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Eye and hand: Differential sampling of form and orientation properties
Ne~op~ychologh,
1969, Vol. 7, pp. 365 to 373. Pergmon
Press. Printed in England
EYE AND HAND: DIFFERENTIAL SAMPLING OF FORM AND ORIENTATION PROPERTIES JACQUELINE J. G~~DNOW The GeorgeWashingtonUniversity, Washington,
D.C. 20006, U.S.A.
(Received 14 March 1969) Abstract--The eye and the hand may sample different properties of the same stimulus, with the properties most salient to one being different from those most salient to the other. This possibility is confirmed by asking children in kindergarten and second grade to judge which of two changes to a figure, both discriminable, leave the figure least changed. Visually, a change in curvature is highly significant, but a change in orientation is not. The reverse is usually true haptically. The haptic response appears based on the way the hand and its activity offer reference points for determining a change in a focal part of the figure.
WHAT is the difference between inspecting an object by eye and by hand? Answers to this question put us in a better position to understand both haptic perception-perception by active, exploratory hand movements-and the phenomena of cross-modal matching and transfer. One possibility is a differential responsiveness to the properties of a stimulus. Most properties are discriminable by both eye and hand, but the properties most salient to one may well be different from those most salient to the other. This kind of differential sampling of cues or properties has been proposed, in the area of problem solving, as an obstacle to seeing relationships between events [l]. The same kind of concept may well be useful for comparing visual and haptic responses to the same stimulus. In fact, such a concept is implied by several comments on cross-modal tasks. WILSONand SCHAFFER [2], for example, account for poor cross-modal transfer in terms of the eye and the hand attending to different parts of the same stimulus object. BJ~SRKMAN et al. [3] have altered the likelihood of transfer between vision and touch by leading Ss to pay attention to a property-color-that is sampled only by eye. And, as a general alternative to explanations stressing the separateness of modalities and the role of language, RUDEL and TEUBER[4] have suggested that the unravelling of cross-modal effects will depend on finding stimulus properties that favor the hand or are at least equally appropriate for eye and hand. In two recent studies, the spatial position of a stimulus appears as a property responded to differentially by eye and by hand, with the hand showing the greater responsiveness. With a Levine-type analysis of responses on a learning set task, WILSON[5] has reported for monkeys a predominance of responses haptically to the left or right position of an object as against a predominance of responses visually to the object’s shape. With human Ss from age six to adulthood, PICK and PICK [6] have reported that changes in the orientation of a figure are discriminated at an earlier age haptically than visually. In contrast, changes in a form property-curvature-were discriminable at an earlier age by eye than by hand. 365
366
JACQUELINE J. G~~DNOW
In haptic studies, the most discriminable dimension is not always the one preferred in a choice situation (cf. [7]) so that the agreement between WILSON[5], and PICK and PICK [6] is especially interesting. The present study is a check and an extension of the study by PICK and PICK. As they point out, their visual-haptic comparison is in some respects an indirect one. The haptic results they obtained were compared with the visual results of a previous study [7] and the procedures for the two studies were not identical. The immediate aim of the present study is to determine whether the same differential response to orientation and curvature occurs when the visual and haptic procedures are made identical and when the measure of responsiveness is not the PICKS’measure of discriminability. The more general aim is to investigate the bases of haptic judgments. If the hand should be highly responsive to spatial position, for example, we have no ready-made explanation for why it should be. In fact, there is a general dearth of information on how haptic judgments are made, even though haptic activity is a phenomenon of clinical and theoretical interest, both in its own right and as a check on the generality of any results found with vision (cf. [8]). METHOD Material
The stimulus figures are illustrated in Fig. 1. The original figures were developed for a visual discrimination study by GIBSONet al. [9], and tactual equivalents of the visual outlines were first used by PICK and PICK [6]. The tactual equivalents were used throughout the TRANSFORMATIONS: STANDARD
;
SIZE
I
LEFT-RIOHT POSlTlON
CHANGES
IN
WVERTED C”R”*T”RE POS,TlW OF UNES
ll”LleER OF LINES
1
A
B
C
D
E
;
A
B
C
D
E
FIG. 1. Stimulus designs (from GIBBON et al. [9]). present study, for both the visual and tactual forms of the task. We used, however, only four of the original standards and five transformations of each. For each design, the five transformations cover a change in overall size, left-right position, “up-down” position (a rotation of 180” or 90” as needed to produce a different figure), curvature of lines and number of lines.
EYE AND
HAND:
DIFFJZRENTTAL SAMPLING
OF FORM AND
ORIENTATION
PROPERTIES
367
Subjects
The main body of subjects consists of 74 children tested towards the end of second grade. The mean age was 8 : 2, with a range from 7 : 8 to 9 : 2. A smaller group of 30 children was tested at the end of kindergarten (mean age 5 : 10, range 5 : 4-6 : 1). At both age levels, children can tell that a standard and a transformation of the standard are not identical, a statement based on PICK and PICK’S [6] results and on an independent check for discriminability. For some kindergarteners, however, the haptic task was not easy, and the second-grade children were the better choice for the main sample. Both groups came from the same private school and both were well above average in performance on intelligence tests.
Procedure
On each trial, three figures-a standard and two transformations-were placed horizontally on a table in front of the child. Figures were secured in place by a strip of velcro. The standard was always on the child’s left, with the transformations to the side and with all figures about one and a half inches apart. On each trial, the child explored the standard figure, and then the transformations, and was asked to choose the transformation that was more like the standard. For the child, the standard was “the one that stays,” and the question was : “Which of these two is most like the one that stays?” In all, the child was told: “I am going to put some designs down here, for you to see (or feel). Here is a design (a standard). The one I put here will stay here all the time. Next to it I will put two others. They are like the one that stays, but not exactly like it. Each time I would like you to look at (feel) the one that stays, then the ones that are like it, and then tell me which one of the two over here is the most like the one that stays. This is the one that stays (E points or places the child’s hand on the standard), and these are the other two (E points or places the child’s hand). Look at (feel) the one that stays, then look at (feel) the other two, and tell me which of these two is the most like the one that stays”. Each trial carried this reminder to attend first to the standard and then to the other two designs, and a child was told to check all three forms if he gave a judgement after attending to only two. Apart from this restriction, Ss were free to choose their own method of visual or tactual scanning. In the tactual form of the task, the child was given some additional directions. He was told the object of the game was to see what his hands could do without his eyes, and he went through some preliminary tasks like finding his nose or ears with his eyes closed. The curtain under which he placed his hands was explained as a way of saving him from keeping his eyes closed all the time, and he was allowed to inspect the board with its velcro strip both with and without the curtain. In addition, the child was told that a design was made by a line on a metal square, and he was helped, if necessary, to find the first design. The procedure calls for paired comparisons. The ten trials cover the ten possible pairs of the five transformations, each transformation appearing four times, twice on the left and twice on the right. Most Ss were given only one design, with comparisons to be made either visually or haptically. A small group of Ss (fourteen of the second-graders) were given two designs, one visually and one haptically, but the double procedure was difficult for some children and was discontinued.
