Executive functions and the frontal lobes: a conceptual view The understanding of executive functions and their relationship to the frontal lobes is complex. This review discusses several problems in understanding these functions and presents data from our studies to support the following statements: (1) examining patients with focal frontal lobe lesions is a necessary first step in defining the relationship between executive functions and the frontal lobes; (2) there is no single executive function, but distinct processes related to the frontal lobes can be differentiated, which converge on a general concept of control functions; (3) a simple control-automatic distinction is inadequate to explain the complexity of control-automatic processes; (4) the distinction between complex and simple tasks cannot explain the differences in functions between the frontal lobes and other brain regions; and (5) the most important role of the frontal lobes may be for affective responsiveness, social and personality development, and self-awareness and unconsciousness. A major problem has been the inconsistent and interchangeable use of psychological and anatomical definitions of executive and frontal functions. While the effects of frontal lobe damage have been studied, many researchers use "frontal functions" as a synonym for "executive functions" without reference to anatomy. The relationship between "executive" or "supervisory" functions and "frontal lobe" functions is not clear. Even those studying frontal lobe damage often do not clearly define the anatomical limits of the pathology. Studying frontal lobe functions is difficult because there is no clinical condition specifically related to the frontal lobes. It is time-consuming to find patients with well-defined focal frontal lobe lesions. Additionally, many "executive" tests are multi-factorial, and performance could be impaired for reasons other than frontal lobe dysfunction. This is particularly true for complex tests. The multi-factorial nature of these tests is also responsible for low correlations among frontal lobe tests. Many tests used to assess frontal lobe damage were developed for other reasons. The current knowledge of how to dissociate processes within a task was not available when these tests were developed. Another methodological issue is the limited evidence on the validity and reliability of frontal function tests. The experience of the examiner and the structure of the testing situation are also important factors. The quality of the dependent measures themselves may raise obstacles. We have reported that individuals with traumatic brain injury vary in their performance on a reaction time task, which may be related to frontal lobe dysfunction. The study of executive or frontal functions has been conceptually difficult, as terms such as "executive" functions, "dysexecutive control", "supervisory system", and "control" functions are not easily operationalized. This has made it difficult to devise precise experimental manipulations to study these processes.Executive functions and the frontal lobes: a conceptual view The understanding of executive functions and their relationship to the frontal lobes is complex. This review discusses several problems in understanding these functions and presents data from our studies to support the following statements: (1) examining patients with focal frontal lobe lesions is a necessary first step in defining the relationship between executive functions and the frontal lobes; (2) there is no single executive function, but distinct processes related to the frontal lobes can be differentiated, which converge on a general concept of control functions; (3) a simple control-automatic distinction is inadequate to explain the complexity of control-automatic processes; (4) the distinction between complex and simple tasks cannot explain the differences in functions between the frontal lobes and other brain regions; and (5) the most important role of the frontal lobes may be for affective responsiveness, social and personality development, and self-awareness and unconsciousness. A major problem has been the inconsistent and interchangeable use of psychological and anatomical definitions of executive and frontal functions. While the effects of frontal lobe damage have been studied, many researchers use "frontal functions" as a synonym for "executive functions" without reference to anatomy. The relationship between "executive" or "supervisory" functions and "frontal lobe" functions is not clear. Even those studying frontal lobe damage often do not clearly define the anatomical limits of the pathology. Studying frontal lobe functions is difficult because there is no clinical condition specifically related to the frontal lobes. It is time-consuming to find patients with well-defined focal frontal lobe lesions. Additionally, many "executive" tests are multi-factorial, and performance could be impaired for reasons other than frontal lobe dysfunction. This is particularly true for complex tests. The multi-factorial nature of these tests is also responsible for low correlations among frontal lobe tests. Many tests used to assess frontal lobe damage were developed for other reasons. The current knowledge of how to dissociate processes within a task was not available when these tests were developed. Another methodological issue is the limited evidence on the validity and reliability of frontal function tests. The experience of the examiner and the structure of the testing situation are also important factors. The quality of the dependent measures themselves may raise obstacles. We have reported that individuals with traumatic brain injury vary in their performance on a reaction time task, which may be related to frontal lobe dysfunction. The study of executive or frontal functions has been conceptually difficult, as terms such as "executive" functions, "dysexecutive control", "supervisory system", and "control" functions are not easily operationalized. This has made it difficult to devise precise experimental manipulations to study these processes.