A new psychological test battery was designed toprovide a much-needed comprehensive tool forassessing the perceptual and cognitive abilitiesof visually handicapped children in using activetouch. The test materials consist of raised-line,raised-dot, raised-surface shapes and displays,and familiar and novel 3-D objects. The researchused 20 sub-tests, ranging from tactualdiscrimination, systematic scanning and shapecoding to short-term and longer-term memorytasks. The research sample consisted of 119participants. Fifty-nine were blind and visuallyimpaired schoolchildren, aged from 3 to 16 years(the total visually handicapped population of theregion), and 60 sighted school children, matchedto them on age, gender and social class, living inthe Madrid region (capital and province). Thedual aim here is to report the reliability, validityand relation to age and visual status of the sub-tests, and to use the data to refine and shortenthe test battery further for more general use.

Introduction

Despite more than a hundred years of research,psychometric tests for assessing perceptual andmental abilities in children and adults have beenconstructed mainly for sighted people. Tests basedon vision are not suitable for assessing blind andvisually impaired children whose perceptualexperience is haptic rather than visual. For thisreason there is an urgent need for an effectivepsychological instrument specifically designed toassess the development of blind children.

A research project was therefore undertaken thatwas designed to develop a new battery of haptictests for blind and sighted school children aged from3 to 16 years (Ballesteros and Bardisa, 2002). Theproject was supported by the Spanish NationalOrganization for the Blind (ONCE). The aim was tofill an important gap in the psychometric assessmentof these children, which would be useful forpsychologists and teachers concerned with theeducation of visually handicapped children.

Haptic perception depends on complementaryinformation from touch, active movement, and spatialcues, and depends on stimulus size and familiarity(Millar, 1994). Studies on active touch have shownthe importance of movements, and of systematicexploration for haptic perception (e.g. Berlá andButterfield, 1967; Gibson, 1962; Klatzky andLederman, 1987; Locher and Simmons, 1978). Thesub-tests were consequently designed to assessabilities in processing perceptual information fromhaptic surfaces, raised-dots, raised-lines, and 3-Dfamiliar and unfamiliar objects.

The battery of 20 tests also included short-termmemory span tests, and two longer-term recognitiontests for haptic spatial and shape information.

Criteria for the selection of sub-tests

The original battery included 20 sub-tests. The reasonsfor selecting the sub-tests are briefly set out below.

The first three sub-tests, here called manualdexterity, verbal regulation of movements, andcutaneous sensitivity, respectively, were adapted

© 2005 SAGE Publications The British Journal of Visual Impairment • Volume 23 • Number 1 • 2005 • ISSN 0264-6196 11DOI:10.1177/0264619605051717

The haptic test battery: A newinstrument to test tactualabilities in blind and visuallyimpaired and sighted childrenby Soledad Ballesteros, Dolores Bardisa, Susanna Millar and Jose M. Reales

from the Luria-DNI neuropsychological battery(Manga and Ramos, 1991). These sub-tests assesslow-level motor abilities and memory, and have beenused to detect possible cerebral malfunctioning(Levin et al., 1984). They were included in ourbattery for that reason.

The remaining sub-tests were designed by the firsttwo authors (Ballesteros and Bardisa, 2002).Perception of texture, of 2-D raised-line shapes, andof 3-D objects, as well as perception of their spatialorientation, and memory for familiar and for novelobjects, are major aspects of haptic perception andcognition (Ballesteros et al., 1999; Lederman, 1983;Millar, 1986). These factors were, consequently,included in a number of sub-tests.

Three sub-tests were designed specifically to assessthe detection of bilateral symmetry. Previousresearch had shown symmetry detection to be animportant differential factor in haptic perception. Thedesign of these three sub-tests was based onprevious studies with university students, which hadshown better detection of symmetry by blindfoldedsighted adults for 3-D objects, but not for smallraised-line shapes. The participants had judgedasymmetric raised-line shapes more accurately thansymmetric ones when using only one finger forexploration. Two-finger exploration increased thedetection of symmetry in raised-line shapes(Ballesteros et al., 1997). These findings wereconsistent with the results from a new series ofexperiments (Ballesteros et al., 1998) which used anindirect task. Detecting whether a small symmetric orasymmetric raised-shape was open or closedshowed greater accuracy for symmetric thanasymmetric shapes when scanning with two fingers,if the fingers had been aligned previously to the bodymidline for reference.

The ability to name objects explored by touch is animportant developmental step. Sub-tests usingnaming responses were, therefore, included in orderto identify possible learning deficits.

Three sub-tests in the last section of the batterytested immediate memory for series of discretehaptic items. Immediate (short-term or ‘working’)memory is needed to hold new information in mindfor seconds during the acquisition of new knowledge(Baddeley, 1986). Span tests of immediate memoryfor serial items are particularly important becausethey tap into the limits of the capacity to processinformation and to transform or re-code theinformation into more compact form (Miller, 1956).The span of immediate memory varies with the

modality and type of item and cognitive capacity(Millar, 1999). Purely tactual braille-like dot patternstend to produce very small memory spans unlessthey are quickly recoded into verbal (phonological)form (Millar, 1975), but there is little evidence forhaptic spans for larger dot patterns, or for series ofobjects, or series of movements. New span testswere, therefore, developed not only for dot patterns,but also span tests for 3-D haptic objects and for aseries of movements.

The final two memory sub-tests were designed toassess longer-term haptic recognition. Long-termmemory is important in retrieving knowledge, forschool learning, and for functioning in everyday life(Ballesteros et al., 1999; Reales and Ballesteros,1999). Tests of longer-term memory in the hapticmodality were, therefore, included in the test battery.

All sub-tests were designed to assess thedevelopment of these abilities from preschool levelsto the end of secondary school levels.

Short description of the sub-tests

This section provides a short description of thematerials and specific methods used in the sub-tests,numbered as they appeared in the battery of 20 sub-tests that were subjected to the analyses that we arereporting here.

