|Alternative Title||Estimating The Time-to一collision of Threatening Stimuli|
|Place of Conferral||中国科学院心理研究所|
|Keyword||碰撞时间 威肋 刺激 时距知觉 唤醒度 情绪面孔 虚拟现实|
然而，有一些研究发现情绪对TTC估计会产生影响。例如，相对于中性图片，人们都会更低估威胁场景图片(Brendel, DeLucia, Hecht, Stacy, & Larsen, 2012)和威胁动物图片(Vagnoni, Lourenco, & Longo, 2012)的TTC。不过，研究者还未厘清个体低估威胁刺激的TTC的原因;对社会性威胁刺激(如，愤怒面孔)的TTC是否也存在低估的结果也不一致;通过在计算机显示器上放大刺激的方式模拟物体的靠近运动或多或少与实际碰撞情景不符。
Just imagine that a lion is pouncing on an antelope. The possible collision between the two means a threat for the antelope and a meal for the lion. For both, the estimation of time-to-collision (TTC) is very important for survival. According to different theories, estimation of TTC can be predicted by distance (between organism and object) and looming velocity; or depends on optic information from looming stimuli; or relies on the ratio of the visual angle subtended by the distance between any two points on an object divided by the rate of the change of this angle. From these points of view, the estimation of the TTC to approaching objects is mainly based on physical features at low level.
However, TTC estimation can be affected by emotion. For instance, threatening animal (spider and snake) pictures and scenes shortened estimation of TTC. But the reasons why human observers underestimate TTC for these threatening stimuli are still unclear. In addition, studies have investigated the judgment of TTC for threat facial expression (anger faces), but obtained inconsistent results. In addition, researchers always simulated the approaching movement by expanding the size of visual stimufi across different frames on computer displays in previous studies, which is different from the scene in the real life.
Regarding the disadvantages mentioned above, the current thesis addressed these two questions: (1)What cause people underestimate the TTC of threatening stimuli (Study 1)? (2) Whether the estimation of TTC for threatening stimuli in virtual reality environment shows similar underestimation effect (Study 2)?
There were four experiments in Study I. In Experiment 1 we intended to replicate the TTC judgement task used by Vagnoni et al. (2012). In the task, participants were instructed to imagine each stimulus continuing to approach them after it disappeared and press a button to indicate the moment when the stimulus would collide with them. It was found that Chinese college students also underestimated TTC of threatening stimuli (spiders or snakes) compared with non-threatening stimuli (butterflies or rabbits). In Experiment 2 we aimed to explore whether the underestimation of TTC for threatening stimuli resulted from their general distortion of temporal perception. A temporal bisection task was used. Participants were instructed to judge whether the duration of the stimuli presented was more similar to the standard long duration or to the standard short duration that they just learned. If the participants had a general distortion in temporal perception for threatening stimuli, their judgment of duration for threatening stimuli would tend to be longer than that for non-threatening stimuli. But the results showed that there was no difference between the judgment for the threatening and non-threatening images.
Therefore, the underestimation of TTC for threatening stimuli cannot be explained by a general distortion of temporal perception. The purpose of Experiment 3 was to explore the effect of arousal on TTC estimation. We used spider and snake pictures as threatening stimuli and an equal number of photographs of money and foods as positive no-threatening stimuli and the arousal of these two kinds of stimuli is equal. The participants were also instructed to perform the TTC judgment task. The results revealed that the estimation of TTC for threatening and positive no-threatening pictures had no significant difference, and both estimations were shorter than those for the threatening stimuli in experiment 1 .This result indicated arousal might play a key role on the underestimation of TTC. In Experiment 4, three types of emotional faces (anger faces for threat, happy and neutral faces for non-threat) were used in the TTC judgment task. The results showed that participants did not underestimate the TTC of angry faces (threat stimulus). This finding suggested that TTC is not underestimated for all kinds of threatening stimuli.
Study II contained two experiments. The purpose of Experiment 5 was to repeat Experiment 1 in the VR condition. Inconsistent with Experiment 1，we did not found any difference in TTC estimation between threatening and non-threatening stimuli among all subjects. Interestingly, there was a gender difference, i.e. only female subjects underestimated TTC of the threatening stimuli. The aim of Experiment 6 was to repeat Experiment 4 in VR condition. The results were in line with that of experiment 4, there was no difference in TTC estimation for the three emotional faces.
In this thesis, we found that looming stimuli shorten our TTC estimation. Compared with non-threatening stimuli (butterflies and rabbits), participants tended to underestimate TTC of natural threatening stimuli (spiders and snakes). However, there was no difference between TTC estimation of social threatening stimuli (angry faces) and social non-threatening stimuli (happy and neutral faces). Under VR conditions, the effects of snakes and spiders seem to decrease, and a gender differences was presented. Moreover, the TTC estimation of social threatening stimuli under VR condition was not different from that of social non-threatening stimuli. We supposed these results can be explained from an evolutionary perspective. The threat from snakes and spiders may be of prominently evolutionary implications. In life-and-death situations, individuals need to prepare in advance for the coming threats. In addition, the weakening of TTC underestimation under VR condition may be due to the fact that cues of depth in VR scenes are clearer and more authentic than common computer displays. Therefore, participants may make TTC estimation in different ways in these two conditions. In conclusion, this thesis revealed the important role of emotion in time perception, especially in TTC estimation.
|李才文. 对威胁刺激的碰撞时间估计[D]. 中国科学院心理研究所. 中国科学院大学,2019.|
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