Picture the sun setting over the ocean.
It’s large above the horizon, spreading an orange-pink glow across the sky. Seagulls are flying overhead and your toes are in the sand.
Many people will have been able to picture the sunset clearly and vividly – almost like seeing the real thing. For others, the image would have been vague and fleeting, but still there.
If your mind was completely blank and you couldn’t visualise anything at all, then you might be one of the 2-5 percent of people who have aphantasia, a condition that involves a lack of all mental visual imagery.
“Aphantasia challenges some of our most basic assumptions about the human mind,” says Mr Alexei Dawes, Ph.D. Candidate in the UNSW School of Psychology.
“Most of us assume visual imagery is something everyone has, something fundamental to the way we see and move through the world. But what does having a ‘blind mind’ mean for the mental journeys we take every day when we imagine, remember, feel and dream?”
Mr Dawes was the lead author on a new aphantasia study, published today in Scientific Reports. It surveyed over 250 people who self-identified as having aphantasia, making it one of the largest studies on aphantasia yet.
“We found that aphantasia isn’t just associated with absent visual imagery, but also with a widespread pattern of changes to other important cognitive processes,” he says.
“People with aphantasia reported a reduced ability to remember the past, imagine the future, and even dream.”
Study participants completed a series of questionnaires on topics like imagery strength and memory. The results were compared with responses from 400 people spread across two independent control groups.
For example, participants were asked to remember a scene from their life and rate the vividness using a five-point scale, with one indicating “No image at all, I only ‘know’ that I am recalling the memory,” and five indicating “Perfectly clear and as vivid as normal vision.”
“Our data revealed an extended cognitive ‘fingerprint’ of aphantasia characterised by changes to imagery, memory, and dreaming,” says Mr Dawes.
“We’re only just starting to learn how radically different the internal worlds of those without imagery are.”
Subsets of aphantasia
While people with aphantasia wouldn’t have been able to picture the image of the sunset mentioned above, many could have imagined the feeling of sand between their toes, or the sound of the seagulls and the waves crashing in.
However, 26 percent of aphantasic study participants reported a broader lack of multi-sensory imagery—including imagining sound, touch, motion, taste, smell and emotion.
“This is the first scientific data we have showing that potential subtypes of aphantasia exist,” says Professor Joel Pearson, senior author on the paper and Director of UNSW Science’s Future Minds Lab.
Interestingly, spatial imagery—the ability to imagine distance or locational relationship between things—was the only form of sensory imagery that had no significant changes across aphantasics and people who could visualise.
“The reported spatial abilities of aphantasics were on par with the control groups across many types of cognitive processes,” says Mr Dawes. “This included when imagining new scenes, during spatial memory or navigation, and even when dreaming.”
In action, spatial cognition could be playing Tetris and imagining how a certain shape would fit into the existing layout, or remembering how to navigate from A to B when driving.
In dreams and memories
While visualising a sunset is a voluntary action, involuntary forms of cognition—like dreaming—were also found to occur less in people with aphantasia.
“Aphantasics reported dreaming less often, and the dreams they do report seem to be less vivid and lower in sensory detail,” says Prof Pearson.
“This suggests that any cognitive function involving a sensory visual component—be it voluntary or involuntary—is likely to be reduced in aphantasia.”
Aphantasic individuals also experienced less vivid memories of their past and reported a significantly lower ability to remember past life events in general.
“Our work is the first to show that aphantasic individuals also show a reduced ability to remember the past and prospect into the future,” says Mr Dawes. “This suggests that visual imagery might play a key role in memory processes.”
While up to one million Australians could have aphantasia, relatively little is known about it—to date, there have been less than 10 scientific studies on the condition.
More research is needed to deepen our understanding of aphantasia and how it impacts the daily lives of those who experience it.
“If you are one of the million Australians with aphantasia, what do you do when your yoga teacher asks you are asked to ‘visualise a white light’ during a meditation practice?” asks Mr Dawes.
“How do you reminisce on your last birthday, or imagine yourself relaxing on a tropical beach while you’re riding the train home? What’s it like to dream at night without mental images, and how do you ‘count’ sheep before you fall asleep?”
The researchers note that while this study is exciting for its scope and comparatively large sample size, it is based on participants’ self-reports, which are subjective by nature.
Next, they plan to build on the study by using measurements that can be tested objectively, like analysing and quantifying people’s memories.
What does a person mean when he closes his eyes or ears (figuratively speaking) and says, “I see the house where I was born, the trundle bed in my mother’s room where I used to sleep – I can even see my mother as she comes to tuck me in and I can even hear her voice as she softly says goodnight”?
