A total of 280 the revised Chinese version of Autism Spectrum Quotient (AQ) questionnaires were distributed among undergraduates and postgraduates using convenience sampling, and 249 valid questionnaires were obtained. The groups with high level of autistic traits and low level of autistic trait (hereinafter referred to as "high AQ group" and "low AQ group") was based on grouping criteria of previous studies(Burnett & Jellema, 2013; English et al., 2017; Whyte & Scherf, 2018). Based on total scores, the top and bottom 27% of the individuals were selected, combined with the AQ score range, and according to the willingness of the participants, 63 participants were finally recruited to participate in the study. There were 32 participants (9 males and 23 females) in the high AQ group with an average age of 20.65 ± 1.51 years and average AQ scores ranging from 125 to 161, with an average score of 130.03 ± 5.94. In the low AQ group, there were 31 participants (14 males and 17 females) with an average age of 19.39 ± 1.66 years and an average AQ score of 102.87 ±4.48, in the range of 89-110. An independent samples t-test showed that the AQ scores of the two groups were significantly different. All participants had normal visual acuity or corrected normal visual acuity, were right-handed, and volunteered to participate in the experiment. After completion of the experiment, the participants were able to obtain the corresponding compensation. All participants signed an informed consent form before the experiment, and the study met ethical standards.
The Autistic Spectrum Quotient (AQ) is a widely used tool to measure autistic traits. It was developed by Baron-Cohen et al. (2001) and is mainly used to measure the level of autistic traits in non-clinical populations. The revised Chinese version, by Zhang et al. (2016), was used in this study. AQ includes five dimensions: social skills, attention to conversion, attention to detail, communication, and imagination, with a total of 50 questions. Each question has four options, from "completely agree" to "completely disagree," using a four-point, Likert scoring method. The higher the score, the higher the level of autistic traits. The internal consistency coefficient of the revised Chinese version is 0.81, the retest reliability is 0.89, and the internal consistency coefficient of each subscale is between 0.62-0.76. The internal consistency coefficient of the AQ in this study was 0.71.
In Experiment 1, a temporal bisection task was used(Droit‐Volet et al., 2004), which was divided into three stages: training, training test, and formal experiment stage. During the training stage, gray diamonds (with a long diagonal of 5 cm and a short diagonal of 3 cm) were alternately displayed in the center of the screen at 400 ms and 1600 ms, five times each. The participants were informed that 400 ms was the standard short duration and 1600 ms was the standard long duration. At this stage, participants needed to feel subjectively and try to remember the standard long and short duration, but no response was required. In the training test stage, gray diamonds with standard long or short durations were randomly presented in the center of the screen, and the participants were asked to judge "long" or "short" according to the duration length, pressing the "F" or "J" keys, respectively, to respond. Correct and incorrect feedback was provided in this stage. After 10 training trials, the participant could only enter the next stage if all the choices were correct. In the formal experimental stage, the visual stimulus appeared at the center of the screen, randomly, in one of the seven intervals of 400, 600, 800, 1000, 1200, 1400, and 1600 ms, and the participants were asked to judge whether the time interval was closer to the standard long duration or short duration. There were 196 trials in the formal experiment, each duration was randomly presented 28 times, and the interval between trials was random within 1-3 s. The procedure for Experiment 1 is shown in Figure 1.
The proportion of long response, subjective bisection point, and Weber ratio were calculated according to the judgments made by the participants. According to the study by Droit‐Volet et al. (2004), the proportion of long response refers to the proportion of the frequency whose duration is judged to be close to a long duration to the total frequency under a certain condition. The subjective bisection point was the duration corresponding to the proportion of long response of 0.5. The Weber ratio is defined as half of the difference between the duration corresponding to the proportions of long response of 75% and 25%, divided by the subjective bisection point. In this study, the sigmoid function was used to fit the proportion of long response, and the subjective bisection point and Weber ratio of each participant were calculated using the fitting function.
A two-factor of 2 (autistic traits: high AQ group and low AQ group) × 7 (duration: 400-1600 ms) repeated-measures ANOVA was performed for the proportion of long response. As shown in Figure 2a, there was no significant difference in autistic traits. The main effect of duration was significant, and the post-hoc test showed that the difference in the proportion of long response between 1400 and 1600 ms was not significant, the difference in the proportion of long response ratio between the other two durations was significant, and the proportion of long response of the long duration was significantly greater than that for the short duration. The interaction between duration and autistic traits was significant. Further simple effect analysis showed that the proportion of long response of the high AQ group was higher than that of the low AQ group at 400, 600, and 800 ms, but there was no significant difference in the proportion of long response between the two groups at the four durations of 1000, 1200, 1400, and 1600 ms.
The proportion of long response was fitted with an S-shaped curve to calculate the subjective bisection point and Weber ratio. An independent samples t-test was conducted to calculate the subjective bisection and Weber ratio of the two groups. The statistical results showed that there was no significant difference between the high and low AQ groups in the subjective bisection point. The Weber ratio of the high AQ group was significantly higher than that of the low AQ group.
As shown in Figure 2b, there were no significant differences in the levels of autistic traits. The main effect of duration was significant, where the reaction time at 800 ms was significantly longer than that at other durations, the reaction time at 1600 ms was significantly shorter than that at other durations, and the reaction time at 400ms was significantly shorter than those at 600, 800, and 1000 ms, and significantly longer than those at 1400 and 1600 ms. The reaction times at 600 and 1000 ms were significantly greater than those at 1200, 1400, and 1600 ms, and the reaction time at 1200ms was significantly longer than those at 1400 and 1600 ms. The interaction between autistic traits and duration was not significant.
A classical temporal bisection task paradigm was used to explore the difference in time perception between high and low AQ groups in Experiment 1. After learning the standard short duration of 400 ms and the standard long duration of 1600 ms, participants judged the length of seven durations in the range of 400-1600 ms. We found that the proportion of long response in the high and low AQ groups increased with increasing duration, and participants responded faster to the long and short standard durations, especially for the standard long duration. However, we found no differences between groups and interactions on reaction time, suggesting that both groups can make a relatively accurate estimation within the range of duration. The perception of a short duration, ranging from ms to s, is the basis of longer duration perception and reflects purer perceptual processing. Changes in long duration perception may be an accumulation, amplification, and adjustment of short duration perception, and involve the participation of higher cognitive processes such as attention and working memory (Maister & Plaisted-Grant, 2011). Therefore, greater focus should be shifted to the influence of attention and working memory on the exploration of time perception related to autistic traits.
Although there was no difference in the overall trend of time perception between the two groups, a careful analysis of the proportion of long response showed that there was an interaction between duration and autistic traits. Compared with the low AQ group, the proportion of long responses was higher for the group with high AQ at 400, 600, and 800 ms, but there was no significant difference in the longer durations. This is consistent with the central tendency proposed by researchers (Karaminis et al., 2016), in which people tend to overestimate relatively short durations, showing the central trend in the short duration but not in the relatively long duration. In addition, the increase in the Weber ratio in the high AQ group suggests that its temporal sensitivity and temporal accuracy are reduced, which may be related to the change in the internal clock release rate and the adjustment of attention during timing.
In conclusion, we found that individuals with high AQ tended to have similar perceptual abilities to those with low AQ in Experiment 1. The difference was that individuals with high AQ tended to overestimate the shorter duration, and the Weber ratio suggested that the temporal sensitivity of high AQ individuals was relatively poor, which might be one of the reasons for their overestimation of short duration.