If you are told to hold your attention on a string of letters or numbers that are firing by you in quick succession, and told to look for two separate targets, If those targets pass by you in quick enough succession, you will see the first one, but you will not recognize the second. This is called an “Attentional Blink”. Your Attentional Filter “blinks” and misses what should be an activating stimulus.
Source
- Huberman Labs podcast