1. Manual dexterity (Luria-type test): This sub-testcontains 10 items requiring the child to perform aseries of simple to complex movements imitatedfrom the movements executed by theexperimenter. As the child cannot use vision forimitation, the experimenter guides the hands ofthe child to touch the experimenter’s own hands,as she moves them. The first items require thechild to touch the fingers of the same handsequentially with the opposing thumb, first withthe right hand, then with the left hand, and thenwith both hands at the same time. Imitation ofmore complex finger movements follows. Thefinal items in this sub-test involve such manualactivities as pouring liquid into a cap and handwaving. The maximum score is 23.

2. Verbal regulation of movements (Luria-type test):This sub-test assesses the ability to follow verbalcommands. The child has to perform simplesequential movements by following verbalinstructions from the experimenter. Themaximum possible score is 14. According toLuria (1973), the ability to follow verbalinstructions depends on new cerebral

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Figure 1: Examples of some of the materials of the haptic test battery: (a) texture discrimination; (b) dimensional structure; (c) spatial orientation; (d) dot scanning; (e) graphs and diagrams; (f) symmetry (3-Dobjects, surfaces and raised-line shapes); (g) object naming; and (h) memory span (dots)

(a) (b)

(c) (d)

(e)(e)

(f) (f)

(g) (h)

connections that begin to direct children’sactivities from the age of about three to fouryears. Low scores beyond that age indicatesome brain dysfunction.

3. Cutaneous sensitivity and localization (Luria-typetest): This sub-test consists of seven items andhas a maximum score of 18. The child has todiscriminate different forms of passive touch. Forexample, the experimenter touches the child withthe blunt, or with the sharp, end of a pen. Thechild has to respond by saying ‘blunt’ or ‘sharp’.Similarly, in localization tests the child has to saywhere on the hand, arm or finger she is beingtouched. Some responses involve moving therelevant finger.

4. Material and texture discrimination: This sub-testconsists of two matching to sample tests(maximum possible score = 10). The materials inone test consist of six squares made,respectively, of wood, iron, sandpaper, cloth,rubber and cardboard. The child has to find thesquare that matches the one randomly selectedby the experimenter (Figure 1a). The otherconsists of five sandpaper rectangles of differenttexture densities. The child has to find the onethat matches the one selected by theexperimenter.

5. Figure–ground discrimination: This sub-testassesses whether the child perceives the figureas a whole, even if part of the stimulus figure ishidden or occluded by another shape. Thematerial consists of seven wooden plates,carved so as to appear to have (one to three)different shapes superimposed on each shapeon the board. The child has to name the shapeof each of the carved (exposed) shapes, even ifthe rest of that shape is (as if) concealed by asuperimposed shape. In five of the items thecarved figures are geometric shapes. The finaltwo test items consist of larger wooden plates,each with two realistic objects carved on them.The child is first shown smaller examples of thetwo objects carved on each of the two stimulusboards. The task is to name each of the shapes,whether or not it is partly concealed by the othershape. The maximum possible score is 7.

6. Dimensional structure: A matching-to-sample testwith six trials is used to assess whether the childcan use different haptic dimensions concomi-tantly. The materials consist of a series ofstimuli, which are identical to each other oneither one, two or three dimensions (shape, sizeand texture). The number of comparison stimuliin each of the six trial set varies from three toeight. On each trial, the experimenter places astimulus in front of the child and says: ‘Explore

this token and choose the one from amongyours that is the same as this one’ (Figure 1b).The maximum possible score is 14.

7. Spatial orientation: This sub-test measures theability to recognize the spatial orientation of ashape in tabletop space. The stimuli are raised-line shapes, organized in a booklet in whicheach page has a standard on the left side of thepage, and four comparison stimuli on the rightside (Figure 1c). The task is to find the shapethat has the same orientation as the standardfrom the four comparison shapes. The totalpossible accuracy score is 5.

8. and 14. Recognition of incomplete raised-lineshapes and 3-D objects: These two sub-testsassess the ability of the child to verbally identify(name), respectively, incomplete raised-lineshapes, and 3-D objects. In both cases the ideais to assess whether the child can name thedisplays although the shapes and objects areincomplete. There are six trials in each sub-test.Each correct answer for an item scores 1 point.The total possible accuracy score in each sub-test is 6.

9. Efficient dot scanning: This sub-test assessesthe ability to scan a dot-display exhaustively, soas not miss any dots. This ability is important asa precondition for learning to read braille. Thedot patterns are presented in an increasing orderof difficulty in the booklet (Figure 1d). In order toobtain a score (1 point) for each item, the childhas to point to all the dots on a page. Themaximum possible accuracy score is 6.

10. Graph and diagram scanning skills: This test wasinspired by work by Barth (1984). This sub-testhas three parts, each consisting of three items.The first part assesses the ability to scan araised-line continuously, without losing contact.The second assesses the ability to indicate thehighest and lowest point on a continuous zigzagline. The third part of the task is to find threepoints at different locations in a two-dimensionaldisplay. There are three trials. In each, thelocations of the stimulus dots are variedrandomly (Figure 1e). A correct answer scores1 point for each item. The maximum accuracyscore is 18.

11. 12. and 13. Symmetry detection (lines,surfaces, and 3-D objects): Each of these threesub-tests assesses the accuracy of detectingbilateral symmetry. The materials in sub-test 11consist of unfamiliar raised-line shapes. Thematerials in sub-test 12 consist of unfamiliarsurfaces. In sub-test 13, the materials are 3-Dobjects. The shapes in all three sub-tests arepresented in fixed positions. The three sub-sets

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were constructed by progressively extending thez-axis (Ballesteros and Reales, 2004) of figures(Figure 1e). The tests of symmetry detectionconsisted of the same nine symmetric and nineasymmetric stimuli for each type of material(raised-line shapes, raised-line surfaces and 3-Dobjects). In all the three tasks, participantsexplore the fixed shapes with both hands (Figure1f), and give a verbal response of ‘symmetric’ or‘asymmetric’. Each correct answer scores 0.5points. The maximum possible accuracy scoresin sub-tests 11, 12, and 13 are 8, 7 and 10,respectively.

