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Locomotion and search behavior in blind infants
INFANT
BEHAVIOR
AND
DEVELOPMENT
Locomotion
15,
179-189
(1992)
and Search in Blind Infants ANN
Behavior
E. BIGELOW
St. Francis Xavier
University
The relationship between locomotion and object search wos longitudinally studted in blind Infants by exomining the timing between the emergence of crawling ond walking ond the infonts’ performance on reaching tasks indicative of advancement in obiect permanence. The children’s emergence of locomotor skills wos related to their development of oblect permanence despite developmental deloys in both abilities. Crowling occurred at opproximotely the some time os behaviors indicative of Stage 4 ond walking occurred during transition to Stoge 5 or subsequent to entry to Stage 5. Results suggest the relationship between object scorch and locomotion is focilitotive.
blindness
locomotion
obiect
oermonence
There has been increased interest in the relationship between advances in spatial encoding normally acquired during the second half of the first year of life and self-produced locomotion (Acredolo, 1978; Bertenthal, Campos, & Barrett, 1984; Bremner & Bryant, 1977; Harris, 1983). Locomotion has been proposed to be an epigenetic event which affects infants’ ability to successfully encode the spatial information necessary to advance in object permanence (Bertenthal et al., 1984). Self-produced locomotion appears to precede the acquisition of more successfulspatial encoding in most but not all studies (Rader, Bausano, & Richards, 1980; Richards & Rader, 1981). Much of the data to date has been interpreted as indicating that locomotion plays a facilitative role rather than a necessary role (Gottlieb, 1983) in the development of object permanence. Campos, Hiatt, Ramsay, Henderson, and Svejda (1978) found that search for a partially hidden object was frequently unsuccessful for prelocomotor infants but rarely so for locomotor infants of the same age. Horobin and Acredolo (1986) found that infants with more locomotion experience were less likely to show the AB error than agemates with This
research
was
aided
by Social
and
Behavior
Sciences
Research
Grant
No.
12-20
from
March of Dimes Birth Defects Foundation, by the St. Francis Xavier University Research Council, and by an equipment loan from the Nova Scotia Department of Social Services. Gratitude is expressed to the blind children who participated in the study and their families. Sylvia Keet, medical advisor to the project, and Bernadette MacLellan. Oona Landry, and Marie White, research assistants on the project. Correspondence Xavier University,
and requests for Antigonish, Nova
reprints Scotia,
should Canada
be sent to Ann B?G ICO.
E. Bigelow,
St.
Francis
179
180
BIGELOW
less locomotor experience. Kermoian and Campos (1988) found that infants with locomotor experience, whether crawling or walker assisted, were more advanced in object permanence performance than age-matched prelocomotor infants. Locomotion is thought to facilitate object search ability by increasing the infants’ opportunity for learning about objects and their constancy despite changes in perspective and orientation as well as by increasing the children’s visual attentiveness to objects by requiring the children to keep an eye on the object sought after during movement (Acredolo, Adams, & Goodwyn, 1984). Most of the research examining the relationship between locomotion and object search has focused on the onset of crawling. However, Zelazo (1984) has proposed that walking also is related to increased object knowledge. Learning to walk is generally thought to be related to physical maturation rather than cognitive advancement, yet cognitive changes in object use occur in synchrony with the onset of walking, and the timing of walking coincides with the acquisition of Stage 5 behaviors (Bayley, 1969). When two developments normally coincide in the timing of their acquisition, it is challenging to demonstrate the relationship between the developments (e.g., Loveland, 1984). A useful and under-used method of assessing the effect of the development of one skill on another is by restricting the development of one of the skills (Bertenthal, 1981). For human infants obvious ethical concerns prevent this from being done experimentally, yet one can study children for whom a skill, in this case, locomotion, is naturally delayed or restricted. The few reports of such investigations can be interpreted as supportive of the view that advancement in spatial encoding waits upon locomotion. Kermoian and Campos (1988) reported a study by Telzrow, Campos, Bertenthal, Barnard, Kermoian, Campos, and Benson with spina bifida infants who are normally delayed in locomotion. The infants’ ability to solve a two-choice hiding task improved only after locomotion, even when locomotion was delayed beyond the first year of fife. Bertenthal et al. (1984) reported testing spatial encoding in an infant who was in a full body cast due to an orthopaedic handicap. The child’s ability to choose the correct window in a two-choice spatial orientation task improved after the cast was removed and experience with locomotion occurred, although the body cast delayed locomotion only 1% months beyond the mean age at which crawling emerges. More data on spatial search performance from locomotor-delayed infants would help clarify the relationship between locomotion and object search. One group of such infants which is ideally suited to addressing this issue is blind infants. Self-produced locomotion is delayed in blind infants, yet they are not restricted in their limb movement nor is their limb development impaired by their handicap (Fraiberg, 1977). Many motor skills, such as sitting and standing, are attained at ages on par with their sighted peers, but motor skills having to do with mobility are delayed. Fraiberg (1977), who
LOCOMOTION
AND
SEARCH
BEHAVIOR
181
studied the motor skill development of 10 totally blind infants without other handicaps over a IO-year period, speculated that blind children are physically ready to locomote at ages similar to their sighted peers but do not do so because they have no visual incentive. The children do not move into space because they do not understand that objects exist in that space, objects to which they could gain access. Evidence for this speculation was that Fraiberg’s (Adelson & Fraiberg, 1974; Fraiberg, Siegel, & Gibson, 1966) children did not begin to become mobile until after they demonstrated reaching to sound cues, a behavior which Fraiberg took to indicate the emergence of Stage 4 object permanence. Thus, Fraiberg proposed that active search for objects suggestive of advancement in object permanence preceded locomotion rather than locomotion leading to advanced search strategies as proposed in the literature on sighted children. Because of the differences between the experience of blind and sighted children, caution should be used in comparing their spatial understanding and locomotor ability. Nevertheless, useful information can be obtained from more precisely mapping the relationship between locomotion and object permanence in blind children. Such information would provide a unique perspective on assumptions about development acquired from research with sighted children as well as provide a better understanding of the development of blind children themselves. For both blind and sighted children, there may be a cyclical relationship between self-produced movement and advancement in object knowledge. Both blind and sighted infants must know something about objects prior to reaching and subsequent locomotion, but blind children may need to rely more strongly on their cognitive understanding of objects and space to initiate these self-produced movements. For sighted children, the acquisition of reaching and locomotion is primarily visually motivated. These actions in turn lead to increased object knowledge and spatial understanding of the relationships between objects and how these relationships are transformed during movement. At a glance, sighted children are informed of the spatial relations among objects, and as the children move through space, they have access to immediate and simultaneous updating of the spatial relationships between objects and between objects and self. This increased knowledge and understanding further influences the children’s motivation to explore and locomote. Blind children are faced with the difficult task of having to learn about objects and their relations without visual information. For them, reaching and subsequent forms of locomotion may be delayed until certain cognitive understandings of objects and space are acquired. They may need to understand that objects exist in space independent of their tactual contact with them and that they, through their own actions, can be effective agents in acquiring these objects. The locations of and relationships among objects which sighted children see in a glance, blind children must learn sequentially, primarily
