consisted of three main themes; spatial representation, attention
disengagement and eye-hand coordination.
gaze shifts from object to object, the retinal co-ordinates of
environmental features change. A robust spatial perception requires the
combination of retinal and extra-retinal information to produce a
body-centred representation (Abrams, 1992).
The double-step saccade paradigm (DSSP)
involves consecutive eye movements to sequentially flashed targets. On the
standard version of the task, both targets disappear prior to initiation
of the first saccade, creating a spatial dissonance between retinocentric
information of the second target and the movement needed to reach it (Heide,
Blankenburg, Zimmermann, Kompf, 1995).
development of the visual system an infant will correctly respond to the
double-step saccade paradigm by about seven months of age (Gilmore and
carried out three versions of the DSSP. The traditional version with
a target duration of 100ms, an middle version with a target duration
of 250ms and an easy version with a target duration of 500ms.
Posnerís model of covert attention states that a covert shift of
attention involves disengaging from the fixation point, shifting attention
to a new target and re-engaging on the new target.
These three processes must occur before an eye movement can be
initiated (Posner, 1984).
paradigm: A temporal gap inserted between
fixation offset and target onset shortens time taken to initiate a saccade
(Saslow, 1967). This has since been called the gap effect, and consists of
two conditions; the gap condition, when a temporal gap is inserted between
target onset and target offset, and the overlap condition, when target
onset and target offset overlap. Shorter saccade latencies are found in
the gap condition and the difference between saccade latencies on gap and
overlap trials indicates the time taken to disengage attention.
Visual feedback is vital for fast and
accurate hand movements, and as such an efficient co-ordination of the eye
and hand is needed. The way the eye and hand are co-ordinated has been
under scrutiny for many years.
pointing paradigm: Research using a target jump paradigm (location of the
target shifts during the eye movement) has shown that if the target jump
occurred early enough, then a smooth hand movement was made to the new
target location with participants unaware of the move (Goodale, Pelission,
& Prablanc, 1986). These findings suggest that when rapid eye and hand
movements are directed to a target, a set of initial signals are sent to
the muscles controlling the eye and hand. These signals contain
information regarding the position of the target on the retina. Following
the first saccade to the target these signals are updated using the
extra-retinal information gained during the eye movement.