Table Of ContentThe Role of Visual Experience
in Changing the Size of Objects
in Imagery Processing
Magdalena Szubielska and Bogusław Marek
Structured abstract: Introduction: This paper investigates the question of whether
or not subjects who are congenitally blind experience greater difficulties mentally in
resizing images of objects than those who have low vision or are adventitiously
blind. Methods: Two experiments were conducted: one in which subjects were asked
to mentally enlarge objects they previously explored manually, and one in which
subjects were tested for the ability to demonstrate the change in the size of an object
imagined to be moving away. Three groups of high school students with visual
impairments took part in the experiment: congenitally blind, “late blind,” and those
with low vision. Results: When showing the linear size of an object enlarged in their
imagination, congenitally blind participants overestimated its size more frequently
than those who were late blind. The degree of mental reduction of the size of an
object imagined to be moving away was comparable for all groups. Discussion: The
results suggest that the difficulties experienced by congenitally blind participants
with the mental resizing of objects may be related to problems with performing
mental scaling transformations. In the low vision group, the etiology of the subjects’
visual impairment was not taken into consideration. The group turned out to be
heterogeneous with respect to imagery processes. Implications for practitioners:
When using models for explaining new concepts, it is important to ensure that
congenitally blind learners understand the change of scale.
T
he influence of visual experience on stood. Although numerous experiments
spatial imagery is still not fully under- have been interpreted as showing consid
erable limitations in the functioning of
imagery processes in people who are to
This work was supported by the Ministry of
tally blind, especially those who were
Science and Higher Education, Republic of Po
land, grant no. N N106 279339. The authors born blind or had early onset of blindness,
would like to thank the anonymous reviewers there are studies suggesting that no sig
for their detailed comments and helpful critical nificant differences in this area can be
remarks on an earlier version of this article.
detected between blindfolded sighted and
Special thanks go to Professor John. M. Ken
nonsighted individuals. There are claims
nedy for drawing our attention to some impor
tant publications and for his helpful method
ological advice. Last but not least, we would tive speaker’s intuition to make the language
like to thank Robert Looby for lending his na of this article more digestible.
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©2015 AFB, All Rights Reserved Journal of Visual Impairment & Blindness, January-February 2015
that in some cases persons deprived of size—that is, the angle at which the ob
visual experience perform better than served object subtends at the eye—
blindfolded sighted individuals (for a re changes with the distance between the
view, see Cattaneo et al., 2008). The dif object and the observer. Angular size is
ferences in the results of the experiments usually measured in degrees of the arc,
reported in this and in other sources seem although in some research it was shown
to follow from the specificity of the im by pointing to the ends of the imagined
agery task rather than from the imagery object. In those cases the pointing span
operation (mental imagery activity) being indicated the angular size (see, for exam
tested (see, for example, Cornoldi &Vec ple, Arditi et al., 1988).
chi, 2003). Testing imagery scaling oper In visual perception, identical objects
ations may serve as an example. Mental placed at different distances from the ob
scaling transformation is an operation that server create images on the retina that
involves changing the size of an image differ in size. It is also possible to deter
found, for example, when sighted persons mine the changing pointing span for these
compare objects (Larsen & Bundesen, objects. The size differences are reflected
1978). The reaction time increased with the in verbal descriptions: a lake observed
size ratio of objects (see also Bennett & War from an airplane may be compared to a
ren, 2002; Craddock & Lawson, 2009). Some puddle, and a dog observed from a dis
research suggests that adults without prior vi tance may seem as small as an ant. We get
sual experience do not understand that the size this impression despite being aware that
of an object imagined to be moving away the linear size of these objects does not
must be reduced in accordance with the prin change (this is the mechanism of size con
ciple of perspective (Arditi, Holtzman, & Ko stancy). Visual angular size has its analogy
sslyn, 1988; Vanlierde & Wanet-Defalque, in imagery. Kosslyn (1978) defines angular
2005). There is, however, research providing size as the visual angle of the mind’s eye, and
evidence that it is unlikely that these difficul provides empirical evidence that sighted per
ties result from an inability to perform the sons imagine objects as being a certain dis
operation of mental scaling (Kennedy, 1993; tance away from the mind’s eye.
