Philosophers always ask their readers to imagine things, and this piece will prove no exception: imagine the seaside. You probably imagined something like seeing the waves rolling in. But my bet is that you also imagined some of the following:
- Hearing the seagulls overhead
- The smell and taste of salt in the air
- The feeling of sand on your feet
If you imagined any of these, you used different kinds of mental imagery corresponding to the different sensory systems. Imagining hearing the sound of seagulls uses auditory imagery; imagining tasting the salt in the air uses gustatory imagery, and so on. Though we do sometimes imagine using only one kind of imagery, they often come together as multisensory imagery (Nanay, 2018). But despite this interconnectedness, one kind of imagery has predominantly captured the attention of researchers: visual imagery. In this blog post, I will argue this has wrongly skewed the study of the mind, and I use aphantasia as a case study to bring this point out.[i]
But first, whence the interdisciplinary spotlight on visual imagery (Currie 1995; Schwitzgebel 2002; Pylyshyn 2002; Kosslyn, Thompson, and Ganis 2006; Gregory 2010; Brogaard 2012; Pearson 2020)?[ii] The study of perception has long been visuo-centric, and the study of imagery is no different (O’Callaghan, 2017). The modern study of imagery started with a dramatic paradigm shift: behaviourism was abandoned in favour of cognitivism (Neisser, 1972). This kickstarted the research on visual imagery in the 1960’s, and since then there have been big debates about the nature of visual imagery itself, and the mechanisms that generate it. The former was extensively discussed during the Imagery Debate, where the central question concerned whether visual imagery represents in an analog format, using continuous variables representing ‘spatially’, or a digital format, using discrete variables representing ‘linguistically’. The debate dominated visual imagery research through much of the 70’s and 80’s, and it continues to this day (Kosslyn 1973; Pylyshyn 1973; Kosslyn et al. 1979; Block 1981; Pylyshyn 2002; Tye 1991; Pearson and Kosslyn 2015). More recently, there has been a shift in focus to the mechanisms that generate visual imagery, where it has been argued that vision and visual imagery are realised in many of the same neural structures (Pearson, 2019; Winlove et al., 2018) and that performing eye movements, similar to when seeing, facilitates its generation (Laeng & Teodorescu, 2002).
But there is a danger in focusing too much on visual imagery. Recently, it has affected how we determine whether a person has aphantasia, a condition where a person cannot sensorily imagine.[iii] More specifically, it has affected the sampling method, which is the method used to determine the sample of a study, where this is supposed to be representative of the general population. In the case of aphantasia, the sample is determined by a questionnaire – the Vividness of Visual Imagery Questionnaire (VVIQ) (Marks, 1973) – which tests whether subjects can voluntarily generate visual imagery. It asks subjects to visually imagine four different scenes, and rate how vivid the scenes seem to them on a scale from 1 (‘no image at all’) to 5 (‘perfectly clear and lively as real seeing’).[iv] If they score significantly below average, they are classified as aphantasic. The reason for using this method is that aphantasia is believed to be a visual imagery condition where people lack the ‘mind’s eye’ (Bainbridge et al., 2020; Dawes et al., 2020; Fulford et al., 2018; Greenberg & Knowlton, 2014; Keogh & Pearson, 2018; Milton et al., 2020; Zeman et al., 2020). For example, Zeman et al. (2020) define aphantasia as the ‘lifelong lack of visual imagery’ and Dawes et al. (2020) claim that it is a condition where people ‘lack the ability to visualise altogether’.
This sampling method is problematic for a simple reason: aphantasia does not only affect visual imagery. It can affect all kinds of imagery. Multiple studies have reported subjects with poor imagery across all sensory systems (Dawes et al., 2020; Zeman et al., 2015, 2020). For example, in the study by Dawes et al., aphantasics rated the vividness and clarity of imagery in various sensory systems, including the visual, auditory, tactile, kinesthetic, gustatory, olfactory, and affective systems, and results showed that 26.2% reported a complete lack of imagery in all sensory systems, with a further 73.8% reporting an overall reduction of vividness in all non-visual sensory systems.
If aphantasia does not only affect visual imagery, we have a skewed sample, since using the VVIQ excludes anyone with non-visual impairments from the studied sample. This is because the VVIQ only asks questions about visual imagery, and so a person who only has an auditory imagery impairment, or even a person who is impaired with respect to all non-visual kinds of imagery, would not qualify for the study sample. This is problematic as the study sample is then not representative of the general aphantasic population.
There are some circumstances in which this sampling method could still be used to provide a representative sample. For example, if the people with non-visual imagery impairments were a subset of the people with the visual imagery impairment – that is, if everyone with a non-visual imagery impairment also necessarily has a visual imagery impairment. But this does not seem to be the case, as a study by Bensafi and Rouby (2007) found subjects who score below average on generating olfactory imagery without scoring below average on visual imagery. This indicates that at least people with the olfactory imagery impairment are not a subset of people with the visual imagery impairment. And so, the sample captured by the VVIQ is indeed unrepresentative.
Luckily, there is a relatively easy remedy to this problem: change the sampling method. The study of non-visual imagery has been on the rise in recent years, and this research could inform our sampling method. Before drawing to a close, let me point to one example. The imagery of wine (!) has been studied by Croijmans et al. (2019), since it involves multisensory mental imagery. We imagine seeing, sniffing, and tasting wine. Here, another questionnaire has been developed which investigates visual, olfactory, and gustatory imagery – the Vividness of Wine Imagery Questionnaire (VWIQ). So, we already have another questionnaire testing three different kinds of mental imagery, and which could be used as a sampling method in aphantasia research (perhaps switching wine for squash for younger participants…). Of course, it is still not ideal because it is missing out other kinds of mental imagery, but it sets us on the right track.
Coming back to the general argument, I hope to have illustrated that a narrow focus on visual imagery ought to be abandoned in favour for the study of mental imagery as a whole. Using the case study of aphantasia, I showed that this narrow focus has led to a skewed non-representative sample, which in turn could hinder researchers from getting to the bottom of what aphantasia is or how it affects people. As a remedy, I suggested adopting a different sampling method which focuses on the production of a wider range of mental imagery. The study on visual imagery has taught us a lot about the mind, and we now stand to learn a lot more by studying its relatives.[v]
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[i] The BBC Radio 4 show Blind Mind’s Eye features many aphantasics describing their experience with aphantasia and it highlights the creativity of people with aphantasia (Armstrong, 2020).
[ii] A notable exception is motor imagery, which has been studied extensively in psychology, for a seminal paper see: Jeannerod (1994). Though it has not enjoyed the same interdisciplinary interest as visual imagery, it has attracted some attention from philosophers too, see for example Currie and Ravenscroft (1997).
[iii] Further symptoms include the inability to voluntarily and/or involuntarily generate mental imagery, impaired episodic memory, and impaired future and atemporal imagination. See Blomkvist (manuscript) for a defence of the view that aphantasia is an episodic system condition.
[iv] The original questionnaire used reverse scoring.
[v] For research on auditory imagery, see Zatorre et al. (2010), Halpern et al. (2004), Jakubowski (2020); for olfactory imagery, see Gilbert et al. (1998), Bensafi et al. (2005); for gustatory imagery see Croijmans et al. (2019); for motor imagery see Guillot (2020); for temporal imagery see Viera and Nanay (2020); for spatial imagery see Byrne et al. (Byrne & Becker, 2009); for affective imagery see Blackwell (2020).
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