THE AMBIENT OPTIC /Haptic ARRAY Part Two

The point of observation• The point of observation for an ambient optic array is not occu-

pied. • The point has been thought of as a position at which observation

could be made, a position that could be occupied but need not be.• It was important to establish this principle that the point of obser-

vation is public, not private, but now we must consider the other side of the coin.

• When a point of observation is occupied, there is also optical in-formation to specify the observer himself, and this information cannot be shared by other observers.

• For the body of the animal who is observing temporarily conceals some portion of the environment in a way that is unique to that an-imal.

• I call this information propriospecific as distinguished from extro-specific, meaning that it specifies the self as distinguished from the environment.

THE SPECIFYING OF THE SELFBY THE FIELD OF VIEW

• The field of view of an animal is the solid an-gle of the ambient light that can be registered by its ocular system. The field of view, unlike the ambient array, is bounded; it is a sort of sample of the whole sphere.

• The angular scope of the field of view depends on the placement of the eyes in the head, some animals having lateral eyes and a nearly panoramic field of view and others having frontal eyes and a roughly hemispherical field of view.

The lateral eyes of a horse and the frontal eyes of a man and the respective fields of view

Visual solid angle

The ego as seen by the left eye. The temporary field of view of the left orbit of an observer.

• The drawing is an updating of one made by Ernst Mach in the 1880s that he enti-tled "The Visual Ego."

• What is being illustrated here is the sta-tionary field of view of an eye socket with the head fixed and the eye mobile, not the shifting field of view with a fixed eye and a turning head; the latter is different and will be described later.

• For this drawing, the artist had to turn his eye in order to see clearly the peripheral details in the field of view.

Projected and Unprojected Surfaces in a Stationary Optic Array 

Optical Occlusion and Edge-In-formation in an Optic Array

A field of view• A field of view is a large visual solid angle, with

an envelope. • The important fact about a field of view is its

boundaries, vague and indefinite boundaries, to be sure, but still boundaries.

• They are in some ways like occluding edges, the occluding edges of window.

• The edges of the field of view hide the environ-ment behind them, as those of a window do, and when the field moves there is an accretion of op-tical structure at the leading edge with deletion of structure at the trailing edge.

• Ask yourself what it is that you see hiding the sur-roundings as you look out upon the world-not darkness surely, not air, not nothing, but the ego’.

A point of observation is occupied by a human

• Whenever a point of observation is occupied by a human, about half of the surrounding world is revealed to the eyes and the remainder is concealed by the head.

• What is concealed is occluded not by a surface, a projected surface of the sort described when the laws of occluding and occluded surfaces were formulated, but by a unique entity.

• It is not a part of the world, but it does conform to the princi-ple of reversible occlusion, by which those surfaces that go out of sight with one movement come back into sight with the opposite movement.

• The head turns, and whatever was in back of the head at one time will be in front of the head at another and vice versa.

• This fact is fundamental for the theory of perception to be proposed.

The experience of a central self in the head and a peripheral self in the body

• Still other occluding edges appear within it, those of the nose, the body, the limbs, and the extremities, some of which can be seen in the drawing. The edges of the eye socket, the eyebrows, the nose and cheek bones are only the nearest;

• the edges of the arms, legs, hands, and feet are more dis-tant, but they still occlude the surfaces of the "outer" envi-ronment. The hands and feet behave more like the occlud-ing edges of an object than like the occluding edges of a window; they are actually protrusions into the field of view from below.

• When these semi objects move, there is deletion of optical structure at the leading edge and accretion at the trailing edge, just as with objects in the world.

• Information exists in a normal ambient array, therefore, to specify the nearness of the parts of the self to the point of observation-first the head, then the body, the limbs, and the extremities.

Deletion of optical structure at the leading edge and accretion at the trailing edge

NONVISUAL INFORMATIONABOUT THE SELF

• The observer's movements usually produce sights and sounds and impressions on the skin along with stimulation of the mus-cles, the joints, and the inner ear. Accordingly, information that is specific to the self is picked up as such, no matter what sen-sory nerve is delivering impulses to the brain.

• The point is that information about the self is multiple and that all kinds are picked up concurrently.

• An individual not only sees himself, he hears his footsteps and his voice, he touches the floor and his tools, and when he touches his own skin he feels both his hand and his skin at the same time.

