Why is it easier to spot a mistake in someone else’s notebook than in your own? Why does the teacher use a red pen to correct mistakes?

In his notebook, a person’s eyes see their usual handwriting, that is, certain configurations of letters. In someone else’s notebook, the visual analyzer encounters new information, so attention is sharper and it is easier to notice the error. Red color against the background of the main text color is a bright visual stimulus, draws attention to the error and improves memorization.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.