The Modulation Of Working Memory On Number-Time Association:Evidence From The Number Magnitude Congruency Effect

Number is critical in our daily life. Numerical magnitude can be activated automatically——in a temporal discrimination task this automatic leads to a subjective time expansion for stimuli with a large number and a time compression for stimuli with a small number, though no magnitude processing is required. Such an effect was called number-time association. Recent researches suggested that numerical magnitude affected temporal memories but not time encoding. According to the extension of the resource allocation model, temporal and nontemporal tasks share attentional and memory resources, thus, numerical magnitude representation which was kept in working memory is likely to modulate the number-time association in subsequent temporal tasks. Temporal processing is a multistage process including time encoding, holding the perceived time into memory and making decision of temporal judgment. Recent researches suggested that numerical magnitude affected temporal memories but not time encoding. According to the extension of the resource allocation model, temporal and nontemporal tasks share attentional and memory resources, thus, numerical magnitude representation which was kept in working memory is likely to modulate the number-time association in subsequent temporal tasks. However, up to now there is no experimental study to explore this question directly. The present study aims to examine systematically whether the number stored in working memory affects the number-time association and its underlying mechanism by using a dual task paradigm consisting of number memorization and time reproduction.Five experiments were conducted to investigate this question. Participants were asked to complete time reproduction task in experiment 1,3 and dual-task composed of time reproduction task and number memorization in experiment 2,4,5. In experiment 1, we replicated the classic number-time association, which demonstrated that time of lager magnitude numbers were reproduced longer than that of smaller ones, especially when the stimulus durations were relatively longer. In experiment 2, participants were asked to memorize a number and then reproduced a time interval after perceiving it. To ensure that participants did exactly memorized the number, they were asked to input the memorized number at the end of the trial. Our results showed that the number-time association was abolished when the magnitude of memorized number was incongruent with the magnitude of stimulus number, whereas the interference effect didn’t occur when the magnitude of the two numbers were congruent. Experiment 2 revealed that the numerical magnitude kept in working memory modulates the number-time association during subsequent temporal tasks. In order to explore whether the effect we found in experiment 2 was due to the automatic activity of the memorized number, we conducted experiment 3, which used the same physical stimuli as that in experiment 2 with no memorization requirement of the memory number. We found disappearance of the congruent effect, suggesting that the memory processing is a necessary component for the modulation of working memory on time-number association.In terms of underlying mechanisms of the congruent effect, it is possible that the congruent effect was due to an integration of two types of magnitude information (induced by memory number and stimulus number, respectively). We conducted experiment 4 and 5 to further investigate whether the congruent effect was due to a direct modulation of the memory number on time perception or an indirect modulation of the memory number on time perception via the stimulus number. Experiment 4 and 5 were the same as experiment 2 except that stimulus number was changed into either a black cross (in experiment 4) or a constant number 5 (in experiment 5), the result show that memory number had no effect on time perception when the stimulus was a black cross, whereas memory number affected time perception when the stimulus was a constant number 5. Experiment 4 and experiment 5 supported the’indirect’ hypothesis. Taken together, our study suggests that the numbers kept in working memory modulate time number association, and this effect was likely due to an indirect modulation of memory number on time perception via the stimulus number.