Touching, of course, but sheer bunk. We are merely dramatizing. The behaviourist finds no proof in imagery in all this. We have put these things in words long, long ago and we constantly rehearse those scenes verbally whenever the occasion arises’
John B Watson
The study of visual imagery has been a controversial topic for many years, as the above quote from the behaviourist John Watson demonstrates. This quote exemplifies the long running imagery debate of the 1970s and 80’s, which centred on the question of whether imagery can be depictive in the format of its representation (Kosslyn, 2005), or only symbolic or propositional in nature (Pylyshyn, 2003).
However, in the last few decades psychologists and neuroscientists have made great strides in showing that visual imagery can be measured objectively and reliably, and indeed can be depictive/pictorial in nature, see Pearson and Kosslyn (2015) for a detailed
discussion of the evidence. Research has shown that visual imagery, like weak perception, impacts subsequent perception in a myriad of ways (Ishai & Sagi, 1995; Pearson, Clifford, & Tong, 2008; Winawer, Huk, & Boroditsky, 2010; Zamuner, Oxner, & Hayward, 2017). For example, the effect of imagery on subsequent rivalry is specific in orientation and location space, showing strong evidence for a depictive representation (Pearson et al., 2008).
Imagery has also been shown to activate early visual cortex and the content of imagery can be decoded in these areas using an encoding model based on low-level depictive visual features, such as spatial orientation and contrast (Naselaris, Olman, Stansbury, Ugurbil, & Gallant, 2015), and recently using features based on a multi-level con- volutional neural network (Horikawa & Kamitani, 2017).
Additionally, visual imagery has been shown to be closely related to many cognitive functions such as visual memory (Albers, Kok, Toni, Dijkerman, & de Lange, 2013; Keogh & Pearson, 2011, 2014), spatial navigation (Ghaem et al., 1997), language comprehension (Bergen, Lindsay, Matlock, & Narayanan, 2007; Zwaan, Stanfield, & Yaxley, 2002), making moral decisions and making a decision to help others (Amit & Greene, 2012; Gaesser & Schacter, 2014).
Visual imagery also appears to be elevated (stronger or more vivid) in some psy- chological and neurological disorders (Matthews, Collins, Thakkar, & Park, 2014; Sack, van de Ven, Etschenberg, Schatz, & Linden, 2005; Shine et al., 2015). Visual imagery has even been employed to assist in cognitive behavioural therapies such as imaginal exposure and imaginal rescripting (Arntz, Tiesema, & Kindt, 2007; Holmes, Arntz, & Smucker, 2007; Pearson, Naselaris, Holmes, & Kosslyn, 2015) and the use of visual imagery during cognitive behavioural therapy has been shown to be more effective than just verbal pro- cessing (Pearson et al., 2015).
With strong evidence that visual imagery can be a depictive cognitive mechanism, the question arises, were Watson, Pylyshyn and their ilk wrong?
Or is it possible that they had a distinctly different experience of visual imagery that was not depictive, but more propositional or phonological in nature? Interestingly, a study investigated exactly this idea and found that those researchers who were more likely to have been on the ‘imagery is depictive’ side of the debate tended to report more vivid imagery, while those who reported weaker imagery were more likely to be on the imagery is propositional side of the debate (Reisberg, Pearson, & Kosslyn, 2003).
One of the hallmarks of visual imagery is the large range of subjective reports in the vividness of an individual’s imagery. For example, when people are asked to imagine the face of a close friend or relative some people report imagery so strong it is almost akin to seeing that person, whereas others report their imagery as so poor that, although they know they are thinking about the person, there is no visual image at all. Sir Francis Galton gave one of the earliest accounts of these subjective differences in visual imagery in 1883.
Galton devised a series of questionnaires asking participants to imagine a specific object then describe the ‘illumination’, ‘definition’ and ‘col- ouring’ of the image. He found, to his surprise, that many of his fellow scientists professed to experience no visual images in their mind at all: ‘To my astonishment, I found that the great majority of the men of science to whom I first applied protested that mental imagery was unknown to them, and they, looked on me as fanciful and fantastic in supposing that the words “mental imagery” really expressed what I believed everybody supposed them to mean.
They had no more notion of its true nature than a colour-blind man, who has not dis- cerned his defect, has of the nature of colour. They had a mental deficiency of which they were unaware, and naturally enough supposed that those who affirmed they possessed it, were romancing.”
