Zhi Li and his lab members extended the classic load theory by reconceptualizing perceptual load as a rate problem, which emphasized the importance of time in the allocation of selective attention.
The classic load theory (Laive & Tsal, 1994) proposed that whether task-irrelevant information would be selected by attention depends on whether there are enough attentional resources. Although Load theory has made a great honor in explaining the allocation of selective attention, some researches still showed contradictory results. Li and his lab summarized these findings and concluded it as a debate on the nebulous nature of perceptual load itself. Lavie (2005, p. 75) suggested that “increased perceptual load means that either the number of different-identity items that need to be perceived is increased, or that for the same number of items perceptual identification is more demanding on attention”. Previous researches simply used the number of items to manipulate the perceptual load of tasks. Li and his lab members, however, proposed that the time available for processing the task information could also affect the demanding on attention, which in turn, affect perceptual load. Thus, we should consider perceptual load as a quantity of information per unit of time.
Four experiments has been used to prove their hypothesis.Experiment 1a (block design) and 1b (mixed design) used the classic flanker task paradigm to test the distractor interference, but varied the stimulus exposure duration when the quantity of information was held constant.The results showed that the extent of distractor processing increases with ED even if the quantity of information was held constant (Figure 1).
Figure 1. Results of Experiment 1a Figure 2. Results of Experiment 2a
Experiment 2a used the staircase method to test the exposure duration which was barely enough for processing the task-relevant information, and a cuing paradigm was used to manipulate the distractor condition. The results showed that a letter in the cued location (defined as the distractor) can be selectively ignored, irrespective of the total number of letters in the display, as long as the exposure duration was extremely short (Figure 2, the intercept difference between two lines is equal to the slopes, showing that the distractor could be perfectly ignored in the informative-cue condition). While Experiment 2b used a similar cuing paradigm, but with RTs to assess the extent of distractor processing, showing that the results in Experiment 2 was not due to the cuing effect alone.
The relevant research results “Reconceptualizing Perceptual Load as a Rate Problem: The Role of Time in the Allocation of Selective Attention” has been published in Journal of Experimental Psychology: Human Perception and Performance, 2018. DOI: 10.1037/xhp0000547.