15. Object naming: Adults are very fast and accuratein identifying familiar haptic objects by name(Ballesteros et al., 1999; Klatzky et al., 1985;Reales and Ballesteros, 1999). This sub-testassesses this ability in children, using 14 familiarobjects. The child explores each object haptically(Figure 1g) and names it. Each correct responsescores 0.5 points, with a maximum possibleaccuracy score of 7.

16. Dot span (short-term memory or STM) test: Spansub-tests consist of a series of items that thechild has to repeat immediately in the correctorder. Materials for the dot span sub-test consistof series of dominoes, which the child exploresfrom left to right. She then immediately namesthe number of dots in each domino in the dominosequence. The test starts with one domino. Thesequence of dominoes increases from one to six.There are two trials for each length sequence(Figure 1h). Testing stops when the child fails toreport the correct number of dots in each dominoin the correct sequence. The span size equalsthe number of dominoes in the last sequencereported correctly before failing. The maximumpossible is 6.

17. Object span (short-term memory or STM) test:The object span test consists of one to sixfamiliar objects. The method of testing isidentical to the dot span test with dominoes. Thespan size is the largest number of objects namedcorrectly in sequence before failing. Themaximum possible is 6.

18. Movement span (short-term memory or STM)test: The movement span test consists of repro-ducing a series of four movements demonstratedby the experimenter. The experimenter asks thechild to feel her hands while she performs themovement series in each case. The child thenhas to reproduce the same movementsimmediately in the correct sequence. The spansize equals the number of discrete movementsreproduced correctly in the correct sequence.The maximum possible is 4.

19. LTR (longer-term recognition) memory test forfamiliar objects: Longer-term recognition istested by interpolating a secondary task during afive-minute delay period before recall. In thelonger-term memory sub-test 19, the experi-menter displays six familiar objects on the tableand asks the child to explore them for threeminutes. The interpolated (or ‘distractor’) taskfollows immediately and lasts for five minutes. Itconsists of taking matches from a small box, andforming as many piles of two matches aspossible. If this interpolated task is completedbefore the five-minute delay is up, the interpo-lated task continues by producing piles of threematches. After the five-minute delay period, theexperimenter presents the previously studied sixobjects and six new objects in random order.The child explores all the objects, and tells theexperimenter whether the object she is touchingis ‘old’ (a previously studied object) or ‘new’ (notpreviously presented). The total number of trialsis 12 with objects presented in a random order.The maximum score is 6 (hits minus false alarms).

20. LTR (longer-term recognition) memory forunfamiliar objects: The second longer-termmemory sub-test uses eight 3-D plastic nonsenseobjects. Four of these objects are shown duringthe study phase (called ‘old objects’). The otherfour are interspersed randomly with the studiedobjects in the recognition (test) phase. The studyperiod allows 20-second exploration time foreach object. The interpolated (‘distractor’) taskconsists of transferring chips from one box toanother and back again until the five-minutedelay period is up. In the test period, thepreviously studied four objects (old objects) arepresented in random order with the four newobjects. As the child explores each object, shesays whether it is ‘old’ (presented during thestudy-phase) or ‘new’ (not presented before). Themaximum score is 4 (hits minus false alarms).

Method

Participants, materials and procedures

Participants were 119 schoolchildren. Of these 59were blind or visually impaired. The other 60 childrenwere sighted controls. The criteria for selecting theblind and the visually impaired children were that thechild was totally blind or only read braille. For pre-school children we obtained the nursery teacher’sprediction about the child’s need to learn braille. Onlychildren without known physical or psychologicalhandicaps, apart from the visual impairment, wereincluded.

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The control group consisted of sighted children whowere matched to each blind child on age, gender,social class, and school experience. The controlchildren were randomly selected from the sameschool as the blind in all cases in which the blindchild attended an integrated school. In other cases,the sighted children were selected from a school inthe same area and social class as the visuallyimpaired children. The children were drawn mainlyfrom the population living in the Madrid area. Tocomplete the blind and visually impaired sample,eight children who attended schools from theSpanish provinces of Seville, Valencia, and Alicantewere selected. For practical reasons, the relativelyfew blind children to whom the selection criteriaapplied were divided into six age groups (3–5, 6–7,8–9, 10–11, 12–13 and 14–16 years of age). Thesame age grouping consequently applied to thesighted (control) participants.

The materials selected for inclusion were preparedprofessionally by the Spanish National Organizationfor the Blind (ONCE). Throughout testing, thestimulus material was hidden from the child’s view bya cloth screen. Three carefully trained experimentersconducted the tests. Each child was testedindividually in a quiet room in his/her own school.

Results

Three types of statistical analyses were conductedon the scores. One tested the reliability of items foreach sub-test. The second was conducted toascertain the validity of the test battery in terms ofthe factors that it explained. The third type ofanalysis was needed to understand the effect of ageand visual status for each sub-test. Analyses ofvariance were, therefore, run for each sub-test withage (developmental index in terms of the six agegroups) and visual (blind or sighted children)condition as the important factors.

The results for the three types of analyses arepresented in turn in the following sections.

Reliability

Item analysesAn item analysis on the raw (number correct) scoresfor each item of each sub-test was carried out, usingCrombach’s α coefficient. The results showed that afew items in some sub-tests showed large discrep-ancies relative to the other scores in that particularsub-test. These items were consequently dropped asunreliable from further statistical analyses of therelevant sub-tests. The total number of items dropped

from further analyses in any sub-test were as follows:one item in sub-test 7; two items in sub-test 11; threeitems in sub-test 12; one item in sub-test 15.

The reliability for each sub-test was then calculated,using Crombach’s α coefficient. The coefficients(except for memory tests, because they required aunique score based on several trials, see earlier), areshown in Table 1.

The reliability coefficients ranged from 0.43(incomplete shapes) to 0.98 (cutaneous sensitivity).The coefficients for the sub-tests that were retainedhere for the final test battery (see later) showed avery satisfactory degree of sub-test reliability (0.54 to0.88) for the battery.

