4 Level 2 VPT in Typically Developing Children
4.7.4 Developmental Trajectories
In order to examine how the different processes examined in this study (MR, VPT2S, VPT2O and body representation) change in relation to age and verbal ability, the developmental trajectory for each task was plotted separately against age and BPVS standardised score.
Both VPT2S and VPT2O show a steep linear increase with age, as does body representation with performance reaching the highest levels of accuracy at around 10 years old in all 3 tasks (Figure 4.6). Mental rotation however shows a much more subtle linear slope, with even the oldest children still not reaching ceiling on this task. This suggests that mental rotation develops more slowly than the other abilities in TD children in relation to age.
For verbal ability, all processes (VPT2S, VPT2O, MR and body representation) show a linear increase in performance with BPVS standardised score (Figure 4.7). Body representation is the most well developed ability in relation to BPVS, with higher scoring children showing performance closer to ceiling level on this task.
Figure 4.7 Developmental Trajectories for the development of mental rotation,
VPT2S & O and Body representation across children plotted against BPVS standardised score.
Figure 4.6: Developmental Trajectories for the development of mental rotation,
VPT2S & O and Body representation across children plotted against age.
R² = 0.0861 R² = 0.4036 R² = 0.3044 0 20 40 60 80 0 2 4 6 8 10 12 % c o rr e ct Age Linear (MR) Linear (VPT2S) Linear (VPT2O) R² = 0.0305 R² = 0.1165 R² = 0.0574 R² = 0.0204 0 20 40 60 80 100 0 50 100 150 % C o rr e ct BPVS Standardised Linear (mr) Linear (vpts) Linear (vpto) Linear (BODIES)
4.8 Discussion
The results of experiment three showed that TD children are able to put themselves in another place in order to predict what things would look like if they were at a different point in space. They also revealed that this ability is not predicted by mental rotation performance. The results of experiment four showed that VPT2 self and other appear to be related in TD children and that general VPT2 ability is predicted by body representation. Here these results are discussed in relation to previous findings of VPT2 in TD people.
The results in this chapter showed that VPT2 S and O were highly correlated. Research has shown that whether we are asked to take someone else’s point of view or transform ourselves to a different perspective, the same underlying egocentric transformation occurs (Kessler & Wang, 2012; Mazzarella, et al., 2012) suggesting that they share the same underlying processes. The results of the current study confirmed this suggestion, showing that both are predicted by body representation ability in TD children. Though studies have shown that neurally, self and other perspective taking activate different brain areas (Mazzarella, et al., 2013), behaviourally they show similar patterns between response times and angular disparity. The results in this chapter provide further behavioural evidence for VPT2 self and other being closely linked and support the notion that they are both driven by the same underlying processes.
The results of experiment three showed that VPT2 self was not predicted by mental rotation ability. These results are unsurprising, as it has been suggested that egocentric spatial transformations are the process which underlie the ability to take a different perspective (Yu & Zacks, 2010). In experiment four, further investigation into the underlying processes involved in VPT2 showed that body representation is a strong predictor of VPT2 ability. These findings support the suggestion that the ability to understand bodies from different points of view relates to the ability to take a different perspective in typically developing people. Research has shown that TD people put themselves in someone else’s place by first mentally creating a motor representation of the target viewpoint and transforming themselves to match the target (Grush, 2004). Kessler and Thomson (2009) provided evidence for this process in a study which showed that manipulating the body posture of the viewer to be more or less congruent with that of the target affected time taken to transform perspectives. The evidence from this study shows that the link between body representation and VPT2 begins to develop in childhood.
In Hamilton’s original study ToM ability was found to predict VPT2O performance. In the current chapter SAS was used as a proxy for ToM to examine how social skills impacts on both VPT2S and VPT2O. No relationship was found between these abilities. However, in both experiments the children generally scored similarly on the SAS with few
children demonstrating evidence of poor social skills. This could go some way to explaining why no relationship was found. Further studies should look at using both ToM and measures of general social skills to examine the relationship between both of these abilities and VPT2.
Across experiments one and two different results were found in regards to which task the children showed better performance. The results of experiment three showed that the TD children performed better on the mental rotation task compared to VPT2S, whereas in experiment four, the children performed better on VPT2 S and O compared to mental rotation. Both groups of children were of a similar average age and range, as well as a similar average BPVS and range. However, the developmental trajectories between the studies are different in regards to verbal ability. Both groups of children show similar developmental trajectories for mental rotation in relation to age. However the developmental trajectory for mental rotation in relation to verbal ability is flatter in the children in experiment three (Figure 4.3), whereas in experiment four mental rotation ability increases with verbal ability (Figure 4.7). These findings suggest that differences between studies are a result of possible individual differences in regards to the development of mental rotation in the samples used. Both VPT2 and mental rotation develop steadily across childhood. The developmental trajectories for both abilities in relation to age are similar according to the data collected in this chapter. It is possible that some children may develop better mental rotation quicker whereas others will develop better VPT2
quicker. Future research could consider how individual differences contribute towards the development of these different abilities.
4.9 Broader Implications
The results of these studies provide an interesting insight into the development of VPT2 abilities in TD children. They suggest that VPT2 in TD children is highly related to the ability to represent bodies from different points of view and draw information from postures. However, so far it is unclear as to what predicts VPT2 ability in children with autism and whether it will be the same as in TD children. Chapter 5 will use the methods developed in this chapter to examine VPT2 alongside spatial transformations and body representation in children with ASD.