182
BIGELOW
through their own tactual discovery. As blind children learn more about objects and how to locate them in space, they become more motivated to explore and move into that space. Fraiberg said little about the development of locomotion per se other than to indicate that it followed reaching to sound cues and that typically both crawling and walking were substantially delayed compared to sighted children. She measured the critical behavior of reaching to sound by presenting sounding objects directly in front of the infants at chest level. In her later writing (Fraiberg, 1977), she noted with regret that she had not tested for reaches to other positions, but she suspected that such reaches would occur after chest-level reaches and may demonstrate later developments in object awareness. The present study investigates the relationship between locomotion and object search in totally blind infants by examining the timing of crawling and walking and mastery of an increasingly complex series of sound and touch tasks indicative of the advancement of object permanence. METHOD Subjects
Subjects were three boys born totally blind with no mental or other sensory handicaps. Their eye conditions were retinal dystrophy (1) and congenital optic nerve hypophasia (2). Their ages of referral to the study were 13, 17, and 32 months. They participated in the study for 13, 25, and 13 months, respectively. In the 3 years of the study, 16 children participated. Most, however, showed evidence of minimal vision and/or multiple handicaps and, therefore, did not meet the criteria of blindness from birth without other handicaps. Only the three children reported here met the criteria and completed the reaching study.’ Procedure The children were seen once a month in their own homes. Their locomotor abilities were observed on each session, and their parents were asked about new motor behavior observed since the previous visit. There was 100% agreement between the observation of new locomotor abilities and the parents’ report of the emergence of these behaviors since the previous visit. The development of the children’s reaching and search behavior has been reported in detail elsewhere (Bigelow, 1986). This development was studied by analyzing the children’s mastery of 10 sound and touch tasks. Below is a
I Two of the infants have grown to middle childhood and arc integrated into their neighborhood schools with normally sighted peers. Their academic performance has consistently been the upper half of their classes. The other infant died due to causes unrelated to his blindness.
in
LOCOMOTION
AND
SEARCH
BEHAVIOR
183
brief description of the tasks. The tasks are listed in the order in which they were mastered by the children. This order is based on the data rather than a priori predictions other than those taken from the findings of Fraiberg and her colleagues which were that tasks involving sounding objects pulled away from the children’s hands would elicit reaches before tasks involving sound cues alone. Task 1 Task
2
Task
3
Task
4
Task
5
Task
6
Task
7
Task
8
Task
9
Task
10
A toy was placed on the child’s body. On some trials, the toy was a silent toy and on others, it was a sounding toy. A sounding toy was taken away from the child and held in front of the child where it was pulled away. The toy continued to sound. A sounding toy was presented in a stationary position at chest level. A sounding toy was moved slowly in a horizontal 180” arc around the child’s head. The child was playing with a toy, and it dropped to the floor. The toy was either a silent toy or a sounding toy which continued to sound in its dropped position. A sounding toy was placed in front of the child and covered. The toy continued to sound from under the covering. A sounding toy was presented in a stationary position above the child’s head or below the child’s waist. A silent toy was taken away from the child and held in front of the child, where it was pulled away. A sounding toy was pulled away from the child and moved in a horizontal arc to one side, where it remained stationary. The toy continued to sound throughout the procedure. A sounding toy was intermittently sounded as it was moved through a 180” arc around the child’s head.
The tasks were presented to the children on their monthly home visits. The children’s responsesto the tasks were videotaped. A task trial was judged to be successful if the children reached directly to the toy without any scanning or groping movements on their first response to the trial presentation. An attempt was made to present each task for a minimum of three trials in each session. But because this was not always possible, a criterion for mastery of a given task was adopted in which 50% or more of the trials were judged to be successful on two successive sessions. The first session then became the mastery session. In trying to assesswhat the mastery of the tasks demonstrates about the development of object permanence in blind children, two approaches were taken: (a) The underlying cognitive abilities which the standard visual object permanence tasks demonstrate were examined and matched to similar underlying abilities in the present tasks, and (b) the performance of sighted children, whose level of object permanence was known, was examined on tasks similar to the present tasks. Such approaches suggestthat Task 1 was a Stage
BIGELOW
184
3 task, Tasks 2 through 7 were Stage 4 tasks, Task 8 was a transition task, and Tasks 9 and 10 were Stage 5 tasks. Rationale for the justification of the tasks as designating particular stage levels is presented in the original report of the data (Bigelow, 1986). RESULTS Table 1 shows the blind children’s ages for mastery of their locomotive skills, reaching to sound cues, and search behavior indicative of Stages 4 and 5 object permanence and the mean ages of acquisition of these skills for sighted children. The ages at which blind children mastered the tasks and abilities varied considerably, yet the sequential pattern of their mastery reveals a similar developmental progression. Child 1 showed the entire sequence of behavior. His performance indicates that the first locomotions occurred at approximately the same time as chestlevel reaches and emergence of behaviors indicative of Stage 4. Nine months elapsed between the time the child learned to crawl and when he learned to walk. Child 2 and Child 3 were already crawling, reaching to sound cues at chest level, and demonstrating behavior indicative of Stage 4 on their first session at ages 13 and 32 months, respectively. Child 3 also was reaching to sound cues in positions higher and lower than chest level on his first session: Child 1 and Child 2 reached for sound cues at chest level before they did so when the sounding objects were at positions higher or lower than chest level. For all three children, the latter reaching occurred before (or at approximately the same time as) they began to walk unsupported. All the children
Age
in Months
for Mastery
of the
Behoviors
TABLE 1 Locomotive Skills,
Indicative
of Stage
4 and
Reaching
to Sound
5 Obiect
Permanence
Children
Age
in months
when
first seen
Crawling Task 2: Stage 4 Task 3: Reaching
to sound
at chest
Task
to sound
higher
or lower
between
Stages
4 and
Task
7: Reaching level 8: Transition
Task 9: Stage 5 Walking unsupported Note. 0 Age b Age ‘Age
An asterisk taken from taken from taken from
indicates Bayley Flavell Wishart,
1
2
3
17 23
13 *
32 *
l
*
23 23
level than 5
Cues,
Age Children’s
and
Search
of Srghted Acquisition
,‘I
lo’
l
l
25 28 30
17 17 21
35 34
12b
32
17
36
12”
chest
the child showed mastery on the (1969). (1963). Bower, and Dunkeld (1978).
l
first session.