Construct validity

Factor analysis

A factor analysis was performed on the sub-tests tounderstand the underlying factors, and their validity

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Sub-tests Reliability coefficients

1. Manual dexterity 0.95

2. Verbal regulation of movements 0.93

3. Cutaneous sensitivity 0.98

4. Material and texture discrimination 0.65

5. Figure–ground discrimination 0.61

6. Dimensional structure 0.73

7. Spatial orientation 0.69

8. Incomplete shapes 0.43

9. Dot scanning 0.78

10. Graphs and diagrams 0.88

11. Symmetry (raised-lines) 0.54

12. Symmetry (surfaces) 0.57

13. Symmetry (3-D objects) 0.64

14. Incomplete objects 0.64

15. Object naming 0.73

Note: The reliability coefficients for the five memory sub-testswere not calculated because the score for each item in each of thesub-tests was unique although it was obtained from performanceon several trials with different strings (see text).

Table 1: Cronbach’s α coefficients (reliability) for15 sub-tests

in terms of the haptic abilities that we intended totest. The raw (accuracy) scores from all 119participants in all sub-tests (except the three Luria-type tests, which produced only maximum scoresand no variance) were subjected to this analysis. Thecorrelation matrix for all the sub-tests was calculatedfirst. The rotation of Normalization Varimax with‘Kaiser’ converges at 10 iterations. Six factors witheigenvalues larger than 1 were obtained. Theseexplained 70.56 per cent of the variance of the testscores. Table 2 shows the factorial weights of thesub-tests.

Factor I explained 20.3 per cent of the variance andwas labelled spatial comprehension. Table 2 showsthat it loaded highly on the sub-tests: spatialorientation (0.83), raised-line symmetry (0.73), objectsymmetry (0.72), surface symmetry (0.59), graphs and diagrams (0.60), and also on longer-term novelobject recognition (0.55) and dimensional structure(0.46).

Factor II explained 16.37 per cent of the variance,and was labelled short-term memory because itloaded on movement span (0.83), object span (0.77)

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Sub-tests Factors1 2 3 4 5 6

1. Manual dexterity These (ceiling level) scores did not enter into the analysis (see text)

2. Verbal regulation

3. Cutaneous sensitivity

4. Material and texture discrimination 0.54 0.81

5. Figure–ground discrimination 0.58

6. Dimensional structure 0.46

7. Spatial orientation 0.83

8. Incomplete shapes 0.64

9. Efficient dot scanning 0.84

10. Graphs and diagrams 0.60

11. Symmetry (raised-lines) 0.73

12. Symmetry (surfaces) 0.59

13. Symmetry (objects) 0.72

14. Incomplete objects 0.82

15. Object naming 0.76

16. Dot span (STM) 0.71

17. Object span (STM) 0.77

18. Movement span (STM) 0.83

19. LTR (familiar objects) -0.68

20. LTR (novel objects) 0.55 0.62

Total variance explained 20.30% 16.37% 9.18% 8.40% 8.31% 7.99%

Factors Spatial Short-term Object Raised-shape Sequential Longer-termcomprehension memory identification identification scanning coding for

(STM) new objects

Table 2: Factor analysis: Weights corresponding to six factors obtained from sub-tests scores

and dot span (0.71). The finding that the material andtexture discrimination sub-test also loaded (0.54) onthis factor, as well as on Factor VI, is considered inmore detail later.

Factor III explained 9.18 per cent of the variance. Itwas labelled object identification, because it loadedonly on incomplete object recognition (0.82) andobject naming (0.76), both of which involvedidentification by naming the objects.

Factor IV explained 8.40 per cent of the variance,and was labelled shape identification. It loadedpositively on incomplete shapes (0.64) and onfigure–ground discrimination (0.58), and negatively(–0.68) on longer-term recognition (LTR) of familiar

objects. The finding suggests that naming incompleteoutline shapes or incomplete solid (wood) shapes isbased quite differently from recognizing familiar 3-Dobjects as old or new (see later).

Factor V explained 8.31 per cent of the variance. Itwas labelled efficient exploration because it loadedsolely on efficient dot scanning (0.84), a task that isimportant for learning braille.

Factor VI explained 7.99 per cent of the variance. Itloaded on material and texture discrimination (0.81),and also on longer-term recognition of novel objects(0.62). Prima facie, the two sub-tests seem to involvevery different skills. However, unlike any of the othersub-tests, each of these sub-tests also loaded on

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Group Age Mat & Figure–Dimen. Spatial Incom. Dot Graph- Sym. Sym. Sym. Incom Object Dot Move LTR LTR LTRtext. grd. Struct. orient. shapes scan. diagr. lines surfac. 3-D obj. names span span famil. novel

Blind 3–5 6.63 6.40 11.29 2.43 1.78 2.60 9.0 4.29 3.38 5.63 5.29 5.79 1.88 2.38 1.89 4.89 1.13(0.92 (.89) (.95) (1.40) (.44) (1.65) (3.61) (1.70) (1.41) (1.51) (.76) (.64) (.99) (.91) (1.17) (1.62) (1.55)

6–7 6.56 6.11 12.63 3.00 2.70 3.50 10.8 5.70 3.90 6.80 5.56 5.61 3.11 3.78 2.89 5.9 2.72(.01) (.93) (1.30) (1.33) (.82) (1.35) (2.58) (1.70) (1.10) (1.40) (.73) (.92) (1.45) (1.78) (.78) (.32) (1.06)

8–9 7.11 6.67 13.22 3.78 3.00 4.11 14.63 6.33 5.56 8.44 5.44 5.92 4.44 4.22 3.56 6.00 2.67(1.36) (.50) (.97) (.97) (1.00) (1.76) (2.56) (1.12) (1.51) (1.24) (.73) (.56) (1.13) (1.39) (.73) (.00) (1.41)

