Why do we need a new test of visual inattention? 

Visual inattention most commonly arises after right hemisphere stroke. Clinicians often note that some patients who show behavioural signs of visual inattention are not detected by existing tabletop tests. The Balloons Test has been designed as a screening test which can be used in conjunction with more extensive test batteries such as the Behavioural Inattention Test (Wilson, Cockburn and Halligan, 1987). 

Why use the Balloons test? 

• It is quick, simple to administer and can be used as a bedside test 

• It detects a higher proportion of visual inattention in right brain damaged patients than other tests 

• It enables the generalized inattention index and an index of left sided inattention (the lateralized inattention index) to be derived 

• It provides a method for establishing whether unilateral omissions can be entirely attributable to visual field defects 

• The time limit reduces the likelihood of false positive findings caused by people ‘giving up’ prematurely because of sustained attention deficits. 

The test is based on the phenomenon of pop-out (Treisman and Gelade, 1980; Treisman and Gormican, 1988). Detection of balloons among the circles (as in subtest A), has been shown to be a relatively parallel process - i.e. the time taken to detect targets of this kind does not increase significantly as the number of distractors increases (Eglin et al., 1989). 

The nature of the test 

In subtest A - the control test - 22 of the 202 items are targets to be cancelled. Targets are circles with a line adjoining, which are termed ‘balloons’; other items in the array are circles. Patients are simply required to locate and put a line through each balloon in a fixed time limit of three minutes. 

Subtest B is a test of serial search. The number and position of balloons and circles is exactly the reverse of subtest A. Thus, 90 balloons and 10 target circles are presented on either side of the midline, with two central circles used to demonstrate the task. In subtest B participants are asked to cancel out as many circles as they can find in three minutes. The targets do not pop out, rather they have to be effortfully searched for in a serial fashion. This makes greater demands on attention than subtest A, hence, a higher number of omissions on B than on A allows exclusion of the possibility that the omissions are caused by visual field deficits unrelated to attention. There must be an attentional deficit for the omissions to differ so markedly when both arrays are visually similar although varying the attentional demands on the subject. This view is supported by several studies which show that serial search performance is much more impaired than parallel search in unilateral visual neglect (Riddoch and Humphreys, 1989; Eglin et al., 1989). 

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