JACQUELINEJ. G~~DNOW
368
RESULTS The major results are as follows: 1. Orientation and curvature are responded to differentially by the eye and the hand. In the haptic task, left-right reversals and up-down changes produce figures that are felt to be very unlike the original, even when children are aware that the figure has only been turned around. Visually, the same changes produce very little sense of change from the original. A change in curvature reverses the pattern : a sharp sense of difference from the standard visually and little sense of difference haptically. 2. We can suggest some basis for the haptic response to changes in orientation. Haptically, each design seems to be composed of a strong or focal part, plus some weaker or subsidiary parts. If the change in figure orientation changes the position of the focal part, the whole figure is felt to be changed from the original. But if the focal part is left unaltered, the figure itself is felt to be little changed. The precise method by which the hand picks up a change in the focal part is not clear, but the parts of the hand may provide a set of coordinate points, or the sequence of steps in tracing out the figure may act as a framework against which change can be readily detected. The general pattern of response to all transformations can be seen in Fig. 2. The figure shows, for the four designs combined, the mean number of times that second-graders chose each transformation as the more like the standard. z %
4
8
w 5
t
0
B
A
LEFT- RIGHT !‘OSlTlON
SIZE
(for
.--.
BY HAND
-
BY EYE
C INVERTED POSITION
D CURVATURE OF LINES
E NUMBER OF LINES
TRANSFORMATIONS four designs combined)
FIG. 2. For children in Grade 2, mean number of times a transformation is chosen as like the standard.
In Fig. 2, the visual and tactual judgments meet at some points and diverge on others. By both eye and hand, a transformation only in size is judged to be the most like the standard. Eye and hand are also fairly close together in their response to a change in the number of lines. On the other transformations, however, visual and haptic judgments diverge sharply. Left-right reversals, for example, are chosen visually as like the standard
EYE AND
HAND:
DIF’FERENTIAL
SAMPLING
OF FORM AND
ORIENTATION
PROPERTIES
369
a mean 3.19 times out of a possible four. Haptically, left-right reversals are seldom chosen (the mean is 1.85 times). Inversions or rotations are also seldom chosen haptically (the mean number of times is 1.53), but the divergence from vision is less sharp, since up-down changes apparently give rise visually to a weaker sense of similarity than left-right reversals do (the visual mean is 2.38). For both left-right reversals and up-down changes, however, the difference between visual and haptic judgments is statistically significant (with a twotailed t test, p is <0401). So also is the difference in response to curvature (p is
Results are not identical for all designs, and Fig. 3 shows the main variations. The variability is most marked in the haptic response to changes in orientation, ranging from very little difference between visual and haptic judgments with either change in orientation (Design II), through a difference mostly on left-right reversals (Design I), to a difference on both left-right reversals and up-down changes (Design III). I
z
01.
f
A
o(PJ?
dd C
B
0
FIG.
3. By
BY HAND
-
BY EYE
LJCl!LD E
A. s)ZE : 8s LEFT-RIOHT: E - NUMBER
.--.
ABC
DE
TRANSFORMATIONS C * INVERTED: 0. CURVATURE
?m
D
OF LINES :
OF LINES
design,mean number of timesa transformationis chosen as like the standard.
The difference among designs is actually helpful. It leads to a definite hypothesis about the basis of the haptic response, viz. that the hand’s response to a change in the orientation of a figure is based on what happens to a focal or salient part of the figure. This hypothesis developed slowly,* and is essentially in two parts: first that the figure is responded to as made up of a strong or organizing part plus some subsidiary parts, and second that * Chronologically,the beginningwas with Design IV and kindergartenchildren. The task could be done by these very bright kindergartenchildren,but gave little pleasureto some of them. I shifted accordingly to second-gradechildren and found that the results still held up well for Design IV and also for DesignI. To replicate with still another design, I chose Design II and found, unexpectedly, little difference between visual and tactual judgments. The effects seemed to make sense when I looked at the comments of Ss and the figure parts that seemed “strong” or “focal”, and Design III was an attempt to locate ahead of time a figure with a clear focal part that would yield again a clear difference between the eye and the hand. The difficulty, one should note, is not so much in locating a focal part as in finding a figure where Ss quickly settle on the same focal part. Design III, incidentally, is a left-right reversal of the design as originally developed. It was turned around in the present study to allow the focal part to fall on the right-hand side of the figure for a change, since the focal parts of Designs I and IV had both turned out to lie on the left-
hand side.