10–11 7.57 6.67 13.41 4.00 2.78 4.70 14.70 6.20 5.70 8.00 5.90 5.83 3.80 4.50 3.60 5.50 2.50(1.93) (.50) (.83) (.82) (.83) (.95) (2.66) (1.87) (1.34) (2.12) (.32) (.50) (1.13) (1.27) (.52) (1.27) (1.27)

12–13 7.89 6.67 13.70 4.00 2.50 4.90 14.78 6.70 5.90 8.60 5.90 5.98 5.11 5.22 3.56 5.70 2.80(.32) (.71) (.67) (1.25) (.71) (1.45) (2.88) (1.25) (.99) (1.26) (.32) (.38) (1.05) (1.09) (.73) (.95) (1.48)

14–16 7.29 7.00 13.91 4.36 2.73 4.91 16.86 7.09 6.75 9.45 5.82 6.07 5.90 5.80 3.60 5.82 3.18(1.70) (.01) (.30) (1.03) (.79) (1.30) (1.72) (1.45) (.69) (1.21) (.60) (.23) (.32) (.42) (.70) (.60) (1.25)

Sight 3–5 6.67 3.60 9.50 1.17 2.00 1.00 1.64 3.00 3.00 5.00 5.29 4.85 1.30 2.00 0.80 3.33 0.22(.58) (1.78) (1.96) (.41) (.01) (.87) (4.13) (.01) (.01) (2.83) (.76) (1.27) (1.06) (1.25) (1.03) (2.83) (1.48)

6–7 6.22 5.11 12.20 2.00 2.00 2.60 7.28 4.11 3.44 6.56 5.89 5.81 2.90 3.80 2.90 5.56 1.22(1.30) (1.96) (1.40) (.82) (.01) (1.84) (2.58) (.60) (.88) (1.01) (.33) (.76) (1.20) (1.23) (.87) (.73) (.67)

8–9 6.56 5.89 13.22 2.67 2.00 4.22 12.89 5.56 4.67 7.89 5.67 5.89 3.33 4.11 3.33 6.00 1.78(1.13) (1.36) (1.39) (1.41) (.01) (1.56) (2.62) (1.59) (2.06) (1.36) (.71) (.59) (.87) (.93) (.87) (.00) (1.64)

10–11 7.33 6.30 13.30 3.00 2.00 3.80 14.61 5.80 4.40 8.40 5.60 6.15 4.50 5.10 3.60 6.00 2.60(1.50) (.95) (.95) (1.41) (.01) (1.75) (2.41) (1.14) (1.26) (1.65) (.70) (.34) (1.08) (.74) (.52) (.00) (1.27)

12–13 7.63 6.50 13.10 4.10 2.00 4.80 14.44 6.20 5.50 9.30 5.70 6.00 4.89 5.78 4.00 6.00 3.40(1.06) (.53) (1.91) (.99) (.01) (1.72) (1.03) (1.03) (1.27) (1.34) (.67) (1.16) (1.36) (.67) (.00) (.00) (.52)

14–16 7.22 6.00 13.40 4.20 2.00 5.11 15.19 6.33 5.78 8.78 5.89 6.28 4.50 5.60 3.90 6.00 3.00(1.20) (1.25) (1.07) (1.03) (.01) (1.36) (2.64) (.71) (.83) (.97) (.33) (.26) (1.18) (.70) (.32) (.00) (1.12)

Note: Mat & text. = material & texture discrimination; Figure–grd. = figure–ground discrimination; Dim. struct. = dimensional structure;Spatial orient. = spatial orientation; Incom. shapes = recognizing incomplete shapes; Dot scan. = efficient dot scanning; Graph-Diag. =graphs & diagrams; Sym. lines = detecting symmetry in raised-line shapes; Sym. surface = detecting symmetry in surface shapes; Sym.objects = detecting symmetry in 3-D objects; Dot span = short-term memory (STM) span for dot numbers; Object span = STM span forobjects; Move. span = STM span for movements; LTR fam. = longer-term recognition memory of familiar objects; LTR novel = longer-termrecognition memory for new objects. The three Luria-type ceiling level test (no variance) scores are not listed.

Table 3: Mean raw scores in the sub-tests (mean spans for the three span tests) and standard deviations (inbrackets) for blind and sighted children at the six age levels

another factor, which suggested that the factorexplained longer-term coding for new objects. Theinterpretation is discussed in some detail later.

Influence of age and visual condition

Visual condition and age were important factors inthis study, because the test battery was developedprecisely as an instrument that would assess thedevelopment of abilities involved in haptic perceptionand memory by visually handicapped children.

A two-factor analysis of variance was thereforecarried out on each sub-test, except for the threeLuria-type tests, which were dropped, because theyproduced maximum scores (no variance). TheANOVA for each sub-test was based on the numberof correct responses for each participant. Table 3shows the mean (raw) scores for the sub-tests(mean spans for the three span test), and thestandard deviations. Age (3–5, 6–7, 8–9, 10–11,12–13, and 14–16 years) and visual condition (blindand sighted) were between-subjects factors.

Analyses of variance

The ANOVA results are listed below in terms of theidentifying name (and original number) of the sub-test:

4. Material and texture discrimination: The ANOVAshowed a significant effect of age (F (5,84) =2.93, p < 0.05). Visual condition did not producea significant difference, nor was the interactionbetween age and visual status significant (p > 0.05, respectively).

5. Figure–ground discrimination: The ANOVAshowed a significant effect of age (F (5,109) =5.26, p < 0.001) and of visual condition (F (1,98)= 27.51, p < 0.001). The interaction between thetwo factors was also significant (F (5,98) = 2.69,p < 0.025). The interaction, graphed in Figure 2,resulted from a steep improvement with age bysighted children, who scored much more poorlythan young blind children until the age of about12 to 13 years. Beyond the age of 14 to 16performance by the sighted dropped againsignificantly (p < .015). The pattern of resultssuggests an effect of greater experience withtangible materials by the blind children,particularly in the early years, and again at theend of the school years.

