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Reach on sound: A key to object permanence in visually impaired children

Elisa Fazzi a,, Sabrina Giovanna Signorini b, Monica Bomba a, Antonella Luparia b,Jose Lanners c, Umberto Balottin d

a Unit of Child Neurology and Psychiatry, Spedali Civili, Mother and Child Department, University of Brescia, Italyb Unit of Child Neurology and Psychiatry and Child Neuro-ophthalmology, IRCCS C. Mondino Foundation, University of Pavia, Pavia, Italyc Fondazione Robert Hollman, Cannero Riviera (VB), Italyd Unit of Child Neurology and Psychiatry, IRCCS C. Mondino Foundation, University of Pavia, Pavia, Italy

a b s t r a c ta r t i c l e i n f o

Article history:

Received 24 September 2010

Received in revised form 16 January 2011

Accepted 18 January 2011

Keywords:

Visually impaired children

Object permanence

Reach on sound

Cognitive development

Background: The capacity to reach an object presented through sound clue indicates, in the blind child, the

acquisition of object permanence and gives information over his/her cognitive development.

Aim: To assess cognitive development in congenitally blind children with or without multiple disabilities.

Study design: Cohort study.

Subjects: Thirty-seven congenitally blind subjects (17 with associated multiple disabilities, 20 mainly blind)

were enrolled.

Outcome measures: We used Bigelow's protocol to evaluate reach on sound capacity over time (at 6, 12, 18,

24, and 36 months), and a battery of clinical, neurophysiological and cognitive instruments to assess clinical

features.

Results: Tasks n.1 to 5 were acquired by most of the mainly blind children by 12 months of age. Task 6

coincided with a drop in performance, and the acquisition of the subsequent tasks showed a less

agehomogeneous pattern. In blind children with multiple disabilities, task acquisition rates were lower, with

the curves dipping in relation to the more complex tasks.

Conclusions: The mainly blind subjects managed to overcome Fraiberg's conceptual problem i.e., they

acquired the ability to attribute an external object with identity and substance even when it manifested its

presence through sound only and thus developed the ability to reach an object presented through sound.Instead, most of the blind children with multiple disabilities presented poor performances on the reach on

sound protocol and were unable, before 36 months of age, to develop the strategies needed to resolve

Fraiberg's conceptual problem.

2011 Elsevier Ireland Ltd. All rights reserved.

1. Introduction

In the construction of sensorimotor intelligence, vision is the most

important sense [13]. Vision allows the child to develop an

awareness of his external world: it is through vision that the child

learns to know and recognise his mother's face and acquires object

permanence and the earliest notions of causality.

The sensorimotor development of the blind child [46] differs

from the pattern that emerges in the normally-sighted child due to

the presence, in the former, of specific neuromotor and cognitive

difficulties [711]. In accordance with other authors, the mobility that

normally follows each postural achievement is considerably delayed

in blind children without multiple disabilities. A visual function deficit

implies difficulties developing an awareness of physical causality, of

spatial relations and, above all, of object permanence [4].

Fraiberg [12,13] maintains that the capacity to reach an object that

is presented through sound is, in the blind child, the behavioural

indicator of the acquisition of object permanence. Also in the

normally-sighted child, sound plays a developing role in the

construction of the object; since Piaget's stage 4, sound becomes a

more and more powerful cue in directing the child's active search for

the object [14]. While locomotion plays a necessary facilitative role in

the development of object permanence [15], motor achievements are

in turn supported by the progressive construction of the object

through sound. In a previous study we reported that the onset of self-

initiated mobility in blind children is related to the demonstration of

each child's ability to reach out and take an object presented by sound

clue alone. In particular, we observed that all of the subjects of our

group of blind children learned to walk independently only after

gaining the ability to find their bearings when guided by a sound [9].

Our survey provided further confirmation of the findings of Fraiberg

Early Human Development 87 (2011) 289296

Corresponding author. Tel.: +39 0303995724; fax: +39 0303995723.

E-mail address: [email protected] (E. Fazzi).

