关键词: 序列依赖效应, 数量感, 任务相关性, 线性分布的特征

Abstract:

Serial dependence refers to the phenomenon where current perception is influenced not only by the current stimulus input but also by preceding events in recent history. This effect plays a crucial role in the establishment of relatively stable perceptions in dynamically changing environments. Previous studies have shown that the extent and direction of serial dependence are related to the task relevance of stimulus features. It is still unclear, though, if task relevance in linearly distributed features affects this impact, given that the majority of these researches have mostly focused on experiments using circularly distributed features. The current study investigated the impact of task relevance of linearly distributed features on serial dependence by using estimation tasks with dot arrays as stimulus materials, which were varying orthogonally in two dimensions: number/area (Experiment 1) or number/size (Experiment 2).

The study employed a 7 (number of dots) × 7 (dot array area in Exp 1/average dot size in Exp 2) × 2 (task relevance: relevant vs. irrelevant feature) block design. In the number estimation task, participants were instructed to focus on the number of dots, thus prioritizing the number as a relevant feature, while deeming the field area irrelevant. Conversely, the field area estimation task directed attention to the field area of dot array, making it the relevant feature and relegating the number to irrelevance. Experiment 2 followed the same experimental paradigm as Experiment 1, with the key difference being that it replaced the field area estimation task with an average item size estimation task. Each participant underwent all experimental conditions, with the order of the two tasks balanced across them. Initially, a fixation cross was presented for 1350−1450 ms, followed by a dot array image shown at the center of the screen for 250 ms. Task instruction then appeared at the top of the screen, accompanied by an axis beneath. Participants were instructed to accurately estimate the number of dots in the array by selecting a point on the number line through mouse click. The mouse click would trigger the appearance of a white marker, indicating the selected position, and its corresponding numerical value was exhibited underneath. Participants then affirm their estimation by pressing the “Enter” key. A response window of 15 seconds was provided; failure to respond within this period led to a 'no response' recording (marked as “N/A”) for that trial, and the program automatically proceeded to the next trial.

Our findings revealed that the effect of a feature from previous trial on current perception consistently counteracted the influence of the same feature in the current trial, regardless of the feature's task relevance. From a serial dependence perspective, the effects of previous task-relevant features were always repulsive; however, whether the previous task-irrelevant features showed attractive or repulsive serial dependence effects, was depended on the specific feature. This highlights the dual influence of task relevance and feature characteristics on the serial dependence effect of linearly distributed features. Notably, the persistence of the serial dependence of the irrelevant features implies that serial dependence can also arise at the object level.

Key words: serial dependence, numerosity perception, task relevance, linear distributed feature