6. Dimensional structure: The ANOVA showed asignificant main effect of age (F (5,102) = 17.09,p < 0.001) and a significant main effect of visualcondition (F (1,102) = 6.04, p < 0.001) and nosignificant interaction. All children improved with

age, but blind children received higher scoresthan the sighted.

7. Spatial orientation: The ANOVA showedsignificant effects of age (F (5,99) = 11.93, p <0.001) and of visual condition (F (1,99) = 11.86,p < 0.001). Performance on this sub-testimproved with age in both groups, and blindchildren performed better at all ages. There wasno significant interaction between the twofactors.

8. Incomplete shapes: The ANOVA for incompleteraised-line shapes showed no significant effectof age. Visual condition was significant (F (1,84)= 20.067, p < 0.001). There was no significantinteraction. Performance by the sighted childrenwas uniformly low at all ages. The blind werebetter, but without showing any markedimprovement with age. The fact that the sub-testdid not produce a significant age effect, as wellas its relatively low item-reliability (Table 1),suggests that this sub-test is best discarded fromthe test battery.

9. Efficient dot scanning: The ANOVA showed thatage was highly significant (F (5,105) = 12.83, p < 0.001). Performance improved significantlywith age. Visual status was just below significantlevel (p < 0.058). Blind children tended toperform marginally better at younger ages thanthe sighted. But the interaction between age andvisual condition was not significant. The resultsuggests an almost equal improvement insystematic exploration, based on factors that donot differ significantly between the blind andsighted.

10. Graphs and diagrams: The ANOVA showed asignificant main effect of age (F (5,93) = 37.139,p < 0.001) and a main effect of visual condition,

© 2005 SAGE Publications The British Journal of Visual Impairment • Volume 23 • Number 1 • 2005 • ISSN 0264-6196 19

Figure 2: Interaction between age groups and visualcondition found for the figure–ground discriminationsub-test

(F (1,93) = 21.59, p < 0.001). There was also asignificant interaction between age and visualcondition (F (5,93) = 3.76, p < 0.005), which isgraphed in Figure 3. Simple effects showedsignificantly better performance by blind thansighted children in the 3–5 age group (p <.006),and in the 6–7 year age group (p <.009). But thesighted improved to the same level as the blindafter these ages, so that the scores no longerdiffer significantly. The test should be useful as adiagnostic tool for instruction in the use ofraised-line diagrams and maps.

11. Symmetry detection (raised-line shapes): The ANOVA showed a significant effect of age (F (5, 94) = 7.77, p < 0.005) and of visualcondition (F (1,94) = 9.37, p < 0.005). There was no significant interaction. Performance byboth groups of children improved with age. Blind children performed better than sightedchildren at all age levels, suggesting that haptic experience is involved in the detection of symmetry by touch. The test promises well as a diagnostic tool.

12. Symmetry detection (surfaces): The ANOVAshowed a significant effect of age (F (5,95) =12.34, p < 0.001) and of visual condition (F (1,95) = 7.47, p < 0.001). The factors did notinteract significantly. Blind and sighted childrenimproved with age, but the blind scoredsignificantly higher than the sighted at all ages.The test also promises well as a diagnostic tool.

13. Symmetry detection (3-D objects): The ANOVAshowed a significant effect of age (F (5,94) =12.172, p < 0.001). Visual condition had nosignificant effect, and there was no interactionbetween the two factors. Blind and sightedchildren improved with age to achieve scoresnear ceiling level by the age of 13–14. Thissymmetry test also promises to provide an

effective diagnostic tool for assessing hapticperception of 3-D objects.

14. Incomplete 3-D object discrimination: TheANOVA for the incomplete object test showed nosignificant effects of age or of visual condition,and no interaction between these. The test wasevidently relatively easy for most participants.Since the sub-test has no discriminatory power itis best discarded from the test battery.

15. Object naming: The ANOVA showed a significantmain effect of age (F (5,94) = 3.70, p < 0.005).Visual condition had no significant effect, andthere was no interaction between the two factors.Both blind and sighted children improved with age.

16. Dot span (short-term memory or STM) test: TheANOVA significant effects of age (F (5,101) =27.52, p < 0.000) and visual condition, (F (1,101)= 6.208, p <.026). The interaction was just belowsignificance level (F (1,101) = 2.257, p < .054).Span sizes for the blind were larger, althoughnot consistently at all age levels (see Table 3).

17. Object span (short-term memory or STM) test:The ANOVA showed a significant main effect ofage (F (5,101) = 26.339, < 0.000). Visualcondition was not significant, and there was nosignificant interaction. The size of the immediatememory span for objects increased with age forboth blind and sighted children.

18. Movement span (short-term memory or STM) formovements: The ANOVA showed a significantmain effect of age (F (5,102) = 29.76, 18.436,p < 0.001). Visual condition was not significant.Span size increased with age for blind andsighted children. There was a significantinteraction between age and visual condition (F (5,102) = 2.49, p < 0.036). The interaction is

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3Figure 3: Interaction between age groups and visualcondition found for the graphs and diagrams sub-test

igure 4 Figure 4: Interaction between age groups and visualcondition found for the movement span sub-test

Age groups

Mea

n sc

ores

Age groups

Mea

n sc

ores

(co

rrec

t)

Visual condition

graphed in Figure 4. Simple effects showed thatyoung blind children aged 3–5 years achievedsignificantly larger movement spans than sightedchildren of that age (p <.006). Figure 4 showsthat movement spans by the sighted no longerdiffered from the blind after the age of 6–7 years,and were marginally larger than for the blindbeyond the age of 12–13 years.

19. Longer-term recognition (LTR) for familiar objects:The ANOVA conducted on hits minus false-alarmscores showed a significant main effect of age(F (5,104) = 6.936, p < 0.001). Visual conditionwas not significant, and there was no interactionbetween the two factors. Longer-term recognitionmemory for familiar objects increased steeply forblind as well as for sighted children until 6–7years of age. The test was evidently too easy forall age groups after that.