• He feels his head turning, his muscles flexing, and his joints bending. He has his own aches, the pressures of his own cloth-ing, the look of his own eyeglasses-in fact. he lives within his own skin.

EGORECEPTION AND EXTEROCEPTIONARE INSEPARABLE

• The optical information to specify the self, including the head, body, arms, and hands, accompanies the optical information to specify the environment. The two sources of information coex-ist.

• When a man sees the world, he sees his nose at the same time; or rather, the world and his nose are both specified and his awareness can shift. which of the two he notices depends on his attitude; what needs emphasis now is that information is available for both.

• The supposedly separate realms of the subjective and the ob-jective are actually only poles of attention. The dualism of ob-server and environment is unnecessary. The information for the perception of "here" is of the same kind as the information for the perception of "there," and a continuous layout of sur-faces extends from one to the other.

• Self-perception and environment perception go together.

The Specifying of Head turn-ing• The head can be turned as well as displaced.

Turning the bead is looking around; displacing it is locomotion.

• They are specified by what I have called the sweeping of the field of view over the ambient ar-ray during head turns and the wheeling of the field over the array during head tilts.

• The sweeping and wheeling of this window with its special private occluding edges are not simply "motions" but deletions and accretions of optical structure.

• To say only that the field of view "moves" over the world as the head moves is inexact and insuf -ficient; the world is revealed and concealed as the head moves, in ways that specify exactly how the head moves.

A sequence of overlapping fields of view obtained by turning the head to the right.

His feet are now lined up with the window instead of with the corner of the room. The head turns through an angle of about 90". His nose is always at the right-hand

edge of the field. The field of view is a sliding sample of the ambient array.

The optical texture that is deleted is subsequently accreted

• Binocular disparity refers to the difference in im-age location of an object seen by the left and right eyes

• The combined field of view of two eye sockets (and all higher animals have two eyes) consists of two samples of the ambient array.

• They overlap more or less, more in humans than in horses, and thus the same structure is included in both segments.

• But it is not quite the same structure, because the two points of observation are slightly separated and there is a resulting disparity of the two structures.

This disparity, ormismatch, is at a maximum

• The edge of the nose is the left-hand edge of what the right eye sees but the right-hand edge of what the left eye sees, and this maximum mismatch constitutes in-formation for the zero of distance, that is, for the awareness of oneself at the center of a layout of surfaces receding from here.

• The minimum of mismatch is at the hori-zon.

THE SPECIFYING OF LIMB MOVEMENTS

• Consider in more detail the protrusions into the field of view of those complex shapes with deforming outlines that are the projec-tions of the limbs and extremities of the ob-server's body.

• They normally enter and leave the field at its lower edge, or else the field sweeps down to reveal them. They are almost never at rest.

• They specify objects in some ways, but of course they are only semi objects.

Subjective objects• This paradox would emphasize the fact that no line can be drawn

between the subjective and the objective. • In the primate and the human, the five pronged shapes that

specify the hands are especially meaningful. Their deforming contours and the underlying invariants make possible what psy-chologists have called, very inadequately, eye-hand coordina-tion.

• More exactly, they are the basis of the visual control of manipu-lation. And when an object grasped by the hand is used as a tool, it becomes a sort of extension of the hand, almost a part of the body.

• Infants, both monkey and human, practice looking at their hands for hours, as well they should, for the disturbances of optical structure that specify the niceties of apprehension have to be distinguished.

The optical minification and magni-fication

• The optical minification of the squirming silhouette of the hand specifies extension of the arm, reaching out, while optical magnification specifies flection of the arm, pulling in.

• A hand occludes progressively less of the environment as it re-cedes and progressively more of the environment as it ap-proaches. A certain nonsymmetrical magnification of the hand will bring it to the mouth, as every baby learns.

• A symmetrical magnification of the hand will cause it to cover the eyes so that nothing can be seen.

• The visual solid angle of the hand cannot be reduced below a certain minimum; the visual solid angle of a detached object like a ball can be made very small by throwing it.

• These ranges of magnification and minification between limits link up the squirming silhouette extremes of here and out there, the body and the world, and constitute another bridge between the subjective and the objective.

Contact of the hand or foot with a surface

• You might think that contact of the hand or foot with a surface dur-ing extension of the limb is specified by a mechanical impression on the skin, by touch, and that there would be no use for an optical specification as well.

