A post by Dan Cavedon-Taylor.
One issue that has recently gained attention in the literature on mental imagery is the existence of perceptual-imagery hybrids. Consider the following:
Seeing Constellations: Seeing a constellation in the night sky may be partially a matter of projecting into one’s visual experience imagery of lines connecting stars (Briscoe 2011)
Seeing Cats: Seeing a cat that is partially occluded by a picket fence, as a whole object, may be partially a matter of projecting into one’s visual experience imagery of the occluded parts of the cat (Thomas 2009; Nanay 2010; Kind forthcoming)
Avoiding Skunks: Seeing what path to take to avoid a skunk may be partially a matter of projecting into one’s visual experience the trajectory of the skunk’s spray (Van Leeuwen 2011)
The fact that imagery can combine with perception in these ways seems to tell us something important about the nature of mental images: that they are fundamentally perceptual. After all, what imagery does in these examples is aid perception in discharging its essential functions: tracking the objects before us, identifying the objects before us and guiding our actions with respect to those objects.
The idea that mental imagery is a perceptual (or at least quasi-perceptual) state seems the default view in contemporary philosophy and psychology. And this view appears supported on multiple fronts, not just because of perceptual-imagery hybrids. For one, consider imagery’s phenomenology: visual mental imagery straightforwardly has a visual quality to it and auditory imagery an auditory quality. Ditto for the content of imagery and also its format: both perception and imagery are about colours, shapes and spatial relations, and both seem to format their contents iconically like a picture, rather than discursively like a sentence. Moreover, empirical evidence suggests that mental imagery and perception share exceptionally fine-grained neural correlates. How could the place of imagery in the mind be anything but perceptual?
I worry that by studying mental imagery through the lens of perception we miss out on what is potentially unique and very exciting about it: that it serves both perceptual and cognitive functions (and more besides), and so refuses to be pigeonholed as either. On this view, mental imagery is an architecturally flexible state of mind, an all-purpose ‘helper’ that does not fully reside in any one category of mind. For, just as there are perceptual-imagery hybrids, there are likewise cognitive-imagery hybrids:
What to Do? Deciding what city to move to, or what to have for lunch, may be partially a matter of mentally comparing imagery of one’s future self in each scenario (Gauker 2011; Nanay 2016a)
Same Shape? Judging whether two objects are identical in shape may be partially a matter of mentally rotating imagery of each object (Shepard & Metzler 1971)
Larger or Smaller? Judging whether one object is larger than another may be partially a matter of mentally comparing imagery of each object (Moyer 1973)
Is is Possible? Judging whether it is possible for one to jump across a river may be partially a matter of having imagery of one’s being able (or unable) to jump across a river (Williamson 2016)
In the case of perceptual-imagery hybrids, imagery helps perception discharge its essential functions. In these examples, imagery helps cognition discharge its essential functions: piecing together information, weighing options and reaching conclusions.
A further role played by imagery, vastly overlooked in contemporary philosophy of mind (though not in psychology), is how it may help sustain or bolster the motivational force of desire (see McMahon 1973 for a historical overview; the idea goes back to at least Aristotle). For instance, a flagging desire to keep fit and healthy may be reinvigorated by imagery of the benefits of a fit and healthy lifestyle, e.g., a more toned body.
The examples above of cognitive-imagery hybrids are ones already circulating in the philosophical and psychological literature. So why is imagery persistently conceptualised as perceptual, and not all-purpose? A good question! (But see Kind 2013.)
One reason might be that we are under the spell of a snapshot conception of thought. On this view, thinking is a bit like turning a light on in a room. The light’s either on, or it’s not; a thought is had, or it is not. But thinking is more process-like and temporally structured than this view allows. Thinking can unravel gradually, as one puts the pieces in place and grasps more fully how matters stand. (Light may dawn slowly.) And imagery is an element that may help one grasp such matters. Those who lack imagery are slower to reach correct verdicts on mental rotation tasks (Zeman et al. 2010), as in Same Shape?, and report difficulty deciding what to choose off a menu (Moro et al. 2008), as in What to do?
A second reason for neglect of the all-purpose view may be that we are under the spell of too simplistic a framework for thinking about the imagination. Many philosophers think that when imagination is doing thought-like things, then this must be a matter of propositional imagining, i.e. imagining that such-and-such is the case, rather than having imagery. On the all-purpose view, this is too blinkered. The janus-faced nature of the imagination is not simply reflected in the distinction between mental imagery and propositional imagining; mental imagery is itself janus-faced insofar as it finds its way into thought no less than into perception.
A third reason for the neglect of the all-purpose view might be that the empirical evidence seems stacked against it. For what can the all-purpose view say about the fact that imagery and perception share substantive neural correlates, even in V1, the earliest part of the visual brain?
