What is the purpose of counting out loud during the walk stage of Walk and Turn?

The purpose of counting out loud during the walk stage of the Walk and Turn test is to assess cognitive function. This component of the test evaluates a subject's ability to divide their attention, which involves both physical coordination and mental processing. As the subject walks heel-to-toe along a straight line while simultaneously counting each step, it allows law enforcement officers to observe how well the individual can perform a task that requires focus and coordination at the same time.

Distractions, increased difficulty, or maintaining rhythm are not the primary goals of this action; instead, it's specifically the cognitive processing and the ability to multitask that are being analyzed. This test is often used to determine if a driver's impairment may be affecting their capacity to safely operate a vehicle.