# Individual differences in how infants change behaviours from spontaneous to instrumental

## TL;DR

The study shows that infants display unique learning patterns when adapting behaviors through interaction with their environment.

## Contribution

The paper introduces a novel approach combining time-series clustering and dynamical systems modeling to analyze individual infant learning.

## Key findings

- Infants showed diverse learning patterns that cannot be captured by group-averaged data.
- Differences in spontaneous movements before learning predict distinct behavioral changes.
- Learning reduces individual differences by leveraging unique spontaneous behaviors.

## Abstract

Young infants can change their behaviour and learn through interactions with novel environments. This ability has been demonstrated through group-averaged analyses. However, it remains unclear whether averaged behavioural changes accurately capture the diverse changes occurring at the individual level. To address this, we measured limb movement alterations in 185 infants aged 2 to 3 months before and after their arm was tethered to an overhead mobile and analysed individual differences in addition to conventional group analyses. While the group-averaged data showed a gradual increase in arm movements, individual learning curves rarely exhibited such simple gradual increases and instead displayed more complex patterns. To disentangle the complex movement patterns, we applied time-series clustering and dynamical systems modelling to our large-scale dataset. As a result, the infants were divided into distinct clusters with significant differences in spontaneous movements before learning, rather than after. A dynamical systems model further demonstrated that only differences in spontaneous movements could explain the diversity of overall behavioural changes. These findings indicate that the varying degrees of behavioural change reflect infants’ unique learning processes rather than their learning capabilities. Furthermore, learning, as a process that reduces individual difference, suggest that infants harness their unique spontaneous movements to acquire instrumental behaviours.

Dynamic patterns of infants’ behaviour (n = 185) during environmental interactions were investigated using time-series clustering and dynamical systems modelling, revealing an aspect of learning that reduces individual differences.