Psyehol Res (1986) 48:57-62 Psychological Research © Springer-Verlag 1986

A "visual" explanation of facial vision*

H. Ono, A. Fay, and S.E. Tarbell

Department of Psychology, York University, 4700 Keele Street, North York, Ontario, Canada M3J 1P3

Summary, The existence of facial vision has been doubted, perhaps because of its identification with dermo-optical percep- tion. To determine whether more credence should be granted to this alleged phenomenon, we studied both blind and sighted people. Ninety-two percent of the partially blind people report- ed experiencing facial vision, but only 30% of the totally blind people reported the experience. Eighty-five percent of the sighted people also reported experiencing facial vision when a shadow moved across their eyelids. In response to a question- naire asking about subjective visual experiences, 43% of the sighted people reported seeing as though through a window on their face. The boundaries of two monocular fields mapped by apparent locations of pressure phosphenes agreed with the boundary of the area in which facial vision is experienced. The findings indicate that facial vision can be experienced by both blind and sighted persons and that it can be explained in part by the principles of visual direction.

Facial vision refers to the subjective experience of the blind of perceiving objects as though through the skin of their faces, Some early theories of facial vision claimed that the blind sense light through the skin (e.g., Romains, 1919/1924, pp. 43-107). In the 1940s and 1950s, a series of experiments, now known as the Cornell study, concluded that the blind do not detect obstacles by skin sensations but rather by a process similar to echolocation (e.g., Cotzin & Dallenbach, 1950; Supa et al., 1944). Although these studies made it clear that facial vision is not a dermo-optical phenomenon, they did not explain its origins. Because the subjective experience of facial vision occurs while the blind are using sound information to localize objects, the term 'facial vision' has sometimes been used synony- mously with 'echolocation' (Kennedy et al., 1978). This usage, however, is misleading, because a distinction can be made between functional and phenomenal aspects of the 'obstacle sense' (Juurmaa, 1970). The successful detection of an obstacle

* This research was supported by grant no. A0296 from the Natural Sciences and Engineering Research Council of Canada and a Canada Summer Internship Grant. The authors wish to thank S, Anstis. I. Howard. M. Komoda, M. Steinbach, N. Wade, J. Cod& and those associated with our laboratory for their helpful comments on an earlier version of this paper. The authors would also like to thank Joanne Gallagher for her help in collecting data; Milan Tytla. at the Toronto Hospital for Sick Children. for testing the blind participants; and the Canadian National Institute for the Blind, for their assistance in recruiting blind participants

by the totally blind requires echolocation, but echolocation may not be the determinant of the phenomenal or subjective experi- ence of facial vision. What determines it is still unknown.

The aim of this paper is to examine the phenomenal, not the functional, aspect of facial vision. Interviews and a series of experiments were conducted testing the hypothesis that facial vision is a visual experience. By 'a visual experience' we do not mean that it necessarily stems from stimulation of the eye by light; for example, we would refer to a cortical phosphene as a visual experience. By 'a visual experience' we mean the pheno- menal or psychological event of ~seeing', as opposed to the physical or physiological event which is associated with seeing. For a discussion of this distinction, see Mach (1886/1959). Our hypothesis is that facial vision is a visual experience, not externalized in space, but instead experienced on the face. In Study 1, we interviewed totally blind and partially blind people (with only light perception) about their experience of facial vision. Studies 2 and 3 were designed to explore some of the conditions under which sighted people experience facial vision. Study 2 explored the experience of sighted subjects using light through the eyelids and in Study 3 sighted subjects were asked to respond to a questionnaire concerning facial vision. Study 4 compared the region of facial vision with the limit of the visual field measured by pressure phosphenes.

Study 1: Interviews with the blind

Our hypothesis that facial vision is a visual experience predicts that the partially blind are more likely to experience it than the totally blind. We tested this prediction by means of interviews.

Ten totally blind people and 12 partially blind people (legally blind but with some light perception) volunteered to be inter- viewed. Most of them were recruited for this study by a radio broadcast network of the Canadian National Institute for the Blind. In general, our subjects were articulate and well educa- ted. They ranged in age from 28 to 56 years, with half (11 of 22) of them being in their thirties. The cause and degree of blind- ness varied considerably. Five of the participants had retro- lentral fibroplasia; the remainder had blindness attributable to diabetes, glaucoma, retinitis pigmentosa, trauma, and others. The participants whose degree of blindness could not be deter- mined from the interview were asked to undergo an examina- tion at a hospital. There, they were presented with a light with different temporal modulations in various visual eccentricities and asked to tap a desk top synchronously with any sensory experience.

