We shall now look at three classic studies, significantly sited in current research, that have used this comparative approach.
Norris et al., (1957):
Longitudinal study between 1945 and 1952 that sought to establish developmental norms for children with visual impairments. The sample consisted of 295 children sixty of which were studied intensively under supervision of psychologists, social workers and the project staff. All the children had no additional handicaps aside from blindness although 85% were premature babies which subsequently developed retrolantal fibraplosia (current name: as retinopathy of prematurity - ROP). Intelligence, sensorimotor and social development were assessed with the Cattell Infant Intelligence Scale, the Interim Hayes-Binet Intelligence Test, the Kuhlman Scale of Intelligence and an adapted version of the Vineland Social Maturity Scale (Ashcroft, 1959). The researchers also gathered information on the level of mobility, medical factors, and created a prognostic rating scale to estimate the child’s potential for optimal development and future functioning (Warren, 1994). Finally, a rating scale was created to assess the influence of environmental characteristics and the child’s opportunities for learning. That is, the impact of the family and environment on the development of the child’s motivation and independence. The scale measured the family’s capacity to meet the child’s basic needs (especially those related to their visual impairment), family stability and their reaction to their child’s condition.
Results from the Cattel Infant Intelligence Scale revealed that the blind children took longer to achieve certain developmental milestones particularly motor skills (fine & gross), perception and perceptual motor integration. (Ferell, 1986). Lack of vision was also found to limit awareness of space and spatial relationships (Chess & Gordon, 1984). Fraiberg (1977) notes that only 50% of the blind children from the Norris et al., intense group were independent walkers at twenty-four months. This is a considerable lag if compared to sighted children who typically begin walking in their first year. A delay was also observed in the awareness of object permanence.
According to Warren (1994) one should be careful when interpreting these results given that no age correction for prematurity was used to control for the ROP subjects. He argues that if a three month correction factor is applied most motor and locomotor tasks fall within the age appropriate norm. The same is true for language development where the blind children showed a developmental lag when compared to the Catell norms but these differences diminish if a correction for prematurity is applied.
Several conclusions can be derived from this study. There was no significant correlation between degree of functional vision and any of the other measures except level of mobility. Overall, the development of the children in the “intensive” group was approximately equal to that of the sighted control. More important however, was the fact that “favourable opportunities” for learning were seen as the fundamental determinant of the child’s functioning level. Opportunities for learning can be understood as the stimulation necessary to elicit appropriate development. Providing the right environment and education at the appropriate time was more important than the degree of blindness, measured intelligence or the socioeconomic status and education background. The authors also suggest a “geometrical effect” to explain developmental delays. That is, the achievement of developmental milestones (or the skills that categorizes this milestone) is related to the time the child is ready to learn and when the opportunity to learn is provided. The authors conclude there was no relation between brain defect and ROP and that no specific mental deficiency could be directly attributed to blindness. The study is also one of the first to report that there was a considerable range of individual differences. That is, some of the children in the intensive group were on par (or sometimes advanced) with sighted developmental norms while others were not.
There are however a few methodological problems associated with this research. As noted above the subjects were chosen on the basis of no additional handicaps. This allowed the researchers to conclude that on the absence of mental or neurological deficiencies individual differences can be related to contrasting environmental circumstances. In a series of subsequent evaluations (Cohen et al., 1961; Cohen et al., 1964; Cohen et al., 1966) it was found that many of the participating children revealed patterns of neurological abnormalities.* The studies also revealed significant differences in intelligence scores. The authors have also been criticised for an uneven population where approximately two-thirds were females and the fact that the pre-testing level of intelligence for children in “intense group” was considerably higher than those in the control group. Finally, results should be carefully considered given the prematurity factor of the individuals blinded from ROP even with the proposed age corrections.
*One should be cautious when associating the concept of abnormal brain activity and brain damage especially when comparing a visually impaired population to a sighted control. Differences in brain activity (electroencephalogram and the attenuation or absence of alpha activity) are expected in situations of restricted sensory input.
Maxfield & Fjeld (1942) and Maxfield & Buchholz (1957):
Researchers have a used a variety of standardized scales to measure social development and adjustment of children with visual impairments. These are diagnostic tools but can also provide important information on the developmental norms of this population.
The Vineland Social Maturity Scale (Doll, 1930) was designed as an indicator of social competence, self help skills and adaptive behaviour for sighted children from infancy to adulthood. The scale consists of 117 items divided in the following categories: daily living skills (general self-help, eating, dressing); communication (listening, speaking, writing); motor skills (fine, gross & locomotion); socialization (interpersonal relationships, play, leisure and coping skills); occupational skills and self direction.
Maxfield and Fjeld (1942) adapted the Vineland scale for children with visual impairments. This became known as the Maxfield-Fjeld (MF) scale. The adapted version allowed for comparisons with norms for sighted children and to uncover specific areas in which the visually impaired are developmentally delayed. The scale avoided the measurement of intelligence, personality, habits, skill and focused instead “on the composite capitalization of such abilities for socially significant behaviour” (Maxfield & Fjeld, 1955, p. 2).
