In psychology and neuroscience,<unk>  is the longest list of items that a person can repeat back in correct order immediately after presentation on 50% of all trials. Items may include words, numbers, or letters. The task is known as digit<unk>  when numbers are used.<unk>  is a common measure of working memory and short-term memory. It is also a component of cognitive ability tests such as the WAIS. Backward<unk>  is a more challenging variation which involves recalling items in reverse order.
Memory span
Visual object recognition 
Serial memory processing
Natural scene perception
Visuospatial function
Working memory
Associative memory 
Face time