370
JACQUELINEJ.GOODNOW
the response to the oreintation of the whole figure is determined by what happens to the strong or focal part. The presence of a focal part was indicated by several behaviors, by the way children explored the figure, the comments they made when they met a change in orientation, and the way they drew the standard figure at the end of the task. In each design, there appeared to be a part that Ss tried to locate first as a kind of home-base. When they could not find it in an expected place, they commented on its being “missing” or “in the wrong place”. And when they drew the design, they tended to draw this part first and with least error. In Design I, for example, the focal part haptically is the circle. After haptic experience, the design was often drawn as a circle first, with two tails that were separate and did not always emerge from the same point. After visual experience, the design was always drawn as a single, flowing line. For the other designs, the focal parts are the two parallel lines in Design II (for some Ss only the upper curve), the oval in Design III (for some Ss the total outside curve), and the vertical line in Design IV. How do these focal parts affect the hand’s response to a change in the orientation of a figure? To take Design I as an example again, the sense of difference from the standard is marked with a left-right reversal, less marked but still clear with an up-down change (Fig. 3). The focal part is the circle. A left-right reversal confronts S with the ends of two lines where he expects a circle, and, to locate all of the circle again, he must locate the final rounding of lines at the far right of the design. There were often comments that “the circle’s not in the right place” or that “I can’t find the circle.” An up-down change also shifts the circle, but less drastically. S finds at least one curve where he expects to find a circle, and the rest of it is closer to hand. In contrast, with Design II, the sense of difference from the standard is minimal with either change in orientation from the standard. The focal part is the pair of horizontal lines, sometimes both, sometimes only the upper curve, whose appeal seems to come from a niceness of fit to the width of a finger. A left-right reversal changes neither the position nor the curvature of either horizontal line. An up-down change alters the direction of curvature and the position of one line in relation to the other. But these are weak changes. They are not always discriminated (some Ss draw the horizontal lines as two equal, straight lines) and, where discriminated, not salient (a change in curvature elicits little sense of change on any design). The overall effect is one of little difference between the standard design and its upside-down version. Similar arguments can be applied to Designs III and IV. With Design III, the focal part is usually the oval and sometimes the total outside frame. Either focal part yields a sense of difference between the standard and either change in orientation. With Design IV, the focal part is the vertical line. A left-right reversal often brings such comments as “the line is missing” and a hunt to locate it before further exploration. An up-down change leaves the vertical line in the same position but changes its feel, often eliciting the comment that now “the line has a sharp point to it.” In short, what happens to the focal part is a highly feasible way of accounting for the response to the orientation of the whole figure. And without some knowledge of the focal parts in any particular set of designs, it would be hard to predict exactly what the response would be or to account for the variability from one design to another. It is critical to note that the child is well aware that the focal part is not the entire figure, and in fact many
EYE AND
HAND:
DIFFERENTIAL
SAMPLING
OF FORM
AND
ORIENTATION
371
PROPERTIES
second-graders say explicitly that a left-right reversal or an inversion is the same figure “just turned around.” Nonetheless, the phenomenal sense of the figure being different still remains. The stability of the difference between eye and hand can be seen in Table 1. Table 1. Mean number of times that a transformation is chosen as more lie standard (range O-4); visually (V) or haptically (H)
Grade 2 All designs
Transformation
I
Grade 2, By design II III
IV
Iv*
the
Kindergarten IV
A. Size
V H
3.09 3.18
3.14 2.86
3.40 3.07
2.25 3.33
3.57 3.43
3.43 2.57
3.29 3.07
B. Left-right
z
3.19 1.85
3.43 1.43
2.90
2.33
3.50 1.63
3.00 1.71
3.14 2.14
3.14 1.64
c. “up-down”
V H
2.38 1.53
2.43 1.71
2.10 1.67
3.12 1.37
1.86 1.43
2.14 1.71
2.50 1.36
D. Curvature
:
0.87 2.45
0.71 2.29
1.20 2.20
1.13 2.87
0.29 2.29
0.57 2.86
0.64 2.21
E. Number of lines
:
0.47 0.98
0.29 1.71
0.40 0.73
0.00 0.80
1.28 1.14
0.71 0.71
0.43 1.71
N Us)
V H
32 44
10 15
8 15
7 7
7 7
14 14
7 7
* Visual judgments on IV preceded by tactual judgments on I. Factual judgments on IV preceded by visual judgments on I.
The same pattern holds throughout : similarity in response to changes in size and in number of lines, but difference in response to changes in curvature and orientation. The pattern holds for kindergarteners and second-graders, for children whose only experience is with one design, either visually or tactually, and for children who have seen or felt one other design before. The difference in response between eye and hand is clearly a stable and replicable one. DISCUSSION The results strongly substantiate PICK and PICK’S [6] report of a possible difference between the eye and the hand in judgements of curvature and orientation. The agreement is all the better for occurring with two different procedures: preferred basis of similarity in the present study, discriminability in the PICK and PICK study. The problem now is to account for the difference between eye and hand, or at least to account for why each is highly responsive to changes in one property of an object and relatively unresponsive to changes in another. For the hand, there is a single hypothesis that could be applied to judgments of both curvature and orientation. The critical factor in both cases could be the extent to which the hand and its activity offer reference points for judging a stimulus property.
372
JACXXJELJNE J. G~~DNOW
In judging the curvature of an edge, for example, the hand itselt traces an arc, with the wrist, elbow or shoulder as the pivot. Ss might well have difficulty differentiating the curved stimulus line from the curved response movement, and practice in making the differentiation could account for the relatively rare result of more accurate judgments by blind than by sighted Ss [IO, 61. For judging orientation, the critical factor is the position of a focal part. But “change in position” implies the existence of some framework, and it is here that the hand and its activity appear critical. The hand can supply three possible frameworks: A framework of time, stemming from the sequence of parts that the hand encounters. This kind of framework is implied when Ss comment on when rather than where they find the focal part: “I can’t find that line and it’s usually the first thing I find.” A framework jiom the stimulus setting. Each design is on a metal piece about one and a half inches square, and the edges of the square are often encountered in the course of locating the design. It is possible to develop a sense of the usual distance of the focal part from the first edge encountered, and a change in this usual distance could signal a change in the orientation of the design or yield the sense of a different design. A framework provided by the hand itself. This is the kind of framework stressed in some Soviet approaches (cf. [I 1, 121). Using it, one might expect the fingers of the hand to serve as co-ordinates, points to which the landmarks or salient parts of the stimulus are referred. The asymmetry of the hand, probably together with the discreteness of the fingers, would help make the co-ordinates especially clear and discriminable. This kind of interpretation is particularly suggested by ANANYJZV’S stress on the role of co-ordinates in any spatial judgement and on the importance of “functional asymmetry” (cf. [12], pp. 185-206). For all three possibilities, the critical factor is the way in which the hand and its activity make it easier or harder to establish a useful set of coordinates or reference points. Ideally, one would like to be able to point to some similar features for vision, features that might help account for the reverse picture of greater responsiveness to curvature than to orientation. Such features, however, are by no means obvious at the present time. What we have for the moment is a viable hypothesis for the haptio judgments, and some data that takes us a step further in describing haptic perception and in unravelling crossmodal judgments. Haptic perceptions and productions, in REVESZ [13] terms, are more sums of separate parts than their visual equivalents are. To REVESZ’description, we can add the qualification that some parts are more important than others, and are responsible for judgements about the whole figure, in much the same way that GHENT [14] has argued for the role of focal parts in children’s judgments of the upside-downness of a figure. GHENT[14] is able, however, to specify what makes a part visually focal, and we are not yet able to do the same for haptic focal parts, short of observing the way a child scans and remembers a figure. As a working rule, one might look for the role of closed figures-circles, triangles, ovals-parallel lines and vertical lines, but this order of importance may not hold for other figures. For cross-modal effects, we have now some additional support for approaches in terms of a differential sampling of stimulus properties. The difficulties that occur in cross-modal matching, it has been suggested, may be not primarily a function of the modalities and their separateness, but a function of difference in the cues attended to [4]. One of the difficulties with this approach has been a dearth of evidence for a differential sampling of stimulus properties, evidence that begins to be supplied by the results of PICK and PICK [6], WILSON and SCHAFFER[2], WILSON[5], and the present study.
