INTRODUCTION AND PURPOSE
For a long time the age of attaining certain skill has been used as a quick but crude index of child development. Such age-bound indices are called “milestones.” One cannot rely on such indices for assessing the development of a child especially if the deviation from normal is minimal. For careful assessment and follow-up, a battery of tests must be employed which incorporate activities or items that relate to the development of skills. Each test item in such developmental tests must be clearly defined with respect to the method of administration and the interpretation of the child’s performance. In other words tests should be standardized so that interpersonal differences are minimized.1
Development is influenced by heredity and environment.2 One of the environmental factors that affects development is culture which may affect performance of a child on a developmental test that does not reflect typical cultural experiences for a specific population. Because differences in motor development have been found among various ethnic groups, the cultural relevance of standardized developmental tests must be examined.3 Use of scales that are developed for western populations are not applicable to all the diverse cultural groups and regions of the world. So the cultural and regional relevance of a scale must be checked before its use. Such a project is especially important because these tests are used to determine whether a child is developing typically or is in some way delayed, requiring special services.4
The Peabody Developmental Motor Scales-2 (PDMS-2) were developed by authors whose backgrounds were in education and physical education. The scales were developed with the intent to identify children whose gross and fine motor skills are delayed or aberrant relative to the normative group; allow for comparison of abilities both within and between the 2 motor areas assessed (Gross motor and Fine motor); enable performance to be measured across time or in response to a specific intervention; be appropriate for use with children having motor handicaps; and provide a mechanism which would link assessment and programming when used in conjunction with the activity cards.5
Phatak et al1 in 1970 found differences in the age of achievement of certain skills between the children in United States and the children from Baroda in India. Miller et al6 in 1984 also found cultural variations on the Denver Developmental Screening Test (DDST) for the children from Southeast Asia on the personal-social, fine motor-adaptive, and language sections of the scale. Crowe et al7 in 1999 studied the differences in scores of Native American children from the normative sample of the PDMS and concluded that there was a significant difference in the scores (p ≤ 0.0001).
PDMS-2 have been developed and normed for the western population. There has been no study conducted to check the cultural sensitivity of the PDMS-2. Thus, the regional relevance of PDMS-2 must be examined, specifically when scores are used to determine whether a child is “normal” or delayed.
An estimated cluster sample of 20 wards from the total wards present in Mangalore City Corporation, Mangalore, India, was studied; with 15 subjects from each ward, reaching a total of 300 participants in the study.8 Children of either gender with ages from just born to 60 months were included. Children were excluded if they failed the screening test (the DDST II), or had active medical conditions or were uncooperative on 3 trials.
The DDST II is a valuable tool designed to be used with apparently well children between birth and 6 years of age. It consists of 125 tasks or items that are arranged in 4 sectors to screen the following areas of function: personal-social; fine motor-adaptive; language; and gross-motor. Also included are 5 test behavior items to be competed after administration of the test. The scoring is normal, suspect, or untestable.9
PDMS-2 are norm-referenced and a standardized motor skill test that consists of 6 subscales of which the scores from 4 subscales can be combined to give a gross motor quotient (GMQ) and 2 subscales can be combined to give a fine motor quotient (FMQ). For each item on the scales, the manual describes the child’s beginning position, the materials needed, and directions for administering the item and the criterion for scoring. The criterion for scoring each response is written in a behavioral objective format which specifies the number of trials permitted or the time allotted. Each response is scored on a 3-point scale (0 = unsuccessful, 1 = clear resemblance to item criterion but criterion not fully met, 2 = successful performance, criterion met). The administration of both Gross Motor Scale and Fine Motor Scale takes approximately 45 to 60 minutes.5
The subjects were recruited for the study by door to door survey, from nursery schools and play schools. A written signed informed consent was obtained from the parents after explaining the purpose of the study and the procedure in the language they were able to understand best. Basic information regarding the family and the child was obtained (see Appendix 1, which is available at the journal Web site, www.pedpt.com).
Screening was done by administering the DDST II as per the guidelines given in the manual. The child was included in the study if he or she was scored normal (no delays and a maximum of 1 caution) on the scale.
The PDMS-2 was then administered according to guidelines provided in the manual, using the floor and ceiling rules to minimize the administration time.5 The data were recorded in the examiner record booklets.
The obtained raw scores for each subtest of the scale were converted to age equivalent, percentile, and standard scores. The sum of the standard scores for the gross motor subscale and fine motor subscale were converted to GMQ, FMQ, and a total motor quotient (TMQ). All the values were recorded on the summary score sheet. The standard scores and the quotients were converted to z-scores to reduce the data for analysis and the means were used for comparison with the mean values given in the PDMS-2 manual.
Data analysis was done using SPSS ver.14.0 and Arcus software packages. The mean and standard deviations were calculated for the raw scores, standard scores, and quotients (GMQ, FMQ, TMQ) for different age groups (0–11 months, 12–23 months, 24–33 months, 34–44 months, 45–55 months, >55 months).
The z-scores for the standard scores for all the subscales and the quotients (GMQ, FMQ, and TMQ) were calculated and compared with the z-scores provided in the manual for the US population using the Student t test.
The range, mean, and standard deviations for the standard scores for all the subtests and the quotients (GMQ, FMQ, and TMQ) are presented in Table 1.
The z-score comparison of the standard scores for all the age groups and subtests and quotients is presented in Table 2. The comparisons vary from very highly significant to not significant.