0378-3782/$ see front matter 2011 Elsevier Ireland Ltd. All rights reserved.

doi:10.1016/j.earlhumdev.2011.01.032

Contents lists available at ScienceDirect

Early Human Development

j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / e a r l h u m d ev
http://dx.doi.org/10.1016/j.earlhumdev.2011.01.032http://dx.doi.org/10.1016/j.earlhumdev.2011.01.032http://dx.doi.org/10.1016/j.earlhumdev.2011.01.032mailto:[email protected]://dx.doi.org/10.1016/j.earlhumdev.2011.01.032http://www.sciencedirect.com/science/journal/03783782http://www.sciencedirect.com/science/journal/03783782http://dx.doi.org/10.1016/j.earlhumdev.2011.01.032mailto:[email protected]://dx.doi.org/10.1016/j.earlhumdev.2011.01.032


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and Bigelow who demonstrated that reach on sound is the crucial

moment in terms of the blind child's access to the world of

representation, as well as being an activity that indicates the child's

readiness to achieve locomotion.

To deepen this aspect, Freiberg affirms that the blind child must be

able to overcome a conceptual problem in order to acquire thereach on sound capacity [13]: since, for the blind child, objects do

not possess the sensory and perceptible qualities which make them

recognisable to sighted children, in order to conceive of grasping anobject with a sound, he/she must manage without the merely visual

information relating to that object and form a mental image of it

[14,15]. From Fraiberg's descriptions [12,13], the acquisition of this

ability emerges as a significant moment in the development of the

blind child, being at once a condition of and a catalyst for all his

subsequent development. This is why it is particularly important to

promote reach on sound in theblindchild: it represents the solution

to Fraiberg's conceptual problem, guaranteeing the attribution of

substance even to objects that are presented exclusively through

sound.

The importance of reach on sound is analysed by Bigelow [14

16], who has developed an 11-item protocol specifically designed to

investigate the sequential development, in blind children, of the

ability to seek and reach objects presented through sound and tactile

clues. The progressive acquisition and mastering of these items appear

to be related to a growing awareness of object permanence in the

absence of sight. Furthermore, Bigelow establishes a correlation

between the Piaget's stages in the acquisition of object permanence

and the stages in the acquisition of reach on sound, suggesting that

the eleventasks in the reach on sound protocol reflect theprocess of

the acquisition of sensorimotor intelligence, and thus represent a

measure of cognitive development. In the presence of multiple

developmental disabilities this process of acquisition is likely to be

altered.

We set out to evaluate the development of the reach on sound

function in a sample of congenitally blind children without and with

other neuromotor and/or cognitive disabilities, paying particular

attention to differences and/or similarities in their acquisition of this

ability.

2. Methods

2.1. Sample description

The study sample was made up of 37 congenitally blind children,

consecutively referred to the Centre of Child Neuro-ophthalmology at

the C. Mondino Institute of Neurology in Pavia (Italy) for diagnostic

and therapeutic assessment. The Institutional Ethical Committee

approved the research project. The parents of all the enrolled children

signed an informed consent form in order to participate to the study.

Congenital blindness was diagnosed according to the International

Classification of Functioning, Disability and Health ICF [17];

cerebral visual impairment was defined according to Good [18,19].

2.2. Procedure

Visual impairment was assessed on the basis of clinical behaviour

(absence of any response to light or minimal perception of light, or

visual acuity less than 0.02, as evaluated using Teller Acuity Cards

[20]), and a neuro-ophthalmological assessment according to previ-

ous records [21]. In addition,all thesubjectsunderwent a neurological

examination and neurophysiological investigations (VEPs, BAEPs and

EEG) in order to establish whether their blindness was isolated or

associated with other neuromotor or sensory disabilities. The socio-

demographic and clinical features of the sample are detailed in

Table 1.

All the 37 subjects underwent the assessment of developmental

level through the administration of The ReynellZinkin Scales:

Developmental Scales for Young Visually Handicapped Children

[22]. For this study, we used the total scores and the cut-offs proposed

by the authors to qualify normal mental development, slight and

severe mental delay. Mental development was assessed at the follow-

up session of 12 months of age.On the basis of the results of the clinical and instrumental

examinations the subjects were divided into two groups (see Table 1):

Group I of blind children (10 males and 10 females) with a normal

mental development at the ReynellZinkin Scales and without

associated motor handicaps or focal signs at the neurological

examination. For brevity, we will call these subjects as mainly

blind; they are, indeed, children in which blindness, at the

moment of the evaluation, is the outstanding problem; the termmainly is used in order to not exclude the possibility of a future

development of a neuropsychological problem, but this kind of

handicap wasn't present at the evaluation time. We presume that,

in the first years of life, prior cognitive hitches might be present

but not yet describable.

Group II of children (7 males and 10 females) with associatedhandicaps (16 with cerebral visual impairment and 1 with Jubert

syndrome). There was clinical evidence of cerebral palsy with

developmental delay in 88% of the Group II subjects and of

developmental delay only in the remaining 12% (p=0.000; see

Table 1).