EYE AND HAND: DIFFEFSNTIAL SAMPLING OF FORMAND ORIENTAnoNPROPERTIES
373
Acknowledgements-My largest debt is to ANNE and HERBERT~CK, for a provocative first study and a generous loan of stimulus material. I am also indebted to SHARONLARSONfor thoughtful assistance with Ss, and to LILA GHENT BRAINEfor helping to clarify a number of ideas. The research was supported by grants from the National Institute for Child Health and Human Development (IK03 HD36791, 1 ROl-HDO3105, and 1 TOl-HDOO203). The author’s address is the Department of Psychology; George Washington University; Washington, D.C. 20006.
REFERENCES 1. DUNCKER, K. On problem-solving. Psychol. Monogr. 58, 1-113, 1945. 2. WILSON, W. A., JR. and SCHAFFER,0. C. Intermodality transfer of specific discriminations monkey. Nature 197, 107, 1963.
in the
3. BJ~~RKMAN, M., GARVILL,J. and MOLANDER,B. Crossmodal transfer as a function of preparatory set and distinctiveness of stimulus aspects. Reports from Psychological Laboratory, Univ. Stockholm, No. 186, 1965. 4. RUDEL, R. and TEUBER, H. L. Crossmodal transfer of shape discrimination by children. Neuropsychologia 2, l-8, 1964. 5. WILSON, M. Tactual discrimination learning in monkeys. Neuropsychologia 3, 353-361, 1965. 6. PICK, A. D. and PICK, H. L., JR. A developmental study of tactual discrimination in blind and sighted children and adults. Psychonom. Sci. 6, 367-368, 1966. 7. GLINER, C., PICK, H. L., JR., PICK, A. D. and HALES,J. A developmental investigation of visual and haptic preferences for shape and texture. Monogr. Sot. Res. Child Dev. 1969, in press. 8. GIBSON,J. J. Observations on active touch. Psychol. Rev. 69,477-491, 1962. 9. GIBSON,J. J., GIBSON, E. J., PICK, A. D. and OSSER, H. A developmental study of the discrimination of letter-like forms. J. camp. physiol. Psychol. 55, 897-906, 1962. 10. HUNTER,I. M. L. Tactile-kinesthetic perception of straightness in blind and sighted humans. Q. JZ exp. Psychol. 6, 149-154, 1954. 11. PARACHEV,A. M. The algorithmic structure of active touch. Vop. Psikhol. 1,67-79,1963. (Translated
document published by U.S. Dept. of Commerce, JPRS # 19665.) 12. SHEMYAKIN,F. N. Orientation in space. In Psychological Science in the U.S.S.R., ANANYEV,B. G., KOSTYUK,G. S., LEONTYEV,N., LIJRIE, A. R., MENCHINSKAYA. N. A., RUBINSIFTEIN, S. L., S~~IRNOV, A. A., TEPLOV,B. M. and SHEMYAKIN, F. N. (Editors), pp. 186-255. Academy of Pedagogical Sciences, RSFSR, MOSCOW,1959. (Translation oublished bv U.S. Deot. of Commerce. JPRS # 11466.) 13. REVESZ,~G. PsychoIogy aid Art of the ‘B[ind. Lo&mans, Gieen, New York, ‘1950. -14. GHENT, L. Form and its orientation: a child’s eye view. Am. J. Psychol. 74,177-W, 1961. R&um&L’oeil et la main peuvent tbmoigner des diffkrentes propri&& du msme stimulus. les propri&ts les plus marquantes pour l’un &ant di&rentes de celles les plus marquantes pour l’autre. Cette possibilitC se trouve confirm&e lorsqu’on demande aw enfants du jardin d’enfants et d’kole du second niveau de juger laquelle des deux modifications apportks a une figure, toutes deux &ant discriminables, laisse la figure la moins chang&e. Visuellement, une modification de courbure est hautement significative, alors qu’un changement d’orientation ne 1’at pas. L’inverse est Bgalement vrai sur le plan haptique. La rbponse haptique apparalt bask sur la faGon dont la main et son activitt? prksentent des points de rkf&ence pour determiner une modification d’une partie focale de la figure. Zusammenfassung-Auge und Hand k&-men sich verschiedenen Teileigenschaften eina gleichen Objektes zuwenden, wobei die bevorzugten Eigenschaften des einen sich von denjenigen des anderen unterscheiden. Dieses m5gliche Verhalten Ii& sich such bei Kindem der Vorschule und der zweiten Klasse demonstrieren, wenn man sie fragt, welche von zwei Abtiderungen an gestalteten GegenstLnden die Form am wenigsten tidert. Im optischen Bereich ist in dieser Hinsicht eine KriimmungsZnderung signifikant, w&rend das fii eine Anderung der rlumlichen Anordnung nicht zutrifft. Die Verhaltnisse beim Tasten liegen dagegen ganz anders. Hier sucht die Hand Anhaltspunkte, ob ein kritisches Formdetail gelndert wurde.
