Decomposition of ID-DT relation as function of ID range and age group. Circles represents low IDs and triangles high IDs. Grey markers are used for young participants black markers for elderly. Mean data, linear fittings and their corresponding equations are presented. The “§” marked coefficient was not significant at 5%. It can be seen how DT is affected differently by ID at low and high difficulty levels and between age groups. Interestingly, the slope value for low IDs in older participants is found to be comparable to that for high IDs in younger participants.