Cognitive deficits refer to impairments or difficulties in cognitive functions, which include memory, attention, perception, problem-solving and reasoning. These deficits can result from various factors such as brain injuries, neurological disorders, developmental delays, mental illnesses, or exposure to certain substances. Cognitive deficits can manifest in different ways, ranging from mild difficulties with memory or concentration to more severe impairments that affect an individual's ability to perform daily tasks and maintain independence.