-
LOCOMOTION
AND
SEARCH
BEHAVIOR
185
learned to walk unsupported during transition to Stage 5 or subsequent to entry into Stage 5. Spearman rank correlations were done between the orders in which the blind infants mastered the skills. If tasks in which Child 2 and Child 3 showed mastery on their first session are included in the calculations as tie rankings, which indicate only that they were mastered for these children prior to the other tasks, then the correlations are .88 between Child 1 and Child 2, .91 between Child 1 and Child 3, and .71 between Child 2 and Child 3, all of which are significant at the .05 level or above (one-tailed tests of significance). It could be argued, however, that the tasks which showed mastery on the first session should be excluded from the calculations because the order of the acquisition of these skills for the children who mastered them is unknown. When these tasks are excluded from the calculations, the correlations are .70 between Child 1 and Child 2, .80 between Child 1 and Child 3, and .35 between Child 2 and Child 3. Based on one-tailed tests of significance, the correlations are significant at the .lO level, .lO level, and .35 level, respectively. Although the latter correlations are reduced, the correlations suggest that the children were unlikely to have acquired these skills in the order they did by chance alone. The mean ages of the acquisition of these skills by sighted children indicate some similarities to the developmental pattern of the blind children, although the ages of acquisition of the skills are different. For sighted children, crawling is followed closely by Stage 4 behaviors, and walking coincides with the onset of Stage 5 behaviors. Wishart, Bower, and Dunkeld (1978) studied children’s reaches to sound cues alone by presenting them sounding objects in the dark. They found evidence of early reaches at 4 and 5 months followed by a decline in reaching until about 10 months. The early reaches are likely the result of intersensory coordinations of sound and reach which become less integrated in early infancy. Later, when infants are in Stage 4, they respond to sound as specifying the existence of an object. Wishart et al. commented that reaches to objects in off-center positions were more difficult than reaches to objects in midline, suggesting that for sighted infants as well as blind infants, directional reaches to sound cues are more difficult than midline reaches. Further evidence that sighted infants must be in Stage 4 before they can search for objects to sound cues alone comes from studies in which children find objects which are surreptitiously hidden and then sounded (Bigelow, 1983; Freedman, Fox-Kolenda, Margileth, & Miller, 1969; Uzgiris & Benson, 1980). DISCUSSION The blind children’s emergence of locomotive skills appears to be related to their development of object permanence despite considerable age differences in the children. For Child 1, behaviors indicative of Stage 4 occurred at
186
approximately the same time as crawling, which is supportive of Fraiberg’s (1977) findings. All the children began walking unsupported during transition to Stage 5 or subsequent to entry to Stage 5. These results suggest that, for blind children, there is a sustained relationship between advancement in locomotive skills and object knowledge, a relationship proposed by Zelazo (1984) to exist in sighted children. Fraiberg (1977) found that reaching to sound cues at the midline was a precursor to initial locomotive skills which followed close behind. Without the aid of visual stimulation, reaching to sound cues may be one of the initial indications of blind children’s emerging knowledge that objects exist autonomously in space. Although blind infants gain knowledge of objects through their oral and tactual exploration, reaching is one of the first self-initiated acts which suggests their growing understanding,that objects exist independent of their physical contact with them. Reaching and locomotion may be on a continuum of behaviors having to do with blind children’s extension into space and which indicate their increased spatial and object awareness. As Fraiberg suspected, the ability to locate objects by sound at positions other than chest level developed later than the ability to locate objects by sound at chest level. Psychophysically this is predictable because it is more difficult to locate objects by sound in an up/down plane than in a right/left plane (Bower, 1977). These out-of-midline reaches occurred before or a? approximately the same time as the children learned to walk. Perhaps the children did not risk walking until they were secure in their ability to locate objects out of their midline plane, an ability which suggests an increased understanding of the location of objects autonomous from the children’s own body space and position. Walking is not the first locomotor skill, yet it is a distinctively significant ability in its own right (Jones et al., 1990). It frees the child’s hands so that the child can locomote, explore, and manipulate the environment at the same time. Also it typically produces parental delight with increased expectations and changed interactions between parent and child. A sighted child also gains a new visual perspective. For sighted children, usually there is about 5 months between learning to crawl and learning to walk. For Child 1, who learned both to crawl and to walk in the course of the study, 9 months elapsed between the acquisition of these skills. Fraiberg (1977) noted that the blind children she followed also typically had a longer interval between the learning of these two skills. To be sure, blind children lack the visual incentive of seeing others walk and then trying to model them. Yet it is interesting that blind children also appear to have a protracted Stage 4. There is evidence that initial self-produced locomotion in sighted children is related to Stage 4 behavior (Campos et al., 1978; Horobin & Acredolo, 1986; Kermoian & Campos, 1988). Although there are no specific studies on the relationship between the emergence of Stage 5
LOCOMOTION
AND
SEARCH
BEHAVIOR
187
behavior and learning to walk, sighted children typically learn to walk at approximately 12 months of age (Bayley, 1969), which coincides with the usual age of entry into Stage 5 object permanence (Flavell, 1963). With few exceptions (Zelazo, 1984), learning to walk has traditionally been thought to be related to physical maturation rather than cognitive advancement. However, blind children are as physically mature as their sighted peers, yet they are delayed in learning to walk and entry into Stage 5. Blind children know less about objects and space than their sighted peers. To release themselves from the security of locomoting by four-point tactile contact with the environment which crawling provides, the children have to be confident in their spatial/object awareness. They may need a Stage 5 knowledge of objects’ locations in space. Their lack of such knowledge may delay their attempts to locomote more freely. The results suggest that for blind children, the development of object permanence mediates advancement in locomotive skills. Thus, the relationship between object permanence and locomotion is facilitative. Although this conclusion supports the interpretation given