20. Longer-term recognition (LTR) for novel objects:The ANOVA on hits minus false-alarm scoresshowed a significant main effect of age (F (5,102)= 9.248, p < 0.001). The visual condition wasjust below significance level (F (5,102) = 3.774,p < 0.056). The interaction between the twofactors was not significant. Young blind children

produced marginally better scores before theage of 10–11 years. From 10 to 16 years of ageblind and sighted children did not differ.

The separate ANOVA results, reported above, werebased on raw scores for each sub-test (means inTable 3), to enable us to eliminate individual sub-teststhat failed to reach optimal criteria. Scoring methods(hence maximal scores) necessarily differed for thetasks required by different sub-tests (see descrip-tions). Table 4 enables the reader to compare relativecompetence levels in different sub-tests in terms ofproportions (raw accuracy scores achieved in a givensub-test as a proportion of the maximum scores thatwere possible in that sub-test). The mean span sizesfor the three STM tests are shown in Table 3.

Summary and discussion

The new haptic test battery of 20 sub-tests wasconstructed to fill an important gap in the assess-ment of blind children, by providing a psychometricinstrument that would be useful for professionals(teachers and psychologists) working with blindchildren (Ballesteros and Bardisa, 2002).

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Visual Age Mat- Figure– Dimen Spatial Incom Dot Graphs Sym. Sym. Sym. Incom Object LTR LTRcondition text. ground struct. orient. shapes scan & diag. lines surface objects objects name fam. novel

Blind 3–5 .57 .91 .75 .17 .30 .43 .50 .54 .48 .56 .88 .89 .81 .18

6–7 .61 .87 .84 .21 .45 .58 .60 .71 .56 .68 .93 .86 .98 .45

8–9 .71 .95 .88 .27 .50 .68 .81 .79 .79 .84 .91 .91 1.00 .44

10–11 .72 .95 .89 .29 .46 .78 .81 .77 .81 .80 .98 .90 .92 .42

12–13 .81 .95 .91 .29 .42 .82 .82 .84 .84 .86 .98 .92 .95 .47

14–16 .81 1.00 .93 .31 .45 .81 .94 .89 .96 .94 .97 .93 .97 .53

Sighted 3–5 .38 .51 .63 .08 .33 .17 .09 .37 .43 .50 .88 .75 .55 .04

6–7 .59 .73 .81 .14 .33 .43 .40 .51 .49 .66 .98 .89 .93 .20

8–9 .66 .84 .88 .19 .33 .70 .72 .69 .67 .79 .94 .90 1.00 .30

10–11 .71 .90 .89 .21 .33 .63 .81 .72 .63 .84 .93 .95 1.00 .43

12–13 .76 .93 .87 .29 .33 .80 .80 .77 .78 .93 .95 .92 1.00 .57

14–16 .95 .86 .89 .30 .33 .85 .84 .79 .83 .88 .98 .97 1.00 .50

Note: Mat.-text. = material & texture discrimination; Dimen. struct. = dimensional structure; Spatial orient. = spatial orientation; Incom.shapes = incomplete shapes; Dot scan. = efficient dot scanning; Graphs & Diag. = graphs & diagrams; Sym. lines = detecting symmetry inraised-line shapes; Sym. surface = detecting symmetry in surface shapes; Sym. objects = detecting symmetry in 3-D objects; Incom.objects = naming incomplete objects; Object name = naming familiar objects; LTR Fam. = longer-term recognition memory for familiarobjects; LTR novel = longer-term recognition memory for new objects.

Table 4: Proportions correct in each sub-test (span sizes are shown in Table 3) by blind and sighted children atthe six age levels

The present aim was to refine the test battery furtherfor more general use, as well as reducing the timeneeded to administer it, by retaining only the mostreliable and valid sub-tests that also assessed thedevelopment of the relevant haptic ability. Theimplications of the results on the reliability of sub-testitems, the construct validity of the sub-tests, and therole of age and visual condition in each of the 20sub-tests are discussed in turn.

The reliability of sub-test items, calculated byCrombach’s α coefficients, was very satisfactory. Thesub-test with the lowest reliability (incompleteshapes) needs to be dropped on other grounds (noage difference, see earlier), in any case. As notedearlier, the three Luria-type (based on Luria-DNItests) sub-tests were eliminated, becauseperformance was error-free (no variance) at all ages.They were thus not suitable for the present purposeand proposed population range either. The ‘no-error’finding is consistent with the use of these tests todetect cerebral malfunctioning (Levin et al., 1984).The finding also shows that the representativepopulation in the present study functioned within thenormal range of mental abilities.

The most interesting results, from the point of view ofthe construct validity of the test battery, and thepsychological interpretation of sub-tests, are thecombination sub-tests that load on different factors inthe factorial analysis, and the effects of age on thesesub-tests.

By far the largest number of sub-tests loaded onFactor I, which explained more than 20 per cent ofthe total variance of the scores. It was labelledspatial comprehension because all the sub-testsinvolved aspects of shape and spatial perception andcognition. Spatial orientation had the highest load(0.83). But the graph and diagram task, and thethree symmetry tasks, which were also designed totest spatial aspects of perception, loaded highly onFactor I too, thus validating that intention. Thedimensional structure test involved size and texture,as well as shape dimensions, which may explain itsslightly lower weight. However, the test also loadedonly on Factor I. The longer-term recognition of novelobjects sub-test loaded on Factor VI as well as on I,and is therefore considered further in relation to thatfactor later. Age was significant in all seven sub-tests, showing them to be valid also in assessing thedevelopment of the abilities that were involved (seeTable 4). The blind were better than the sighted infive of the tests. An interaction in the graphs anddiagram sub-test showed that only the younger blindchildren were better, and that sighted schoolchildren

caught up by the age of seven (see earlier). Takentogether, the results show that spatial processing isan important factor in haptic perception, and that thesub-tests under Factor I provide valid assessmentsof haptic spatial processing and development.

