Neuropsychologia 40 (2002) 282 – 290 Effects of visible and invisible cueing on line bisection and Landmark performance in hemispatial neglect Bettina Olk, Monika Harvey * Department of Experimental Psychology, Uniersity of Bristol, Bristol BS81TN, UK Received 8 December 2000; received in revised form 18 May 2001; accepted 21 May 2001 Abstract A total of 12 patients with hemispatial neglect (and two control groups) were tested to examine the effects of lateralized cues on line bisection and Landmark judgements. The experiment was designed to investigate whether bisection and landmark biases induced by cueing are simply a result of a direct perceptual lengthening of the cued part of the line caused by the fact that the cue is visible, thus creating a composite ‘line plus cue’ or whether cueing indeed induces an attentional bias. Secondly, earlier work by Harvey et al. [Harvey M, Milner AD, Roberts RC. An investigation of hemispatial neglect using the landmark task, Brain and Cognition 1995; 27: 59 – 78] has shown that in neglect patients cues work by inducing orientational biases rather than via the alteration of subjective length perception. An attempt was made to replicate this finding and extend it to cues that are not physically present. The bisection data clearly showed that cues bias attention rather than work via a direct lengthening of the line: both visible and invisible cues biased bisection performance equally well. The Landmark data, however, revealed much less clear-cut results and we failed to repeat the earlier observation by Harvey et al. that cues induce orientational biases. Even when the neglect patients were categorised into premotor and perceptual categories a clear effect failed to emerge. It is hypothesised that the earlier reported effect may be linked to neglect severity rather than to perceptual type neglect. © 2001 Elsevier Science Ltd. All rights reserved. Keywords: Line bisection; Landmark; Cueing; Hemispatial neglect www.elsevier.com/locate/neuropsychologia 1. Introduction The influence of cueing procedures on line bisection behaviour in hemispatial neglect patients as well as on healthy participants has frequently been demonstrated. Generally, a cue presented at one end of the line biases bisection performance to the side of the cue, e.g. to the right with a cue on the right side and to the left when a cue is presented on the left side of the line [18,24]. The typical rightward bisection errors exhibited by neglect patients when bisecting horizontal lines tend to decrease with unilateral left cues [18,24,26] and are usually en- hanced with unilateral right cues [26]. These observed cueing effects were traditionally obtained by placing either numbers or letters at the left, right or at either end of the line and requiring participants to read out the letters/numbers prior to bisection. Milner et al. [20] explained cueing effects in terms of attentional mechanisms, proposing that a cue draws attention to that side and thereby renders the cued side more salient. As a result, the cued side of the line is overestimated in length and the mark is placed towards the side of the cue. This attentional account has been challenged both by Mattingley et al. [18] and Fischer [11] who pointed out that since cues are positioned beyond the true endpoints of the line, they extend the line’s horizontal extent by several millimetres. This is especially problematic with unilateral cueing as it be- comes impossible to separate the relative contributions of an attentional manipulation from those caused by the alteration in the perceptual ‘point of balance’ of the stimulus in the horizontal plane. For these reasons, Mattingley et al. [18] used a different cueing paradigm which included an invisible cue condition where sub- jects had to place invisible marks at the end of the lines. * Corresponding author. Tel.: +44-1179-288572; fax: +44-1179- 288588. E-mail address: m.harvey@bristol.ac.uk (M. Harvey). 0028-3932/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved. PII:S0028-3932(01)00095-1