Do “Frontal tests�? measure executive function? Issues of assessment and evidence from fluency tests

The executive processes which control and regulate cognition have been the subject of intense interest in recent years. In particular there has been a growing consensus that the frontal lobes of the brain are intimately involved in executive function (e.g. Duncan, 1986; Shallice, 1988; Stuss & Benson, 1986). There have also been a large number of studies into childhood development of frontal and executive function (e.g. Riccio, Hall, Morgan, Hynd, Gonzalez, & Marshall, 1994); the operation of executive processes in adulthood and normal ageing (e.g. Parkin & Walter, 1992); and the effects of degenerative diseases on executive function (e.g. Bhutani, Montaldi, Brooks, & McCulloch, 1992). Most of this research involves tasks which are interchangeably called “frontal lobe�? or “executive�? tests, commonly accepted within neuropsychology as measures of executive function. However, the term “frontal lobe tests�? is problematic because such measures are often not sensitive to, or specific to, lesions in that particular brain area (Reitan & Wolfson, 1994). Also, the use of the term “executive tests�? seems somewhat premature, given that little is known about the reasons for poor performance, and few studies have attempted to determine whether these tasks really assess executive function. Nevertheless, these “executive�? tests are widely used in both clinical and healthy populations, so it is imperative that we increase our understanding of the factors influencing performance upon them.