No child in either group showed hearing impairment at the BAEPs.

The subjects in Group I were first assessed at a mean age of

9.1 months (SD=5.1; range=424) and those in Group II at a mean

age of 10.8 months (SD=8.2; range=628). They were followed up

through longitudinal controls every three months for the period

ranging from the 6th to the 36th month of age, with all the children in

the two groups reaching the last follow up at 36 months. Infants were

tested individually, in the presence of their mother, in a dedicated

room in our Institution, by a familiar experimenter (always the same

Table 1

Socio-demographic and clinical features of the two groups.

Gr ou p 1 G roup 2 p

n= 20 n = 17

Gender: male n(%) 10(50%) 7(41.2%) n.s.

Gestational age: mean(S.D.) 38.9(0.8) 36.8(1.0) n.s.

Born: n(%) n.s.

At term 17(85%) 8(47.1%)

Moderately preterm 2(10%) 5(29.4%)

Severely preterm 1(5%) 4(23.5%)

Visual damage: n(%) n.s.

Complete bilateral blindn ess 10(50%) 9(52.9% )

Light perception 10(50%) 8(47.1%)

Type of visual damage: n(%)

Disord er s of ext er na l p art s of the eye 1( 5% ) 0

Retinal disorders

Leber's congenital amaurosis 12(60%) 0

Joubert syndrome 0 1(5.9%)

Retinal haemorrhage 1(5%) 0

Retinopathy of prematurity 1(5%) 0

Retinal dysplasia 1(5%) 0

Cerebral visual impairment 0 16(94.1%)

Optic atrophy 3(15%) 0

Norrie disease 1(5%) 0

Cognitive level (ReynellZinkin Scales): n(%) 0.000

Normal 20(100%) 0

Slight mental delay 0 4(23.5%)Severe mental delay 0 13(76.5%)

n.s. = not significant.

S.D. = standard deviation.

290 E. Fazzi et al. / Early Human Development 87 (2011) 289 296


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operator in all the control-sessions). Each follow up comprised an

interview with the parents, a neurological examination, ascertain-

ment of the achievement, or otherwise, of the main gross motor

milestones, a video-recording to explore the child's spontaneous

behaviour in the presence of the mother. The latter was performed

during a separate fifteen minute session of observation of both the

baby and his/her mother staying together.

2.3. Reach on sound protocol

In this study we focused on the ability to reach objects presented

through sound clue. This ability was evaluated through the Bigelowreach on sound protocol [16], the eleven tasks of which are

described briefly in Table 2. The sequence of tasks set out in the

protocol parallels the process of the acquisition of object permanence,

each task belonging, according to Piagetian thought, to a specific stage

in this process (Table 3).

In accordance with Bigelow's indications [16], the procedure was

explained to the mother, who was asked not to give any specific cues

to the child during the tasks. Nevertheless the mother was asked to

paraphrase the experimenter's verbalizations when appropriate or

necessary to elicit the best possible response from the child. The

infant was on the floor in a sitting position (with or without back

support, accordingly with the age and the motor development of the

subject).

Each task was tried to be presented for a minimum of 3 trials in

each session, with the exception of Tasks 1, 3, 5 and 7. We used

Bigelow's criterion for mastery to consider a task successful when

50% or more of the trials were correct at a certain follow-up time and

also at the subsequent control. The task was judged successful if the

infant reached directly to the toy used as the target and contacted it

without any scanning or groping movements. Reaches directly in the

direction of the toy or its sound which did not result in the child

securing the toy were also judged to be successful if the reaches were

off target by approximately 5 cm or less. Exceptions to this second

criterion for success were when the child had continuous tactile

contact with the toy (Task 1), there was continuous movement of acontinuously sounding toy (Task 4),or there were based on thechild's

first response to the trial presentation. All the tasks were presented in

the order described in Table 2 in all the follow-up sessions. The

children's responses to the tasks were scored from videotapes of the

sessions.

2.4. Reach on sound tools and targets

The stimulus toys used were the ones of the experimenter's and

were the same for all the subjects. Moreover, we asked the mother to

bring one or two familiar child's toys in order to optimise the

children's response to the tasks. As indicated by Bigelow's protocol

[16], mechanical-sounding toys (such as a buzzing robot or a music

box), manually operated sound toys (such as a hand bell and a giraffe

squeeze toy), and toys without sound (like a doll and a rubber ball)

were used. The children's toys used as targets were squeeze toys,

rattles, and stuffed sounding animals.

