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Mental rotation abilities in individuals with Down syndrome - a pilot study
Claire Hinnell and Naznin Virji-Babul
This pilot study was designed to examine mental rotation ability in individuals with Down syndrome. 7 individuals with Down syndrome (mean mental age = 8.18 +/- 2.73 years; mean chronological age = 29.8 +/- 5.4 years) and a group of 9 typically developing children, matched for mental age, (mean mental age = 8.40 +/- 1.73 years; mean chronological age = 7.2 +/- 1.2 years) were given a version of Cooper and Shepherd's (1973) mental rotation paradigm. On each trial, participants viewed a symbol representing an upper case 'F' or a mirror image of an 'F'. The symbol was presented at one of eight different orientations. The participant's task was to determine whether the letter was reversed or non-reversed. Interestingly, both groups showed similar trends in increased reaction times with increasing angular disparity, suggesting that both groups were performing mental rotations. There was no significant difference in reaction time between the typically developing and Down syndrome groups, however, the Down syndrome group made significantly more errors than the typically developing group. Participants with Down syndrome were able to carry out the mental rotations at well above chance level and mental rotation ability was shown to correlate with mental age.
Down syndrome is the most frequently occurring chromosomal abnormality, resulting from the presence
of an extra partial or complete 21st chromosome. This relatively small increase in genetic material
disrupts all aspects of an individual's physical, mental and social development with cognitive
development posing particular challenges. Intellectual disability is present in Down syndrome
but the extent of the impairment is quite variable, ranging from mild impairments to severe
mental retardation. The specific manner in which the chromosomal disorder influences cerebral
development and the resulting intellectual and information-processing deficits is not well understood.
Hartley (1986) and Pipe (1988), drawing from their work on dichotic listening paradigms, proposed
that the difficulties in information processing may be attributed to a reversed pattern of cerebral
specialization. That is, individuals with Down syndrome may be using the less optimal right
hemisphere for processing speech and language. However, Elliott, Weeks and Gray (1990) and Elliott
and Weeks (1990) have shown that adults with Down syndrome have greater difficulty with tasks
that involve both speech perception and movement organization. They suggest that individuals
with Down syndrome have atypical right hemisphere specialization for speech perception and typical
left hemisphere specialization for motor control. This separation of systems that are normally
controlled by the same left hemisphere may be the underlying basis for the information processing
difficulties typically seen in Down syndrome (Elliott & Weeks, 1993).
A standard method for evaluating the ability to perform spatial transformations is through the
use of mental rotation tasks originally described by Shepard and Metzler (1971). In their task, Shepard and Metzler showed pairs of line drawings of shapes and asked subjects whether the shapes
were identical or a mirror image of the original. The figures were presented in different orientations.
Interestingly, the response times increased as the angle from vertical increased. These behavioural
data have been replicated and reported by many investigators (Kosslyn, 1980; Shepard & Cooper,
1982;). However, the neural mechanisms underlying this behaviour remain unclear. While there
is some speculation that mental rotation is sub served by right hemisphere processing (Deutsch,
Bourbon, Papanicolaou & Eisenberg, 1988), there is more recent evidence from imaging studies
to indicate that there is bilateral activation of the hemispheres and that there appears to
be a great deal of variability across subjects and no clear hemispheric asymmetries (Cohen et
There are very few studies investigating the problem solving abilities of individuals with Down
syndrome using mental rotation tasks. Uecker, Obrzut and Nadel (1994) compared the mental rotation
abilities of children with Down syndrome (Mean CA = 8 years, 4 months, Mean MA = 3 years, 1
month), learning disabled children (Mean CA = 10 years, 3 months, Mean MA = 7 years, 5 months)
and a group of typically developing elementary school children (Mean CA=9 years, 2 months, Mean
MA = 11 years, 2 months). They were most closely matched for chronological age but not for mental
age. The stimulus used was a stick figure holding a ball in either the right or left hand. The
stick figure was rotated from 0 to 360 degrees and the children were asked to determine on which
the side the stimulus figure was holding the ball. Both the control and learning disabled children
showed a characteristic linear relationship between angular disparity and reaction times. The
children with Down syndrome did not show this characteristic relationship. Uecker et al concluded
that, since the Down syndrome group performed at low levels, this was indicative of difficulties
with spatial transformations.
There are however a number of limitations to this study that make this conclusion debatable.