Wnuczko & Kennedy, 2014). Sighted persons first experience size
For clarity of argumentation, it is im constancy in infancy (Slater, Mattock, &
portant to distinguish between linear size Brown, 1990). This constancy, functioning
(which can, for example, be measured in as automatic inference, makes it possible to
centimeters), and angular size. The linear assess the linear size of an object on the
size of a particular object is an objective basis of its optical size and the distance.
property that does not change over time. The accuracy of the inference involved in
The ability to evaluate the linear size can the process of visual perception improves
therefore be treated as an indication of gradually, and at early school age is not yet
conceptual knowledge related to typical fully developed (Granrud & Schmechel,
sizes of objects encountered in the real 2006). Developmental progress in under
world. These sizes may change only in standing the relationship between angular
fantasy (for example, in Alice in Wonder and linear size can be observed in drawings
land). In visual perception, the angular made by sighted children. On reaching the
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Journal of Visual Impairment & Blindness, January-February 2015 ©2015 AFB, All Rights Reserved
stage of visual realism around the age of easily recognized by sighted persons but who
eight or nine (Luquet, 1927), they apply the also uses the principle of convergence (Ken
principle of perspective. At the visual real nedy & Juricevic, 2006a, 2006b).
ism stage in the development of drawing, Some research suggests that persons
children typically represent only what can who are blind tend to have problems with
be observed from a particular vantage point reducing the angular size of objects. Ar
and show how it is perceived by the ob diti et al. (1988) conducted an experiment
server; for example, by using foreshorten in which congenitally blind and sighted
ing (Luquet, 1927). More recent studies adult subjects were asked to imagine
(Bremner & Batten, 1991; Cox, 1981) pro three different objects at growing dis
vide evidence that at the age of as early as tances (3, 10, and 30 feet), and to evaluate
five or six sighted children employ perspec the objects’ size by demonstrating the po
tive and can show the depth relationship sition of their edges with their hands: “to
between objects. point to where the ends would be if the
Persons who are congenitally blind experi object were actually present and being
ence the change of angular size through touch. seen as it appeared in the image” (p. 9). In
By extending their hands or arms, visually the experiment, congenitally blind sub
impaired persons can understand the principle jects correctly showed large pointing
of convergence to the horizon (see, for exam spans for large objects but failed to de
ple, Kennedy, 1993; Kennedy & Juricevic, crease the angles as the distance at which
2006c). Also, living in a “sighted world,” they the objects were to be imagined was in
gain declarative knowledge of the functioning creased. They argued that the imagined
of visual perception and use it in interactions objects were of the same size in all loca
with sighted persons (see Bigelow, 1988; tions (or even that they got larger as they
Brambring, 2005). Understandably, although moved away because touching them re
persons who are blind progress in their quired reaching out farther). The re
drawing abilities (with a delay, but oth searchers interpreted this as “a fundamen
erwise similarly to sighted persons), the tal lack of perspective” in congenitally
stage of visual realism is in most cases blind subjects’ images (p. 9).
beyond their reach (D’Angiulli & A similar procedure was adopted by
Maggi, 2003; Heller, Calcaterra, Tyler, Vanlierde and Wanet-Defalque (2005),
& Burson, 1996; Kennedy, 1993). There are, who asked three groups of adults—“early
however, exceptional individuals—for exam blind” (those who experienced vision loss
ple, Tracy, a totally blind adult woman who before age 3), “late blind,” and fully sighted
lost her sight before the age of two—whose subjects—to imagine an object at distances
drawings confirm full understanding of the of 1, 3, and 9 meters. The task was to show
principle of perspective. In Tracy’s drawing the size of the object at each distance: “to
of three rows of tumblers, she showed depth: point on a ruler (attached to the table in
the glasses were smaller in rows more distant front of them) to the left and right sides of
from the observer (Kennedy & Juricevic, the object with their left and right index
2003). Similarly, an untypical case is that of a fingers” (p. 173). The authors of the article
51-year-old man, totally blind since birth, who do not say which kind of size (linear or
can not only make drawings of objects that are angular) was to be demonstrated by the
45
©2015 AFB, All Rights Reserved Journal of Visual Impairment & Blindness, January-February 2015
subjects. One can only speculate that the wall using both hands. The procedure that
experimenters were interested in the angu was adopted for the experiment may help
lar size but no such definite statement is explain the differences in the results of this
made (which suggests that the subjects may test and those obtained with adult subjects
have had similar doubts about the task). in the experiments described earlier (Arditi
Late blind persons, retaining memories et al., 1988; Vanlierde & Wanet-Defalque,
of visual experience and effectively using 2005). The angle between the arms depends
the visualization strategy (Vanlierde & on the imagined distance to the edges of the
Wanet-Defalque, 2004), which involves the object being pointed at, which explains why
creation of a visual image in the mind’s eye the children in Kennedy’s experiment re
(Pearson, 2010), perform image-building duced the angle between their arms when
tasks in a way similar to that typical for they tried to point to the edges of the whole
sighted individuals. Both groups decreased wall from which they had stepped back.