to most of the research on locomotion and spatial awareness in sighted children, the epigenetic event appears to be different. In the literature on sighted children, locomotion is proposed to affect the increase of more spatial/object awareness. Fraiberg (1977) proposed that, for blind children, it is reaching and the object knowledge it implies which leads to locomotion. The present study supports Fraiberg’s proposal in that advanced search strategies lead to advanced locomotive skills. The discrepancy may be due to differences in the way in which blind and sighted children acquire spatial knowledge. For blind children, knowledge of the independent existence of objects, of how to locate objects, and that one can operate effectively in space and influence one’s environment leads to the extension of self into the world through locomotion. This is also true for sighted children, but sighted children acquire such knowledge easier and faster because of their visual abilities. They initially reach and locate objects on visual cues and are visually motivated to locomote. For both blind and sighted children, there is a cyclical relationship between self-produced movement and advancement in object knowledge. As sighted children move through the environment, their visual perspective changes, and they learn more about objects and space. For them, one of the major incentives for walking over crawling is that they can manipulate objects while moving and exploring their environment from various perspectives. For blind children, the cyclical relationship may be initially generated by advancement in object knowledge rather than self-produced movement. As blind children learn more about objects and how to locate them in space, they become more facile in locomotive skills and more motivated to explore. The data from blind and sighted children together suggest that the relationship between locomotion and object permanence can be mutually facilitative and is unrelated to age
188
BIGELOW
and maturation factors. Even in a population of children with very different perceptual experience and object/space awareness, locomotion and object permanence are linked. REFERENCES Acredolo, L.P. (1978). Development of spatial orientation in infancy. Developmemal Psychology, 23. 224-234. Acredolo. L.P.. Adams, A., & Goodwyn, S.W. (1984). The role of self-produced movement and visual tracking in infant spatial orientation. Journal of Experimenral Child Psychology, 38, 312-327. Adelson, E., & Fraiberg, S. (1974). Gross motor development in infants blind from birth. Child Development, 45. 114-126. Bayley, N. (1969). Bayley Scales of Infanf Developmem. New York: Psychological Corporation. Bertenthal, B.I. (1981). The significance of developmental sequences for investigating the what and how of development. New Direcrions for Child Developmenr, 12, 4%54. Bertenthal, B.I.. Campos, J.J., & Barrett, K.C. (1984). Self-produced locomotion: An organizer of emotional, cognitive, and social development in infancy. In R.N. Emde & R.J. Harmon (Eds.). Continuities and disconrinuities in development. New York: Plenum. Bigelow, A. (1983). The development of the use of sound in the search behavior of infants. Developmenral Psychology, 19. 3 17-32 I. Bigelow, A. (1986). The development of reaching in blind children. British Journal of Developmental Psychology, 4, 355-366. Bower, T.G.R. (1977). A primer on infant development. San Francisco: Freeman. Bremner, J.G., & Bryant, P.E. (1977). Place versus response as the basis of spatial errors made by young infants. Journal of Experimenral Child Psychology, 23, 162-171. Campos, J.J., Hiatt, S., Ramsay, D., Henderson, C.. & Svejda, M. (1978). The emergence of fear on the visual cliff. In M. Lewis & L. Rosenblum (Eds.), The developmem of affect. New York: Plenum. Flavell, J.H. (1963). The developmemal psychology of Jean Piaget. New York: Van Nostrand. Fraiberg, S. (1977). Insights from the blind: Compararive studies of blind and sighted infanrs. New York: Plenum. Fraiberg, S., Siegel, B., & Gibson, R. (1966). The role of sound in the search behavior of a blind infant. Psychoanalytic Study of the Child, 21, 327-357. Freedman, D.A., Fox-Kolenda. B.J., Margileth. D.A.. & Miller, D.H. (1969). The development of the use of sound as a guide to affective and cognitive behavior-A two-phase process. Child Developmenr, 40. 1099-l 105. Gottlieb, G. (1983). The psychobiological approach to developmental issues. In M.M. Haith & J.J. Campos (Eds.). P.H. Mussen (Series Ed.), Handbook of child psyrhology: Vol. 2. Infancy and developmenfal psychobiology (4th ed.). New York: Wiley. Harris, P.L. (1983). Infant cognition. In M.M. Haith & J.J. Campos (Eds.). P.H. Mussen (Series Ed.), Handbook of child psychology: Vol. 2. Infancy and developmemal psychobiology (4th ed.). New York: Wiley. Horobin. K., & Acredolo, L. (1986). The role of attentiveness, mobility history, and separation of hiding sites on Stage IV search behavior. Journalof Experimemal Child Psychology, 41. 114-127. Jones. D.. Biringen, Z.. Butterfield, P., Henderson, C., Robinson, N.. Aman, C., Emde, R.N., & Campos, J.J. (1990, April). Affective development and walking onset. In R. Telzrow (Chair). Locomotor experience and psychological development. Symposium presented at the meeting of the International Conference on Infant Studies, Montreal, Canada.
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AND
SEARCH
189
BEHAVIOR
Kermoian, R., & Campos. J.J. (1988). Locomotor experience: A facilitator of spatial cognitive development. Child Development, 59, 908-917. Loveland, K.A. (1984). Learning about points of view: Spatial perspective and the acquisition of ‘I/you’. Journal of Child Language, II, 535-556. Rader, N., Bausano. M., & Richards, J.E. (1980). On the nature of the visual-cliff-avoidance response in human infants. Child Developmenf. 51. 61-68. Richards. J.E., & Rader, N. (1981). Crawling-onset age predicts visual cliff avoidance in infants. Journal of Experimental Psychology: Human Perception and Performance, 7, 382-387. Uzgiris, I.C., & Benson, J. (1980, April). Infants’ use of sound in search for objecrs. Paper presented at the meeting of the lnternational Conference on Infant Studies, New Haven, CT. Wishart, U.G., Bower, T.G.R., & Dunkeld, J. (1978). Reaching in the dark. Perception. 7, 507512. Zelazo, P.R. (1984). “Learning to walk”: Recognition of high order influences. In L. Lipsitt & C. Rovee-Collier (Eds.), Advances in infancy research (Vol. 3). Norwood, NJ: Ablex. 11 October
1990; Revised
21 May
1991
n
BEHAVIOR
AND
DEVELOPMENT
Locomotion
15,
179-189
(1992)
and Search in Blind Infants ANN
Behavior
E. BIGELOW
St. Francis Xavier
University
The relationship between locomotion and object search wos longitudinally studted in blind Infants by exomining the timing between the emergence of crawling ond walking ond the infonts’ performance on reaching tasks indicative of advancement in obiect permanence. The children’s emergence of locomotor skills wos related to their development of oblect permanence despite developmental deloys in both abilities. Crowling occurred at opproximotely the some time os behaviors indicative of Stage 4 ond walking occurred during transition to Stoge 5 or subsequent to entry to Stage 5. Results suggest the relationship between object scorch and locomotion is focilitotive.