Factor II, labelled short-term memory, explained over16 per cent of the variance. It loaded most highly onthe dot span, object span and movement span sub-tests, which had been designed specifically to testimmediate short-term memory spans for haptic items.The material and texture sub-test also loaded onFactor II, suggesting a short-term memory componentin that task. However, since this sub-test loadedmore highly on Factor VI (0.81), it is considered inmore detail in relation to that factor later. All threespan sub-tests had significant age effects.

The dot span test depended on recalling thepreviously named number of dots in each domino insequence. The object span test depended onrecalling the names of the objects in sequence. Themean spans with age for dots and objects (Table 3)are quite similar, and resemble span sizes reportedfor in other studies. The finding is thus quiteconsistent with evidence that verbal/phonological re-coding increases immediate memory spans with ageand mental age (Baddeley, 1986; Conrad, 1971;Millar, 1975; Miller, 1956). The findings suggest thatthe span tests function similarly for haptic inputs. Dotnumbers were somewhat easier for the blind,probably due to school experience. There was nodifference in spans for objects. The new movementspan test is of particular interest, because it dependson reproducing series of discrete movements,instead of naming. The size of span scores wasconsistently lower than for dot or object span tests,except for the youngest blind. However, movementspans for the older sighted were close to the maximumpossible for this test (see earlier), possibly due to theuse of visualization. But that is speculative.

More important for the present purpose, all three newspan tests loaded on the same factor, and on noother factor, as well as producing age effect. Theythus provide valid developmental assessments oflimited processing capacity for different haptic tasks.The tests access the ability to maintain discreteitems in memory, which is an important factor inacquiring and manipulating new knowledge.

Factor III, or object identification, loaded highly onincomplete objects and on complete object naming.Both were easy naming tests. But since theincomplete objects sub-test did not discriminate onage (see Table 4), it is unsuitable for inclusion in the

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test battery. By contrast, although object naming wasalmost equally easy, it did produce significant ageeffects, and can thus be retained as a validdevelopmental test of the important skill of identifyinghaptic objects by name.

Factor IV was labelled raised-shape identificationbecause it loaded positively on figure–grounddiscrimination and incomplete shape discrimination,and loaded negatively (–0.68) on longer-termrecognition of familiar objects. Unlike the first twosub-tests, which both involved naming, the LTR testdepended on judging which familiar objects had justbeen presented before a delay period. Although agewas significant for that sub-test, it was too easy todiscriminate development beyond the 6–7 age level(see Table 4), and is, therefore, best eliminated. Theincomplete shape sub-test was unsuitable for theopposite reason. It was too difficult to discriminate onage, and thus needs to be dropped also. The figure–ground discrimination sub-test, which producedsignificant effects of age, visual status and aninteraction between these (see Figure 2), showedthat blind children were more competent at this task,and suggested that improvements by the sightedwere due to experience of tangible materials duringthe school years (see earlier). Since the ability toidentify raised shapes clearly differs from the abilityto identify familiar 3-D objects (Factor III), it needs tobe tested. The figure–ground discrimination sub-testprovides that assessment and indicates how itrelates to age and visual status.

The finding that efficient dot scanning, and no othersub-test, loaded highly on Factor V, and alsodistinguished significantly between age groups,shows that the sub-test assesses the ability to scanpatterns and lines of dots efficiently and exhaustively.The ability is important in learning braille, and alsonecessary for fast braille reading later (Millar, 1997).The development of this ability is clearly wellassessed by the sub-test.

Factor VI permits an intriguing insight into abilitiesthat seem to be associated with longer-termrecognition of novel objects. This sub-test loaded notonly on Factor VI, but also on Factor I (see earlier),which was identified as spatial comprehension.Furthermore, the highest load on Factor VI was formaterial and texture discrimination (0.81), which alsoloaded (0.54) on short-term memory (see Factor II,earlier). The link of Factor VI sub-tests with Factors Iand II implies that non-spatial discrimination, but alsospatial processes and immediate retention of items,are associated, in one way or another, with longer-term recognition memory for unfamiliar objects. There

is, in fact, some evidence that the recognition ofunfamiliar shapes by touch may depend initially asmuch on recognizing materials and textures as onspatial reference (Millar, 1997). However that may be,the fact that longer-term memory for unfamiliarobjects, as well as material and texture discriminationloaded on Factor VI, and produced age effects, sug-gests that these sub-tests assess important abilities inhaptic coding of novel objects. Factor VI was labelledlonger-term coding for new objects for that reason.

It is of considerable interest that five of the final sub-tests showed a main effect of visual status in favourof the blind (dimensional structure, spatialorientation, symmetry detection in raised-line and inraised surface shapes, and dot spans). Interactionsof visual status with age (figure–grounddiscrimination, graphs and diagrams, and movementspan), and tendencies to interactions (dot span andLTR for novel objects), showed the advantageparticularly at the youngest age levels. The oldersighted tend to catch up. The internal evidencesuggests the effectiveness of specific early trainingthat the blind children received at school.

We conclude that the final 14 sub-tests satisfy thefurther criteria of reliability, concept validity and ageeffects used here to shorten and refine the testbattery further. Seven sub-tests assess differentaspects of spatial comprehension. A further fourinvolve short-term or immediate memory, and include important new span tests. The remainingsub-tests assess object identification, shapeidentification, efficient haptic exploration and abilitiesinvolved in longer-term memory for new objects bytouch. This final battery of haptic tests will take lessthan an hour to administer. It should prove to be avery useful, as well as valid and reliablepsychometric instrument.

Acknowledgement

This research was supported by a grant from ONCE(the Spanish National Organization for the Blind).Elena Muñoz, Paloma Gómez and Marmia Díazparticipated with the data collection.

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Soledad BallesterosFacultad de Psicologia (UNED)Juan del Rosal 1028040 MadridSpainEmail: mballesteros@psi.uned.es

Dolores BardisaMinisterio de EducacionSpain

Susanna MillarOxford UniversityUK

Jose M. RealesUniversidad Nacional de Educacion a Distancia(UNED)Spain

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