Neuropsychologia 39 (2001) 132–139
Visual illusions and the control of children arm movements
Maurizio Gentilucci *, Francesca Benuzzi, Luca Bertolani, Massimo Gangitano
Istituto di Fisiologia Umana, Uni6ersita` di Parma, Via Volturno
Received 15 July 1999; received in revised form 17 July 2000; accepted 27 July 2000
The aim of the present study was to determine whether children like adults (Gentilucci M, Chiefﬁ S, Daprati E, Saetti MC, Toni
I. Visual illusion and action. Neuropsychologia 1996;34:369–76; Gentilucci M, Daprati E, Gangitano M, Toni I. Eye position
tunes the contribution of allocentric and egocentric information to target localisation in human goal directed arm movements.
Neurosci Lett 1997;222:123 –6) are inﬂuenced by visual illusions when they transform visual information in motor command.
Children and adults pointed to a shaft extremity of the Mu¨ller-Lyer conﬁgurations, as well as to an extremity of a control
conﬁguration. Movements were executed in two experimental conditions. In the vision condition subjects saw both the stimulus
and their hand before and during movement. In the no vision (memory) condition subjects saw the stimulus and their hand before,
but not during movement. Movement started 5 s after vision was precluded. The Mu¨ller-Lyer illusion affected pointing kinematics
of both children and adults. As found previously (Gentilucci M, Chiefﬁ S, Daprati E, Saetti MC, Toni I. Visual illusion and
action. Neuropsychologia 1996;34:369– 76; Gentilucci M, Daprati E, Gangitano M, Toni I. Eye position tunes the contribution
of allocentric and egocentric information to target localisation in human goal directed arm movements. Neurosci Lett
1997;222:123–6), subjects undershot and overshot the shaft extremity of the closed and of the open conﬁguration, respectively.
The illusion effect was greater in the no vision than in the vision condition. These results show that in children like in adults the
system underlying visual perception in an object-centered frame of reference and that involved in motor control functionally
interact with each other. Although the processes of target localisation were the same, the transformation of target position
information in a sequence of motor patterns was different in children from that in adults. Even if both children and adults
lengthened duration of the deceleration phase in the vision condition, only adults shortened duration of the acceleration phase in
order to maintain constant movement time (Viviani P, Schneider R. A developmental study of the relationship between geometry
and kinematics in drawing movements. J Exp Psychol 1991;17:198–218). This result suggests that children are yet unable to
co-ordinate temporally acceleration with deceleration phase. © 2000 Elsevier Science Ltd. All rights reserved.
Mu¨ller-Lyer illusion; Children; Pointing; Kinematics; Vision and no vision conditions
It is commonly accepted that an object is analysed
differently in the ventral and dorsal visual streams of
cortex in order to perceive an object and to prepare a
motor response, respectively. Corresponding to this
anatomical and functional separation, behavioural dis-
sociations have been observed [3,13,34]. However, other
behavioural studies show that visuo-motor transforma-
tion can be inﬂuenced by perception [6,8,10,14]. This
suggests that the analyses performed in two visual
streams can be functionally related to each other .
In particular, the Mu¨ller-Lyer illusion  affected
pointing to the shaft extremity of the conﬁgurations
and grasping them [6,8,10]. The illusion effect was
found on movements executed under visual control and
it was even greater for memory driven movements. In
these studies not only movement amplitude and move-
ment time, but also initial kinematic parameters more
related to planning, were inﬂuenced by the illusion. In
addition, in memory driven movements the illusion
effect increased when time delay was longer and it did
not affect ﬁnal variability and deviation of arm trajec-
tory. Taken together these results suggest that, accord-
ing to movement constraints, target was localised by
using also perceptual representation, and, in particular,
object centered cues.
* Corresponding author. Tel.: +39-521-903899; fax: + 39-521-
email@example.com (M. Gentilucci).
0028-3932/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.