image and in it the actors and sets recorded, and then uses imagery to imagine these to be fictional characters and locations.³

These claims are not mandatory. Other analyses of amodal perception — and of the role of imagery in action-guidance and filmic experience — are available. What is mandatory is recognizing the existence of imagery-assisted perception. This is not just a matter of naive introspection or thought experimentation. Imagery-assisted perception is either presupposed or strongly evidenced by a number of reputable paradigms in experimental psychology.

• In C. W. Perky’s (1910) experiments, and Segal’s later variants (1971; 1972), subjects confused seen figures, faintly back-projected on a dimly lit screen, with imagery that they were directed to mentally project onto the screen.

• Subjects directed to project imagery of stripes onto a colored background experienced visual aftereffects of color when, a short time later, they were presented with achromatic stripes at an identical orientation to those projected (Finke and Schmidt 1977).

• Studies measuring the acuity and resolution of imagery rely on subjects mentally projecting imagery of two dots onto a blank background before mentally ‘moving’ them (Finke and Kosslyn 1980).

• In temporal integration studies, subjects directed to mentally project a previously seen figure onto a screen, and combine it with an occurrent stimulus, were able to experience a fused composite of imagery and occurrent stimulus (Brockmole et al. 2002).

From the perspective of experimental psychology, imagery-assisted perception is a highly tractable phenomenon: “real, reliable, and replicable” (Segal 1972, 226).

In the philosophical literature there exist some mistaken notions about imagery-assisted perception. Discussing these is useful for fully characterizing the phenomenon and its relation to MGT. For instance, Van Leeuwen (2011, 56 and 66), for all he says that is illuminating about imagery-assisted perception, wrongly characterizes the phenomenon as necessarily involving a nonveridical representation (the projected image) combining with a veridical one (the perceptual experience). Granted, imagery’s utility in some cases of imagery-assisted perception is that it represents an absent object. Then, the image tokened will indeed be nonveridical. Van Leeuwen gives an example along the following lines:

Skunk Skirting

You are jogging along a road when you suddenly see a skunk. In order to work out where to move to avoid being sprayed, you must make an educated guess as to the spray’s potential distance and direction. But you must do so in a way that can directly guide your actions. Solution: you use mental imagery to project, out into the scene before you, an arc that strikes you as the length and angle that the skunk’s spray is likely to be, should the animal become riled.

Here, the projected image is nonveridical insofar as it represents something (the skunk’s spray) that is absent from the scene before your eyes. Still, one should be careful not to think that this is how imagery-assisted perception works in general. Crucially, an image might be projected into visual experience in an attempt to match objects and properties present before one, but which one cannot see very well, or perhaps at all. When this mental action is performed successfully, the image will be veridical. This is certainly how those who claim that imagery-assisted perception explains amodal perception are thinking about matters. For instance, contrast Skunk Skirting with the following:

Cat Completing

You are looking at your cat, partially occluded by picket fencing. Some parts of the cat directly stimulate your retinae. Other parts, i.e. those behind the pickets, do not. Still, there looks to be a whole, complete cat before you. Question: why is that what you experience instead of discrete, detached cat-parts? Answer: you undergo projected mental imagery of the parts of the cat present in the scene before you, but which happen to be occluded by the pickets.

In saying that imagery-assisted perception involves non-veridical imagery, Van Leeuwen’s characterization of the phenomenon begs the question against using the phenomenon to explain amodal perception in this way.

Whether amodal perception is a matter of projected mental imagery is controversial (Briscoe 2011). But we needn’t take a stand on that to construct counterexamples to Van Leeuwen’s characterization of imagery-assisted perception. Consider a different vignette:

Precarious Passing

You are driving at night and visibility is drastically reduced. Suddenly, a car appears on the road before you. At least, you assume it to be one; all you can make out are two headlights. In order to work out whether there is space for your car to pass on the narrow lane, you must make an educated guess as to the size of the other car, given the position of its headlights. But you need to do so in such a way that can directly guide your action. Solution: you use mental imagery to project, out into the pitch black and surrounding the headlights, the outline shape of a car that strikes you as the correct size and shape.

Here, projected mental imagery combines with your visual experience to help guide action where the latter would be insufficient. In this, Precarious Passing is like Skunk Skirting. But familiarity with meeting cars along this difficult stretch of road may enable you to project a veridical image of the outline shape of the car, given the positioning of the seen headlights. There is thus no reason why the image in imagery-assisted perception must be nonveridical, as claimed by Van Leeuwen.