First, the average mental age of the children with Down syndrome, as assessed by the Peabody
Picture Vocabulary Test -Revised (PPVT-R;
Dunn & Dunn, 1997), was 3 years, 1 month (SD
= 1.1) while the mean mental age of the typically developing controls was 11 years 2 months
(SD = 2.3). This rather large discrepancy in mental age limits any meaningful comparisons
between the two groups. In addition, Marmor (1975) has reported that imagery representing movement
first emerges at about the age of 5 years. She demonstrated that the reaction times of 5 year
old children showed the characteristic linear relationship with angular disparity when asked
to visually rotate panda bear-like shapes differing in orientations. Given that the mean mental
age of the children with Down syndrome in Uecker et al's (1994) study was much less than 5 years,
it is not surprising that they were unable to perform the task.
Furthermore, with respect to training, all groups in Uecker et al (1994) appeared to have been
given the same number of pretraining trials and instructions. Given the large discrepancy in
mental age it is highly likely that the Down syndrome group may not have had appropriate or
adequate instruction in how to perform the task.
The present study arose out of an interest to address the question of whether individuals with
Down syndrome with a mental age greater than 5 years have the ability to perform spatial transformations.
|Mental Age Mean SD Range
||8.18 2.73 (5-12.3)
||8.40 1.73 (6-11.92)
|Chronological Age Mean SD Range
||29.8 5.4 (22-36)
||7.2 1.2 (6-9)
||5R, 1L, 1M
Key: Gender: F = female, M = male.
Handedness: R = right handed, L = left handed, M = mixed.
Participant characteristics including mental age (PPVT-III), chronological
age, gender and handedness.
Materials and methods
The Down syndrome group consisted of 7 participants who were recruited through the Down syndrome
organization in Victoria, British Columbia. Mean mental age (PPVT-III) was 8.18 years (SD
= 2.73). The mental age matched group consisted of 9 typically developing children recruited
through faculty members in the School of Physical Education at the University of Victoria, British
Columbia. Mean mental age as assessed by the Peabody Picture Vocabulary Test -Third Edition
(PPVT-III) was 8.40 years (SD = 1.73). Handedness was assessed by the modified Edinburgh
Handedness Inventory (Oldfield, 1971). See
Table 1 for participant characteristics.
'F' mental rotation test
A version of Cooper and Shepard's (1973) mental rotation paradigm using an upper case 'F'1
was used in the current study. The symbol was presented as either a letter 'F' or as a mirror
image (Figure 1). The participant saw either a non-reversed or reversed stimulus on the screen
at one of 8 possible orientations relative to the vertical plane (00, 450,
900, 1350, 1800, 2250, 2700, 3150).
The experimental apparatus consisted of a computer and keyboard with specific keys colour-coded
for various tasks. Individuals were tested either in a laboratory setting at the University
of Victoria or in their homes. As a result both laptops and desktop computers were used; the
screen size and resolution therefore varied slightly. The computer screen was parallel to the
participant's frontal plane and at eye level. Reaction times were measured by computer from
stimulus onset to the pressing of a key by the participant and were recorded in milliseconds.
Figure 1. The reversed and non-reversed stimuli for the F-test.
All participants were administered the PPVT-III, a modified version of the Edinburgh handedness
test (Oldfield, 1971), and the mental rotation task following the training protocol described
In order to teach the task to the participant and ensure he/she understood the task, a training
session was completed first. Four three-dimensional wooden 'F's (two reversed and two non-reversed)
were glued to separate circular cards. Two of these 'F's, one reversed and one non-reversed
were used as references and remained visible to the participant at all times, including during
the practice and test trials on the computer. The participant was shown a stimulus (a reversed
or non-reversed 'F' glued to the card) at an angle away from vertical, and was asked to physically
rotate the card until the 'F' was vertical and match it to either the reversed or non-reversed
reference 'F'. When the participant was able to carry this out satisfactorily, he/she was then
asked not to touch the card, but to rotate the 'F' in his/her mind and then match it to one
of the reference 'F's. Once the participant could do this successfully, he/she continued on
to the practice trials on the computer.
A stimulus was presented on the screen; it was either a reversed or non-reversed 'F' presented
at one of the eight possible orientations. The participant was asked to mentally rotate the
stimulus in his/her head until it was upright, to decide if it was reversed or non-reversed,
and once a decision was made, to hit the appropriate coded-coded key on the keyboard as quickly
as possible. If it was non-reversed, he/she pressed the '/' key which was coloured red; if it
was reversed, they pressed the 'z' key which was coloured blue. Following 16 practice trials,
the participant performed the test trials.
