Time-on-task effect in pseudoneglect

Abstract

Neurologically normal subjects systematically misbisect space during visual line-bisection or similar tasks, generally erring to the left of the veridical center when bisecting horizontal lines, a phenomenon referred to as pseudoneglect. This phenomenon is usually interpreted as enhanced attention toward the left hemispace resulting in an overestimation of the leftward extent of a line. While most studies have examined the role of attention in spatial bias using spatial cueing methods in bisection tasks, Manly et al. (Neuropsychologia 43(12):1721-1728, 2005) proposed an original paradigm in which the participants' alertness was diminished by sleep deprivation or prolonged execution of a line-bisection task. The authors reported a significant rightward shift in attention related to declining alertness, but they did not control eye movements and, consequently, modifications of scanning and fixation strategies with fatigue cannot be ruled out in their study. Here we examine whether a diminution in alertness induced by a 60-min-long Landmark task would diminish (or even reverse) this attentional bias, when eye movements are absent. Participants performed a forced-choice judgment about the location of a transaction mark in relation to the veridical center of a horizontal line. The results confirmed a significant decrease in the leftward bias over the course of the session but, in contrast to the findings of Manly et al. (2005), we did not observe a reverse bias from the left to the right hemispace. The results are discussed within the context of the hemisphere-activation model.

Upper and lower visual field differences in perceptual asymmetries

“…Spatial biases have subsequently been observed on several measures, including both manual and computerized line bisection (i.e., Jewell & McCourt, 2000;McCourt & Jewell, 1999), cancellation tasks (Vingiano, 1991), the landmark task (Dufour, Touzalin, & Candas, 2007), the greyscales task (Nicholls, Bradshaw, & Mattingley, 1999), and measures looking at judgments of numerosity, size (Nicholls et al, 1999) and distance (Krupp, Robinson, & Elias, in press). Lateral biases have also been identified on more real-world behaviours, such as passing through a doorway (Nicholls, Loftus, Mayer, & Mattingley, 2007;Nicholls, Loftus, Orr, & Barre, 2008), choosing a seat in the theatre (Okubo, 2010), completing a route following task (Thomas, Stuckel, Gutwin, & Elias, 2009) or multiple-choice questionnaire response patterns (Nicholls, Orr, Okubo, & Loftus, 2006).…”

“…This left bias has been observed on several tasks, including line bisection (Luh, 1995;McCourt & Jewell, 1999), the landmark task (Dufour et al, 2007) and the greyscales task (Nicholls et al, 1999;Thomas & Elias, 2010). There are two types of line bisection tasks: manual line bisection (Luh, 1995), where participants use a stylus to bisect a line and perceptual line bisection (i.e., Dufour, et al, 2007;McCourt & Jewell, 1999;Rolfe et al, 2008), where participants are presented with a pre-transected line and asked to make a judgment regarding the location of the transection mark.…”

“…This left bias has been observed on several tasks, including line bisection (Luh, 1995;McCourt & Jewell, 1999), the landmark task (Dufour et al, 2007) and the greyscales task (Nicholls et al, 1999;Thomas & Elias, 2010). There are two types of line bisection tasks: manual line bisection (Luh, 1995), where participants use a stylus to bisect a line and perceptual line bisection (i.e., Dufour, et al, 2007;McCourt & Jewell, 1999;Rolfe et al, 2008), where participants are presented with a pre-transected line and asked to make a judgment regarding the location of the transection mark. When bisecting manually (Luh, 1995), participants bisect to the left of centre and when asked to select whether the transector is located to the left or right of centre on computerized line bisection tasks (i.e., McCourt & Jewell, 1999;Rolfe et al, 2008), participants typically indicate that the mark is to the right of centre, meaning the left side of the line is longer.…”

“…This task has also been used to examine perceptual asymmetries in neurologically normal individuals, who tend to select the image with the salient feature on the left side (Nicholls et al, 1999). Similarly, participants typically bisect lines to the left of centre in manual (Barrett et al, 2000;Luh, 1995) and computerized line bisection (McCourt & Jewell, 1999), and most often falsely indicate that the left end of a line is longer on the landmark task (Dufour et al, 2007). It has been suggested that the leftward bias exhibited by neurologically normal individuals, and referred to as pseudoneglect (Bowers & Heilman, 1980;Jewell & McCourt, 2000), from the same neural mechanisms as the rightward bias in hemispatial neglect (Loftus, Vijayakumar, & Nicholls, 2009;McCourt & Jewell, 1999).…”

“…This phenomenon has been examined using a variety of tasks, such as line bisection (Luh, 1995;McCourt & Jewell, 1999) and the landmark task (Dufour et al, 2007). Line bisection tasks typically demonstrate a leftward bias as individuals tend to bisect lines to the left of centre in both manual (i.e., Barrett et al, 2000;Luh, 1995) The greyscales task (Nicholls et al, 1999) has been used to investigate perceptual asymmetries in judgments of luminosity.…”