Presentation on theme: "Kate Wilmut, Janice H. Brown and John P. Wann University of Reading Figure 2. Order of presentation. Four possible target locations Target two Target one."— Presentation transcript:
Kate Wilmut, Janice H. Brown and John P. Wann University of Reading Figure 2. Order of presentation. Four possible target locations Target two Target one Fixation 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 1 st saccade latency (time to start saccade after target 1 appeared) and 2 nd saccade latency (time to start a saccade after target 2 appeared). Gaze monitoring camera 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. Fixation Targets Saccade to target one Time Body-centred Retinocentric Figure 1. Using retinal information produces an incorrect retinocentric response pattern, combining retinal and extra-retinal information produces a correct body-centred response pattern.
Predicting target location Target 2 always appeared opposite target 1 so the position of target 2 could be predicted If this pattern was learnt 2 nd saccade latency would decrease over trials. No decrease was seen across blocks on either version (see figure 4). Adults did show a decrease in 2 nd saccade latency for the 500ms and 250ms duration. Figure 4. Mean 2 nd saccade latency across blocks of 4 trials 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). 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. Figure 3. 1 st and 2 nd saccade latency Results; Saccade latency Latency to target 2 increased as target duration increased (see figure 3). Not seen in adults Figure 5. Events in the gap paradigm. GAPOVERLAP 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. Kate Wilmut Action research Laboratory The University of Reading