blindness
locomotion
obiect
oermonence
There has been increased interest in the relationship between advances in spatial encoding normally acquired during the second half of the first year of life and self-produced locomotion (Acredolo, 1978; Bertenthal, Campos, & Barrett, 1984; Bremner & Bryant, 1977; Harris, 1983). Locomotion has been proposed to be an epigenetic event which affects infants’ ability to successfully encode the spatial information necessary to advance in object permanence (Bertenthal et al., 1984). Self-produced locomotion appears to precede the acquisition of more successfulspatial encoding in most but not all studies (Rader, Bausano, & Richards, 1980; Richards & Rader, 1981). Much of the data to date has been interpreted as indicating that locomotion plays a facilitative role rather than a necessary role (Gottlieb, 1983) in the development of object permanence. Campos, Hiatt, Ramsay, Henderson, and Svejda (1978) found that search for a partially hidden object was frequently unsuccessful for prelocomotor infants but rarely so for locomotor infants of the same age. Horobin and Acredolo (1986) found that infants with more locomotion experience were less likely to show the AB error than agemates with This
research
was
aided
by Social
and
Behavior
Sciences
Research
Grant
No.
12-20
from
March of Dimes Birth Defects Foundation, by the St. Francis Xavier University Research Council, and by an equipment loan from the Nova Scotia Department of Social Services. Gratitude is expressed to the blind children who participated in the study and their families. Sylvia Keet, medical advisor to the project, and Bernadette MacLellan. Oona Landry, and Marie White, research assistants on the project. Correspondence Xavier University,
and requests for Antigonish, Nova
reprints Scotia,
should Canada
be sent to Ann B?G ICO.
E. Bigelow,
St.
Francis
179
180
BIGELOW
less locomotor experience. Kermoian and Campos (1988) found that infants with locomotor experience, whether crawling or walker assisted, were more advanced in object permanence performance than age-matched prelocomotor infants. Locomotion is thought to facilitate object search ability by increasing the infants’ opportunity for learning about objects and their constancy despite changes in perspective and orientation as well as by increasing the children’s visual attentiveness to objects by requiring the children to keep an eye on the object sought after during movement (Acredolo, Adams, & Goodwyn, 1984). Most of the research examining the relationship between locomotion and object search has focused on the onset of crawling. However, Zelazo (1984) has proposed that walking also is related to increased object knowledge. Learning to walk is generally thought to be related to physical maturation rather than cognitive advancement, yet cognitive changes in object use occur in synchrony with the onset of walking, and the timing of walking coincides with the acquisition of Stage 5 behaviors (Bayley, 1969). When two developments normally coincide in the timing of their acquisition, it is challenging to demonstrate the relationship between the developments (e.g., Loveland, 1984). A useful and under-used method of assessing the effect of the development of one skill on another is by restricting the development of one of the skills (Bertenthal, 1981). For human infants obvious ethical concerns prevent this from being done experimentally, yet one can study children for whom a skill, in this case, locomotion, is naturally delayed or restricted. The few reports of such investigations can be interpreted as supportive of the view that advancement in spatial encoding waits upon locomotion. Kermoian and Campos (1988) reported a study by Telzrow, Campos, Bertenthal, Barnard, Kermoian, Campos, and Benson with spina bifida infants who are normally delayed in locomotion. The infants’ ability to solve a two-choice hiding task improved only after locomotion, even when locomotion was delayed beyond the first year of fife. Bertenthal et al. (1984) reported testing spatial encoding in an infant who was in a full body cast due to an orthopaedic handicap. The child’s ability to choose the correct window in a two-choice spatial orientation task improved after the cast was removed and experience with locomotion occurred, although the body cast delayed locomotion only 1% months beyond the mean age at which crawling emerges. More data on spatial search performance from locomotor-delayed infants would help clarify the relationship between locomotion and object search. One group of such infants which is ideally suited to addressing this issue is blind infants. Self-produced locomotion is delayed in blind infants, yet they are not restricted in their limb movement nor is their limb development impaired by their handicap (Fraiberg, 1977). Many motor skills, such as sitting and standing, are attained at ages on par with their sighted peers, but motor skills having to do with mobility are delayed. Fraiberg (1977), who
LOCOMOTION
AND
SEARCH
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studied the motor skill development of 10 totally blind infants without other handicaps over a IO-year period, speculated that blind children are physically ready to locomote at ages similar to their sighted peers but do not do so because they have no visual incentive. The children do not move into space because they do not understand that objects exist in that space, objects to which they could gain access. Evidence for this speculation was that Fraiberg’s (Adelson & Fraiberg, 1974; Fraiberg, Siegel, & Gibson, 1966) children did not begin to become mobile until after they demonstrated reaching to sound cues, a behavior which Fraiberg took to indicate the emergence of Stage 4 object permanence. Thus, Fraiberg proposed that active search for objects suggestive of advancement in object permanence preceded locomotion rather than locomotion leading to advanced search strategies as proposed in the literature on sighted children. Because of the differences between the experience of blind and sighted children, caution should be used in comparing their spatial understanding and locomotor ability. Nevertheless, useful information can be obtained from more precisely mapping the relationship between locomotion and object permanence in blind children. Such information would provide a unique perspective on assumptions about development acquired from research with sighted children as well as provide a better understanding of the development of blind children themselves. For both blind and sighted children, there may be a cyclical relationship between self-produced movement and advancement in object knowledge. Both blind and sighted infants must know something about objects prior to reaching and subsequent locomotion, but blind children may need to rely more strongly on their cognitive understanding of objects and space to initiate these self-produced movements. For sighted children, the acquisition of reaching and locomotion is primarily visually motivated. These actions in turn lead to increased object knowledge and spatial understanding of the relationships between objects and how these relationships are transformed during movement. At a glance, sighted children are informed of the spatial relations among objects, and as the children move through space, they have access to immediate and simultaneous updating of the spatial relationships between objects and between objects and self. This increased knowledge and understanding further influences the children’s motivation to explore and locomote. Blind children are faced with the difficult task of having to learn about objects and their relations without visual information. For them, reaching and subsequent forms of locomotion may be delayed until certain cognitive understandings of objects and space are acquired. They may need to understand that objects exist in space independent of their tactual contact with them and that they, through their own actions, can be effective agents in acquiring these objects. The locations of and relationships among objects which sighted children see in a glance, blind children must learn sequentially, primarily
