Associative learning via eyeblink conditioning differs by age from infancy to adulthood

Abstract

Associative learning is a key feature of adaptive behaviour and mental health, enabling individuals to adjust their actions in anticipation of future events. Comprehensive documentation of this essential component of human cognitive development throughout different developmental periods is needed. Here, we investigated age-related changes in associative learning in key developmental stages, including infancy, childhood, adolescence, and adulthood. We employed a classical delay eyeblink conditioning paradigm that consisted of two sessions with a total of 48 paired trials. Our initial hypothesis was that performance in associative learning would increase linearly with age. However, our findings suggest that performance peaks during the primary school years: Children in this age-group exhibited superior performance compared to all other age-groups and displayed the most consistent and least variable learning. Adults and adolescents exhibited faster association learning than infants. An additional learning session supported learning in infants and adolescents indicating that during these developmental stages, consolidation processes are vital for learning. A comprehensive account of the development of associative learning may inform theories on aetiology and treatment options in clinical psychology and neurosciences.

Fig. 1. Conditioned responses on day one and two per age-group.

a Conditioned responses for each trial (black squares: blink yes/grey squares: no/ red squares: missing) and each participant in each age-group. b Mean conditioned responses per trial on day 1 and 2 for each age-group as defined by ratio of blinks vs. no blinks in a window of 5 trials. Visualisation is baseline centred (yellow line: 12 month-olds (n = 24), bright red line: 18-month-olds (n = 26), orange line: 24-month-olds (n = 30), brown line: 36-month-olds (n = 28), turquoise line: primary school children (n = 28), light blue line: adolescents (n = 30), dark blue line: adults (n = 64)). c Linear daily increase in conditioned responses as predicted by piecewise linear mixed model parametrised for 2 separate phases (day 1 and 2) (yellow line: 12 month-olds, bright red line: 18-month-olds, orange line: 24-month-olds, brown line: 36-month-olds, turquoise line: primary school children, light blue line: adolescents, dark blue line: adults). d Group-wise violin plot of blink-per-trial ratio. Point represents mean estimate and error bars represent ± 1 SE. Distributions around the mean represent the density within the respective group. (yellow line: 12 month-olds (n = 24), bright red line: 18-month-olds (n = 26), orange line: 24-month-olds (n = 30), brown line: 36-month-olds (n = 28), turquoise line: primary school children (n = 28), light blue line: adolescents (n = 30), dark blue line: adults (n = 64)).

Fig. 2. Mean blinking tendencies per tone alone and air puff alone trials for each age-group.

N per age-group (12 month-olds: n = 24, 18-month-olds: n = 26, 24-month-olds: n = 30, 36-month-olds: n = 28, primary school children: n = 28, adolescents: n = 30, adults: n = 64). Trials 1–6 were administered on day 1, and trial 7–8 were administered on day 2. Dashed lines mark the transition from day 1 to day 2.

Fig. 3. Learning Cluster and their distribution across age-groups (12 month-olds: n = 24, 18-month-olds: n = 26, 24-month-olds: n = 30, 36-month-olds: n = 28, primary school children: n = 28, adolescents: n = 30, adults: n = 64).

a Dendrogram of the hierarchical cluster analysis on conditioned responses. b Conditioned responses for each trial and each participant in each cluster (black squares: blink yes/grey squares: no blink/red squares: missing). c Blinking trajectories over the course of day 1 and 2 per learning cluster. d Distribution of learning clusters across age-groups.