Preston Lennon is a postdoctoral associate at the Rutgers Center for Cognitive Science. He received his Ph.D. in philosophy from The Ohio State University in 2022, and his main research interests are in the philosophy of mind with a focus on conscious thought.
A post by Preston Lennon
Take a moment to answer the following question: how many windows are there in your kitchen? Once you’ve reached an answer, reflect now on how you arrived on it. If you are like most, then you might have called up a visual mental image of your kitchen and used this image to arrive at the correct number. Some, however, can answer questions like this without performing this process of visual imagining. There has recently been a flurry of research in cognitive psychology on the phenomenon of aphantasia (Zeman et al 2010, 2015, 2016, 2020). Subjects with aphantasia report having impoverished mental imagery, with some aphantasics completely lacking mental imagery altogether.
Aphantasia has implications for a number of live issues in philosophy of mind. In this post, I consider some the consequences of aphantasia for debates over the nature of conscious thought.
The Sensory Constraint on Conscious Thought
Examples of phenomenal consciousness are typically those associated with the senses: the experience of bitterness when taking a swig of coffee, the blue visual experience I have when glancing outside my window. But we are no less familiar with instances of conscious thought, such as the one I have when I consciously calculate that a dime and a quarter give me thirty-give cents. While it’s uncontroversial that we sometimes have conscious experiences when thinking, the nature of these thoughts—in particular, whether our thoughts themselves are conscious—is disputed.
Some philosophers hold that the only kind of consciousness that exists is sensory (Lormand 1996, Tye and Wright 2011; Prinz 2007, 2011; Carruthers and Veillet 2011). According to these philosophers, a mental state is phenomenally conscious only if it has a kind of phenomenal character had by sensory perception, broadly construed to include bodily sensation, perceptual imagery, and inner speech. These philosophers explain the experiences we have when we think in terms of associated sensory episodes. So, when I have the conscious thought that snow is white, this state might be accompanied by some state of visual mental imagery, perhaps of a white snowbank, or by auditory mental imagery, such as hearing myself saying “snow is white” in inner speech. Once we account for this accompanying sensory mental imagery, these philosophers hold, there is nothing left over, phenomenologically. Prinz (2007, 2011) argues that any putative conscious thought without such imagery is a failure of introspection: “On any plausible view, the phenomenology of thought is underwritten by both verbal and non-verbal imagery. Thus, [my opponents] face the difficult challenge of having to find cases in which the phenomenal character of thought transcends these rich sources” (Prinz 2011, p. 189). Prinz thus accepts:
The sensory constraint on conscious thought: for any thought, if it is phenomenally conscious, then it has a sensory reduction base.
A phenomenally conscious thought has a sensory reduction base when it is accompanied by some sensory mental imagery that can serve as a plausible candidate to constitute the experience of thinking. For example, my experience of thinking that snow is white might by constituted by the visual mental image of a white expanse of snow or the auditory image of “snow is white.” In holding that the experience of thinking is fully constituted by sensory phenomenology, proponents of the sensory constraint deny that conscious thoughts have some non-sensory cognitive phenomenology that can come apart from this sensory phenomenology (proponents of cognitive phenomenology include Strawson 1994; Siewert 1998; Horgan and Tienson 2002; Pitt 2004).
Against the sensory constraint: the argument from aphantasia
Here is my argument from aphantasia against the sensory constraint on conscious thought:
(1) Aphantasics have some thoughts, aphantasic thoughts, that have no sensory reduction base.
(2) Aphantasic thoughts are phenomenally conscious.
(C) Therefore, there are some phenomenally conscious thoughts that have no sensory reduction base (i.e., the sensory constraint on conscious thought is false).
Begin with the first premise. I argue for the truth of the first premise abductively: it best explains the introspective reports, performance on psychological tasks, and neural activity of aphantasics.
In studies conducted by Adam Zeman and coauthors (2015, 2016), aphantasic subjects scored much lower than a control group on the Vividness of Visual Imagery Questionnaire (VVIQ). The VVIQ asks subjects to perform certain imaginative tasks and to quantitatively rate the vividness of their imagery during these tasks. Subjects were asked, among other things, to visualize a rising sun and notice any surrounding clouds or blue sky, and to think of a storefront and rate the vividness of the overall appearance of the shop from the other side of the road. As for their performance on psychological tasks, Zeman (2020) found that aphantasic patients were much less likely to use visual imagery strategies to perform tasks thought to require imagery. For example, when asked to mentally count the number of windows in their house or apartment, most aphantasics said they instead relied on “knowledge” or “memory” models (Zeman et al 2015). Finally, these subjective reports have objective backing in the form of fMRI and other objective measures of mental imagery. An aphantasic subject used largely frontal networks when asked to imagine, while a control group employed the posterior visual network when imagining. Taken together, these considerations support the premise that aphantasics sometimes have thoughts that are unaccompanied by sensory mental imagery (e.g., “there are two windows in my apartment.”)
Turn now to the second premise of the argument from aphantasia, that aphantasic thoughts are phenomenally conscious. I support this premise by appeal to introspective report from aphantasics: aphantasics report that their own thoughts are conscious, and it seems reasonable to take these reports at face value in the absence of evidence otherwise.
When describing how they think, aphantasics in online communities appear to be describing their subjective experience. The following quotes from aphantasics describing their thinking, culled from reddit.com/r/aphantasia, is instructive:
I don’t have a good way to describe what goes on in my head. I FEEL my thought, in a more abstract way.
Most of the time my mind feels blank, with an occasional thought zipping through it… not in visual form, but not in an auditory form either.