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The interviews were conducted in person or by telephone by an advanced graduate student in clinical psychology. After explaining the general aim of the interview and asking for their medical history, the following first-person account of facial vision, taken from William James's Principles (1890), was read to them and used as a basis for further questioning: Whether within a house or in the open air, whether walking or standing still, I can tell, although quite blind, when I am opposite an object, and can perceive whether it be tall or short, slender or bulky ... I seem to perceive objects through the skin of my face, and to have impressions immediately transmitted to the brain. The only part of my body possessing this power is my face. (p. 204)

When asked whether they had a similiar experience, they answered confidently, and there was no difficulty deciding if a participant had experienced facial vision. Those who reported facial vision were definite in their answers, and described their experiences most often as a sensation of something being in their way or 'blocking their view'. According to their descrip- tions, the area of this experience was limited to the face. There were no reports of sensation on the shoulder, neck or the back of the head (cf. Juurmaa, 1970). Furthermore, there was noth- ing phenomenologically auditory or cutaneous about their de- scriptions. In Table 1 the number of participants possessing facial vision is presented separately for the totally and the partially blind. Facial vision was experienced by all but one of the twelve partially blind and by only three of the ten totally blind. This difference is statistically significant Z 2 = 6.50, df = 1, P < 0.02).

Table 1. Number of blind participants possessing facial vision by level of blindness

Blindness level Facial vision No facial vision

Partial blindness 11 1 Total blindness 3 7

We do not have a completely satisfactory explanation for the facial vision reported by the three totally blind participants, but we can offer two speculations. One speculation invokes a process akin to 'visual capture'. Blind persons with previous visual experience may have had sufficient experience to estab- lish the dominance of vision over other sensory modalities, and accordingly, may have experienced information from other modalities as visual. (One of these participants did use the word 'visualizing'.) The second speculation, not necessarily a compet- ing one, is that some neural events produce facial vision in the same manner as the cortical phosphene or the phantom limb experience is produced. Perhaps, these neural events occur when the blind person tries to visualize an Object. Either of these processes could account for the facial vision reported by the three blind participants, all of whom had previously had visual perception.

Despite our incomplete understanding of the results of three subjects, the different proportions of the two types of blind people reporting facial vision, as well as their phenomenally visual descriptions of facial vision, are consistent with the idea that the visual modality is involved in facial vision.

Study 2: The experiences of the sighted to light through the eyelids

If the visual modality is involved, as suggested by the results of the interviews, there should be a viewing condition in which

sighted people experience facial vision. We tried to evoke this experience by shining a light through the eyelids of sighted subjects.

Method

Subjects. The participants were 13 males and seven females from our university community. The participants included facul- ty. students, staff, and their relatives. The ages ranged from 11 to 70, with two participants in each ten year age group. All subjects were naive concerning the purpose of the study and had normal vision.

Procedure and apparatus. Subjects were asked to keep their eyes closed tightly throughout the experiment. Diffused light (30 cd/m 2) from two 24 watt light bulbs was presented through filters (exposed X-ray films) and a 26 cm square surface of a milk screen 1 m away. There were three experimental condi- tions: no light, light, and moving shadow. Three corresponding control conditions were run in which light and a moving shadow were presented to the face but not to the eyes. To produce this difference, two pairs of swimming goggles were used; one pair had the transparent glass in place, the other had all the trans- parent surfaces covered with black tape. The shadow moving across the face and eyes was created by a cylinder, 8.5 cm in diameter, swinging silently 28 times a minute in a frontal plane 40 cm from the face. The stimulus presentation lasted until 10 questions concerning facial vision were answered (see Table 2). It was repeatedly emphasized that the subjects should report only their experience, not inferences about what they thought was occurring. About 1 rain elapsed between conditions while participants changed the goggles for the next condition. The order of the conditions was randomly determined for each subject.

Results and discussion

The questions and the participants' responses are shown in Table 2. The high proportion of 'yes' responses in the experi-

Table 2. Proportions of participants responding 'Yes' to the ques- tions asked in the experimental and control (in brackets) condi- tions a

Condition

Question No hght Light Moving shadow

Do you sense/perceive 0.00 1.00 1.00 light? (0.10) (0.10) (0.20)

Do you get the impression 0.05 0.60 0.85 of light shining on your face? (0.00) (0.05) (0.05)

Do you get the impression 0.00 0.10 0.70 of a shadow on your face? (0.05) (0.00) (0.20)

Do you feel light on your 0.00 0.50 0.50 face? (0.05) (0.05) (0.10)

