The cognitive function that refers to the ability to focus on only one thing at a time is called "selective attention." Selective attention is a fundamental cognitive process that allows individuals to concentrate on specific stimuli or tasks while ignoring or filtering out irrelevant or distracting information.
This ability is crucial for staying focused and achieving tasks efficiently in a world filled with various sensory inputs and information. By selectively attending to one thing at a time, individuals can better allocate their mental resources and process information more effectively. However, it's essential to note that selective attention can vary from person to person and can be influenced by factors such as individual differences, context, and cognitive load.