Abstract Variability of performance is a recognized characteristic of patients with cerebral lesions. Variability is partially explained by general inattention and by perseveration (handling of multiple, consecutive data). Cuing or prompting the patient with a perceptual deficit frequently allows the patient to perform a function he previously could not accomplish. Sensory analyzer systems are modality-specific regions which usually begin analysis of a sensory stimulus by categorization. This is followed by further analysis of the object, based upon the initial hypothesis. The context in which the stimulus appears or artificial cues may alter the patient's analysis of the stimulus and may also be factors in the variability of perceptual function.