Children and adults rely on different heuristics for estimation of durations.

Time is a uniquely human yet culturally ubiquitous concept acquired over childhood and provides an underlying dimension for episodic memory and estimating durations. Because time, unlike distance, lacks a sensory representation, we hypothesized that subjects at different ages attribute different meanings to it when comparing durations; pre-kindergarten children compare the density of events, while adults use the concept of observer-independent absolute time. We asked groups of pre-kindergarteners, school-age children, and adults to compare the durations of an "eventful" and "uneventful" video, both 1-minute long but durations unknown to subjects. In addition, participants were asked to express the durations of both videos non-verbally with simple hand gestures. Statistical analysis has revealed highly polarized temporal biases in each group, where pre-kindergarteners estimated the duration of the eventful video as "longer." In contrast, the school-age group of children and adults claimed the same about the uneventful video. The tendency to represent temporal durations with a horizontal hand gesture was evident among all three groups, with an increasing prevalence with age. These results support the hypothesis that pre-kindergarten-age children use heuristics to estimate time, and they convert from availability to sampling heuristics between pre-kindergarten and school age.

An implicit task reveals space-time associations along vertical and diagonal axes.

In previous studies investigating the space-time compatibility effect, the experimental task always invites explicit spatial or temporal processing or both. In this study, we kept space and time irrelevant to the task. In a go/no-go task, participants (N = 50) were asked to either press a single button when they found the target or refrain from responding when there was no target in a search array. We manipulated the duration of the target-alone presentation that preceded a 7 × 7 search array consisting of either target plus distractors or distractors alone. The results revealed faster responses to shorter durations when the target appeared in the upper relative to the lower space. A similar effect also appeared along the diagonal axis with faster responses to shorter durations in upper-left relative to lower-right space. In contrast, no such difference was found along the horizontal axis. We hypothesize that vertical and diagonal space-time associations arise from the grounding of mental representation of time in physical experiences.