Friday, September 28, 2012
Laura Otis and Krish Sathian
CLICK HERE FOR LINK TO PODCAST
Laura Otis (English, Emory) and Krish Sathian (Neurology, Rehabilitation Medicine and Psychology, Emory) came together in the first CMBC lunch of the year to discuss the formation of mental images.
Otis spoke of work towards a book to be titled, Thirty Thinkers, which draws from interviews with a range of creative people about the phenomenology of their mental imagery. Inquiry into the phenomenology of mental imagery is nothing new in itself, even if it is only in the last forty years that the study of mental imagery has been taken seriously as a subject of scientific research. Continental phenomenologists like Sartre, Husserl, and Merleau-Ponty pioneered the systematic study of the phenomena of imagination in the first half of the twentieth century. However, they did so according to the methodology of classical phenomenology – by describing what they took to be the essential structures of the formation of mental imagery by conscious subjects. In contrast, the interest and promise of Otis’ empirical approach lies in what it reveals about the range of ways in which people form mental images. The diversity of mental image formation from individual to individual emerged as one of the key take-aways from the lunch.
If you close your eyes and think of the word “bridge,” what do you see? As you read fiction, what sorts of images do you form in your mind? These are the sorts of questions that Otis asked the participants in her book research, and she posed them to the lunch participants as well. The latter reported bridge images ranging from “a covered bridge in Indiana” (absent color) to “the river that runs under a bridge” to less specific, more generic images. No one reported no images at all, but one participant testified to knowing someone who claims never to form mental images. The range of responses at lunch was in line with the findings of Otis’ book research. In response to queries about images formed while reading fiction, some participants in Otis’ study said that they read fiction because forming images is intrinsically pleasant; others reported not seeing anything at all and enjoying simply following the play of language.
In the 1970s it became popular to distinguish people who are more verbal in their thinking from those who are more visual or spatial on the grounds of functional differences between the brain’s hemispheres. While it might seem that participants’ reports in Otis’ study reinforce this dichotomy – with those who read for the words, on the left side, as it were, and those who read for images, on the right – Otis urged that the situation is in fact more complicated, citing Maria Kozhevnikov (Radiology, Harvard Medical School), whose research has challenged the old linear spectrum (from verbal to spatial), and who will speak on the subject of differences between object and spatial imagery at a CMBC-sponsored event on October 10th.
Sathian posed the question of mental imagery from the neuroscientific perspective: what are the neural substrates of image formation? How much overlap is there between the neural pathways involved in mental imagery with those involved in visual perception? Evidence suggests that the overlap is substantial, as might be expected. PET scans and functional MRIs show that visual cortical areas are active in the formation of mental images. Damage to these cortical areas, moreover, interferes not only with perception but also with image formation: patients with right parietal stroke, for example, who suffer from neglect of the left side of the spatial field, not only can’t see the field, but they fail to mention anything on the left side when asked simply to imagine a familiar, remembered scene.
Although visual perception and mental imagery share neural substrates, Sathian underscored important differences: while visual cortex subtends the images of both visual perception and mental imagery, the neural pathways that lead to image formation in each case are very different. Mental imagery stems – in “top-down” fashion – from the frontal cortex, while what we see is received through the eyes. Sathian was careful to qualify this dichotomy, however, pointing out that in actual cases of perception, and especially in cases of perceiving unfamiliar objects, the activity of mental image formation plays an important role in “interpreting” the data, and therefore in determining the images we actually see.
One of Sathian’s most intriguing points concerned non-visual imagery. Object properties are encoded in multi-sensory representations, not just visual ones. One interesting question of on-going debate is whether spatial imagery is specifically visual, or rather “amodal”? The question of the relationship between different kinds of sensory imagery is a fascinating one. In this regard, Sathian left off with a reference to Oliver Sack’s recent book, The Mind’s Eye, in which Sacks discusses the phenomenon of blind people actually becoming more visual in their image formation after the loss of vision. This would seem to underscore the connection between the tactile and the visual (along with providing an interesting variation on the famous problem of Molyneaux, who in a letter to John Locke asked whether a person born blind, able to distinguish a sphere and cube by touch, would be able, with vision restored, to distinguish the objects with sight alone).
What about a friend who claims never to form images? Is it possible that images could never appear in someone’s mind? I must admit, being someone who forms images easily and takes the delight in them that I do in vivid dreams, it is (somewhat ironically?) hard to imagine an inner life without them. Perhaps those who report no images are merely misreporting their inner world? Perhaps they are merely less conscious of the images they are forming than others? In response to this line of questioning, Sathian pointed out that there is some tendency for brain scans to correlate with reports of the vividness of imagery, suggesting that if someone reports a lack of imagery, there may well be some neural basis to the claim. In addition, Sathian explained, even if someone lacks vivid visual imagery, they most likely form other kinds of sophisticated sensory image, such as auditory or spatial. For her part, Otis offered the image-less friend her vote of confidence, cautioning against the presumption that others’ inner worlds need be akin to our own. In illustration, she drew an analogy that elicited laughs from the audience: we don’t talk to one another about our bathroom routines, and in consequence just imagine that everyone’s is just like our own. We cannot know, however, whether this is the case. Likewise, since we never see what is going on in other people’s minds, we naturally imagine it to be just like our own. This is hasty.
The discussion of the image-less friend nicely encapsulated what were perhaps the chief upshots of the lunch: on the phenomenological side, there is increasing appreciation of the diversity of ways in which and degrees to which people form images in the mind; on the neural side, advances in brain imaging techniques, and, more generally, advances in the understanding of the interplay of distinct neural functions are helping to make neuroscientific sense of the range of phenomenological reports. Because of the need to reconcile the phenomenology with the neuroscience, and because of the importance of image formation for the work of both humanists and scientists alike, the study of mental imagery is an apt poster child for collaboration across traditional disciplinary boundaries. In other words, it was a perfect subject for a CMBC lunch.