Do you feel a shadow on 0.05 0.10 0.60 your face? (0.05) (0.00) (0.10)

Do you have the sensation of 0.10 0.35 0.40 warmth, pressure, or wind (0.10) (0.05) (0.15) on your face?

aN= 20

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mental, but not in the control conditions, indicates that facial vision is experienced by a high proportion of sighted people, and that this experience is caused by visual stimulation, not by effects of light on the skin. When asked for the locus of sensation of light or shadow, those who experienced facial vision replied in terms of different parts of the face: for example, 'covers my forehead and ends at the bottom of my nose'. Two subjects also mentioned shoulders; for example, 'forehead to shoulders'. Those subjects who did not report experiencing the light or the shadow on the face described the light or the shadow as being very close to the face; some described it as being two or three inches away from the face.

Reports of facial vision by the sighted in the experimental conditions are consistent with Mach's (1886/1959) statement: 'Reflections ... for the field of vision may be made with regard to the province of touch and the perceptual domains of other senses' (p. 20). For example, he cites his friend who remarked upon seeing the drawing of a visual field that a visual object appeared to 'pass through his skin' (p. 20). These quotes are compatible with Our working definition of facial vision, the subjective experience of perceiving objects as though through the skin of the face. These responses prompted us to conduct the next study.

The preamble of the questionnaire began by expiaining that we were concerned with thesubjective experience of vision. Sub- jects were asked not to confuse their subjective experience with their knowledge of the physical and physiological events related to it. We stated explicitly that we wanted to know how things appeared to the subject, rather than the subject's knowledge of the physics or the physiology of the visual system. The following examples were provided to help clarify this distinction: '... In movement, sitting on a train that is stationary and having a train beside you begin to move, is a physical event. Having the feeling that you are moving and the other train is stationary is your subjective experience. In vision, light rays being refracted by the cornea and lens, lk)rming upside down images on your retinae is a physical event. Photopigment change triggering neural responses which travel to the brain is a physiological event. Seeing the world right side up is your subjective experience."

The first two questions of the questionnaire were designed to clarify further what was meant by subjective experience (see Table 3). The third and fourth questions asked for the size and location of the opening that one seems to see through. The fifth question had four parts, three asked about the sensation experi- enced (i.e., cutaneous vs. visual), and one asked for the parts of the face included in the experience.

Study 3: A questionnaire concerning facial vision

That one must ask specific questions in a particular way to ~tap' the experience of facial vision in sighted people is implied by the different proportions of ~yes' responses elicited by the questions in Study 2. In some related research, Flora (Personal Com- munication, May 7, 1982) asked his subjects to imagine looking out a window very close to the face and then to estimate how large the window must be in order to see what is seen. The size and location of 'Flom's window' reported by some subjects corresponds to the area of facial vision reported by our blind subjects. Using Flom's question as a guide, we constructed a questionnaire to assess the occurrence of facial vision with the eyes open. Our questionnaire consisted of a relatively long preamble stating our interest in subjective visual experience rather than in knowledge of the physical and physiological events related to subjective visual experience.

Our original intention was to have two questionnaires, both having the same questions but only one having a preamble emphasizing the difference between knowledge and subjective experience. We found that, without the preamble, the ques- tions did not 'make sense' to the subjects and not many discriminated between knowledge and subjective experience, that is, respondents claimed to experience light on the retina, to see two upside down images, etc. (Even with various versions of the preamble, it was not entirely successful, as we will note later).

Method

Subjects. One hundred and nine students attending introduc- tory psychology summer courses volunteered to complete the questionnaire at the end of a lecture.

Procedure. The questionnaire was designed so that subjects would understand the distinctions between physical, physiolog- ical, and psychological events before they answered the ques- tions (for a discussion of the distinctions, see Mach, 1886/1959).

Results and discussion

The results are presented in Table 3. There were relatively high proportions of 'yes' responses to Questions 1 and 2. Even with our best version of the preamble some participants did not discriminate between knowledge and experience. Almost a quarter of the subjects reported having the subjective experi- ence of seeing through two separate openings and 12% re- ported having the subjective experience that the openings are the size of the pupil (see Table 3). The surprising responses may be due to the questionnaire having been administered after two hours of lecture.

There were, however, subjects who made the distinction: 27% of the subjects reported feeling or seeing through the skin of the face and 43% reported having the perception as if seeing through a window on the face (see Table 3). When asked to describe the parts of the face that the window seemed to cover, 22% of these subjects reported 'only the eyes' , '72% reported the area of the face, for example, 'forehead to lower chin,' or 'central parts of the face' (6% reported 'cannot answer'). No one reported the area on the side or the back of the head. The basis of this report is, we think, the same as the basis of the remark made by Mach's friend that a visual object appears to 'pass through his skin' (p. 20). The fact that the area of Flom's window agrees with the area of facial vision reported by the blind and sighted subjects suggests strongly that the three groups experienced the same phenomenon and that this experi- ence involves the visual sense.

