# Duration, numerosity and length processing in healthy ageing and Parkinson’s disease

## TL;DR

This study explores how aging and Parkinson’s disease affect the ability to judge time, number, and length, finding that discrimination precision declines but not in a domain-specific way.

## Contribution

The study is the first to compare duration, numerosity, and length processing within the same experimental framework in healthy and pathological aging.

## Key findings

- Discrimination precision varied across domains, with higher accuracy in judging number and lower in judging time.
- Both healthy aging and Parkinson’s disease led to reduced discrimination abilities, but no domain-specific impairments were found.
- The decline in discrimination may stem from a general cognitive decline or a shared system for quantity processing.

## Abstract

People constantly process temporal, numerical, and length information in everyday activities and interactions with the environment. However, it is unclear whether quantity perception changes during ageing. Previous studies have provided heterogeneous results, sometimes showing an age-related effect on a particular quantity, and other times reporting no differences between young and elderly samples. However, three dimensions were never compared within the same study. Here, we conducted two experiments with the aim of investigating the processing of duration, numerosity and length in both healthy and pathological ageing. The experimental paradigm consisted of three bisection tasks in which participants were asked to judge whether the presented stimulus (i.e. a time interval, a group of dots, or a line) was more similar to the short/few or long/many standards. The first study recruited healthy young and elderly participants, while the second recruited healthy elderly participants and patients with Parkinson’s disease, a clinical condition commonly associated with temporal impairments. The results of both experiments showed that discrimination precision differed between domains in all groups, with higher precision in the numerosity task and lower sensitivity in judging duration. Furthermore, while discrimination abilities were affected in healthy elderly and, even more so, in Parkinson’s disease group, no domain-specific impairments emerged. According to our research, reduced discrimination precision might be explained by an alteration of a single system for all quantities or by an age-related general cognitive decline.

The online version contains supplementary material available at 10.1007/s10433-024-00807-z.