The toys used in the intermittent sound task (see Task 10 and 11)

were manually operated sound toys which were manipulated to

produce a sound approximately every 2 s.

A metal screen, 44 cm square cloths, and small pillows were used

as coverings for the stimulus objects in the cover object task 6.

2.5. Statistical analysis

Continuous variables were expressed as mean and standard

deviation (SD), and were compared using the parametric T-test.Categorical variables have been presented as counts and percentages

and compared with the test. A pb0.05 was considered statistically

significant.

The statistical analysis was performed using the statistical package

SPSS 13.0 (SPSS Inc. Corp., USA).

Table 2

Reach on sound protocol.

Task n. Tasks' description

1 Reaching of a non-sonorous object that touches the child's body

( continuous tactile stimulation in the absence of sonorous information)

2 Reaching of a sonorous object that wasfi

rst touched and then taken away while continuing to make a sound( tactile stimulation initially, followed by continuous sonorous stimulation)

3 Reaching of a sonorous object in a fixed position

( continuous auditory stimulation in the absence of tactile information)

4 Reaching of a moving sonorous object moved in a horizontal 180 arc around the head


5 Reaching of a s onorous o bject and of a no n-so norous object that the child has dropped (obse rva tion al test)

6 Reaching of a sonorous object concealed by a screen

7 Reaching of a sonorous object that designs a vertical arc


8 Reaching of a n on-sonorous object taken out of the child's hands an d positi oned in a s et poin t close to hi m

( discontinuous tactile stimulation in the absence of sonorous clues)

9 R eac hing of a sonor ous obj ec t p ulled aw ay f rom t he c hild a nd m oved in a horizont al a rc to one sid e while c ontinu ing to sou nd

( continuous auditory stimulation)

10 Reaching of an intermittently sounding object that designs a horizontal arc

( discontinuous auditory stimulation in the absence of tactile information)

11 Reaching of an object that sounds intermittently at fixed points in space

( discontinuous auditory stimulation in the absence of tactile information)

Table 3

Correlation between the 11 tasks in the reach on sound protocol and the stages in the

development of object permanence according to Piaget [16].

Reach on sound

task n.

Piaget stages Age of

acquisition

(months)

1 III: Start of object permanence 4/58/9

From 2 to 7 IV: Active searching for the object that has

disappeared but without taking into account its

series of visible movements

8/911

8 Transitional stage

From 9 to 10 V:The child nowtakesinto account the seriesof

visible movements of the object, but not yet its

invisible movements

11/1218

Completed protocol VI: The child has acquired the concept of object

permanence

1824

291E. Fazzi et al. / Early Human Development 87 (2011) 289 296


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3. Results

As regards the neuromotor development (Table 4), at the last

follow-up visit, the children in Group I showed a homogeneous

profile:all thesubjectshad acquired good head control, andthe sitting

and standing positions. Independent walking was achieved by 19 of

the Group I subjects (95%) by the end of the follow up, at a mean age

of 19 months (SD=8.7), at which stage the one remaining subject

(5%) had achieved only assisted gait. Of the 20 subjects in Group I, 9

didn't crawl (45%). Of the 11 remaining subjects, 4 (36.4%) achievedcrawling at a normal time, 3 (27.3%) crawled at the same time as

walking, 3 (27.3%) crawled after learning to walk independently and

one crawled but was not walking at 36 months.

A very different neuromotor profile, characterised by failure to

achieve, or markedly delayed achievement of, almost all the functions,

both postural and locomotor, emerged in the blind children with

associated multiple disabilities: four children (23%) did not achieve

postural control, seven (42%) acquired only control of the head (at a

mean age of 15 months), four children (23%) achieved the sitting

position at the mean age of 24 months, and two children (12%)

affected by a less severe form of cerebral palsy were able to stand at

the mean age of 26 months. Therefore, none of the Group II children

had acquired the ability to walk by the age of 36 months, when the

follow-up period ended.As regards the acquisition of prehension (Table 4), all the blind

children (100%) of Group I achieved bimanual grasp and (index)fingerthumb grasp at the mean ages of 6 and18 months respectively.

Like the acquisition of neuromotor functions, development of

manipulatory function was also found to be deficient in the blind

children with associatedhandicaps: prehension was absent in 65% (11

children) of the Group II and present, although inadequate (poorly

functional attempts that did not result in the complete grasping of the

object) in 12% of the cases (two children). Only 4 of the Group II

subjects(22%) acquiredbimanualgrasp, at the meanage of 24 months.