We wish to argue that the principles of visual direction partially explain the size of Flom's window and the area of facial vision. These principles were proposed first by Wells (1792) and by Hering (1879). They state that: (a) any stimulus on a visual axis (line of sight) will be seen on the common axis (or the cyclopean axis), which is a line passing through the intersection of two visual axes and the midpoint between the eyes, and (b) any angular deviation of a stimulus from the visual axis will be seen as that angular deviation from the common axis, the axis from the midpoint between the eyes (the cyclopean eye). (For more recent discussions of the principles see Howard, 1982; Ono, 1979.) These principles summarize how the two eyes work

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Table 3. Proportions of participants responding 'Yes' and 'No' in the Facial Vision Questionnairea,b

Response

Question Yes No

Do you have the subjective experience of seeing through two separate openings? 0.23 0.70

Do you have the subjective experience that the opening or openings you see are the size of your pupil? 0.12 0.81

Does your subjective experience include a non-visual 'feeling' through the skin of your face? 0.27 0.55

Does your subjective experience include a perception as if you are seeing with or through the skin of your face? 0.27 0.55

Does your subjective experience include a perception as if you are seeing through a window on your face? 0.43 0.40

a . •

. Missing percentages represent no response ON= 109

together as one and state that we see as though we have one 'cyclopean' eye.

As an illustration of the principles of visual direction, we ask the reader to do the following: (a) Draw two lines on a sheet of cardboard such that at one edge they are about 6 cm apart and

o n the opposite edge they converge to a point. (b) Place the midpoint of the 6 cm separation on the bridge of the nose so that the vertex is straight ahead of the nose. (c) Direct your binoc- ular gaze to the vertex. (d) Note that you see a line or two lines close together pointing to the bridge of youJ" nose and two other lines each pointing to one of your ears. (e) By moving the cardboard so that the midpoint is directed toward another part of the face at eye level, note that a line can appear to point to another part of your face, for example, a line pointing to the bridge of your nose appears to point to your eyes (for an illustration of this demonstration, see One, 1979).

The principles of visual direction predict one's perception of the lines, and can be extended to account for facial vision. If the end point of the line pointing to one of the eyes is seen to be at the nose, then the termination point of the light directed to the center of the foveae should be experienced on the nose. The termination point of the light directed to the noncentral part of the retina should be experienced on part of the face, Thus, it is reasonable that the light seen with the eyes is experienced on the face, as if through the skin.

Study 4: The apparent location of pressure phosphenes

If the spatial limits of visual direction (the boundaries of the visual field) agree with the boundaries of Flom's window and with the spatial limits of facial vision, then the idea that facial vision is a visual experience would be more convincing. One way to map the limit is to stimulate the edge of one retina while the other retinal stimulation is minimal. This can be accomplish- ed by means of a pressure phosphene, that is, by applying a mechanical force to the edge of the retina while the eye is closed, producing an apparent spot of light on or very close to the face. We asked subjects to indicate the apparent locations of the spots on the face when different parts of the edge of the retina were stimulated.

Method

Subjects. Seven persons from our university community served as subjects. Three of the subjects were completely naive con- cerning facial vision.

Procedure. Subjects were asked to close their eyes and with one hand, to tap lightly the edge of their eyeball at a given location. They were then asked if they perceived a light or dark spot and if so, to indicate with the other hand where the spot appeared to be. The experimenter recorded the apparent location on a full-size drawing of a face. This procedure was repeated for eight stimulation points on each eye. Each point was separated by 45 degrees (starting from the top) from the adjacent point. There were two conditions: in the first condition, subjects first touched the bridge of their nose with the hand to provide a reference point for the response before indicating the location of the phosphene. In the second condition, subjects only in- dicated the location of the phosphene. The order in which the eyes and pressure points were stimulated was randomized for each subject in each condition.

Results and discussion

Figure I shows the means of eight phosphene locations for each eye. The results from the two conditions were combined be- cause there was no obvious difference. Each point in the figure represents the mean of 16 points, two points per subject. Note that the joint area defined by the two boundaries is similar to the area of facial vision reported by the blind. The area extends from the lower brow to the cheeks and out to the sides of the face. Furthermore, the area of the two maps overlap, resulting

Fig. 1, The mean apparent locations of pressure phosphenes. The numbers around the eye indicate the location pressure was applied and the outer numbers indicate the corresponding apparent loca- tions. They also indicate the order in which pressure was applied. (Different participants had different starting positions.) The num- bers are deleted for the left eye to simplify the figure

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in one area, very similar to the area reported in Study 2 and to the area of the window described by the subjects in Study 3.