the size of the image with increasing dis This finding, however, does not necessarily
tance. No effect of distance change, how mean that they reduced the angular size of
ever, was found in the group of early blind the image of the wall, although such a pos
subjects. Moreover, 40% of early blind sub sibility cannot be excluded (see the concept
jects were of the opinion that the task did of amodal spatial images, Loomis, Klatzky,
not make sense, as objects do not change & Giudice, 2013).
their size. These results may be an effect of Kennedy (1993) examined two groups of
ambiguous instructions or of literal interpre blind children, one from Haiti and the other
tation of the instructions. It is possible that from the United States. All children evalu
congenitally blind persons, who cannot ob ated the length of the wall as shorter when
serve the change of angular size, indicated they pointed to it from a more distant loca
the typical (linear) size of the object, while tion. The children from Haiti, aged from 9
those participants who were late blind or to 18, were all adventitiously blind, with an
sighted evaluated the angular size. Also, the average onset of blindness at the age of 8.5
constant distance marked by the location of years (some of the participants became
the ruler may have biased the performance. blind before age 2, but it must be noted that
Kennedy’s experiment (1993) shows that although the age was declared by the par
blind children understand that as distance ticipants themselves, not all of them were
increases objects appear to decrease in size. sure that the information they provided was
The experiment was performed as follows: correct). Their visual memory may have
initially, the children were moved from the contributed to their success in performing
central section of a 4.5-meter-long wall to the experimental task (Vanlierde & Wanet-
one of the corners of the room, then back to Defalque, 2005). The American children
the starting point, then to the other corner (from Tucson) in Kennedy’s (1993) exper
and again back to the central section. In the iment (who were congenitally blind and
next part of the experiment, the children ranged in age from 5 to 14 years) had prior
were asked to step away from the wall. The exposure to tactile graphics, which are be
children were placed at two distances from lieved to stimulate development of spatial
the wall—first 1 meter and then 3.5 meters. imagery (Dulin & Hatwell, 2006). It is not
Their task was to point to each end of the known, however, if the adults taking part in
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Journal of Visual Impairment & Blindness, January-February 2015 ©2015 AFB, All Rights Reserved
the experiments described earlier (Arditi et years of life (classified by the researchers
al., 1988; Vanlierde & Wanet-Defalque, as congenitally blind) and adventitiously
2005) had similar tactual experience. An blind persons. The results achieved were
other difference between the two studies calculated for the group as a whole and
that may have led to different results was not for each subgroup.
the age of the subjects. Although the par Persons who are blind are also more
ticipants of the experiments conducted by accurate at evaluating the real length, sur
Arditi et al. (1988) and by Vanlierde and face area, and volume of familiar objects,
Wanet-Defalque (2004) were all adults, the which was confirmed in experiments in
subjects studied by Kennedy (1993) were volving children aged nine to thirteen
children. (Andreou & Kotsis, 2005). Both sighted
Also, Wnuczko and Kennedy (2014) have and blind adults (congenitally, early, and
empirically confirmed that blind persons have late blind) and sighted children with se
no problems reducing the angular size of dis vere vision loss were found to be more
tant objects. In their experiment, subjects were accurate in evaluating the real, typical
asked to point to different azimuths. The re size of common objects if they were al
sults obtained from blind participants did not lowed to apply subjective units of mea
differ significantly from those of sighted sub surement (for instance, indicating the
jects. In both cases the azimuth decreased number of steps that needed to be made to
with growing distance. The study was similar cover a certain distance) than when asked
to that described in Kennedy (1993) in that the to describe the size or a distance in cen
subjects could touch the objects and were able timeters or meters (Andreou & Kotsis,
to move within the space containing the ob 2005; Dulin, 2008). This finding suggests
jects. In the 2014 experiment, subjects guided that in order to avoid mistakes in the
by experimenters explored two paths of tactile evaluation of blind persons’ ability to
circles, touching them with a one-meter-long estimate the size of objects, it is advis
stick. A limitation mentioned by the research able to avoid using objective units of
ers was the small number of blind subjects measurement and to not ask the subjects
(six) as well as the fact that the group was to give the estimated values in, for ex
diverse. Only two subjects were blind since ample, centimeters.