Crucially, whether the image that is involved in episodes of imagery-assisted perception is veridical, as in Precarious Passing, or nonveridical, as in Skunk Skirting, MGT sheds light on these situations. The mental image is integrated into visual experience in order to aid perception in discharging a central, if not defining, function: the guidance of particular actions within, and navigation through, one’s immediate environment (Watzl 2014; Wu 2014; Schellenberg 2018).

Let us consider one way that this function can be bolstered by imagery. As Denis Buehler (2019, 2122–3) has made vivid, agents may, via switches in perceptual attention, usefully alter their degree of control over their actions. For instance, a pianist may switch perceptual attention from her left hand to her right hand at various points in a performance in order to more fully, and reliably, control her actions with each hand. In both Precarious Passing and Skunk Skirting, a similar effect is achieved via the use of imagery. In these situations, projecting mental imagery to particular locations in the visual field assists you in exercising a greater degree of control over your actions with respect to those locations and the objects situated there. After all, you might plausibly skirt the skunk and pass the car without relying on imagery. Whether you could do so reliably, however, particularly in Precarious Passing, is somewhat doubtful. Mental imagery helps you here to not merely skirt the skunk and pass the car tout court, but skirt the skunk more effectively/pass the car less precariously than you might otherwise. By focusing your attention on relevant spatial locations, the imagery you project into these scenes allows for more reliable control over your actions with respect to objects in those scenes.

Again, alternative analyses of imagery’s role in action-guidance are possible. But a second account of the functional role of imagery in imagery-assisted perception is available to the defender of MGT: that such cases show how imagery can assist perception in the representation of sensory properties.⁴ In Skunk Skirting, the sensory property represented (the spatial arc of a spray) is a non-instantiated property that may, fairly disastrously, be instantiated in the near future. Thus, you use mental imagery here not only to guide occurrent action, but to prepare for possible, future action. In Precarious Passing, by contrast, the property represented (the outline shape of a car) is, in fact, instantiated. However, viewing conditions preclude it from featuring in your perceptual content in a bottom-up manner. Crucially, if an agent is to use their visual experience to guide their action in this case, then they need to fill in the details of its content for themselves. This is what infusing perceptual experience with imagery does.⁵ The mental action of imbuing perceptual experience with imagery allows perception to better guide one’s actions insofar as it enables one to represent, within one’s visual experience, the car’s suspected outline shape. Cases of imagery-assisted perception are thus right at home within the framework of MGT, showing how imagery can assist perception twice over: in guiding action and in facilitating the representation of sensory properties.⁶

3. Architectural Promiscuity II: Imagery-Assisted Cognition

Several discussions of what I am calling “imagery-assisted perception” can be found in the philosophical literature.⁷ By contrast, and a few examples aside, sustained discussions of imagery-assisted cognition are more difficult to find.⁸ In general, the idea that imagery can interact with thought has, in contemporary philosophy of mind at least, received much less attention than the idea that imagery can interact with perception. At least two explanations for this seem likely. First, one might worry that admitting imagery into thought entails regressing to an early-modern empiricism on which cognition is fundamentally composed of images (but see Prinz 2002). Second, we face a “format” problem of having to explain how iconically/pictorially structured mental states can combine with ones that are propositionally/sententially structured. This latter worry does not arise when dealing with imagery-assisted perception. For there, a common iconic/pictorial format, one shared by perception and imagery, may be assumed.⁹

I won’t address either of these issues here. My aim is to make a case for the reality of imagery-assisted cognition, examine some of its details and show how it supports MGT. I leave for another occasion the task of attempting to resolve puzzles that arise from doing so.

4. Psychopathological Relevance

The second neglected feature of mental imagery that MGT helps us to better understand is its psychopathological relevance. There is scant discussion of this feature of imagery in the philosophical literature. I’ll first explain some relevant findings from clinical psychology before spelling out the relation between imagery’s psychopathological relevance and MGT.

Recent work in clinical psychology has identified abnormalities of mental imagery across a range of psychological disorders. The following is a small sample:

• Post-traumatic stress disorder (PTSD) is associated with imagery-based “flashbacks” to adverse life events (Pearson et al. 2013, 8).

• Social phobia is associated with negatively-valenced third-person imagery, i.e. from the point of view of an interlocutor (Hirsch et al. 2003) and socially phobic individuals have been found to perform worse than controls on tests for generating imagery of neutral stimuli, such as letters of the alphabet (Morrison et al. 2011).

• Schizophrenia is associated with a high score on tests for imagery vivacity (Oertel et al. 2009), yet individuals with schizophrenia typically perform worse than controls on tests that measure the abilities to inspect (Aleman et al. 2005) and maintain (Kang et al. 2011) imagery.

