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The secret of change blindness: Why do we miss big changes in our environment?
In everyday life, our visual system is constantly taking in and interpreting our surroundings. Whether it is a busy street, a fragrant meadow, or a familiar living room, these natural scenes appear in our field of vision at any time. Yet, why do we sometimes miss these changes, even obvious and significant ones? The reasons behind this make us start to reflect on the role of attention and our cognitive processes.
Studies show that when our visual attention is focused on a specific task, large changes in our surroundings may go unnoticed. This is what is called the “change blind spot”.
The battle for the role of attention
A major area of disagreement in theories of natural scene perception is the role of attention. Some theories suggest that focused attention is necessary, while others argue that the process does not require focused attention. In early models, focused attention played a partial role, and these models were usually divided into two stages: the first stage was non-focused, which registered low-level features such as brightness gradients and motion in a parallel manner; The second stage requires focused attention to register high-level object descriptions.
These studies show that when our vision is focused on a task, some significant changes in the environment that are irrelevant to the task may escape our attention.
Evidence that challenges earlier models
With the advent of the attentional freedom hypothesis, it challenged the views of earlier models. Many studies have shown that basic visual features emerge automatically during visual search; for example, when searching for a target in a natural scene, objects with high-order representations are rapidly acquired, seemingly without requiring focused attention. Furthermore, studies have shown that humans and primates can quickly and accurately recognize and categorize natural images, even after brief exposure.
Re-evaluating the need for focused attention
A recent study once again emphasizes the need for focused attention. The study found that participants did show the phenomenon of change blind spot in certain multi-object tracking and rapid sequence visual presentation tasks. When participants’ primary task was sufficiently challenging, their natural scene perception abilities were impaired. This study raises the question of whether previous studies may not have truly adequately required participants’ full attention.
Participants' perception of natural scenes was impaired under the dual-task condition, suggesting that focused attention does play a key role in processing complex scenes.
Various models proposed
To explain the process of natural scene perception, scientists have proposed several different models. Evans and Treisman's hypothesis proposed that humans are able to detect discrete features of object categories in parallel without them being fully recognized. This model posits that natural scene perception begins with a one-time patrol of the visual processing hierarchy, followed by more detailed analysis if necessary.
In Evans and Treisman's studies, participants were able to identify the object within a split second but were often unable to report its location immediately.
Fast Visual Classification Model
Models of ultra-fast visual categorization argue that such high-order object representations are formed automatically without focused attention. Some experimental results show that some neurons are already highly selective at the initial stage of visual response, which means that no feedback mechanism is needed to increase response selectivity. Some functional magnetic resonance imaging and event-related potential studies have shown that even masked visual stimuli that participants are not aware of can produce significant adjustments in the activity of the motor system.
Neural Object Archive Theory
According to Xu and Chun's neural object profile theory, the human visual system first selects four or so objects from a crowded scene and then encodes the details. Their research shows that the object representation at this stage is rough, and as the stage progresses, the object's characteristics and identity information will be further absorbed.
The significance of natural scene statistics
Understanding the process of natural scene perception is undoubtedly of great significance for deepening our understanding of human cognitive methods. Perhaps we should think about this: In our daily lives, how many environmental changes are quietly appearing before our eyes, but we ignore them?
