Exp Brain Res (2003) 153:378–381 DOI 10.1007/s00221-003-1559-5 RESEARCH NOTE Christina Rival · Isabelle Olivier · Hadrien Ceyte · Carole Ferrel Age-related differences in a delayed pointing of a Müller-Lyer illusion Received: 6 March 2003 / Accepted: 19 June 2003 / Published online: 26 September 2003  Springer-Verlag 2003 Abstract It has been suggested that movements to visible or remembered targets are differently sensitive to the Müller-Lyer (ML) illusion. Indeed, when the target is continuously visible, movements rely on the veridical object characteristics, whereas remembered movements are thought to reflect the perceived characteristics of the object. The aim of the present study was to determine how movements to visible or remembered targets are influ- enced by the ML illusion in children aged 7 to 11 years old. Participants were asked to make a perceptual judgment or to point a shaft extremity of the ML configurations (Closed, Control, and Open) in three visual conditions (Closed Loop, Open Loop-0-s delay, and 5-s delay). Perceptual (Perceived Length, PL) and motor (Movement Magnitude, MM, and Peak velocity, PV) variables were measured. Results showed that PL was influenced to the same extent by the ML illusion in the three visual conditions. Moreover, it appears that in subjects as young as 7 years old, the activation of the ventral system features may give rise to the perceptual illusion effect observed in all three experimental condi- tions. However, regardless of the subject’s age, MM and PV were only sensitive in the delay condition, suggesting that delayed movements are also mediated by the ventral stream. These data suggested that the distinction between perception and motor visual pathways appears quite early during childhood (before 7 years). Our data also demon- strated that children were relying on both visual process- ing streams during perceptual as well as visuomotor tasks during remembered movements. Keywords Children · Kinematics parameters · Müller-Lyer illusion · Pointing · Visual pathways Introduction According to Milner and Goodale (1995), the visual system accommodates two distinct functions which rely respectively on the ventral and dorsal systems: vision for perception and vision for action. The ventral system allows the construction of long-term perceptual represen- tations of objects’ features and relationships. Conversely, the dorsal system performs on-line visual processing involved in object-oriented actions, retaining visual information for only around 2 s (Elliott and Madalena 1987). This dissociation between perception and action has been observed in experiments involving visual illusions which show that visual perception is deceived by the illusion whereas action is not (Haffenden and Goodale 1998). Other studies reject the claim that visual illusions do not impact action and question the main assumption that perception and action are neurologically dissociated (Donkelaar 1999). Effects of visual illusion have been observed on many parameters of action such as movement time (Donkelaar 1999) and also on movements executed without visual feedback (Gentilucci et al. 1996) and delayed movement (Westwood et al. 2000a). Milner and Goodale (1995) and Westwood and colleagues (2000a) suggested that movements to remembered targets might be guided by the ventral system, while natural actions are mediated by the dorsal system. Developmental data show that, during the performance of a perceptual task, children as young as 5 years old are deceived by visual illusions (Piaget 1961) and are less sensitive than adults (Kovàcs 2000). Gentilucci et al. (2001) studied visuomotor processes during a pointing task in children aged 7–8 years old and adults in the context of the Müller-Lyer (ML) illusion. Regardless of age, all participants undershot and overshot the shaft extremity of the closed and open configurations, respec- tively. Furthermore, the illusion effect was greater in the C. Rival · I. Olivier ( ) ) · H. Ceyte Laboratoire Sport et Performance Motrice, UniversitØ Joseph Fourier, B.P. 53, F-38041 Grenoble Cedex 9, France e-mail: Isabelle.Olivier@ujf-grenoble.fr Tel.: +33-4-76514593 Fax: +33-4-76514469 C. Ferrel LEAD, UMR CNRS 5022, UniversitØ de Bourgogne, France