The difference between the Indian children’s GMQ and the standardization sample was significant for the group above 55 months of age and was very highly significant in the age groups of 12 to 22 months and 34 to 44 months. The FMQ comparison was significantly different for the 12 to 22 months age group, whereas it was very highly significant for the 23 to 33 month group, the 45 to 55 months group, and above 55 months group (Table 2).
Motor assessments designed for children of the dominant or mainstream culture are not always appropriate for those from diverse ethnic backgrounds. This study was undertaken to compare the scores of children from one ethnic group with the sores of the children on whom the test was normed.
It was observed that there were significant differences in the scores of the children from our sample, compared with the normative data given in the manual of PDMS-2 (Table 2). It indicates that cultural differences do significantly affect the scores of the children on the scale.
Overall children in Mangalore scored better on the gross motor subsection of the scale than on the fine motor. GMQ was highly significant for the 12 to 22 months and 34 to 44 months age group, where the scores of children from Mangalore were lower than the normative values given in PDMS-2. The FMQ was highly significant through all the age groups up to 44 months where children in the sample have scored lower than the normative values given in the PDMS-2. From 44 months onwards the scores are significant but show an upward trend, with children in the Indian sample scoring better than the normative scores. This could be explained on the basis of inclusion into play schools or nursery schools after the age of 3 years (36 months) in the Indian sample.
There were also differences in various subtests for different age groups. Usually the Indian children scored poorly on all the subtests up to the age of 44 months and were better after the age of 44 months (Fig. 1).
The Indian infants in the age group of 0 to 11 months were on par with the normative sample of the PDMS-2 for the reflex section and were better in the stationary and visual motor integration subtests. These differences may be due to greater exposure of the children in the Mangalore cohort to a nonrestricted environment as they are mostly left on the floor or bed rather than in cribs or strollers used in western countries. The infants from Mangalore scored poorly on the locomotion and the object manipulation subtests of the PDMS-2 and this may be attributed to lack of exposure to various toys which are provided in western countries. The overprotective attitude of parents in India also may have influenced the scores of infants in the locomotion subtest.
The children in the 12 to 22 months age group scored higher than the normative cohort of PDMS-2 manual in the gross motor subtests which may be due greater freedom to move around and the lower scores on fine motor components may result from the lack of exposure to the toys and objects used for testing.
The lower performance in all the subtests is seen from the age of 23 months and continues till the age of 44 months. The reasons for this are the low scores of children on items like putting pegs in holes, inserting shapes on a form board, stringing beads, building a train, bridge, and other constructional designs, and copying a cross. This probably is due to lack of exposure to items like peg boards, form boards and blocks which are used to evaluate the items for these age groups.
We also observed that many children scored very low on the items that required use of scissors. This could be attributed to the fact that children are not used to using scissors because of parental concern that they may harm themselves or cause damage to objects in the house. Also there is lack of necessity of this skill for day to day activities when compared with western populations where the use of scissors, fork, and knife might be incorporated earlier in life when compared with the culture in India. Scissors use is not very common in our culture except when used for arts and craft, which explains the better scores of children on these items after the age of 44 months when they start attending play schools or nursery schools.
The scores of children in the 23- to 44-month age group was significantly different from the normative sample in the stationary and locomotion section of the gross motor section of the PDMS-2 because of lower scores on items like standing on one leg, standing on tip toes, walking on tip toes, and hopping. This could be due to the genetic differences that result in strength differences in the muscle groups required for these activities or environmental factors like the lack of exposure to such activities during the preschool period.
The Indian children also scored lower on the object manipulation subtest because of low scores on items like kicking a ball and hitting a target. Most of the children aged 34 months and above were not able to perform these activities. This may be due to lack of space in the houses or lack of play grounds in the city which leads to lack of exposure to outdoor games requiring these skills.
In the end, developmental norms and life experiences differ from ethnic group to ethnic group especially for activities that children have not had the opportunity to practice such as using scissors, ball playing, or coloring.
This study has future implications for therapists wanting to administer any subscale or the whole of the PDMS-2 to any child, in that they should consider the cultural upbringing of the child which may influence the child’s score. Also if research is conducted using PDMS-2 as an evaluative or outcome measure the authors should keep in mind the effect of cultural differences on the scores.
Further studies can be undertaken minimizing the limitations encountered during this study such as the use of floor and ceiling rules, which sometimes resulted in a ceiling effect despite our observation that the child could have performed the next item and may have encountered a problem in understanding of the command that was translated into the local language (Kannada). Future studies can be conducted to adapt or modify test items and calculate the normative scores for Indian children reflecting the cultural variations and diversity of our country.
In general, the results showed several significant differences between the scores of children from birth to 5 years (60 months) from Mangalore, India, who are typically developing and the normative sample of the PDMS-2. It is not possible to develop assessment tools which are culturally sensitive across the geographical regions and environments, but it is necessary to evaluate the cultural sensitivity of standardized tests for a particular region and ethnic group, especially when these instruments are being used to diagnose and plan the treatment of a child.
The authors thank the children and the families who participated in this study; the staff of the various nursery schools, play schools, and rotary club members for assistance in recruitment and use of facilities for the support of this project. The authors also thank Ms. Sailakshmi Ganesan, H.O.D., Department of Physiotherapy for giving full support and encouragement for the progress of this study. The authors extend thanks especially to Pro-ed for providing us with the materials required for conducting this study. The authors also thank Ms. Hema S. Patel, PT, who helped in data collection and Ms. Nancy C. Rasch, OTR/L, and Ms. Kathy Patten, OTR/L, for their guidance during the study.