• Bipolar disorder is associated with abnormally high results on several imagery measures, including tests for spontaneous use of mental imagery (McGill and Moulds 2014), e.g., when planning the order of chores, thinking of a friend, or listening to a story on the radio.

• Major depressive disorder (MDD) is associated with several abnormalities of imagery, including an impaired ability to intentionally generate mental imagery of the future (Williams et al. 1996).

In principle, abnormalities of mental imagery might be associated with a psychopathology in at least four ways:

• Partial constitution: Imagery abnormalities may be partially constitutive of a psychological disorder.

• Causes: Imagery abnormalities may be among the causes of a disorder, relevant either for its initial onset or continued maintenance.

• Effects: Imagery abnormalities may be among a disorder’s effects.

• Concomitants: Imagery abnormalities may be mere accompanying concomitants of a psychological disorder.

Crucially, only on the first and second will imagery abnormalities be psychopathologically relevant for a condition, where this means that such abnormalities actively contribute to a condition’s instantiation and associated episodes.

PTSD is perhaps the most obvious condition that falls into the first category. Although the disorder may involve physiological symptoms, part of what it is to have PTSD is to experience imagery-based “flashbacks,” with these being one of the condition’s constitutive “hallmark symptom[s]” (Pearson et al. 2013, 8). Are there any other conditions on the above list that might fall into the first or second category? Two potential cases, among the most well-known and well-studied psychiatric conditions, are Bipolar Disorder and MDD.

5. MGT and Psychopathological Relevance

Imagery’s architectural promiscuity is pictured by MGT as testifying to imagery’s being hugely beneficial to the human mind. But the fact that conditions as diverse as PTSD, bipolar disorder and MDD have their episodes determined (either causally or constitutively) by abnormalities of mental imagery seems to go directly against that. The fact that imagery makes such opposing contributions to the human mind is our second conceptual puzzle: how ought we to think about a mental state that can help and harm the mind to such extreme degrees? Whereas the first puzzle concerned the seemingly unsystematic nature of the interactions between imagery and psychological faculties, this time the puzzle is that there appears to be an outright inconsistency between the (dis)value of imagery to human cognition.

As at the beginning of this paper, I consider MGT to be both a literal thesis, i.e. about imagery’s higher-order functional role, and an analogy. As an analogy, saying that mental imagery “greases” the mind’s gears is to say that imagery is related to the well-functioning of one’s psychology. In greasing the faculties, imagery can help them, and the processes they give rise to, run as they should, i.e. to discharge their characteristic functional roles. That is how MGT pictures imagery’s architectural promiscuity. So what can it say about imagery’s psychopathological relevance? Crucially, imagery’s presence in the mind does not guarantee smooth functioning. For one, there can be too much grease in the gears, as in bipolar disorder, making the mind over-wrought and pushing positive moods to the extremes of mania and hypomania. Alternatively, the “grease” might be of the wrong kind, as in PTSD and MDD, where negative imagery disturbs the mind insofar as it biases one towards negative thinking styles, lowers one’s mood and produces unhealthy behaviors.

Continuing the analogy: when some machines malfunction, the solution may be to intervene on the oil that greases its gears. Some machines work better once excess oil is removed or when the oil is changed or renewed. Likewise, imagery-based therapies and interventions are effective at treating a range of psychological disorders (see Hackmann et al. 2011 for an overview). One particularly effective intervention, imagery rescripting, makes vivid this metaphor of “changing the oil.” Patients are instructed to bring negative imagery to mind as vividly as they can, as if the pictured event is occurring in the here and now. Then, they are instructed to change how the event unfolds, effectively “swapping out” negative images for positive ones. Tellingly, this technique is effective in treating a range of disorders, including PTSD and MDD where, as discussed above, intrusive negative imagery is operative (Arntz 2012). In the case of bipolar disorder, reducing the frequency of intrusive future-directed imagery, akin to removing “excess grease,” is an effective treatment for the condition insofar as it reduces mood instability (Holmes et al. 2016). Imagery can be relevant for a psychopathology not only by determining its onset, maintenance or partial constitution, but also, significantly, its treatment. This is further evidence that imagery plays an active role in shaping these psychopathologies: appropriately changing a patient’s imagery may thereby improve a patient’s condition.¹³

Less figuratively, let us turn to MGT itself: mental imagery is a tool that aids psychological faculties to discharge their functional roles. Although it is difficult to see how this thesis relates to imagery’s being pathologic, imagery’s psychopathological relevance is both consistent with and clarified by MGT.

