Role of Age, Gender and Education in Information Processing Speed

Abstract

Letter Digit Substitution Test (LDST) is based on earlier developed substitution tests – the Wechsler's Digit Symbol Substitution Test (DSST) and the Symbol Digit Modalities Test (SDMT). The performance on these tests depends on many different cognitive processes, including visual scanning, mental flexibility, sustained attention, psychomotor speed, and the speed of information processing. The LDST consists of "over-learned" signs – letters and digits – and participants only have to learn the letter-digit association, which makes performance relatively less dependent on memory and complex visual processes than it is in the DSST or SDMT. The aim of this study was to investigate to what extent age, sex, level of education of the participants and level of education of their parents influence LDST performance. A total of 334 participants (191 females) aged 18-25 years were included in the study. Females and higher-level educated participants outperformed males and lower-level educated participants. Parents educational level only indirectly influenced the performance on the LDST, possibly through the participants level of education. Additionally, we derived normative data for the LDST for the ages between 18 and 25 years. Normative data in percentiles and z-values for the ages 18 to 25 years are presented, according to sex and level of education, which is compatible with and supplements the previously reported norms in other studies.