Inattentional Blindness in Assembly Tasks: Implications of Cognitive and Perceptual Load for Human-Centered Interface Design

Abstract

The inability to perceive a visible but unexpected stimulus is a phenomenon studied in cognitive psychology under the name of inattentional blindness (IB). IB reflects the limited capacity of human attention, as a demanding task may leave few, if any, attentional resources available for an unexpected yet visible stimulus to capture attention. The main cognitive mechanism involved is selective attention, which allows individuals to prioritize information relevant to the task at hand while filtering out irrelevant elements. However, depending on the context, some information may be mistakenly considered as distracting, particularly when it is unexpected. According to load theory, the efficiency of selective attention depends on the level of cognitive and perceptual load during task execution. To date, IB has been primarily explained through the lens of perceptual load, with cognitive load often reduced to executive control tasks. Moreover, the interaction between these two types of load remains underexplored, as does the investigation of IB in applied contexts relevant to everyday activities. To address these gaps, the present study aims to identify the occurrence of IB during manual assembly tasks in industrial settings. A 2x2 within-subject experimental design (N=32) was implemented, independently manipulating perceptual and cognitive load. Participants performed simulated assembly tasks using LEGO components. The main dependent variable was the detection rate of an unexpected stimulus, which was briefly presented on the instruction screen. Results show a significantly higher overall rate of non-detection compared to the control condition. In addition, a high level of either cognitive or perceptual load significantly increased the rate of non-detection. A strong interaction effect between the two types of load was also observed. These findings highlight the importance of considering both cognitive and perceptual load in the design of human-machine interfaces (HMIs), especially when information is delivered dynamically. Inattentional blindness, as a cognitive bias, can affect any individual particularly in high-load environments such as assembly procedures. Modern HMIs increasingly rely on real-time adaptability and contextualized alerts. However, their effectiveness depends on the timely availability of attentional resources, which this study shows to be significantly modulated by task-induced load. Then, a visible but unexpected stimulus may go unnoticed under high load conditions. By demonstrating for the first time the occurrence of IB in an assembly task context, while simultaneously manipulating both types of load, this research reveals limitations of current HMIs and emphasizes the need to integrate this phenomenon into future interface design through a human-centered approach.

Keywords: Inattentional blindness, Cognitive load, Perceptual load, Selective attention, Human-centered, Assembly, Human-machine interfaces

DOI: 10.54941/ahfe1006847