A Re-Evaluation of the Heath Rail Walking Test

Abstract

MOTOR ABILITY and locomotor coordination i are usually regarded as primary aspects of matura tion and development. The latter, as evidenced in the age at which a child begins to walk, is frequent ly taken as supportive confirmation in the diagnosis of mental retardation. That there is nota clear-cut relationship between motor and mental abilities even at early ages, but instead, a large amount of over lapping of functions, has been stressed by Bay ley (1) and Gesell and Amatruda (5). Nevertheless, Myklebust (ll)(12)(13)has pointed out the signifi cance of a motor evaluation in contributing to a dif ferential diagnosis of aphasia, deafness, autism and mental retardation in children. Motor tests for clinical use were developed by Bayley (1), Oseretsky (3), Heath (8), and others. Heath, in particular, devised a rail-walking test to measure gross locomotor ability. It would appear from a review of the literature that no subsequent research has been directed toward confirming Heath's original norms for children by utilizing a sample from a different part of the country. Locomotor ability as exemplified in the act of walking unaided normally develops in the child be tween the ages of 12 and 15 months. Delay in walk ing or poor locomotor ability may be contingent upon mental retardation or injury to the central nervous system. With regard to the former, the relationship between mental age and locomotor ability as meas ured by the Heath Rails Test seems to depend upon the type of mental defect. Thus, Heath (10) reported a partial correlation, with chronological age con trolled, of . 64 between mental age on the 1916 Stan ford Binet Test and the Heath Railwalking Test for 50 endogenous mentally defective children. More recently, Frisina (4) obtained a correlation of . 59 (plus-minus .07) between mental age and Heath's with a group of hearing impaired children whom he described as evincing a familial form of mental re tardation. When, however, mental defect is asso ciated with accident, disease, etc., there is no re lationship between the aforementioned variables. With a population of 80 exogenous mentally defective children Heath (10) found the partial correlation with chronological age held constant between mental age (1916 Stanford-Binet) and railwalking to be. 001. This result obviously indicates the absence of a re lationship. In discussion equilibrium as associated with the railwalking test Heath (8) points out that both sensory and motor pathways are involved. The for mer indicate to the subject that he is off balance. The latter enable him to regain balance. Poor per formance per se is often difficult to attribute to either sensory or motor defect, or to central coor ! dinating mechanisms. In addition to the vestibular I apparatus consisting of the semi-circular canals, j the utricle and the saccule, the cues afforded by vi sion and the kinesthetic senses likewise contribute to equilibrium, Myklebust (13) has supplied evidence of decreased ability of children in schools for the deaf on the railwalking test, particularly, with ref erence to the effects on balance of meningitis which destroys the labyrinth. In general, individual dif ferences in railwalking performance according to Heath are probably associated with the central co ordinating mechanisms rather than to a disturbance in the transmission of sensory stimuli? It would seem then that the lack of correlation between rail walking ability and mental age in the exogenous de fective is possibly due to the variability of the ef fects of the causative agent upon intelligence, the I central coordinating mechanism, and sensory and motor transmission. Conversely, one m ig h trea sonably expect a correlation between the two varia bles in the endogenous defectives who are charac terized by a generalized reduction of potential in all areas. Heath (8) in 1944 proposed an extension of the concepts of endogeny and exogeny to include individ uals with normal intelligence. He further suggested that the bulk of the population was made up of endog