1969, Vol. 7, pp. 365 to 373. Pergmon
Press. Printed in England
EYE AND HAND: DIFFERENTIAL SAMPLING OF FORM AND ORIENTATION PROPERTIES JACQUELINE J. G~~DNOW The GeorgeWashingtonUniversity, Washington,
D.C. 20006, U.S.A.
(Received 14 March 1969) Abstract--The eye and the hand may sample different properties of the same stimulus, with the properties most salient to one being different from those most salient to the other. This possibility is confirmed by asking children in kindergarten and second grade to judge which of two changes to a figure, both discriminable, leave the figure least changed. Visually, a change in curvature is highly significant, but a change in orientation is not. The reverse is usually true haptically. The haptic response appears based on the way the hand and its activity offer reference points for determining a change in a focal part of the figure.
WHAT is the difference between inspecting an object by eye and by hand? Answers to this question put us in a better position to understand both haptic perception-perception by active, exploratory hand movements-and the phenomena of cross-modal matching and transfer. One possibility is a differential responsiveness to the properties of a stimulus. Most properties are discriminable by both eye and hand, but the properties most salient to one may well be different from those most salient to the other. This kind of differential sampling of cues or properties has been proposed, in the area of problem solving, as an obstacle to seeing relationships between events [l]. The same kind of concept may well be useful for comparing visual and haptic responses to the same stimulus. In fact, such a concept is implied by several comments on cross-modal tasks. WILSONand SCHAFFER [2], for example, account for poor cross-modal transfer in terms of the eye and the hand attending to different parts of the same stimulus object. BJ~SRKMAN et al. [3] have altered the likelihood of transfer between vision and touch by leading Ss to pay attention to a property-color-that is sampled only by eye. And, as a general alternative to explanations stressing the separateness of modalities and the role of language, RUDEL and TEUBER[4] have suggested that the unravelling of cross-modal effects will depend on finding stimulus properties that favor the hand or are at least equally appropriate for eye and hand. In two recent studies, the spatial position of a stimulus appears as a property responded to differentially by eye and by hand, with the hand showing the greater responsiveness. With a Levine-type analysis of responses on a learning set task, WILSON[5] has reported for monkeys a predominance of responses haptically to the left or right position of an object as against a predominance of responses visually to the object’s shape. With human Ss from age six to adulthood, PICK and PICK [6] have reported that changes in the orientation of a figure are discriminated at an earlier age haptically than visually. In contrast, changes in a form property-curvature-were discriminable at an earlier age by eye than by hand. 365
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JACQUELINE J. G~~DNOW
In haptic studies, the most discriminable dimension is not always the one preferred in a choice situation (cf. [7]) so that the agreement between WILSON[5], and PICK and PICK [6] is especially interesting. The present study is a check and an extension of the study by PICK and PICK. As they point out, their visual-haptic comparison is in some respects an indirect one. The haptic results they obtained were compared with the visual results of a previous study [7] and the procedures for the two studies were not identical. The immediate aim of the present study is to determine whether the same differential response to orientation and curvature occurs when the visual and haptic procedures are made identical and when the measure of responsiveness is not the PICKS’measure of discriminability. The more general aim is to investigate the bases of haptic judgments. If the hand should be highly responsive to spatial position, for example, we have no ready-made explanation for why it should be. In fact, there is a general dearth of information on how haptic judgments are made, even though haptic activity is a phenomenon of clinical and theoretical interest, both in its own right and as a check on the generality of any results found with vision (cf. [8]). METHOD Material
The stimulus figures are illustrated in Fig. 1. The original figures were developed for a visual discrimination study by GIBSONet al. [9], and tactual equivalents of the visual outlines were first used by PICK and PICK [6]. The tactual equivalents were used throughout the TRANSFORMATIONS: STANDARD
;
SIZE
I
LEFT-RIOHT POSlTlON
CHANGES
IN
WVERTED C”R”*T”RE POS,TlW OF UNES
ll”LleER OF LINES
1
A
B
C
D
E
;
A
B
C
D
E
FIG. 1. Stimulus designs (from GIBBON et al. [9]). present study, for both the visual and tactual forms of the task. We used, however, only four of the original standards and five transformations of each. For each design, the five transformations cover a change in overall size, left-right position, “up-down” position (a rotation of 180” or 90” as needed to produce a different figure), curvature of lines and number of lines.
EYE AND
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367
Subjects
The main body of subjects consists of 74 children tested towards the end of second grade. The mean age was 8 : 2, with a range from 7 : 8 to 9 : 2. A smaller group of 30 children was tested at the end of kindergarten (mean age 5 : 10, range 5 : 4-6 : 1). At both age levels, children can tell that a standard and a transformation of the standard are not identical, a statement based on PICK and PICK’S [6] results and on an independent check for discriminability. For some kindergarteners, however, the haptic task was not easy, and the second-grade children were the better choice for the main sample. Both groups came from the same private school and both were well above average in performance on intelligence tests.
Procedure
On each trial, three figures-a standard and two transformations-were placed horizontally on a table in front of the child. Figures were secured in place by a strip of velcro. The standard was always on the child’s left, with the transformations to the side and with all figures about one and a half inches apart. On each trial, the child explored the standard figure, and then the transformations, and was asked to choose the transformation that was more like the standard. For the child, the standard was “the one that stays,” and the question was : “Which of these two is most like the one that stays?” In all, the child was told: “I am going to put some designs down here, for you to see (or feel). Here is a design (a standard). The one I put here will stay here all the time. Next to it I will put two others. They are like the one that stays, but not exactly like it. Each time I would like you to look at (feel) the one that stays, then the ones that are like it, and then tell me which one of the two over here is the most like the one that stays. This is the one that stays (E points or places the child’s hand on the standard), and these are the other two (E points or places the child’s hand). Look at (feel) the one that stays, then look at (feel) the other two, and tell me which of these two is the most like the one that stays”. Each trial carried this reminder to attend first to the standard and then to the other two designs, and a child was told to check all three forms if he gave a judgement after attending to only two. Apart from this restriction, Ss were free to choose their own method of visual or tactual scanning. In the tactual form of the task, the child was given some additional directions. He was told the object of the game was to see what his hands could do without his eyes, and he went through some preliminary tasks like finding his nose or ears with his eyes closed. The curtain under which he placed his hands was explained as a way of saving him from keeping his eyes closed all the time, and he was allowed to inspect the board with its velcro strip both with and without the curtain. In addition, the child was told that a design was made by a line on a metal square, and he was helped, if necessary, to find the first design. The procedure calls for paired comparisons. The ten trials cover the ten possible pairs of the five transformations, each transformation appearing four times, twice on the left and twice on the right. Most Ss were given only one design, with comparisons to be made either visually or haptically. A small group of Ss (fourteen of the second-graders) were given two designs, one visually and one haptically, but the double procedure was difficult for some children and was discontinued.