birth, including one with light perception in To sum up, persons who are blind since
one eye. birth tend to find it difficult to evaluate the
Persons who are blind create more ac angular size of objects that they imagine to be
curate (that is, closer to linear size) rep moving away (although the findings de
resentations of objects perceived by touch scribed in various studies are not unanimous:
than do sighted persons. This finding was Arditi et al., 1988; Vanlierde & Wanet-
confirmed in experiments with adults Defalque, 2005; vs. Kennedy, 1993; Kennedy
(Smith, Franz, Joy, & Whitehead, 2005) & Juricevic, 2003, 2006a, 2006b; Wnuczko &
who were asked to indicate with their Kennedy, 2014). These findings are why it is
index fingers the size of the image of important to examine whether the difficulties
various grocery items previously ex that children born blind experience when
plored manually. The group included sub evaluating the angular size of mental images
jects who lost their vision in the first three of objects are the result of poor understanding
47
©2015 AFB, All Rights Reserved Journal of Visual Impairment & Blindness, January-February 2015
of the rules governing visual perception, or years and 8 months, SD = 2 years and 6
whether perhaps such difficulties may be re months). Blind subjects had, at most, light
lated to the subjects’ inability to modify the perception. The participants came from two
size of images of objects. Two hypotheses special schools for students with visual im
were proposed. Because they lack visual ex pairments in Poland. All blind students had
perience: (1) congenitally blind students are prior exposure to tactile graphics (in geom
less accurate in enlarging images of objects etry, in classes supporting braille literacy,
previously explored manually (in the pro and while reading books with tactile illus
cess of mental scaling), and (2) they are less trations). Participants declared substantial
likely to reduce the angular size of objects experience with tactile graphics: 72.2% of
imagined to be moving away than are stu the congenitally blind group and 37.5% of
dents with low vision or those who are late the adventitiously blind group.
blind. As was shown earlier, in the sighted
population the understanding of perspective MATERIALS
develops by early school age. This devel A giraffe toy that was 10 centimeters
opment is why it is important to establish (about 4 inches) tall from a LEGO Duplo
whether or not the ability to perform mental set and a piece of string were used in the
scaling by children with significant vision experiment.
loss improves with age.
PROCEDURE
Methods Subjects were asked, in a fixed order, to
The experiments reported in this article mentally enlarge an object (Experiment
are part of a larger project approved by 1) and to estimate the angular size of an
the Scientific Research Ethics Committee object moving away (Experiment 2). The
of the Institute of Psychology at the John independent variable in these experiments
Paul II Catholic University of Lublin. was the visual status of participants.
A toy giraffe was used in Experiment 1.
PARTICIPANTS Before performing the task, students ex
Thirty primary and junior high school stu plored the toy manually. They were free
dents were examined in the experiment. to choose the method of exploration and
The age of the participants ranged from 6 no time limit was set. The toy was then
years and 11 months to 18 years, and the removed, and the subject’s task was to
mean age was 13 years and 4 months imagine that the toy was growing like a
(SD = 2 years and 9 months). The group balloon until it was four times as big as it
included 11 congenitally blind students (7 was originally. Next, the subjects were
females and 4 males aged M = 12 years asked to demonstrate the linear size of the
and 9 months, SD = 3 years); 8 late blind enlarged giraffe on the piece of string.
participants who lost their vision at the The experimenter then measured the rel
age of 3 or later and retained memory of evant section of the string in centimeters.
visual representations (6 females and 2 In Experiment 2, subjects were asked to
males aged M = 15 years, SD = 2 years imagine a spoon placed at three different
and 2 months); and 11 students with low distances (in a particular order): on the sub
vision (5 females and 6 males aged M = 12 ject’s lap, on the lap of a person sitting 10
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Journal of Visual Impairment & Blindness, January-February 2015 ©2015 AFB, All Rights Reserved
Table 1
Assessment of size in experiments 1 (E1) and 2 (E2) by participants who are congenitally blind,
“late blind,” or have low vision.
