Normative data of alternating (repetitive) and sequential speech diadochokinesis in Turkish-speaking healthy adults

The aim of this study was to examine whether diadochokinetic (DDK) production rates differ by age and gender in healthy Turkish-speaking adults and to establish normative data. The study included 300 healthy individuals aged between 18 and 75 years without any neurological, developmental, or communication disorders. Participants were divided into three age groups: 18–35 years (n=131), 36–55 years (n=112), and 56–75 years (n=57). The sample consisted of 168 females and 132 males. Prior to the study, informed consent was obtained and demographic information was collected. Language proficiency was assessed using the Adult and Elderly Language Disorders Screening Test (DTLA), and oral-motor skills were evaluated with the Oral Speech Mechanism Screening Examination (OSMSE-3). Eligible participants were asked to repeat the syllables /pa/, /ta/, /ka/ (Alternating Motion Rate - AMR) and /pataka/ (Sequential Motion Rate - SMR) as fast and accurately as possible for 5 seconds. The recordings were analyzed using Audacity software, and syllables per second (SPS) were calculated. The findings revealed that production rates were higher in SMR tasks compared to AMR tasks. As age increased, production rates decreased significantly in both task types. Task order had no significant effect on overall performance. Gender differences in production rates were not statistically significant. The relationship between reaction time and production rate was weak and nonsignificant. The measurements were evaluated by two independent raters, and high inter-rater reliability was achieved. Keywords: Diadochokinetic Rate, Alternating Motion Rate, Sequential Motion Rate, Normative Data, Healthy Adults