No member of this group acquired (index) fingerthumb grasp.

As regards mental development (Table 1), evaluated through

administration of the ReynellZinkin Scales [22], all the subjects of the

Group I showed normal development. In Group II, on the other hand,

mentaldevelopment seemedto be more impaired,with 23%(4 subjects)

presenting slight mental delay and 77% (13 subjects) severe mental

delay.As regards the acquisition of the items in the reach on sound

protocol, 70% (14 children) of the Group I subjects had completed the

protocol by the age of 36 months, as opposed to just 6% (one child) of

the Group II subjects. Fig. 1 shows the percentage of acquisition at

36 months at each task in the two groups. At each task, the statistical

difference between the groups is highly significant (pb0.001). In

particular, in Group I, one child (5%) had achieved all the tasks at

12 months, 4 children (20%) at 18 months, two children (10%) at

24 months, and seven children (35%) at 36 months of age. A further

15% of the Group I subjects (3 children) achieved all the items except

task n. 6, which the only two Group II children who completed a

reasonable proportion of the protocol (12% of Group II) also failed to

achieve. The remaining 15% of the Group I subjects (3 children)

achieved only the first few tasks in the protocol. These three children

were all affected by Leber congenital amaurosis and were character-

ised by behavioural and relational problems. Fig. 2 illustrates the

percentages of the Group I children who, at each of the ages

considered (6, 12, 18, 24, and 36 months), had mastered the various

tasks. It emerges that tasks n. 1 to 5 were acquired by most of Group I

children by the age of 12 months, whereas acquisition of the

subsequent tasks shows a less age-homogeneous pattern, partly as a

result of the greater difficulty of these tasks, a drop in performance

coinciding, indeed, with task n. 6. This drop in performance was also

seen in the Group II subjects (Fig. 3): in this group the overall trend

was similar to that observed in Group I (illustrated in Fig. 2) but the

task acquisition rates (percentages) were lower, with the curves

dipping in relation to the more complex tasks. Furthermore, at the

ages of 6 and 12 months, none of the Group II children had acquired

task n. 4 or above. Conversely, as illustrated in Fig. 2, zero acquisitionrates were recorded in the Group I subjects only at 6 months of age

and, even then, only in relation to the very last tasks in the protocol.

In Group II, two children (12% of the sample) achieved the first

three items, one child (6%) only the first task, and eleven children

(64%) none of the tasks. Of these eleven subjects, nine (52%) showed

reactions indicating alertness, and two (12%) no reaction.

In this group, only one child (6%) completed the protocol and the 2

children (12%) completed a reasonable proportion of the tasks

Table 4

Gross motor and fine motor abilities.

Group I Group II

No psychomotor acquisition 0 4 (23%)

Head control 20 (100%) 7 (42%)

Sitting 20 (100%) 4 (23%)

Standing 20 (100%) 2 (12%)

Walking supported 1 (5%) 0

Walking independently 19 (95%) 0

No prehension 0 11 (65%)Attempts at prehension 20 (100%) 2 (12%)

Bimanual grasp 20 (100%) 4 (23%)

Fingerthumb grasp 20 (100%) 0

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Task 1 Task 2 Task 3 Task 4 Task 5 Task 6 Task 7 Task 8 Task 9 Task10

Task11

Group 1 Group 2

Fig. 1. Percentage of acquired tasks at 36 months in the two groups. All the differences are highly significant (p= 0.000).



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administered; these subjects were all characterised by cerebral visual

impairment, cerebral palsy, and a slight mental delay. When

observing the acquisition of the main gross motor milestones, these

subjects were three of the less compromised in Group II. Only two

other subjects, who didn't complete the reach on sound protocol,

were characterised by a less profound psychomotor delay: one was

the subject affected by Jubert syndrome and the other one had a

severe mental delay at the ReynellZinkin Scales. Of the other 12

children who didn't complete the reach on sound protocol, one had a

severe psychomotor delay (he could stand seated autonomously just

1 2 3 4 5 6 7 8 9 10 11

6 months

18 months

36 months0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

TASK

6 months 12 months 18 months 24 months 36 months

6 months 20% 25% 15% 5% 5% 0% 5% 0% 0% 0% 0%

12 months 85% 85% 80% 55% 50% 5% 45% 15% 25% 20% 15%

18 months 95% 90% 85% 65% 65% 25% 75% 35% 60% 45% 30%

24 months 100% 95% 90% 80% 70% 35% 80% 45% 60% 50% 40%

36 months 100% 95% 95% 85% 85% 70% 85% 85% 75% 75% 75%

1 2 3 4 5 6 7 8 9 10 11

Fig. 2. Acquisition of reach on sound function in Group I.