Congenitally blind Late blind Low vision
Dependent variable M Me SD M Me SD M Me SD
Linear size of the enlarged giraffe (E1) 59.00 57.00 13.91 47.75 46.00 15.95 47.36 44.00 17.39
Overestimation error (E1) 19.00 17.00 13.91 7.75 6.00 15.95 7.36 4.00 17.39
Pointing span of the spoon on the
lap (E2) 24.09 18.00 20.65 22.00 22.00 5.66 20.00 19.00 2.79
Pointing span of the spoon 10 steps
away (E2) 22.00 16.00 16.31 17.38 17.50 6.19 25.18 14.00 27.83
Pointing span of the spoon 20 steps
away (E2) 21.82 10.00 22.90 16.00 13.50 14.38 28.45 8.00 49.23
The difference in the estimated size
(pointing span) of the spoon
between initial and final
locations (E2) 2.27 7.00 17.83 6.00 7.50 11.56 -8.45 12.00 47.70
M = mean, ME = median, and SD = standard deviation.
steps away and then on the lap of a person EXPERIMENT 1
sitting 20 steps away. Each time the same The linear height of the correctly enlarged
question was asked about the angular size
toy giraffe was 40 centimeters (about 16
of the mental image of the spoon: “How big
inches). One congenitally blind and two
does the spoon appear to you?” Subjects
low vision subjects correctly estimated
showed the size of the spoon by holding the
the size of the giraffe enlarged in imag
string at two ends of a section correspond
ery. After calculating the mean value of
ing to the length of their image of the spoon.
the assessed size, it was confirmed that all
The experimenter measured (in centime
groups had a tendency to exaggerate the
ters) the pointing span; that is, the length of
size of the mentally enlarged toy (see
the section of the string indicated by the
Table 1). However, 23.3% of the subjects
subjects.
(including one congenitally blind, three
Results late blind, and three participants with low
vision) underestimated the size of the gi
Because of the small number of subjects, non-
raffe after mental enlarging.
parametric tests were used for comparing the
The groups differed considerably in the
results received for each group. The median
extent of the overestimation error, under
test, that is, the analysis of k-between-group
stood as the difference between the eval
data, is based on contingency tables. For each
uated size and the objective size of the
group, the number of cases that fall above and
below the median is established. The Mann- enlarged toy, X2 (2) = 7.23; p = .027.
Whitney U-test, that is, the analysis of two- The error of overestimation was greater
between-group data, tests the effects of differ (on the border of statistical significance)
ences in the location of the two trials to in congenitally blind subjects than in sub
check how frequently results obtained jects who were late blind (U = 20.50; p =
for one group are higher (or lower) than .051) (see Table 1). The differences be
in the second group. tween congenitally blind and low vision
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©2015 AFB, All Rights Reserved Journal of Visual Impairment & Blindness, January-February 2015
subjects (U = 35.00; p = .101) and and those who considerably enlarged it
between late blind and low vision groups was instead.
not significant (U =42.50; p =.904).
Correlations between age (measured in Discussion
months) and the average overestimation Hypothesis 1, tested in Experiment 1, was
error were not significant, both for the partly confirmed. Congenitally blind stu
whole group (r = -.07; p = .704), and dents were less accurate in estimating the
for the congenitally blind group (r = linear size of the mentally enlarged toy
-.12; p =.724), the late blind group (r = than the group of late blind participants.
-.05; p = .905), and students with low By applying a visualization strategy, late
vision (r = .09; p = .793).
blind participants could “see” the object
grow in their imagery. Visualization of
EXPERIMENT 2
objects is a strategy preferred by both late
No differences related to the type of im
blind and sighted individuals in perform
pairment were found in the estimation of
ing imagery tasks (Vanlierde & Wanet-
the pointing span of the spoon in the three
Defalque, 2004). We therefore suspect
experiment settings: the spoon placed on
that using the strategy allowed late blind
the subject’s lap—X2 (2) = 1.28; p =
participants to be more accurate in eval
.527—and the spoon on the lap of a per
uating the size of the object enlarged in
son sitting 10 steps away—X2 (2) =1.28;
their imagery than were the congenitally
p = .527—and 20 steps away—X2 (2) =
blind group. The results obtained by low
4.36; p = .112. The difference between
vision participants did not differ signifi
the sizes of the spoon estimated for its
cantly from those found for the congenitally
initial and the most distant locations was
blind group. The question remains: why do
not significant (X2 = 4.98; p = .083).
individuals with low vision have statisti
Correlations between age and the dif
cally similar performance to persons with
ference between the initial and the final
congenital blindness? Unfortunately, no in
setting turned out to be insignificant both
for the whole group (r = .29; p = .125) formation was available about the etiology
of visual impairment in the persons with
and for the individual groups of students:
congenitally blind (r = .07; p = .832), low vision, which is one of the weaknesses
late blind (r = -.39; p = .337) and low of this study. It is possible that only some of
vision (r = .50; p = .116). the individuals had visual memory and
could use the visualization strategy; that is,
Three congenitally blind, one late blind,
and three students with low vision did not could “see the object grow” in their imag
reduce the pointing span of an imagined ery. The remaining low vision subjects may
spoon placed at a greater distance. The large have never seen well enough to apply visu
standard deviations found within the low alization and preferred different imagery
vision group for the distances of 10 and 20 strategies, used also by congenitally blind
steps (see Table 1) suggest that the low persons—hence, persons from both groups
vision group consisted of two subgroups— gave similar answers.