The limit of visual direction corresponds to the boundary of the visual field discussed by Mach (1886/1959) and more recent- ly by Gibson (1979). For drawings of the visual field with its boundaries, see Mach (1886/1959) and Gibson (1979). The boundary of the visual field consists of parts of the face. Consider the left eye view of the nose while it is pointing straight ahead and the right eye is closed. We generally ignore our visual experience of the nose, but when we attend to it, we should see the bridge of our nose located about where the right eye is. This apparent location of the nose is in accordance with the princi- ples of visual direction, In the demonstration discussed in Study 3, the closer end of the line actually pointing to the nose appeared to be pointing to an eye. Although this phenomenal boundary is not really distinct, it is certainly not the right edge of the pupil or the left edge of the retina. The other parts of the boundary are defined by the impression of the cheek and the lower forehead. The sensing of light or shadow on the skin as reported by the partially blind and sighted participants of this study was mostly confined within the visual boundaries of the two eyes. Hence, the joint area defined by the two boundaries explain why facial vision is limited to the face, and the size and location of Flom's window.

General discussion

Perceived objects in a visual field, those seen through Flom's window or those experienced with facial vision, all have a visual direction. The visual field consists of objects in different visual directions and without reference to their distance. What one sees through Flom's window are visually localized objects with visual direction in the joint visual fields of the two eyes. The partially blind see perceptually diffused objects or patterns of brighter or dimmer spots possessing visual directions. The subjects in Study 2 saw a diffused light in a straight ahead direction in one condition and a shadow with changing visual direction in another condition.

Why are the perceived objects experienced on the face in facial vision? An early theory of distance perception (e.g,, Hallway & Boring, 1941) states that as distance information decreases apparent distance also decreases. Given the absence of distance information for the stimulus in facial vision, an argument can be made that the stimulus is seen on the face because the closest possible apparent distance is the face. However, this argument is counter to the more recently found 'specific distance tendency' for stimuli without distance informa- tion, which is said to be around 1.5 m (see e.g., Gogel, 1969). Perhaps a "cognitive' factor, such as what is expected to be seen, is overriding the specific distance tendency. What may be experienced in the absence of distance information is what Rock (1975) called a '~pure extensity" of the stimulus (percep- tion of visual direction without any distance perception) and experiencing the stimulus on the face is determined by a nonsensory factor.

Among the partially blind, there is acceptance (social reality) of facial vision. To say one 'sees' or 'feels' a stimulus with or on the face would not be a strange thing to say among the blind, although such terms may not be used during their contact with a sighted community. Without our probing, two of our blind participants expressed hostility toward the Cornell study and distress with its findings because they interpreted it as negating their experience.

While social contact among the blind may have played a role in defining their experience of facial vision, this factor may have operated in the opposite direction for the sighted subjects. The knowledge that we see with our eyes and not with our face may have limited the number of subjects reporting facial vision in Study 2 and may be responsible for the relatively large propor- tion of negative responses to the questions concerning facial vision in Study 3. (A cognitive factor may have been operating in Study 4 as well. Having told the subjects that they would see a spot of light on or near the face may have biased their percep- tion toward seeing this. A reviewer of this paper reported seeing the spot sometimes in space rather than on the face.)

Our incomplete understanding of facial vision should not detract from the main point of this paper, which is that facial vision is a genuine experience no different from other percep- tual phenomena studied in the laboratory. Our contention is that experiencing light as facial vision is no more mysterious than perceiving a line which is actually pointing to your eye as pointing to your nose. Facial vision is not a paranormal experi- ence or a 'sixth' sense, as suggested by equating it with dermo- optical perception, an alleged ability to distinguish colors or read with the skin of a finger (e.g., Darnley, 1966). Dermo-opti- cal perception received mass media attention in the 1960s, but was discredited by Gardner's (1966) convincing argument that it is due only to the trickery of 'a peek down the nose' while blindfolded. This disclosure led to the waning interest in dermo- optical perception in the 1970s. Interest in facial vision abated at the same time probably because it was confused with dermo- optical perception. Whatever the reason for the decline in interest in facial vision, this paper shows that facial vision is a genuine experience that deserves independent study.

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Received January 30, 1985 / January 23, 1986