Early morning headaches are a frequent symptom of sleep apnea, as are hallucinations which occur while the person is awake but feeling extremely sleepy. Adults who experience such hallucinations report that they are usually, although not always, able to correct their perceptions of reality as they become more awake and alert. In addition, a slight disorientation sometimes occurs after awakening. This typically lasts for between 3 minutes to half an hour and can involve difficulties with memory or giving inappropriate answers to questions. Many refer to this as a "foggy mind" state. Children appear to have much greater difficulty than adults in distinguishing between that which is imagined and that which is real. They may experience the "foggy" morning awakenings with accompanying hallucinations and later in the day have great difficulty recalling which was reality and which was an hallucination.