those who correctly reduced the angular Hypothesis 2, tested in Experiment 2, was
size of the spoon with growing distance not confirmed. All students—congenitally
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Journal of Visual Impairment & Blindness, January-February 2015 ©2015 AFB, All Rights Reserved
blind, late blind, and those with low vision— the congenitally blind group may have used
equally reduced the angular size of the spoon a variety of strategies, both imagery and
that they imagined to be moving away. Opti verbal (see Schmidt, Tinti, Fantino, Mam
mistically, this may be taken to mean that marella, & Cornoldi, 2013), which may
congenitally blind students did not have have contributed to the variety of results
greater problems understanding perspective obtained for this group.
than students who had some visual experi Contrary to the original hypotheses,
ence. Those participants who were congeni students with low vision performed imag
tally blind, like those in Kennedy’s (1993) ery tasks with the same level of accuracy
study, had prior exposure to tactile graphics. as those who were congenitally blind. The
They received special instruction that was in experiments did not take into consider
tended to compensate for the absence of vi ation the type and age of onset of partial
sual experience. It is possible that this experi vision loss, which may be important for
ence helped them gain some knowledge about visuospatial mental abilities (Monegato,
such principles governing vision as perspec Cattaneo, Pece, & Vecchi, 2007). The
tive and depth. The results achieved by the results found in Experiment 2 revealed
American children in Kennedy’s (1993) study heterogeneity in the low vision group.
mentioned earlier may therefore be related This finding must be treated as a limita
not only to the fact that these children tion of our study and suggests that in
stretched their arms to point at the edges of future experiments involving subjects
the wall located at some distance but that with low vision, the variables connected
they could understand the rules governing with the etiology of the visual impairment
vision and the phenomenon of changing must be more strictly controlled.
angular size. The results of Experiment 2 The age of the students in both exper
are incompatible with those achieved in ex iments did not affect their performance in
periments involving congenitally and early imagery tasks. It may be that declarative
blind adults (Arditi et al., 1988; Vanlierde knowledge about vision is more impor
& Wanet-Defalque, 2005), confirming their tant than the age variable for successful
greater imagery ability to reduce the size of mental resizing. This hypothesis must be
objects moving away. verified in future research.
In Experiment 2, evaluating the size of a Summing up the results of the two ex
spoon moving away, less variation in the periments and comparing them with the re
results (smaller standard deviation) was sults of earlier research, it can be stated that
found in the late blind group than in groups the difficulties congenitally blind persons
of congenitally blind and low vision partic experience with the process of reducing and
ipants, where the standard deviation was enlarging the size of imagined objects may
quite high. This finding may confirm the result not only from a lack of understanding
tendency to use the imagery visualization of perspective but may also be related to
strategy by late blind subjects. A tendency difficulties with applying the process of
to apply this strategy in tasks engaging visu mental scaling. It is therefore important to
ospatial imagery was also found by Vanli give congenitally blind students more op
erde & Wanet-Defalque (2004) in blind portunities to develop the ability of reduc
persons with visual memory. Subjects from ing and enlarging images and help them
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©2015 AFB, All Rights Reserved Journal of Visual Impairment & Blindness, January-February 2015
understand the concept of scale. Creating Cox, M. V. (1981). Spatial depth relation
such opportunities is essential for concep ships in young children’s drawings. Edu
cational Psychology, 1, 275–287.
tual development. Not all concepts are ac
Craddock, M., & Lawson, R. (2009) Size-
cessible through direct haptic exploration of
sensitive perceptual representations under
specimens (one thinks here of a lion, for
lie visual and haptic object recognition.
example). Some objects may be too large (a PLoS One, 4, e8009.
house) or too small (an ant). In such cases, D’Angiulli, A., & Maggi, S. (2003). Devel
models can be an aid and may be useful on opment of drawing abilities in a distinct
population: Depiction of perceptual princi
condition that learners are able to accurately
ples by three children with congenital total
perform mental scaling transformations.
blindness. International Journal of Behav
ioral Development, 27, 193–200.
Dulin, D. (2008). Effects of prior experience
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