JACQUELINEJ. G~~DNOW
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RESULTS The major results are as follows: 1. Orientation and curvature are responded to differentially by the eye and the hand. In the haptic task, left-right reversals and up-down changes produce figures that are felt to be very unlike the original, even when children are aware that the figure has only been turned around. Visually, the same changes produce very little sense of change from the original. A change in curvature reverses the pattern : a sharp sense of difference from the standard visually and little sense of difference haptically. 2. We can suggest some basis for the haptic response to changes in orientation. Haptically, each design seems to be composed of a strong or focal part, plus some weaker or subsidiary parts. If the change in figure orientation changes the position of the focal part, the whole figure is felt to be changed from the original. But if the focal part is left unaltered, the figure itself is felt to be little changed. The precise method by which the hand picks up a change in the focal part is not clear, but the parts of the hand may provide a set of coordinate points, or the sequence of steps in tracing out the figure may act as a framework against which change can be readily detected. The general pattern of response to all transformations can be seen in Fig. 2. The figure shows, for the four designs combined, the mean number of times that second-graders chose each transformation as the more like the standard. z %
4
8
w 5
t
0
B
A
LEFT- RIGHT !‘OSlTlON
SIZE
(for
.--.
BY HAND
-
BY EYE
C INVERTED POSITION
D CURVATURE OF LINES
E NUMBER OF LINES
TRANSFORMATIONS four designs combined)
FIG. 2. For children in Grade 2, mean number of times a transformation is chosen as like the standard.
In Fig. 2, the visual and tactual judgments meet at some points and diverge on others. By both eye and hand, a transformation only in size is judged to be the most like the standard. Eye and hand are also fairly close together in their response to a change in the number of lines. On the other transformations, however, visual and haptic judgments diverge sharply. Left-right reversals, for example, are chosen visually as like the standard
EYE AND
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369
a mean 3.19 times out of a possible four. Haptically, left-right reversals are seldom chosen (the mean is 1.85 times). Inversions or rotations are also seldom chosen haptically (the mean number of times is 1.53), but the divergence from vision is less sharp, since up-down changes apparently give rise visually to a weaker sense of similarity than left-right reversals do (the visual mean is 2.38). For both left-right reversals and up-down changes, however, the difference between visual and haptic judgments is statistically significant (with a twotailed t test, p is <0401). So also is the difference in response to curvature (p is
Results are not identical for all designs, and Fig. 3 shows the main variations. The variability is most marked in the haptic response to changes in orientation, ranging from very little difference between visual and haptic judgments with either change in orientation (Design II), through a difference mostly on left-right reversals (Design I), to a difference on both left-right reversals and up-down changes (Design III). I
z
01.
f
A
o(PJ?
dd C
B
0
FIG.
3. By
BY HAND
-
BY EYE
LJCl!LD E
A. s)ZE : 8s LEFT-RIOHT: E - NUMBER
.--.
ABC
DE
TRANSFORMATIONS C * INVERTED: 0. CURVATURE
?m
D
OF LINES :
OF LINES
design,mean number of timesa transformationis chosen as like the standard.
The difference among designs is actually helpful. It leads to a definite hypothesis about the basis of the haptic response, viz. that the hand’s response to a change in the orientation of a figure is based on what happens to a focal or salient part of the figure. This hypothesis developed slowly,* and is essentially in two parts: first that the figure is responded to as made up of a strong or organizing part plus some subsidiary parts, and second that * Chronologically,the beginningwas with Design IV and kindergartenchildren. The task could be done by these very bright kindergartenchildren,but gave little pleasureto some of them. I shifted accordingly to second-gradechildren and found that the results still held up well for Design IV and also for DesignI. To replicate with still another design, I chose Design II and found, unexpectedly, little difference between visual and tactual judgments. The effects seemed to make sense when I looked at the comments of Ss and the figure parts that seemed “strong” or “focal”, and Design III was an attempt to locate ahead of time a figure with a clear focal part that would yield again a clear difference between the eye and the hand. The difficulty, one should note, is not so much in locating a focal part as in finding a figure where Ss quickly settle on the same focal part. Design III, incidentally, is a left-right reversal of the design as originally developed. It was turned around in the present study to allow the focal part to fall on the right-hand side of the figure for a change, since the focal parts of Designs I and IV had both turned out to lie on the left-
hand side.