In recent years very little attention has been given to the ‘poor’ or non-existent side of the visual imagery spectrum, outside of participants with neurological damage. Much research during the imagery debate of the 70’s and 80’s revolved around brain damaged participants who had lost their ability to imagine, but retained their vision, or vice versa (Farah, 1988). Recently the idea that some people are wholly unable to create visual images in mind, without any sort of neurological damage, psychiatric or psychological disorders, has seen a resurgence.
A recent paper by Zeman, Dewar, and Della Sala (2015) coined a term for this phenomenon ‘congenital aphantasia’. This study found that these aphan- tasics all scored very low on the vividness of visual imagery questionnaire (VVIQ).
The VVIQ is a commonly used ques- tionnaire to measure the subjective vividness of an in- dividual’s visual imagery, by asking them to imagine a friend or relative, as well as scenes and rate the vividness of these images on a Likert scale. However, a case study reported a 65- year-old male who became aphantasic after surgery (without any obvious neurological damage) and was still able to perform well on other measures of visual imagery, such as answering questions about the shape of animal’s tails.
The patient was also able to perform two types of mental rotation tasks (manikin and Shepard – Metzler tasks), which are commonly used test of imagery ability (A. Z. Zeman et al., 2010). Interestingly, his reaction times however, did not correspond to the rotation distance, which is the common finding in the literature.
These reports suggest the possibility that aphantasic individuals do actually create images in mind that they are able to use to solve these tasks, however they are unaware of these images; that is they lack metacognition, or an inability to introspect.
Although the visual imagery tasks used in the Zeman et al. (2010) study are used extensively throughout the imagery literature, and in clinical settings to measure visual imagery, the validity of these tasks are somewhat unclear. For example, in the animal tails test it may be that subjects can use prop- ositional semantic information about the images they are asked to imagine, instead of actually creating a visual image in mind.
Additionally, the mental rotation task used (manikin and Shepard-Metzler tests) could be performed using spatial, or kinaesthetic imagery, rather than ‘low-level’ visual object imagery. A relatively new experimental imagery task, which exploits a visual illusion known as binocular rivalry, allows us to eliminate many of the issues related to these visual imagery measures (Pearson, 2014).
Binocular rivalry is an illusion, or process, where one image is presented to the left eye and a different image to the right, which results in one of the images becoming dominant while the other is suppressed outside of awareness (see Fig. 1A for illustration).
Previous work has demonstrated that presenting a very weak visual image of one of the rivalry patterns prior to the presentation of the binoc- ular rivalry display, results in a higher probability of that image being seen in the subsequent binocular rivalry pre- sentation (Brascamp, Knapen, Kanai, van Ee, & van den Berg, 2007; Pearson et al., 2008).
Interestingly, when someone imagines an image instead of being presented with a weak one, a very similar pattern of results emerges. In other words, imagery can prime subsequent rivalry dominance much like weak visual perception (Pearson, 2014; Pearson et al., 2008).
Hence, this imagery paradigm has been referred to as a measure of the sensory strength of imagery, as it bypasses the need for any self-reports and directly measures sensory priming from the mental image.
If an individual is presented with a uniform and passive luminous background while they generate an image, the facilita- tive effect of their mental image is reduced (Chang, Lewis, & Pearson, 2013; Keogh & Pearson, 2011, 2014, 2017; Sherwood & Pearson, 2010).
Previous work has shown that these disruptive effects are limited to visual tasks that require the use of depictive image generation (Keogh & Pearson, 2011, 2014) suggesting that the early visual areas of the brain are likely involved in the construction and maintenance of these images. Further, this priming effect is local in both retinotopic spatial-locations and orientation feature space (Bergmann, Genc¸ , Kohler, Singer, & Pearson, 2015; Pearson et al., 2008), further suggesting the priming is contingent on early visual processes.
This measure of visual imagery also correlates with sub- jective ratings of visual imagery, both trial-by-trial and questionnaire ratings, suggesting that participants have insight into the strength of their own visual imagery (Bergmann et al., 2015; Rademaker & Pearson, 2012). Here we ran a group of Self-described congenital aphantasics on the binocular ri-
valry visual imagery paradigm to measure the strength of their sensory imagery.
If congenital aphantasia is a complete lack of visual imagery, we should expect no facilitative priming effects of visual imagery on subsequent rivalry. However, if congenital aphantasia is instead a lack of metacognition, or failed introspection, then we may expect to observe some priming, despite the subjective reports of no imagery. We further, tested the aphantasics on a range of standard questionnaires to probe the vividness and spatial qualities of their imagery.