1 2 3 4 5 6 7 8 9 10 11

6 months

18 months

36 months0%

20%

40%

60%

80%

100%

TASK

6 months 12 months 18 months 24 months 36 months

6 months 0% 6% 0% 0% 0% 0% 0% 0% 0% 0% 0%

12 months 11% 12% 11% 0% 0% 0% 0% 0% 0% 0% 0%

18 months 11% 12% 11% 11% 11% 0% 11% 6% 11% 0% 0%

24 months 22% 30% 22% 17% 22% 0% 17% 17% 17% 11% 11%

36 months 28% 30% 22% 17% 22% 6% 17% 17% 17% 11% 11%

1 2 3 4 5 6 7 8 9 10 11

Fig. 3. Acquisition of

reach on sound

function in Group II.



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for a few seconds at the age of 4 years) with a slight mental delay at

the developmental scales, two had a less serious psychomotor delay

(one reached the assisted gait at 20 months, one was able to stand at

23 months) and a severe mental delay at the Reynell Zinkin Scales, 9

had both an important psychomotor and mental delay.

Task n. 1 was the only one that all the members of the Group I had

completed by the age of 24 months (see Fig. 2). Moreover, children in

Group I mastered the tasks in sequence, except for tasks 6 and 8 that

were achieved at 36 months of age by the major part of the subjects,meanwhile the tasks n. 7, 9, and 10 were reached earlier.

4. Discussion

We found that the blind child's acquisition of the reach on sound

function shows a characteristic pattern. Most of the children observed

had completed the Bigelow protocol tasks by the age of 36 months,

but from the age of 12 months onwards a peculiar trend seemed to

emerge, characterised by a reduced frequency of achievement on

tasks n. 6 and n. 8 that persisted at follow ups conducted at the ages of

18 and 24 months, with a recovery of these performances not

appearing until the age of 36 months. Tasks n. 6 and n. 8 seemed to

be particularly complex for the blind child, given that they both

present a discontinuity of the tactile stimulus. In task n. 6, the

presence of a cover that hides the object, impeding tactile immediate

recognition and representing a new, unknown tactile substrate that

has to be recognised as a cover, seems to confound the subjects,

slowing the mastering of this task. In task n. 8, the difficulty is

represented by the presence of a discontinuous tactile stimulation in

the absence of sonorous clues. It seems that the discontinuity of the

tactile stimulus represents a specific difficulty for the mastering of the

tasks by the blind children. It is only a few months after acquisition of

the ability to walk independently through space, and thus after the

mean age of two years, that a child learns to know his external world

and develops the strategies needed to overcome these particular

challenges. This would also explain whyonly a smallpercentage of the

Group II children managed to complete the protocol, and in particular

to acquire tasks n. 6 and 8: the presence of a motor and/or cognitive

deficit challenges the child not so much by impeding his execution ofthe task, as by denying him the possibility of moving and gaining

experience of his external world, and thus of finding a solution to

Fraiberg's conceptual problem. In particular, we observed that

walking in Group 1 begun when the first 45 tasks at the reach on

sound protocol were achieved. This observation is in accord with

Bigelow's observations of three blind boys [14]. Children begun to

walk after they entered Piaget's stage IV.Independentgait seemsto be

favoured by the appearance of the child's active searching for the

object, activity that walking seems to support itself. This finding is in

accordance with the hypothesis that the relationship between object

knowledge and the advancement in locomotive skills is facilitative

also in the blind child [14], as it is proposed to be for the sighted

children [23]. Moreover, as observed in a recentstudy [9], congenitally

blind children rarely crawled before walking independently and oftenmissed out this stage altogether. In this aspect, they are similar to

shufflers or scooters who slide on their buttocks rather than crawl.

Even though the motor responses needed in order to perform task

n. 1 are the same as those required for task n. 3, from our results it

would appear that blind children find task n. 3 more difficult to

achieve than task n.1. Thus it might be deduced that a task involving a

continuous tactile stimulus is simpler to perform than one in which it

is the sonorous information that is continuous: in short, tactile tasks

are easier to perform, as suggested by Bigelow's findings [16].

