Spatial Representation in 36 MonthOlds

1
Spatial Representation in 36 Month-Olds The
Double-Step Saccade Paradigm
Kate Wilmut, Janice H. Brown and John P. Wann
University of Reading

• Introduction
• Robust spatial perception requires the
  combination of retinal and extra-retinal
  information.
• Little is known about the developmental progress
  of spatial representation between infancy and
  five years.
• Double-step saccade paradigm (DSSP)
• Involves consecutive eye movements to
  sequentially flashed targets, targets disappear
  prior to initiation of the first saccade.
• This produces a spatial dissonance between the
  retinal information of the second target and the
  movement needed to reach it.

• By seven months of age children start to base
  spatial judgements on body-centred
  representations (Gilmore and Johnson, 1997)
• Groll and Ross (1982) - no difference in saccade
  programming in 5 yr-olds, 8 yr-olds or in adults.
• Aims
• We sought to establish the efficiency of saccade
  programming in pre-school children
• The DSSP was used to look at spatial
  representation
• Methods
• Eighteen children participated (mean age of 37
  months).
• Eye movements were measured using a gaze
  monitoring camera mounted on top of the monitor.

• For the order of presentation see Figure 2.
• Three target durations were used
• 500ms (easiest level)
• 250ms (middle level)
• 70ms (hardest level)
• Durations were presented in blocks and were
  always presented in the order shown above.
• Measured 1st saccade latency (time to start
  saccade after target 1 appeared) and 2nd saccade
  latency (time to start a saccade after target 2
  appeared).

Gaze monitoring camera
2

• Conclusion
• Children show slowness disengaging attention and
  moving away from foveated targets.
• In addition, these children do not use predictive
  information in the same way as adults.
• Further work Attention disengagement
• Following these findings the gap paradigm was
  used to look at attention disengagement in 36
  month-olds (see figure 5).

• Results
• Saccade latency
• Latency to target 2 increased as target duration
  increased (see figure 3).
• Not seen in adults

Figure 4. Mean 2nd saccade latency across blocks
of 4 trials
Figure 3. 1st and 2nd saccade latency

• Discussion
• Children show a long recovery period when moving
  from targets which have been presented for
  longer.
• This may be caused by a slowness in disengaging
  attention from foveated targets.
• 500ms biggest effect, targets foevated
• 250ms a smaller effect, covert attention engaged
• 70ms no effect, attention not engaged.
• Children did not predict position of target 2
  suggesting that
• Children did not learn the simple pattern
• Or they do not use learnt information whilst
  planning saccades.

• Predicting target location
• Target 2 always appeared opposite target 1 so the
  position of target 2 could be predicted
• If this pattern was learnt 2nd saccade latency
  would decrease over trials.
• No decrease was seen across blocks on either
  version (see figure 4).
• Adults did show a decrease in 2nd saccade latency
  for the 500ms and 250ms duration.

• During a looking task children showed equivalent
  skill at disengaging attention to adults.
• However, during initiation of a hand movement the
  children were slower to disengage attention.
• Suggesting young children have not yet allocated
  attention for action.