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through their own tactual discovery. As blind children learn more about objects and how to locate them in space, they become more motivated to explore and move into that space. Fraiberg said little about the development of locomotion per se other than to indicate that it followed reaching to sound cues and that typically both crawling and walking were substantially delayed compared to sighted children. She measured the critical behavior of reaching to sound by presenting sounding objects directly in front of the infants at chest level. In her later writing (Fraiberg, 1977), she noted with regret that she had not tested for reaches to other positions, but she suspected that such reaches would occur after chest-level reaches and may demonstrate later developments in object awareness. The present study investigates the relationship between locomotion and object search in totally blind infants by examining the timing of crawling and walking and mastery of an increasingly complex series of sound and touch tasks indicative of the advancement of object permanence. METHOD Subjects
Subjects were three boys born totally blind with no mental or other sensory handicaps. Their eye conditions were retinal dystrophy (1) and congenital optic nerve hypophasia (2). Their ages of referral to the study were 13, 17, and 32 months. They participated in the study for 13, 25, and 13 months, respectively. In the 3 years of the study, 16 children participated. Most, however, showed evidence of minimal vision and/or multiple handicaps and, therefore, did not meet the criteria of blindness from birth without other handicaps. Only the three children reported here met the criteria and completed the reaching study.’ Procedure The children were seen once a month in their own homes. Their locomotor abilities were observed on each session, and their parents were asked about new motor behavior observed since the previous visit. There was 100% agreement between the observation of new locomotor abilities and the parents’ report of the emergence of these behaviors since the previous visit. The development of the children’s reaching and search behavior has been reported in detail elsewhere (Bigelow, 1986). This development was studied by analyzing the children’s mastery of 10 sound and touch tasks. Below is a
I Two of the infants have grown to middle childhood and arc integrated into their neighborhood schools with normally sighted peers. Their academic performance has consistently been the upper half of their classes. The other infant died due to causes unrelated to his blindness.
in
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brief description of the tasks. The tasks are listed in the order in which they were mastered by the children. This order is based on the data rather than a priori predictions other than those taken from the findings of Fraiberg and her colleagues which were that tasks involving sounding objects pulled away from the children’s hands would elicit reaches before tasks involving sound cues alone. Task 1 Task
2
Task
3
Task
4
Task
5
Task
6
Task
7
Task
8
Task
9
Task
10
A toy was placed on the child’s body. On some trials, the toy was a silent toy and on others, it was a sounding toy. A sounding toy was taken away from the child and held in front of the child where it was pulled away. The toy continued to sound. A sounding toy was presented in a stationary position at chest level. A sounding toy was moved slowly in a horizontal 180” arc around the child’s head. The child was playing with a toy, and it dropped to the floor. The toy was either a silent toy or a sounding toy which continued to sound in its dropped position. A sounding toy was placed in front of the child and covered. The toy continued to sound from under the covering. A sounding toy was presented in a stationary position above the child’s head or below the child’s waist. A silent toy was taken away from the child and held in front of the child, where it was pulled away. A sounding toy was pulled away from the child and moved in a horizontal arc to one side, where it remained stationary. The toy continued to sound throughout the procedure. A sounding toy was intermittently sounded as it was moved through a 180” arc around the child’s head.
The tasks were presented to the children on their monthly home visits. The children’s responsesto the tasks were videotaped. A task trial was judged to be successful if the children reached directly to the toy without any scanning or groping movements on their first response to the trial presentation. An attempt was made to present each task for a minimum of three trials in each session. But because this was not always possible, a criterion for mastery of a given task was adopted in which 50% or more of the trials were judged to be successful on two successive sessions. The first session then became the mastery session. In trying to assesswhat the mastery of the tasks demonstrates about the development of object permanence in blind children, two approaches were taken: (a) The underlying cognitive abilities which the standard visual object permanence tasks demonstrate were examined and matched to similar underlying abilities in the present tasks, and (b) the performance of sighted children, whose level of object permanence was known, was examined on tasks similar to the present tasks. Such approaches suggestthat Task 1 was a Stage
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3 task, Tasks 2 through 7 were Stage 4 tasks, Task 8 was a transition task, and Tasks 9 and 10 were Stage 5 tasks. Rationale for the justification of the tasks as designating particular stage levels is presented in the original report of the data (Bigelow, 1986). RESULTS Table 1 shows the blind children’s ages for mastery of their locomotive skills, reaching to sound cues, and search behavior indicative of Stages 4 and 5 object permanence and the mean ages of acquisition of these skills for sighted children. The ages at which blind children mastered the tasks and abilities varied considerably, yet the sequential pattern of their mastery reveals a similar developmental progression. Child 1 showed the entire sequence of behavior. His performance indicates that the first locomotions occurred at approximately the same time as chestlevel reaches and emergence of behaviors indicative of Stage 4. Nine months elapsed between the time the child learned to crawl and when he learned to walk. Child 2 and Child 3 were already crawling, reaching to sound cues at chest level, and demonstrating behavior indicative of Stage 4 on their first session at ages 13 and 32 months, respectively. Child 3 also was reaching to sound cues in positions higher and lower than chest level on his first session: Child 1 and Child 2 reached for sound cues at chest level before they did so when the sounding objects were at positions higher or lower than chest level. For all three children, the latter reaching occurred before (or at approximately the same time as) they began to walk unsupported. All the children
Age
in Months
for Mastery
of the
Behoviors
TABLE 1 Locomotive Skills,
Indicative
of Stage
4 and
Reaching
to Sound
5 Obiect
Permanence
Children
Age
in months
when
first seen
Crawling Task 2: Stage 4 Task 3: Reaching
to sound
at chest
Task
to sound
higher
or lower
between
Stages
4 and
Task
7: Reaching level 8: Transition
Task 9: Stage 5 Walking unsupported Note. 0 Age b Age ‘Age
An asterisk taken from taken from taken from
indicates Bayley Flavell Wishart,
1
2
3
17 23
13 *
32 *
l
*
23 23
level than 5
Cues,
Age Children’s
and
Search
of Srghted Acquisition
,‘I
lo’
l
l
25 28 30
17 17 21
35 34
12b
32
17
36
12”
chest
the child showed mastery on the (1969). (1963). Bower, and Dunkeld (1978).
l
first session.