The sameapplies to tasks n. 2 and 8. Again, these tasks demandthe

same motor behaviour in order to reach the object, but the first was

seen to be more easily achieved than the second, in which the object

was presented only through discontinuous tactile clues: this suggests

that sound gives to the blind child important information about the

object, such as its location and direction, clues that a purely tactile

stimulus that is discontinuous cannot give him. Indeed, in task n. 8,

the child is deprived of all contact with and information about the

object and this influences his attempts to find it. The fact that a

substantial percentage (40%) of children were able to perform this

task at 36 months could be an indication that the older child, despite

being deprived of tactilesonorous information relating to the object

when it is taken out of his hands, will still seek it, aware that it

continues to exist even though he is no longer able to perceive it. Thechildren's performances on task n. 8, however, demonstrate that

seeking of the target object is favoured by having previously had

tactile contact with it.

Task n. 4 proved to be very difficult to achieve, probably for two

reasons: one was the lack of tactile contact with the moving object (a

further demonstration of the importance of integration of tactile and

auditory information in the blind child's ability to reach and take hold

of an object), and second, the fact that the blind child, in this task, had

to show increased upper limb control andprecision in order to reach a

moving as opposed to a stationary object. The child's ability to locate

an object through sound improves as demonstrated by our findings

relating to the achievement of tasks n. 3, 4 and 7, which do not include

tactile clues. In these three tasks, the child is required to reach a

sonorous object that is first stationary (task n. 3) and that then moves

along the horizontal plane (task n. 4), and subsequently designs a

vertical arc(taskn. 7).Giventhat psychophysically it is easierto locate

sounds in the horizontal than in the vertical plane, the sequence in

which these three abilities are acquired reflects the psychophysical

principles of location by sound.

Tasks n. 5 and 9 require the child to reach a sonorous object that is

sounding in a position different from the one in which it had been

when he lost tactile contact with it. Children attempting these tasks

thus find themselves with contrasting tactile and sound clues, but

regardless of where they heard the sound coming from, our children

nevertheless sought the object in the place where they had lost

contact with it. Thus, even though blind children are able to respond

to sound clues, as shown by their achievement of task n. 2, in more

difficult tasks like these, which introduce contrasting information,

they can be seen to fall back on old reaching strategies guided bytactile clues. Thus we can affirm that sound clues facilitate the

reaching of the object, but only when they do not conflict with

tactile information. Furthermore, task n. 5 was apparently easier for

the children than task n. 9 thanks to their development and

application of behavioural rules for the retrieving of objects they

have allowed to fall from their hands: blind children will quickly learn

that if they drop an object, then they themselves must go down to

get it. Applying this rule, they do not need to postulate a spatial

construct, which, instead, is precisely what they do when the object is

taken from their hands as opposed to accidentally dropped (task n. 9).

At task n. 9, children stopped and entered in a state of quiet listening

to object movements. Their steps and gestures were guided by sound.

Task n. 6, the one most similar to the object permanence tests

administered to sighted children, was the one that all our blindchildren found hardest to achieve. The difficulty of this task lies in the

need to remove a cover that conceals the object, which goes on

sounding, from underneath the cover, for the entire duration of the

task: achievement of this task depends on the ability to separate the

means from the end. According to Piaget's description of the

development of object permanence, this ability is possible at 8

12 months (or the fourth stage of Piaget's model), despite the fact

that, at this age, the child's perceives the object as an extension of his

own action; in the subsequent stage (fifth stage: 1218 months), the

child will comprehend the permanence of the object only if he is able

to conserve a visible map of its movements. The blind child instead

has to rely on sound clues in place of this visual information, and only

a small proportion of our Group I subjects were able to perform the

task at the age of 18 months. Piaget indicates that at the sixth stage



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(1824 months) the child has acquired the concept of the object as

permanent, although the relatively small proportion (35%) of our

children who had achieved task n. 6 by the age of 18 24 months

would seem to highlight the particular importance of visual

information in the building of the concepts of object permanence

and of the permanence of the outside world.

Tasks n. 10 and 11, the ones associated with the fifth stage in the

development of object permanence according to Piaget, were the

abilitieswhoseacquisition wasmost delayed in our children.For blindchildren, objects that sound intermittently are particularly difficult to

reach, given that, when they fall silent, their location becomes

unpredictable; conversely, an intermittently sounding object that is in

motion is easier to locate, because the perception of its movement

allows the blind subject to predict or guess its position even when it

has stopped emitting its sound (task 10).