370
JACQUELINEJ.GOODNOW
the response to the oreintation of the whole figure is determined by what happens to the strong or focal part. The presence of a focal part was indicated by several behaviors, by the way children explored the figure, the comments they made when they met a change in orientation, and the way they drew the standard figure at the end of the task. In each design, there appeared to be a part that Ss tried to locate first as a kind of home-base. When they could not find it in an expected place, they commented on its being “missing” or “in the wrong place”. And when they drew the design, they tended to draw this part first and with least error. In Design I, for example, the focal part haptically is the circle. After haptic experience, the design was often drawn as a circle first, with two tails that were separate and did not always emerge from the same point. After visual experience, the design was always drawn as a single, flowing line. For the other designs, the focal parts are the two parallel lines in Design II (for some Ss only the upper curve), the oval in Design III (for some Ss the total outside curve), and the vertical line in Design IV. How do these focal parts affect the hand’s response to a change in the orientation of a figure? To take Design I as an example again, the sense of difference from the standard is marked with a left-right reversal, less marked but still clear with an up-down change (Fig. 3). The focal part is the circle. A left-right reversal confronts S with the ends of two lines where he expects a circle, and, to locate all of the circle again, he must locate the final rounding of lines at the far right of the design. There were often comments that “the circle’s not in the right place” or that “I can’t find the circle.” An up-down change also shifts the circle, but less drastically. S finds at least one curve where he expects to find a circle, and the rest of it is closer to hand. In contrast, with Design II, the sense of difference from the standard is minimal with either change in orientation from the standard. The focal part is the pair of horizontal lines, sometimes both, sometimes only the upper curve, whose appeal seems to come from a niceness of fit to the width of a finger. A left-right reversal changes neither the position nor the curvature of either horizontal line. An up-down change alters the direction of curvature and the position of one line in relation to the other. But these are weak changes. They are not always discriminated (some Ss draw the horizontal lines as two equal, straight lines) and, where discriminated, not salient (a change in curvature elicits little sense of change on any design). The overall effect is one of little difference between the standard design and its upside-down version. Similar arguments can be applied to Designs III and IV. With Design III, the focal part is usually the oval and sometimes the total outside frame. Either focal part yields a sense of difference between the standard and either change in orientation. With Design IV, the focal part is the vertical line. A left-right reversal often brings such comments as “the line is missing” and a hunt to locate it before further exploration. An up-down change leaves the vertical line in the same position but changes its feel, often eliciting the comment that now “the line has a sharp point to it.” In short, what happens to the focal part is a highly feasible way of accounting for the response to the orientation of the whole figure. And without some knowledge of the focal parts in any particular set of designs, it would be hard to predict exactly what the response would be or to account for the variability from one design to another. It is critical to note that the child is well aware that the focal part is not the entire figure, and in fact many
EYE AND
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371
PROPERTIES
second-graders say explicitly that a left-right reversal or an inversion is the same figure “just turned around.” Nonetheless, the phenomenal sense of the figure being different still remains. The stability of the difference between eye and hand can be seen in Table 1. Table 1. Mean number of times that a transformation is chosen as more lie standard (range O-4); visually (V) or haptically (H)
Grade 2 All designs
Transformation
I
Grade 2, By design II III
IV
Iv*
the
Kindergarten IV
A. Size
V H
3.09 3.18
3.14 2.86
3.40 3.07
2.25 3.33
3.57 3.43
3.43 2.57
3.29 3.07
B. Left-right
z
3.19 1.85
3.43 1.43
2.90
2.33
3.50 1.63
3.00 1.71
3.14 2.14
3.14 1.64
c. “up-down”
V H
2.38 1.53
2.43 1.71
2.10 1.67
3.12 1.37
1.86 1.43
2.14 1.71
2.50 1.36
D. Curvature
:
0.87 2.45
0.71 2.29
1.20 2.20
1.13 2.87
0.29 2.29
0.57 2.86
0.64 2.21
E. Number of lines
:
0.47 0.98
0.29 1.71
0.40 0.73
0.00 0.80
1.28 1.14
0.71 0.71
0.43 1.71
N Us)
V H
32 44
10 15
8 15
7 7
7 7
14 14
7 7
* Visual judgments on IV preceded by tactual judgments on I. Factual judgments on IV preceded by visual judgments on I.
The same pattern holds throughout : similarity in response to changes in size and in number of lines, but difference in response to changes in curvature and orientation. The pattern holds for kindergarteners and second-graders, for children whose only experience is with one design, either visually or tactually, and for children who have seen or felt one other design before. The difference in response between eye and hand is clearly a stable and replicable one. DISCUSSION The results strongly substantiate PICK and PICK’S [6] report of a possible difference between the eye and the hand in judgements of curvature and orientation. The agreement is all the better for occurring with two different procedures: preferred basis of similarity in the present study, discriminability in the PICK and PICK study. The problem now is to account for the difference between eye and hand, or at least to account for why each is highly responsive to changes in one property of an object and relatively unresponsive to changes in another. For the hand, there is a single hypothesis that could be applied to judgments of both curvature and orientation. The critical factor in both cases could be the extent to which the hand and its activity offer reference points for judging a stimulus property.
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JACXXJELJNE J. G~~DNOW
In judging the curvature of an edge, for example, the hand itselt traces an arc, with the wrist, elbow or shoulder as the pivot. Ss might well have difficulty differentiating the curved stimulus line from the curved response movement, and practice in making the differentiation could account for the relatively rare result of more accurate judgments by blind than by sighted Ss [IO, 61. For judging orientation, the critical factor is the position of a focal part. But “change in position” implies the existence of some framework, and it is here that the hand and its activity appear critical. The hand can supply three possible frameworks: A framework of time, stemming from the sequence of parts that the hand encounters. This kind of framework is implied when Ss comment on when rather than where they find the focal part: “I can’t find that line and it’s usually the first thing I find.” A framework jiom the stimulus setting. Each design is on a metal piece about one and a half inches square, and the edges of the square are often encountered in the course of locating the design. It is possible to develop a sense of the usual distance of the focal part from the first edge encountered, and a change in this usual distance could signal a change in the orientation of the design or yield the sense of a different design. A framework provided by the hand itself. This is the kind of framework stressed in some Soviet approaches (cf. [I 1, 121). Using it, one might expect the fingers of the hand to serve as co-ordinates, points to which the landmarks or salient parts of the stimulus are referred. The asymmetry of the hand, probably together with the discreteness of the fingers, would help make the co-ordinates especially clear and discriminable. This kind of interpretation is particularly suggested by ANANYJZV’S stress on the role of co-ordinates in any spatial judgement and on the importance of “functional asymmetry” (cf. [12], pp. 185-206). For all three possibilities, the critical factor is the way in which the hand and its activity make it easier or harder to establish a useful set of coordinates or reference points. Ideally, one would like to be able to point to some similar features for vision, features that might help account for the reverse picture of greater responsiveness to curvature than to orientation. Such features, however, are by no means obvious at the present time. What we have for the moment is a viable hypothesis for the haptio judgments, and some data that takes us a step further in describing haptic perception and in unravelling crossmodal judgments. Haptic perceptions and productions, in REVESZ [13] terms, are more sums of separate parts than their visual equivalents are. To REVESZ’description, we can add the qualification that some parts are more important than others, and are responsible for judgements about the whole figure, in much the same way that GHENT [14] has argued for the role of focal parts in children’s judgments of the upside-downness of a figure. GHENT[14] is able, however, to specify what makes a part visually focal, and we are not yet able to do the same for haptic focal parts, short of observing the way a child scans and remembers a figure. As a working rule, one might look for the role of closed figures-circles, triangles, ovals-parallel lines and vertical lines, but this order of importance may not hold for other figures. For cross-modal effects, we have now some additional support for approaches in terms of a differential sampling of stimulus properties. The difficulties that occur in cross-modal matching, it has been suggested, may be not primarily a function of the modalities and their separateness, but a function of difference in the cues attended to [4]. One of the difficulties with this approach has been a dearth of evidence for a differential sampling of stimulus properties, evidence that begins to be supplied by the results of PICK and PICK [6], WILSON and SCHAFFER[2], WILSON[5], and the present study.
