Individuals with a healthy nervous system will show a slight left-sided attention bias when they complete spatial attention tasks. This phenomenon is called pseudoneglect.  It is mainly influenced by age, dominant hand, reading direction and material length and type and so forth. The underlying mechanism is the focus of the research community. Some researchers believe that pseudoneglect is caused by the advantage of brain's right hemisphere in spatial attention task, while the others consider that the left side of the attention bias is depending on the reading direction from left to right. Based on attentional biases in the behavior of normal adults, preschoolers and animals, pseudoneglect is thought to be gradually formed by brain matures and reading practice. The influence of reading direction on pseudoneglect is realized by the asymmetric activation of the two hemispheres of the brain, which also reflects the unilateral adaptability and plasticity of human brain.