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learned to walk unsupported during transition to Stage 5 or subsequent to entry into Stage 5. Spearman rank correlations were done between the orders in which the blind infants mastered the skills. If tasks in which Child 2 and Child 3 showed mastery on their first session are included in the calculations as tie rankings, which indicate only that they were mastered for these children prior to the other tasks, then the correlations are .88 between Child 1 and Child 2, .91 between Child 1 and Child 3, and .71 between Child 2 and Child 3, all of which are significant at the .05 level or above (one-tailed tests of significance). It could be argued, however, that the tasks which showed mastery on the first session should be excluded from the calculations because the order of the acquisition of these skills for the children who mastered them is unknown. When these tasks are excluded from the calculations, the correlations are .70 between Child 1 and Child 2, .80 between Child 1 and Child 3, and .35 between Child 2 and Child 3. Based on one-tailed tests of significance, the correlations are significant at the .lO level, .lO level, and .35 level, respectively. Although the latter correlations are reduced, the correlations suggest that the children were unlikely to have acquired these skills in the order they did by chance alone. The mean ages of the acquisition of these skills by sighted children indicate some similarities to the developmental pattern of the blind children, although the ages of acquisition of the skills are different. For sighted children, crawling is followed closely by Stage 4 behaviors, and walking coincides with the onset of Stage 5 behaviors. Wishart, Bower, and Dunkeld (1978) studied children’s reaches to sound cues alone by presenting them sounding objects in the dark. They found evidence of early reaches at 4 and 5 months followed by a decline in reaching until about 10 months. The early reaches are likely the result of intersensory coordinations of sound and reach which become less integrated in early infancy. Later, when infants are in Stage 4, they respond to sound as specifying the existence of an object. Wishart et al. commented that reaches to objects in off-center positions were more difficult than reaches to objects in midline, suggesting that for sighted infants as well as blind infants, directional reaches to sound cues are more difficult than midline reaches. Further evidence that sighted infants must be in Stage 4 before they can search for objects to sound cues alone comes from studies in which children find objects which are surreptitiously hidden and then sounded (Bigelow, 1983; Freedman, Fox-Kolenda, Margileth, & Miller, 1969; Uzgiris & Benson, 1980). DISCUSSION The blind children’s emergence of locomotive skills appears to be related to their development of object permanence despite considerable age differences in the children. For Child 1, behaviors indicative of Stage 4 occurred at
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approximately the same time as crawling, which is supportive of Fraiberg’s (1977) findings. All the children began walking unsupported during transition to Stage 5 or subsequent to entry to Stage 5. These results suggest that, for blind children, there is a sustained relationship between advancement in locomotive skills and object knowledge, a relationship proposed by Zelazo (1984) to exist in sighted children. Fraiberg (1977) found that reaching to sound cues at the midline was a precursor to initial locomotive skills which followed close behind. Without the aid of visual stimulation, reaching to sound cues may be one of the initial indications of blind children’s emerging knowledge that objects exist autonomously in space. Although blind infants gain knowledge of objects through their oral and tactual exploration, reaching is one of the first self-initiated acts which suggests their growing understanding,that objects exist independent of their physical contact with them. Reaching and locomotion may be on a continuum of behaviors having to do with blind children’s extension into space and which indicate their increased spatial and object awareness. As Fraiberg suspected, the ability to locate objects by sound at positions other than chest level developed later than the ability to locate objects by sound at chest level. Psychophysically this is predictable because it is more difficult to locate objects by sound in an up/down plane than in a right/left plane (Bower, 1977). These out-of-midline reaches occurred before or a? approximately the same time as the children learned to walk. Perhaps the children did not risk walking until they were secure in their ability to locate objects out of their midline plane, an ability which suggests an increased understanding of the location of objects autonomous from the children’s own body space and position. Walking is not the first locomotor skill, yet it is a distinctively significant ability in its own right (Jones et al., 1990). It frees the child’s hands so that the child can locomote, explore, and manipulate the environment at the same time. Also it typically produces parental delight with increased expectations and changed interactions between parent and child. A sighted child also gains a new visual perspective. For sighted children, usually there is about 5 months between learning to crawl and learning to walk. For Child 1, who learned both to crawl and to walk in the course of the study, 9 months elapsed between the acquisition of these skills. Fraiberg (1977) noted that the blind children she followed also typically had a longer interval between the learning of these two skills. To be sure, blind children lack the visual incentive of seeing others walk and then trying to model them. Yet it is interesting that blind children also appear to have a protracted Stage 4. There is evidence that initial self-produced locomotion in sighted children is related to Stage 4 behavior (Campos et al., 1978; Horobin & Acredolo, 1986; Kermoian & Campos, 1988). Although there are no specific studies on the relationship between the emergence of Stage 5