Consider the intrusive, negative imagery that partially constitutes PTSD and contributes to the maintenance, if not partial constitution, of MDD. In the case of PTSD, this imagery is usually very vivid. It may feel to those with the condition as if the past, traumatic event is occurring in the here and now. Although deeply distressing, the mind’s capturing of the event in such detail, along with its later imagery-based “replayings,” serves a function. As psychologist Chris Brewin and their collaborators explain:

Flashbacks are an adaptive process in which stored information can be re-presented and processed in greater depth once the danger is past. PTSD … reflects the failure of the represented information to be attended to. (2010, 221)

In effect, involuntary flashbacks are imagery’s attempt to assist memory in encoding important, threat-related information, i.e. about the traumatic event undergone. This information may have been insufficiently attended to at the time that the traumatic event occurred but, qua traumatic, may be survival-relevant for the future. This way of thinking about the value of imagery in PTSD is consistent with the idea that experiences of trauma often involve, at the time they occur, a dissociative response in the agent, e.g., of time’s passing more slowly/rapidly than normal, emotional desensitization, a narrowing of attention, etc. Imagery-based flashbacks can be thought of as assisting memory to encode important information that these earlier dissociative responses may have caused one to overlook. This idea extends naturally from PTSD to MDD too. That is, flashbacks function to correct a deficit of information processing (Schacter et al. 2007). Insofar as the encoding, storage and retrieval of information about past events is the raison d’être of memory (Tulving 2002; Robins 2017), intrusive imagery of past events--whether in PTSD, MDD or other psychopathologies — functions to assist a faculty of mind to discharge a suite of characteristic functions.

Is this a coherent way to understand the role of negative, unpleasant imagery in PTSD and MDD, as a help to the human mind? On the face of it, this appears deeply counterintuitive. The occurrence of intrusive imagery-based flashbacks in these conditions is highly distressing. So how can one speak here of something beneficial occurring in the mind?

At least two points can be made in reply. First, we should distinguish (i) unpleasant imagery being a hindrance for the whole person, functioning as an unwanted distraction from everyday existence and possibly making life unbearable; and (ii) unpleasant, intrusive imagery being of assistance to a faculty of mind, e.g., memory. Some event, state or process, S, might be good for Y, but nonetheless bad for the whole, X, of which Y is a part. Likewise, an event, state or process might be useful for memory, assisting its characteristic functions, while nonetheless be distressing for the person whose memory faculty it is. The objection that MGT, in saying that imagery assists mental faculties, yields a confused picture of imagery’s psychopathological relevance rests on an equivocation between psychological faculties and whole persons.

Second, we should also distinguish: (i) a psychological faculty’s discharging its function from (ii) it being pleasant/unpleasant for a person to have that psychological faculty discharge its function. MGT says nothing at all about whether people enjoy their psychological faculties being aided by mental imagery. Saying that imagery “assists faculties of mind” does not entail that this is something one will necessarily find pleasurable. If one wrongly assumes otherwise, then matters may indeed start to look confused insofar as undergoing negative, intrusive imagery can be anything but enjoyable. However, MGT is silent on these hedonic matters. That is a feature of MGT, not a bug. For it is obvious that it can be unpleasant when a faculty of mind discharges a characteristic function. Not every action that vision helps one to perform will be pleasant and not every truth that belief aims at will be satisfying to discover.

What about bipolar disorder? How is imagery assisting the mind here? The self-descriptions above, in Sect. 4.1, suggest that when imagery transforms positive mood into mania it is thereby influencing the planning of actions, decision-making and setting of goals. This reflects the future-representing nature of the imagery that occurs in the disorder insofar as future-representing mental states are commonly associated with these functions (D’Argembeau et al. 2009).

But what precise faculty is being aided here? I suspect it may be fruitful to picture the futurity-related imagery characteristic of bipolar disorder to be aiding the forming, and maintenance, of intentions. For one, intentions are commonly thought to have a connection to commitment to action in ways that desires do not (Bratman 1987; Audi 1991; see also Broome 2001). By this I mean that intending to Φ involves one’s having made up one’s mind to Φ. A person who intends to Φ is usually understood to have settled on a particular course of action, in ways that someone who merely desires to Φ may not have (Malle and Knobe 2001). This has the potential to explain why bipolar individuals are strongly disposed, in manic and hypomanic states, to actualize the states of affairs represented by their imagery. Recall the patient who experienced imagery of themselves brightly colored. Upon undergoing this imagery, they were then disposed to portray themselves “in the appealing way I see myself in my image” where this involved dressing in vibrant colors. The idea that imagery in bipolar disorder functions to aid the forming of intentions may also explain why irritability commonly accompanies manic and hypomanic states (Altman et al. 1994). Strikingly, the intentions formed by bipolar individuals in elevated moods are often highly impractical, making them difficult, if not impossible, to fully enact. Recall the patient who tried to record the various “design projects” represented by the imagery that kept them awake at night. The clinicians reporting on the case continue:

