Normative data for the numeric vertical line test: a comparison of verticality accuracy at different life stages and with different verticality measures

Objective We used the numeric vertical line test (NVLT) to analyze perceptual accuracy and precision of verticality at various life stages in a healthy population and compared the results of the NVLT with tests of verticality. Methods This cross-sectional study involved three participant groups: (a) 50 children, (b) 50 adults, and (c) 50 older adults. Each participant underwent three tests: (a) the NVLT, (b) the subjective visual vertical (SVV), and (c) the subjective haptic vertical (SHV). The test results for each age group were compared using analysis of variance, and Pearson's correlation coefficients were used to evaluate correlations between all tests. Results In the accuracy analysis, children (p = 0.003) and older adults (p = 0.003) were found to show lower accuracy on the NVLT than adults; children had lower accuracy on the SVV test than adults (p = 0.0008); and children (p < 0.001) and older adults (p = 0.04) had lower accuracy on the SHV test than adults. In the precision analysis, children (p = 0.006) and older adults (p = 0.006) were found to have lower precision on the NVLT than adults; children (p = 0.002) and older adults (p = 0.003) had lower precision on the SVV test than adults; and children (p = 0.0009) and older adults (p = 0.0006) had lower precision on the SHV than adults. Only the NVLT and SVV showed a significant association in adults (r = 0.57; p = 0.02). Conclusion Children and older adults showed less accurate verticality perceptions and lower precision levels for spatial-number displacement and visual and proprioceptive verticalities than adults.