Crucially, it can reply that leading neuroanatomical theories affirm that the brain evolved not by creating neural pathways afresh but by extending, combining and re-using existing ones (Anderson 2010; Sporns & Kötter 2004). If these theories are correct, then we shouldn’t expect isolatable imagery circuitry in the brain, but for it to piggyback on existing ones. In any case, the neuropsychological evidence on the neural correlates of imagery is more mixed than many philosophers recognise, with clinical evidence indicating that perception and imagery are doubly dissociable in the brain (Coslett 1997; Moro et al. 2008; Bartolomeo 2008). On the all-purpose view this is no surprise, since it holds that they are conceptually dissociable too.
Here are some descriptions of mental imagery:
‘seeing’ in the absence of the appropriate immediate sensory input.” Kosslyn (1995, p.267)
“precisely, attempted enactment of seeing.” Goldman (2006, p.152)
“perceptual processing that is not triggered by corresponding sensory stimulation in the relevant sense modality.” Nanay (2016b, p.66)
If these claims are innocuous metaphors, merely highlighting that imagery and perception share salient features, then that’s fair enough. And of course the all-purpose view need not disagree on that.
But if such claims are to be read as claims about the essence of imagery, in particular about how it should be conceptualised, or its place in the architecture of the mind, then we should be more sceptical. Some try to drive a wedge between perception and imagery on account of differing relations each bears to the will (Kind 2001; Currie and Ravenscroft 2002; Soteriou 2013) or their differing in veridicality conditions (Langland-Hassan 2015). But we can drive a wedge between perception and imagery another way: by focussing on the functions of imagery, what it is for, noticing how these outstrip perceptual functions. Mental imagery has many places in the mind, not one.
Anderson, M. (2010). “Neural Re-use as a Fundamental Organizational Principle of the Brain.” Behavioural and Brain Sciences 33 (4): 245-266.
Bartolomeo, P. (2008). “The Neural Correlates of Visual Mental Imagery: An Ongoing Debate.” Cortex 44 (2): 107-108.
Briscoe, R. (2011). “Mental Imagery and the Varieties of Amodal Perception.” Pacific Philosophical Quarterly 92 (2): 153-173.
Coslett, H. (1997). “Neglect in Vision and Visual Imagery: A Double Dissociation.” Brain 120 (7): 1163-1171.
Currie, G. & Ravenscroft, I. (2002). Recreative Minds. OUP.
Gauker, C. (2011). Words and Images. OUP.
Goldman, A. (2006). Simulating Minds. OUP.
Kind, A. (2001). “Putting the Image Back in Imagination.” Philosophy and Phenomenological Research 62 (1): 85-110.
Kind, A. (2013). “The Heterogeneity of the Imagination.” Erkenntnis 78 (1): 141-159.
Kind, A. (forthcoming). “Imaginative Presence.” In F. Dorsch, M. Nide-Rumelin, and F. Macpherson (eds.) Perceptual Presence. OUP.
Kosslyn, S. (1995). “Mental Imagery.” In S. Kosslyn & D. Osherson (eds.) An Invitation to Cognitive Science, Vol. 2: Visual Cognition. MIT Press.
Langland-Hassan, P. (2015). “Imaginative Attitudes.” Philosophy and Phenomenological Research 90 (3): 664- 686
McMahon, C. (1973) “Images as Motives and Motivators: A Historical Perspective.” American Journal of Psychology 86 (3): 465-90.
Moro, V., Berlucchi, G., Lerch, J., Tomaiuolo, F. & Aglioti, S. (2008). “Selective Deficit of Mental Visual Imagery with Intact Primary Visual Cortex and Visual Perception.” Cortex 44 (2): 109-18.
Moyer, R. (1973). “Comparing Objects in Memory: Evidence Suggesting an Internal Psychophysics.” Perception & Psychophysics 13 (2): 180-184.
Nanay, B. (2010). “Perception and Imagination: Amodal Perception as Mental Imagery.” Philosophical Studies 150 (2): 239-254.
Nanay, B. (2016a). “The Role of Imagination in Decision-Making.” Mind & Language 31 (1): 126-142.
Nanay, B. (2016b). “Hallucination as Mental Imagery.” Journal of Consciousness Studies 23 (7-8): 65-81.
Shepard, R., & Metzler, J. 1971. “Mental Rotation of Three-Dimensional Objects.” Science 171 (3972): 701-703.
Soteriou, M. (2013). The Mind’s Construction. OUP.
Sporns, O. & Kötter, R. (2004). “Motifs in Brain Networks.” PLoS Biology 2 (11): e369.
Thomas, A. (2009). “Perceptual Presence and the Productive Imagination.” Philosophical Topics 37 (1): 153-174.
Van Leeuwen, N. (2011). “Imagination is where the Action is.” Journal of Philosophy 108 (2): 55-77.
Williamson, T. (2016). “Knowing by Imagining.” In A. Kind and P. Kung (eds.) Knowledge Through Imagination. OUP.
Zeman, A., Della Sala, S., Torrens, L., Gountouna, V., McGonigle D. & Logie, R. (2010). “Loss of Imagery Phenomenology with Intact Visuo-Spatial Task Performance: A Case of ‘Blind Imagination.’” Neuropsychologia 48 (1): 145-155.