• Nevertheless, there is such optical specification. When the decreas-ing occlusion of the surface by the extremity ceases, and when there is no accretion or deletion of surface texture by the occluding edges of the hand or foot, then the extremity is in contact with the surface and not sliding over it. This specifies, for example, that the foot is on the ground.

• Terrestrial animals are accustomed to have their feet on the ground and to have both cutaneous and optical information for this state of affairs.

• This explains why an invisible glass floor high above the real floor supplies mechanical support but not optical support, and why it is that human infants and other terrestrial animals show distress, flinching and behaving as if falling, when placed on such a transpar-ent floor.

THE SPECIFYING OF LOCOMOTION• Locomotion is specified by flow of the array and

rest by non flow. The flow is a change in per-spective structure, a change in the perspec-tives of the ground if outdoors and of the floor, walls, and ceiling if indoors.

• There is not only a static perspective of the ar-ray but also a motion perspective.

• The main law of flowing perspective is that it is centrifugal in half the array and centripetal in the other half, but these two hemispheres are not invariant.

The two foci of inflow and outflow• More particularly, a focus of centrifugal outflow is

always accompanied by another focus of centripetal inflow at the opposite pole of the sphere.

• This axis is the line of the displacement of the ob-server. Hence, the focus of expansion is the direc-tion in which one is going, and the focus of contrac-tion is the direction from which one is coming.

• This direction may change during locomotion, of course, relative to the permanent environment of earth and sky, and the two foci of inflow and outflow may change correspondingly relative to other in-variants of the ambient array.

The flow pattern• The invariant structure of the array that specifies the per-

sisting world underlies the changing perspective structure. The pattern of outflow and inflow is superposed, as it were, on the nonchanging features of the array.

• One of these nonchanging features is the earth-sky con-trast at the horizon, and another is the texture of the earth. The flow pattern shifts as the observer changes di-rection, now in one direction and then another, and re-verses when the direction is reversed, but the invariants of structure and texture never shift.

• They specify the unmoving terrain, whereas the Flow pat-tern specifies the observer's locomotion with reference to the terrain.

How do we see where we are going?• We guide or steer our locomotion, when we are in

control of it, by locating those invariant features of the array that specify a destination, whatever it may be, and then keeping the focus of optical out-flow centered on that item. In short, we magnify the form that specifies the goal.

• A child runs to his mother by enlarging her image to the limit, that is, to the largest possible solid an-gle;

• a bee flies to a flower by precisely the same rule. The rule is related to the principle of what I have called the '"symmetricalizing'" of stimulation.

The moving self and the unmoving world

• The centrifugal outflow of the array that specifies locomotion does not interfere with the information that specifies surface layout; the invari-ants are all the better for the transformation.

• The moving self and the unmoving world are reciprocal aspects of the same perception. To say that one perceives an outflow of the world ahead and an inflow of the world behind as one moves forward in the environment would be quite false.

• One experiences a rigid world and a flowing array. • The optical flow of the ambient array is almost never perceived as mo-

tion; it is simply experienced as kinesthesis, that is egolocomotion (Warren, 1976).

• Consider, finally, an environment with hidden surfaces. An open envi-ronment projects a continuous flow pattern to the eye of a moving ob-server, but a cluttered environment does not.

• This kind of change is not a flow or a transformation, because the units of the array, some of them, do not map from preceding to succeeding arrays. The invariants that specify the layout of the real environment, then, are not simply invariants under projective transformations.

The flow of the optic array during lo-comotion parallel to the ground.

The outflow of the optic array from the focus of expansion on the horizon.

The flow of the optic array to the right of the direction of locomotion.

The outflow of the optic array in a landing glide. This is what the flier would see if he

aimed down at the landing field.

How is this optical How related to classical kinesthesis?

• Kinesthesis, which is supposed to be the sense of movement.• A person who walks or runs or rides a bicycle does get sensations

from the muscles and joints that specify movement. All I propose is that visual kinesthesis should be recognized along with muscle-joint kinesthesis.

• The latter does not function during passive locomotion in a vehicle. Visual kinesthesis yields the only reliable information about dis-placement. The classical sense of movement is not trustworthy, for a fish in a stream and a bird in a wind have to exercise their mus-cles and joints strenuously merely to stay in the same place.

• The animal is moving in one meaning but not in another. Locomo-tion with respect to the earth, active or passive, is registered by vi-sion, but supplementary information about the movement of a limb relative to the body is picked up by the haptic system (Gibson, 1966b, Ch. 4).