The attention skill allows us to monitor and select the information and stimuli that are given to us by the visual system, allowing us to process and store them. Over the last few years, one of the most promising areas of visual cognition research is precisely the one that focuses on the study of visual attention. Attention involves perceptual resources that allow us to select specific stimuli or activities both intentionally or automatically.

The key aspect of attention includes three features (Pashler, 1998):

1. Some stimuli can be elaborated more than others;
2. There is an apparent limit on the ability to process stimuli simultaneously;
3. The sustained and continuous processing of visual stimuli involves a greater  perception of effort to complete the task.

To have a good attentive index you need six features:

• Continuous sustained attention over time
• Selective attention
• Distributed Attention
• Dynamic attention
• Good peripheral view
• Good use of visual memory