Age and Physical Activity Modulate the Spatial Mapping of Time-Related Words

The processing of temporal concepts is known to be intertwined with spatial cognition. For instance, reaction times (RTs) are shorter when participants classify past- and future-related words with left- and right-lateral responses, respectively, in line with the so-called mental time line hypothesis. While some research has addressed individual differences in processing temporal concepts, it still remains unclear how such space-time congruency effects are influenced by the most crucial time-related factor in our lives - age. To address this question, we asked 94 participants aged 19 to 80 years old to classify past, future, and neutral words as related to time by using left and right response keys. In addition, we collected information regarding participants' self-reported level of physical activity, as it was shown to be a predictor of healthy ageing. We found that younger participants processed future-related words faster than past-related words, whereas older participants processed past-related words faster than future-related words. This ageing effect was modulated by physical exercise: The higher the self-reported level of physical activity in older participants, the smaller the past-related RT bias. Finally, our data revealed an age-related decline in space-time congruency effects among participants with lower self-reported physical activity. These findings indicate that the conceptual representation of time undergoes lifelong changes influenced by multiple factors, including age and physical activity. We suggest an integrative construct of dynamic conceptual time whereby the individual's bodily and life-course experiences lead to gradual changes in the processing of temporal concepts.