It is important to differentiate between intelligence (IQ) and social maturity tests. Warren (1984) notes that intelligence tests are designed to assess intellectual potential while the social quotient (SQ) in the social maturity scale is representative of actual performance rather than potential. This is of particular relevance in this research given that it will be argued that performance in spatial tasks is an indicator of present competence not ability or “capacity to do”. Several researchers (see Warren, 1984 p.226) found significant correlations between the two measures.
The MF scale consisted of 77 items classified under several categories (general, eating, dressing, locomotion, occupation, communication, self-direction and socialisation). Scores are presented in the form of a social quotient (social age/chronological age x 100). The children in their study ranged from nine months to seven years and varied in terms of mental ability (3 categories: superior, normal & retarded) and functional vision (total to minimal).
Maxfield & Buchholz (1957) revised the MF scale and applied to 484 children that varied in functional vision their age ranging from five months to six years. It should be noted that like the Norris et al., (1957) study the majority of these children (60%) were blind due to ROP . The majority of the remaining children suffered from cataracts or optic atrophy. The study’s main aim was to inventory the social development of children with visual impairment based on the general performance of other visually impaired children of the same chronological age (Ferrell, 1986). That is, a social maturity scale normed on blind children.
Several results emerged from this research. First, it was found that the social quotient of the blind and visually impaired children (as a group) was considerably lower (mean VI = 83.54; mean sighted = 100). It should be noted however, that there was a great deal of variation within the visually impaired group with SQ scores ranging from 26 to 163 with a standard deviation of ± 29.28. In addition, the authors did not find any significant differences in the development of locomotion when compared to the sighted children. This results differs from Norris et al., (1957) who found considerable lags in crawling and walking.
Maxfield and Fjeld also compared SQ scores of the total blind with those of the visually impaired. They found only marginal differences between these groups with the visually impaired scoring higher. Here again they note that the “difference is not statistically reliable since the groups are small and the variability [is] great” (Maxfield & Fjled, 1942, p. 12). The authors conclude that the blind tended to be more docile, lack initiative, are less active and introverted.
Closer analysis revealed that health, early intervention, specialized training and environmental stimulation were among the most important factors leading to a higher a SQ in the blind and visually impaired children. Specialized training is of particular importance an this was obvious from a rise in the SQ of during the testing phase. They conclude that if the visually impaired is stimulated to take an interest in the environment a desire to dominate it will develop in much the same manner as the seeing child.
Finally, the authors are quick to point that given the complexity of the problem, it is doubtful that any single diagnostic instrument is sufficiently adequate to measure the development of the visually impaired. The scale should be used as a guide and not as an absolute measure. The same amount of caution should be used with the age norms given the size of the sample and the amount of diversity among the children.
Fraiberg studied the development of ten congenitally blind babies some of which had minimal light perception. This was a 15 year longitudinal study tied with an educational program summarized in her book Insights from the Blind (1977). The babies entered her educational program from ages one to eleven months and were neurologically intact with no additional sensory or motor disabilities. The purity of the sample allowed for inferences to be made about the role of vision in the development and organization of sensory abilities. An in depth review of her work is beyond the scope of this thesis. However, we shall outline some of her major findings in the area of prehension and gross motor development and their implication for a developmental theory of the blind.
In the area of object prehension, she observed that prior to entering the educational program 7 out 10 of her subjects made no “gestures of reach for persons or toys at tactile remove even when voice or sound cues [were provided]” (Fraiberg, 1977, p. 275). In her educational program she argues that vision usually lures the child to discoveries and she encourgaes parents to create exchanges and experience to arouse interest and maximally engage the child with the environment. She notes however, that despite the program’s effort, the blind infants were still developmentally delayed. She attributes this lag to the difficulty the blind infant has with the concept of object substantiality and spatial unity.
In the area of gross motor development she notes that typically the postural attainment of the blind infant were within the norms of the sighted. However, the consequent mobility items (that follow each postural attainment) were considerably delayed falling outside the sighted ranges. Here again, she argues that blindness acts as an impediment to adaptation that restricts “environmental lures” that would initiate locomotor development. Fraiberg regarded the development of an object concept as critical. It is only after the attainment of the concept of object permanence (constancy) that the child is able to confidently let go of the object (or person) and explore the rest of the environment (Warren, 1984). In addition, the absence of stimulation is also associated with a delayed formation of a sense of security and the retardation exploratory behaviour (Warren, 1984).
Her educational program urged for an enhancement of the ties between parents and children and warns of the retarding effects of parental over-protectiveness. Fraiberg puts forward several reasons why her findings should not be generalized to the blind population. She notes that the “blind” population encompasses individuals with a varying amount of useful vision. This is coupled with a high incidence of brain damage and other associated handicaps. Furthermore, the age of onset impairment should also be considered given that many blind individuals have lost their vision after crucial developmental stages.