EYE AND HAND: DIFFEFSNTIAL SAMPLING OF FORMAND ORIENTAnoNPROPERTIES
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Acknowledgements-My largest debt is to ANNE and HERBERT~CK, for a provocative first study and a generous loan of stimulus material. I am also indebted to SHARONLARSONfor thoughtful assistance with Ss, and to LILA GHENT BRAINEfor helping to clarify a number of ideas. The research was supported by grants from the National Institute for Child Health and Human Development (IK03 HD36791, 1 ROl-HDO3105, and 1 TOl-HDOO203). The author’s address is the Department of Psychology; George Washington University; Washington, D.C. 20006.
REFERENCES 1. DUNCKER, K. On problem-solving. Psychol. Monogr. 58, 1-113, 1945. 2. WILSON, W. A., JR. and SCHAFFER,0. C. Intermodality transfer of specific discriminations monkey. Nature 197, 107, 1963.
in the
3. BJ~~RKMAN, M., GARVILL,J. and MOLANDER,B. Crossmodal transfer as a function of preparatory set and distinctiveness of stimulus aspects. Reports from Psychological Laboratory, Univ. Stockholm, No. 186, 1965. 4. RUDEL, R. and TEUBER, H. L. Crossmodal transfer of shape discrimination by children. Neuropsychologia 2, l-8, 1964. 5. WILSON, M. Tactual discrimination learning in monkeys. Neuropsychologia 3, 353-361, 1965. 6. PICK, A. D. and PICK, H. L., JR. A developmental study of tactual discrimination in blind and sighted children and adults. Psychonom. Sci. 6, 367-368, 1966. 7. GLINER, C., PICK, H. L., JR., PICK, A. D. and HALES,J. A developmental investigation of visual and haptic preferences for shape and texture. Monogr. Sot. Res. Child Dev. 1969, in press. 8. GIBSON,J. J. Observations on active touch. Psychol. Rev. 69,477-491, 1962. 9. GIBSON,J. J., GIBSON, E. J., PICK, A. D. and OSSER, H. A developmental study of the discrimination of letter-like forms. J. camp. physiol. Psychol. 55, 897-906, 1962. 10. HUNTER,I. M. L. Tactile-kinesthetic perception of straightness in blind and sighted humans. Q. JZ exp. Psychol. 6, 149-154, 1954. 11. PARACHEV,A. M. The algorithmic structure of active touch. Vop. Psikhol. 1,67-79,1963. (Translated
document published by U.S. Dept. of Commerce, JPRS # 19665.) 12. SHEMYAKIN,F. N. Orientation in space. In Psychological Science in the U.S.S.R., ANANYEV,B. G., KOSTYUK,G. S., LEONTYEV,N., LIJRIE, A. R., MENCHINSKAYA. N. A., RUBINSIFTEIN, S. L., S~~IRNOV, A. A., TEPLOV,B. M. and SHEMYAKIN, F. N. (Editors), pp. 186-255. Academy of Pedagogical Sciences, RSFSR, MOSCOW,1959. (Translation oublished bv U.S. Deot. of Commerce. JPRS # 11466.) 13. REVESZ,~G. PsychoIogy aid Art of the ‘B[ind. Lo&mans, Gieen, New York, ‘1950. -14. GHENT, L. Form and its orientation: a child’s eye view. Am. J. Psychol. 74,177-W, 1961. R&um&L’oeil et la main peuvent tbmoigner des diffkrentes propri&& du msme stimulus. les propri&ts les plus marquantes pour l’un &ant di&rentes de celles les plus marquantes pour l’autre. Cette possibilitC se trouve confirm&e lorsqu’on demande aw enfants du jardin d’enfants et d’kole du second niveau de juger laquelle des deux modifications apportks a une figure, toutes deux &ant discriminables, laisse la figure la moins chang&e. Visuellement, une modification de courbure est hautement significative, alors qu’un changement d’orientation ne 1’at pas. L’inverse est Bgalement vrai sur le plan haptique. La rbponse haptique apparalt bask sur la faGon dont la main et son activitt? prksentent des points de rkf&ence pour determiner une modification d’une partie focale de la figure. Zusammenfassung-Auge und Hand k&-men sich verschiedenen Teileigenschaften eina gleichen Objektes zuwenden, wobei die bevorzugten Eigenschaften des einen sich von denjenigen des anderen unterscheiden. Dieses m5gliche Verhalten Ii& sich such bei Kindem der Vorschule und der zweiten Klasse demonstrieren, wenn man sie fragt, welche von zwei Abtiderungen an gestalteten GegenstLnden die Form am wenigsten tidert. Im optischen Bereich ist in dieser Hinsicht eine KriimmungsZnderung signifikant, w&rend das fii eine Anderung der rlumlichen Anordnung nicht zutrifft. Die Verhaltnisse beim Tasten liegen dagegen ganz anders. Hier sucht die Hand Anhaltspunkte, ob ein kritisches Formdetail gelndert wurde.