Determining whether a patient is capable of giving consent is a decision to be made by the attending physician, taking into account all circumstances of the patient's life situation. These circumstances include the patient's age, physical and mental condition or sociobiographical characteristics. In practice, however, it has proved problematic that the determination is based on a yes/no decision, although there are certainly different degrees of ability to consent. For instance, a patient may understand simpler medical interventions, but not more complex ones. The ability to consent should therefore always be assessed with regard to a concrete intervention. American psychiatrists have developed the MacArthur Treatment Competence Test (MACT) as an aid. This examines the ability to consent based on the criteria of understanding information, reasoning, the ability to make and communicate decisions, and disease insight. However, the use of standardized procedures is viewed critically and according to prevailing opinion does not replace personal assessment by a physician.