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behavior and learning to walk, sighted children typically learn to walk at approximately 12 months of age (Bayley, 1969), which coincides with the usual age of entry into Stage 5 object permanence (Flavell, 1963). With few exceptions (Zelazo, 1984), learning to walk has traditionally been thought to be related to physical maturation rather than cognitive advancement. However, blind children are as physically mature as their sighted peers, yet they are delayed in learning to walk and entry into Stage 5. Blind children know less about objects and space than their sighted peers. To release themselves from the security of locomoting by four-point tactile contact with the environment which crawling provides, the children have to be confident in their spatial/object awareness. They may need a Stage 5 knowledge of objects’ locations in space. Their lack of such knowledge may delay their attempts to locomote more freely. The results suggest that for blind children, the development of object permanence mediates advancement in locomotive skills. Thus, the relationship between object permanence and locomotion is facilitative. Although this conclusion supports the interpretation given to most of the research on locomotion and spatial awareness in sighted children, the epigenetic event appears to be different. In the literature on sighted children, locomotion is proposed to affect the increase of more spatial/object awareness. Fraiberg (1977) proposed that, for blind children, it is reaching and the object knowledge it implies which leads to locomotion. The present study supports Fraiberg’s proposal in that advanced search strategies lead to advanced locomotive skills. The discrepancy may be due to differences in the way in which blind and sighted children acquire spatial knowledge. For blind children, knowledge of the independent existence of objects, of how to locate objects, and that one can operate effectively in space and influence one’s environment leads to the extension of self into the world through locomotion. This is also true for sighted children, but sighted children acquire such knowledge easier and faster because of their visual abilities. They initially reach and locate objects on visual cues and are visually motivated to locomote. For both blind and sighted children, there is a cyclical relationship between self-produced movement and advancement in object knowledge. As sighted children move through the environment, their visual perspective changes, and they learn more about objects and space. For them, one of the major incentives for walking over crawling is that they can manipulate objects while moving and exploring their environment from various perspectives. For blind children, the cyclical relationship may be initially generated by advancement in object knowledge rather than self-produced movement. As blind children learn more about objects and how to locate them in space, they become more facile in locomotive skills and more motivated to explore. The data from blind and sighted children together suggest that the relationship between locomotion and object permanence can be mutually facilitative and is unrelated to age
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and maturation factors. Even in a population of children with very different perceptual experience and object/space awareness, locomotion and object permanence are linked. REFERENCES Acredolo, L.P. (1978). Development of spatial orientation in infancy. Developmemal Psychology, 23. 224-234. Acredolo. L.P.. Adams, A., & Goodwyn, S.W. (1984). The role of self-produced movement and visual tracking in infant spatial orientation. Journal of Experimenral Child Psychology, 38, 312-327. Adelson, E., & Fraiberg, S. (1974). Gross motor development in infants blind from birth. Child Development, 45. 114-126. Bayley, N. (1969). Bayley Scales of Infanf Developmem. New York: Psychological Corporation. Bertenthal, B.I. (1981). The significance of developmental sequences for investigating the what and how of development. New Direcrions for Child Developmenr, 12, 4%54. Bertenthal, B.I.. Campos, J.J., & Barrett, K.C. (1984). Self-produced locomotion: An organizer of emotional, cognitive, and social development in infancy. In R.N. Emde & R.J. Harmon (Eds.). Continuities and disconrinuities in development. New York: Plenum. Bigelow, A. (1983). The development of the use of sound in the search behavior of infants. Developmenral Psychology, 19. 3 17-32 I. Bigelow, A. (1986). The development of reaching in blind children. British Journal of Developmental Psychology, 4, 355-366. Bower, T.G.R. (1977). A primer on infant development. San Francisco: Freeman. Bremner, J.G., & Bryant, P.E. (1977). Place versus response as the basis of spatial errors made by young infants. Journal of Experimenral Child Psychology, 23, 162-171. Campos, J.J., Hiatt, S., Ramsay, D., Henderson, C.. & Svejda, M. (1978). The emergence of fear on the visual cliff. In M. Lewis & L. Rosenblum (Eds.), The developmem of affect. New York: Plenum. Flavell, J.H. (1963). The developmemal psychology of Jean Piaget. New York: Van Nostrand. Fraiberg, S. (1977). Insights from the blind: Compararive studies of blind and sighted infanrs. New York: Plenum. Fraiberg, S., Siegel, B., & Gibson, R. (1966). The role of sound in the search behavior of a blind infant. Psychoanalytic Study of the Child, 21, 327-357. Freedman, D.A., Fox-Kolenda. B.J., Margileth. D.A.. & Miller, D.H. (1969). The development of the use of sound as a guide to affective and cognitive behavior-A two-phase process. Child Developmenr, 40. 1099-l 105. Gottlieb, G. (1983). The psychobiological approach to developmental issues. In M.M. Haith & J.J. Campos (Eds.). P.H. Mussen (Series Ed.), Handbook of child psyrhology: Vol. 2. Infancy and developmenfal psychobiology (4th ed.). New York: Wiley. Harris, P.L. (1983). Infant cognition. In M.M. Haith & J.J. Campos (Eds.). P.H. Mussen (Series Ed.), Handbook of child psychology: Vol. 2. Infancy and developmemal psychobiology (4th ed.). New York: Wiley. Horobin. K., & Acredolo, L. (1986). The role of attentiveness, mobility history, and separation of hiding sites on Stage IV search behavior. Journalof Experimemal Child Psychology, 41. 114-127. Jones. D.. Biringen, Z.. Butterfield, P., Henderson, C., Robinson, N.. Aman, C., Emde, R.N., & Campos, J.J. (1990, April). Affective development and walking onset. In R. Telzrow (Chair). Locomotor experience and psychological development. Symposium presented at the meeting of the International Conference on Infant Studies, Montreal, Canada.
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Kermoian, R., & Campos. J.J. (1988). Locomotor experience: A facilitator of spatial cognitive development. Child Development, 59, 908-917. Loveland, K.A. (1984). Learning about points of view: Spatial perspective and the acquisition of ‘I/you’. Journal of Child Language, II, 535-556. Rader, N., Bausano. M., & Richards, J.E. (1980). On the nature of the visual-cliff-avoidance response in human infants. Child Developmenf. 51. 61-68. Richards. J.E., & Rader, N. (1981). Crawling-onset age predicts visual cliff avoidance in infants. Journal of Experimental Psychology: Human Perception and Performance, 7, 382-387. Uzgiris, I.C., & Benson, J. (1980, April). Infants’ use of sound in search for objecrs. Paper presented at the meeting of the lnternational Conference on Infant Studies, New Haven, CT. Wishart, U.G., Bower, T.G.R., & Dunkeld, J. (1978). Reaching in the dark. Perception. 7, 507512. Zelazo, P.R. (1984). “Learning to walk”: Recognition of high order influences. In L. Lipsitt & C. Rovee-Collier (Eds.), Advances in infancy research (Vol. 3). Norwood, NJ: Ablex. 11 October
1990; Revised
21 May
1991
n