I don’t have an inner monologue, although I can force one if I want to but it feels like a slower extra step. To me it feels like thinking in abstract concepts…
Unless I’m actually thinking very specifically about something, a lot of how I think feels very abstract and hard to explain. It’s like my own thoughts are on the tip of my tongue.
I just think. There aren’t words or images that go with it. I just rapidly go through scenarios in my head, like if I do A then B will happen.
We can distill four distinct points from these reports. First, when aphantasics make reports to the effect that they “feel” their thoughts “zipping” through their mind, they are describing their stream of consciousness: there’s something it’s like for them to experience their thoughts. Second, what it’s like for them to experience the thought is non-sensory in that it’s “not in visual form, or in auditory form either.” Third, the experience of thinking is not the mere occurrence of non-intentional phenomenal qualities, such as “cognitive qualia.” On the contrary, it is an experience of thinking: it feels like “thinking in abstract concepts.” Finally, what it is like to have a thought with one content is different from what it is like to think a thought with another content in the same external circumstances: for example, the experience of having a conditional thought (“if I do A then B will happen”) feels different from, say, having a conjunctive thought (“I will do A and B will happen”).
These introspective reports from aphantasics thus provide defeasible evidence that their aphantasic thoughts are phenomenally conscious. In the absence of defeaters, we should take these introspective reports at face value. It is therefore reasonable to conclude that these thoughts are phenomenally conscious.
Lessons Learned
What do we learn from the argument against the sensory constraint? I close with some conclusions.
First, the existence of aphantasic thought supports the existence of a non-sensory phenomenology of thinking, a sui generis kind of cognitive phenomenology. Aphantasic subjects sometimes have thoughts without a sensory reduction base, and yet their thoughts are phenomenally conscious. This suggests there must exist some phenomenal character that is proprietary to cognitive experiences, such as conscious thoughts: a phenomenology that is different in kind from the phenomenal character of sensory experiences. It might be quite difficult to describe this cognitive phenomenology in language; we might reach, as aphantasics do, for certain phrases like “it feels like thinking in abstract concepts.” But just because an experience is difficult to describe does not mean it doesn’t exist at all.
Second, much of the debate over the existence of cognitive phenomenology trades on introspective arguments. While some claim that we “cannot miss” the cognitive aspects of phenomenology if we “simply pay attention” (Horgan and Tienson, p. 522-3), others report being able to detect only sensory phenomenology. The large degree of variation in imagery illustrated by aphantasia offers a potential diagnosis of this impasse. It may be that opponents of cognitive phenomenology have particularly vivid and ubiquitous sensory phenomenology. Conversely, it may be that proponents of cognitive phenomenology tend to think in imagery less than their opponents: the conceptual or semantic features of their conscious thoughts may stand out to them because they are less typically accompanied by sensory imagery. I put this forward as a tentative hypothesis regarding this disagreement, one which merits a fuller treatment elsewhere.
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This post is based on work conditionally accepted at Oxford Studies in Philosophy of Mind (vol. 3) (ed. Uriah Kriegel); please cite this version when available.
References
Carruthers, P., and B. Veillet. 2011. ‘The Case against Cognitive Phenomenology.’ In Cognitive Phenomenology, edited by Tim Bayne and Michelle Montague, 35-56. Oxford: Oxford University Press.
Horgan, T. and J. Tienson. 2002. ‘The Intentionality of Phenomenology and the Phenomenology of Intentionality.’ In Philosophy of Mind: Classical and Contemporary Readings, edited by David Chalmers. New York: Oxford University Press.
Lormand, E. 1996. ‘Nonphenomenal consciousness.’ Noûs 30 (2): 242-61.
Pitt, D. 2004. ‘The Phenomenology of Cognition, Or, What is it Like to Think that P?’ Philosophy and Phenomenological Research 69: 1-36
Prinz, J. 2007. ‘All consciousness is perceptual.’ In Contemporary Debates in Philosophy of Mind, edited by B. McLaughlin and J. Cohen, 335-57. Wiley-Blackwell.
Prinz, J. 2011. ‘The sensory basis of cognitive phenomenology.’ In Cognitive Phenomenology, edited by T. Bayne and M. Montague. Oxford: Oxford University Press: 174-196.
Siewert, C. 1998. The Significance of Consciousness. Princeton, N.J.: Princeton University Press.
Strawson, G. 1994. Mental Reality. Cambridge, MA: MIT Press.
Tye, M., and B. Wright. 2011. ‘Is There a Phenomenology of Thought?’ In Cognitive Phenomenology, edited by T. Bayne and M. Montague, 326-344. Oxford: Oxford University Press.
Zeman, A. 2015. ‘Lives without imagery – Congenital aphantasia - supplementary data.’ Cortex 73.
Zeman, A. 2021. ‘Blind Mind’s Eye.’ American Scientist 109: 109-117.
Zeman, A., M. Dewar, and S. Della Sala. 2015. ‘Lives without imagery – Congenital aphantasia.’ Cortex 73, 278-80.
Zeman, M. Dewar, and S. Della Sala. 2016. ‘Reflections on aphantasia.’ Cortex 74: 336-7.
Zeman, A., F. Milton, S. Della Sala, M. Dewar, T. Frayling, J. Gaddum, A. Hattersley, B. Heuerman- Williamson, K. Jones, M. MacKisack, and C. Winlove. 2020. ‘Phantasia—The psychological significance of lifelong visual imagery vividness extremes.’ Cortex 130: 426-440.
Zeman, A., S. Della Sala, L. A. Torrens, V. E. Gountouna, D. J. McGonigle, and R. H. Logie. 2010. ‘Loss of imagery Phenomenology with Intact Visuo-Spatial Task Performance: A Case of “Blind Imagination.”’ Neuropsychologia 48 (1): 145-55.