The actual test consisted of 16 trials and was presented in a manner identical to the practice
trials. Every participant was presented with the stimulus at each orientation for both the reversed
and non-reversed conditions. The pattern of the stimulus, whether it was reversed or non-reversed,
the accuracy and the reaction times were recorded for each trial. The stimuli for both the practice
and test trials were presented randomly.
||1548.8 (324.3) 994-1982
||2175 (1576.7) 931-5000
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||2535.8 (2136.2) 1351-6854
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||1510.5 (798.6) 908-3070
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||1988.5 (957.9) 1139-3538
||1999 (679.3) 1114-2918
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||3561.5 (4447.5) 1349-12616
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||2109.1 (854.8) 1140-3503
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||1889.4 (833) 1181-3599
||2357.556 (803.6) 803-3638
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||1904.3 (777.2) 1173-3653
||1608.1 (556.5) 909-2811
||1752.8 (869.1) 1027-3603
||1508.8 (552.6) 791-1932
||1670 (870.8) 787-1992
||2322.1 (1351.7) 1181-3599
||2224.2 (1046.5) 803-3638
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Table 2. Mean correct reaction times (+/- SD and range) for all 8 orientations for the reversed
and non-reversed conditions for both groups.
Table 2 shows the mean (+/- SD) correct reaction times for all 8 orientations and for the reversed
and non-reversed conditions for both groups. In the typically developing group, a general trend
of increased reaction time with increasing angular disparity was observed (Figure 2). In the
Down syndrome group, a similar visible trend of increasing reaction time with orientation with
an exception at 1350 where the reaction time was faster than 900 and 1800.
A 2 (Group: DS vs. TD) x 2 (Pattern: reversed vs. non-reversed) x 5 (Orientation) repeated measures
analysis of variance (ANOVA) was performed. For statistical analysis the following 5 specific
orientations were used: 00, 450 (included data from 450 and
3150) 900 (included data from 900 and 2700), 1350
(included data from 1350 and 2250) and 1800. There was a significant
linear effect of orientation F(4,8) = 12.2 (p= .004). There were no main effects of group,
F(1,13) = 1.87 (p= .192) or pattern, F(1, 8) = 1.694 (p= .200), nor any significant interaction
Both groups performed well above chance levels on accuracy (see Table 3). Overall the Down syndrome
group were correct on 76% of the trials (SD = 17%) and the typically developing participants
were correct on 96% of the trials (SD = 4%). Chance level is 50% for the F-test as
participants discriminate between a reversed or non-reversed 'F'.
Figure 3 shows the average
accuracy for both groups as a function of orientation.
A 2 (Group: DS vs. TD) X 2 (Pattern: reversed vs. non-reversed) repeated measures analysis of
variance (ANOVA) was performed. There were significant main effects of group,
F(1,13) = 5.6
(p =. 034) and pattern F(1,8) = 11.7 (p =. 004), but no significant interaction effects.
Correlation between mental age and accuracy performance
Within the Down syndrome group, mental age was positively correlated with accuracy on the F-test
(Pearson product-moment correlation: r = .816, p < .05) such that increasing mental
age was correlated with increased accuracy.
Figure 2. Average reaction time of correct responses as a function of orientation of stimuli
for both the typically developing and Down syndrome groups on the F-test.
Figure 3. Accuracy as a function of orientation of stimuli for both the typically developing
and Down syndrome groups on the F-test.
The primary objective of this pilot study was to determine whether individuals with Down syndrome
have the capacity to mentally represent the physical process of object rotation. Several observations
of interest came from this data. First, it can be seen that individuals with Down syndrome are
able to perform mental rotation tasks well above chance level, indicating that the skill set
does develop and does exist, although it may be compromised. Second, mental rotation ability
is positively correlated with mental age, suggesting spatial processing skills in the Down syndrome
population may be delayed but not arrested. These data challenge the findings of Uecker et al
(1994) who suggested that individuals with Down syndrome are unable to perform the task due
to arrested development. From our observations, it appeared that providing adequate training
trials as well as the experience of physically manipulating the three dimensional wooden 'F'
was critical to helping individuals with Down syndrome understand the requirements of the task.
Wexler, Kosslyn and Berthoz (1998) have shown that the transformations of mental images may
in part be dependant on motor processes. It is possible then that having had a number of practice
trials in which there was opportunity to physically manipulate and move the object helped to
facilitate the subsequent mental rotation.
We are currently exploring whether the process of mental rotation is determined by the nature
of the task in individuals with Down syndrome. Ultimately, a procedure incorporating neuro-imaging
techniques would allow for more definitive conclusions regarding brain regions involved in the
processing of different types of stimuli in the mental rotation tasks in the Down syndrome population.
Further research is required to substantiate current speculations and to provide a fuller explanation
of mental rotation in people with Down syndrome.
The authors would like to acknowledge all the participants in the study and those who provided
support and advice, including Dr. Kimberly Kerns, Dr. Valerie Gonzales, Richard Abrams and Aidan
Dr. Virji-Babul • Centre for Human Movement Analysis, Queen Alexandra Centre for Children's
Health, 2400 Arbutus Road, Victoria, B.C., Canada V8N 1V7 • E-mail: firstname.lastname@example.org • E-mail:
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