Middle Eastern Journal of Disability Studies

Abstract
Background & Objectives: In a long‌–standing controversy over the source of attentional processing, some believe that information is processed based on physical properties immediately after reaching the sensory modalities (early selection), while others believe that information is not processed at the initial stages, but only after reaching higher levels of information processing, depending on whether or not it is related to the person’s goals, expectations, and background (late selection). To establish a synthesis of these two approaches, the perceptual load theory considers environmental demands or task difficulty to be the determining factor of early or late attentional selection. Accordingly, if the perceptual load of the environment is high, the selection of attention will be early; otherwise, it will be late. Criticisms and concerns, along with the vast body of empirical evidence supporting the perceptual load effect, have led to the acceptance of a weaker form of this effect, in which the perceptual load is not considered the only determining factor of attentional control but one of the determining factors. The present study reviewed conceptual and operational definitions of perceptual load, related concerns, and alternative explanations. Also, its applications in clinical fields and daily life were reviewed.
Methods: Considering that the present review focused on theoretical and practical aspects of the theory, the search for documents in the research literature was conducted on both review/theoretical and research documents. To obtain these documents, a non‌–systematic search was performed in databases, including ScienceDirect, PubMed, and PsycINFO, using related keywords such as “perceptual load,” “attentional control,” “selective attention,” “task difficulty,” “psychopathology,” “addiction,” “pain,” “nutrition,” and “daily life.” Finally, the most important documents were extracted, including review articles, theoretical articles, research methods, and research articles. Review and theoretical documents were used to address conceptual and methodological concerns, as well as alternative explanations for the theory, and research documents were used to identify the practical implications of the perceptual load theory in areas such as psychopathology, pain perception, addictive behaviors, and other areas. The search was conducted among the indexed documents between 2000 and 2023.
Results: It was found that perceptual load can be manipulated in three general ways: changing the number of items on display, the degree of similarity between target and non‌–target stimuli, and the number and complexity of perceptual operators. It was also found that regarding the strong form of the theory, there are concerns, such as confusing attention inefficiency with late attention, the absence of a clear conceptual definition of perceptual load, and the impossibility of increasing the perceptual load without increasing the cognitive load. Meanwhile, hypotheses that compete with the strong form of the theory, such as the salience hypothesis and the dilution hypothesis, were also extracted. Finally, the practical implications of the perceptual load theory in areas such as psychopathology and daily life were identified by reviewing empirical evidence.
Conclusion: A review of the research literature indicated a broad theoretical contribution of perceptual load to various clinical fields and daily life. However, the strong form of the theory cannot be considered free of conceptual and methodological flaws. The present study suggests that while the theory of perceptual load effectively identifies the underlying mechanisms related to attentional selection and investigates attention in practice, it is necessary to use it in a weaker form, taking into account existing concerns and competing hypotheses.