He also said that while initially useful, productive and creative, once mania had taken over the intrusive images stopped being “useful” designs and became impractical, incoherent and unfeasible. (Holmes et al. 2008, 1255)

The frustration of intentions is an intelligible cause of irritability. And in bipolar disorder, the hinderance of intentions may have many sources, from one’s own inability to enact such intentions, to their discovered incoherence, or the dissuasion (or prevention) of others to enact them.¹⁴

Finally, despite all I’ve said here about the roles played by mental imagery in the onset, maintenance, constitution and treatment of various psychopathologies, there is certainly more going on in these disorders than imagery-based abnormalities alone. I am not proposing that our understanding of psychological disorders can be at all monothematic. I only aim to highlight in this section and the last the neglected roles played by imagery in relation to these disorders and address the puzzle of how to understand these problematic roles against the background of the assistive ones discussed in the paper’s opening sections.

In sum: nothing about the psychopathologies discussed here challenges MGT’s assertion that mental imagery aids psychological faculties in discharging their functional roles. Indeed, if what I’ve said in this section is right, then quite the opposite is true. Assisting psychological faculties is precisely what mental imagery is doing in the psychopathological contexts discussed here.

6. Conclusion

Psychologist Joel Pearson begins his entry in the Cambridge Handbook of the Imagination as follows:

[I]magery can be thought of as a cognitive tool (for those who have it), used to aid many everyday cognitive processes … Recently it has come to light that many individuals have no experience of imagery at all — their minds are completely blind: aphantasia. In contrast to this, imagery can play a core role in many anxiety disorders, depression, schizophrenia and Parkinson’s disease … Mapping imagery’s seemingly contradictory contributions to human cognition, whereby imagery can be advantageous, clinically disruptive, or even unnecessary (aphantasia), offers exciting and novel insights into an important dimension of the human mind. (2020, 175)

Here, Pearson summarizes the puzzling features of mental imagery that have taken central focus in this paper and that MGT seeks to elucidate: architectural promiscuity and psychopathological relevance.

One notable feature of how Pearson introduces imagery here is that his characterization differs from that typically offered by philosophers. Philosophical accounts of mental imagery tend to describe it as a perceptual (or quasi-perceptual) state of mind, playing up its commonalities with perceptual experience in terms of, e.g., phenomenal character, representational content or representational format. Here, the dominant conception of mental imagery is that it is a kind of “offline” perception. For instance, juxtaposed with Pearson’s comments are the following remarks in the Stanford Encyclopedia of Philosophy’s entry “Imagination” (Liao and Gendler 2019): “To have a (merely) mental image is to have a perception-like experience triggered by something other than the appropriate external stimulus.”

This idea that imagery should be conceptualized in perception-like ways is a recurrent theme in the philosophical literature, both new and old (see Cavedon-Taylor 2021a and 2021b for discussion). Alvin Goldman, for instance, claims that seeing an object and having imagery of an object are “a shared kind of state, in this instance a visual kind of state” (2006a, 47) and claims that there exists “a strong equivalence between visual perception and imagery” (2006b, 154). Bence Nanay claims that mental imagery is “perceptual processing that is not triggered by corresponding sensory stimulation in a given sense modality.” (2018, 127) Hume (1739/2000), moreover, writes as follows:

That idea of red, which we form in the dark, and that impression which strikes our eyes in sun-shine, differ only in degree, not in nature. (1.1.1.5)

One reason for interest in MGT is that it bucks this trend by offering an alternative picture of imagery. Granted, MGT is a claim about what imagery does whereas these “perceptualist” accounts of imagery aim to say what imagery is. And theories of what X does and what X is are not, of necessity, in conflict. However, an account of mental imagery that defines it as a perceptual experience (or a kind of perceptual processing) will thereby saddle it with purely perceptual functions. Yet if what I have said here is right, then the functions of imagery massively outstrip perceptual ones.¹⁵ More generally, much will be missing from our understanding of mental imagery and the contributions that it makes to human psychology, for good and for ill, if we view it through the “lens” of a single psychological faculty, perceptual or otherwise.¹⁶