The role of physical and cognitive effort on time perception

Abstract

Action and perception are intertwined, and time perception is not an exception to this general principle. In line with that, we have recently reported that the perceived duration of visual stimuli is extended while running. Here we tested the nature of this phenomenon by contrasting two possibilities: one related to physiological changes induced by physical effort (e.g. heart rate, temperature, arousal), and one related to cognitive alterations linked to motor control. To this aim we compared the direction and magnitude of the temporal bias induced by running to that prompted by other two conditions requiring much lower physical effort but both depleting cognitive resources. In these two conditions, participants either performed the timing task while walking backwards (an attentional motor task) or standing still with cognitive resources divided in a concurrent visual-working memory task. Both conditions yielded temporal overestimations virtually identical to that found while running, suggesting that physical activity could modulate temporal processing through the cognitive effort required to perform/control that specific motor routine. The results are informative for the scientific community investigating time perception in ecological sensorimotor contexts, suggesting the importance of considering the potential confounding role of cognitive factors related to motor execution.

Fig. 1

Schematic representation of the paradigm. In the encoding phase, participants were presented with a reference visual stimulus (a blue square) lasting 2 s displayed for five times consecutively and they were required to memorize that duration. This phase was followed by a 3 min without any visual stimulation (consolidation). After this phase, the decoding start with participants judging whether a visual stimulus (with variable durations ranging from 1 to 4 s) lasted the same, or a different amount of time compared to the memorized 2s reference (same-different task). The decoding phase (in different sessions) was performed while standing still with all the cognitive resources available for the temporal task (baseline), while walking backwards, while standing still but executing a concurrent additional visuospatial task (dual task) or while running. The duration of the decoding phase was approximately 5 min for the baseline, running, and backward walking conditions, and about 8 min for the dual-task condition (due to the additional time required for the presentation of “distracting” stimuli and response recording in the concurrent visuospatial task).

Fig. 2

Heart rate. Between participants average heart rate (bold lines) and relative confidence interval (95%, shaded areas) measured as beats per minute (bpm) in the different conditions: baseline (A, red), Dual-Task (B, green), running and walking backward (C, blue and grey respectively).

Fig. 3

Aggregate results. Proportion of “same” responses against test stimuli durations with the corresponding fitted Gaussian functions. Red curves in each panel indicate data for the baseline condition shown along with data obtained while running (A, blue curve), walking backwards (B, grey curve) and in the dual task condition performed while standing (C, green curve). The peaks of the fits (indicated by the arrows) correspond to the point of subjective equality (PSEs). The duration of the standard stimulus was 2 s. All curves were leftward shifted compared to the baseline, indicating an overestimation of the visual stimuli perceived while running (A), walking backwards (B) and while performing a concurrent visual working memory task at rest (C).

Fig. 4

Individual Points of Subjective Equality (PSEs). (A) Visual time PSEs measured while running (blue squares), walking backwards (grey circles) and in the dual task condition (green triangles) against PSEs measured at baseline. Big symbols and arrows report between participant’s average. (B) Normalized time overestimation effect (Eq. 1) measured while running, walking backwards or while performing the timing task while standing but with deprived attentional resources (same colour conventions as A). Error bars report ± 1sem.

Fig. 5

Sensory precision. Standard deviation of the Gaussian curves describing the time estimates for the four different experimental conditions (baseline: red, while running: blue, while walking backwards: grey and dual task: green triangles. Bars reports between participants average, symbols single subject data and error bars ± 1sem.