The difficulties encountered by the blind children of Group I in

performing the tasks of the reach on sound protocol did not seem to

be related to the mental development as measured by the Reynell

Zinkin Scales: in fact, all the subjects presented normal scores. The

three subjects of Group I with a Leber syndrome who achieved only

the first tasks of the reach on sound protocol presented relational

difficulties. A particular psychological fragility is described in some

children with Leber syndrome, characterised by withdrawn and

stereotyped behaviour, in the absence of a diagnosis of an autistic

spectrum disorder [24].

In Group II, most of the subjects possessed neither appropriate

manipulatory functions, nor the ability to reach an object presented

through sound; these children tended to use their hands as means of

self-stimulation more than as a means through which to gain

knowledge of the real world around them. These are behavioural

mannerisms that have been frequently described in congenitally blind

children with and without neurodevelopmental disabilities [24,25].

Upon the presentation of a sound stimulus, most of the subjects

demonstrated nothing more than aspecific reactions, indicating

alertness, or remained immobile; at the very most, they might make

some movement indicating excitement. The profile of acquisitions in

this group was found to be discontinuous andlacking in homogeneity,

and the results obtained were markedly low; however, in consideringthese low results it has to be recalled that the presence of motor

disabilities can preclude or render extremely difficult a subject's

attempts to reach thetarget objects. Forthe childrenin Group II, touch

continued to be the preferred sensory channel when seeking, and

attempting to reach,the targetobject,as demonstratedby thefact that

tasks n. 1 and 2 (involving tactile contact with the object) were the

only ones that a reasonable proportion of them were able to achieve;

moreover, these same tasks were also the ones most easily performed

by theGroupI children.The GroupII children,likethe GroupI subjects,

showed a trend of a lower performance on task n. 6. This finding, that

needsto beconfirmed by further studies,seemsto reveala pattern that

could be specific to severe visual impairment, not being influenced by

the presence or absence of an associated motor deficit.

In conclusion, the subjects affected by an isolated visual deficit,despite showing an initial and slight neuromotor developmental

delay, were able to develop good manipulatory skills and subse-

quently to walk independently, thanks in part to their acquisition of

the ability to reach an object presented through sound.

On the basis of theresults emerging from our administration of thereach on sound protocol, we are able to affirm that when comparing

tasks that differed only in the type of sensory information provided

(i.e., only tactile vs only auditory clues), the tactile tasks seemed to

be theones more easilyachieved: in particular, blind babiespresented

an attentional alert to sound, but seemed to prefer touch to orientate

their exploration. In fact, in the first months of life, our children

tended to reach objects that they had previously touched rather than

those that they had merely heard, and in the presence of conflicting

tactile and auditory clues, they responded first to the tactile

information, acquiring only subsequently the ability to use the

auditory information. Only in specific situations they found to

implement behaviours based on precise reaching modalities, like

the ones needed to perform task n. 5. At older ages, when sensorial

discrimination and multisensorial integration are more mature [26],

touch and sound seemed to guide the child in reaching the object in

like manner. The children whose blindness was associated with

psychomotor and/or mental delay presented, in most cases, severe

clinical pictures in which the delay, which usually persisted, alsoresulted in poor performances on the reach on sound protocol: the

subjects in this group rarely achieved, or achieved only with a very

marked delay, the ability to reach an object presented though sound.

The exploratory and learning techniques adopted by these subjects

continued to be rather primitive (the mouth playing a central role)

and their ability to move in space was often impeded by the difficulty

they had separating themselves from environmental points of

reference and contact. Thus, as we demonstrated in a previous

study [9], when the visual deficit is associated with other handicaps,

the result is a clinical situation of extreme gravity due to the fact that

each of the two pathological conditions seems to reinforce the other,

giving rise to severe psychopathological pictures. On the other hand,

the difficulties encountered in both groups (I and II) on task n. 6 (i.e.

reaching of a sonorous object concealed by a cover) may represent a

characteristic pattern of severe visual impairment and highlights the

particular importance of tactile information in exploring the outside

world and reaching the target objects.

In view of the important role that certain acquisitions play in

neuropsychological development, it is crucial that the blind child be

enabled to acquire through hisothersenses theknowledge thathe is not

permitted to acquire through sight. The acquisition ofreach on sound,

representing the solution to Fraiberg's conceptual problem, emerges

as a significant moment in the development of the blind child, being at

once a condition of and a catalyst for all his subsequent development.

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