DYNAMIC TOUCH IN TYPICALLY DEVELOPING CHILDREN & CHILDREN WITH DCD
David Sugden Amanda Kirby & Lisa Edwards 1 2 ’ University of Leeds, UK, The University of Wales, Newport , UK 1
2
2
BACKGROUND TO THE STUDY
RESULTS
Although some information of the affordances of objects, sufaces and implements can be obtained from static holding of an object such as shape, size and texture, we invariably do not hold an object still but tend to wield it. In daily life we wield objects- scissors, kitchen implements, gardening tools and sports equipment, providing information about the spatial and weight characteristics of the object. This type of perception is often called dynamic touch and variables such as the role of inertia tensor are proposed as providing this information (Carello & Turvey, 2000;Pagano & Turvey, 1995; Solomon & Turvey, 1988).
The mean and standard deviations of the rod estimates are shown in Table 1 and illustrated in Figure 4.
Wielding is a process by which an object is twisted and turned in different directions yet not necessarily in any systematic way. We do this with tennis rackets in sports shops to see how they ‘feel’. But what exactly do we mean by this and what is the information we are receiving in order to make any decisions? Work by Solomon and Turvey (1988) and Pagano and Turvey (1995) examined the ability of adults to perceive the spatial qualities of hand-held rods though dynamic touch that were wielded unseen by movements of the wrist. Solomon and Turvey (1988) also manipulated both the position of an attached weight on a rod and the actual loaction of the grasp. Their results highlighted the significant role that moment of inertia plays as a hapatic variant for perceiving spatial charateristics during hand held rod wielding. Some work has been conducted in children (Beak, 2001) but little if any to our knowledge with children showing coordination difficulties.
AIM OF THE STUDY The aim of this pilot study is to examine the differences in dynamic touch, as operationalised by estimation of rod length, between typically developing children (TDC) and children with developmental coordination disorder (DCD). There is a long and distinguished history of identifying differences between these two groups on a number of variables that range from purely sensory, through to central processing, motor programmes, utilisation of feedback as well as purely motor variables (e.g. Hill, 2005).
Table 1 Mean
Mean
Median
Median
SD
SD
TDC
DCD
TDC
DCD
TDC
DCD
30
26.27
26.38
26
24
9.16
7.78
45
40.58
37
40
38
11.89
11.7
60
49.24
52.15
48
52
14.96
13.99
75
57.96
64.69
59
67
16.94
21.9
90
68.28
78.23
67.5
73
19.98
22.19
TDC
46.5
Participants Fifty eight children, 9-11 years of age, participated: 45 TDC, 21 male and 24 female; 13 children with DCD, 10 male and 3 female.
DCD
38.5
Figure 1
Figure 2
Figure 3
TDC DCD
30
45
60
75
90
Table 2
METHODOLOGY
Equipment The equipment is shown in figures 1, 2 and 3. It consists of a screen on one side of the child with a hole through which the child could place his/her hand and wield an unseen rod. At the other side of the child is a trolley with a marker that the child could move to estimate the length of the rod from a given starting point.
90 80 70 60 50 40 30 20 10 0
The groups were further split into two groups-those that did or did not scale appropriately with increasing rod length with the results shown in Table 2. Scaling appropriately was operationally defined as those children who could place all rods in the correct length order. Table 2 shows the percentage of children in each group who could scale appropriately.
% that scaled
Other characteristics Parents completed questionnaires to assess for any additional difficulties. Two children from the TDC group were elimated due to abnormal difficulties on the Strengths and Difficulties Questionnaire and the ASSQ leaving 43 children in the TDC group.
Mean values for rods
The results showed that both groups placed the rods correctly in order of length although they consistently underestimated the length. This underestimation increased with the length of the rod but as a percentage of the rod length, it remained constant. No statistically significant differences were found between the children with DCD and the TDC irrespective of the error score utilised
Group
Motor Characteristics Of the children with DCD, 11 scored in the lowest 5% on the Movement ABC Test and Checklist; one child was at the 8th% on the test and in the lowest 5% on the Checklist and one child only had a Checklist score which was in the lowest 5%; all fulfilled other DSM IV criteria.
Figure 4
Eyeballing this data shows more of the TD children being able to scale appropriately with increasing rod length but the differences were not significant.
OTHER WORK A further experiment was conducted with a subset of the children who worked with us in the first experiment. This involved weighting the rod. Thirty three children took part: 11 DCD 22 TDC Procedure A rod 80 cms in length was used and a weight was attached to the bottom, middle and top of the rod in a random order without the children knowing. The rod was also presented without a weight. The children were asked to estimate the length of the rod with and without the weight attached. The results are shown in Table 3 Table 3 Means & Standard deviations in cms. Actual Length 80cms. TDC
DCD
No weight
59.91 (11.58)
67.64 (18.68)
Bottom
57 (14.54)
63.55 (17.55)
Middle
65.86 (17.66)
79.1 (26.38)
Top
77.27 (19.24)
86.82 (20.66)
Apart from the DCD group with the weight at the top, there was underestimation of the length of the rod. It does look through eyeballing the data that the results from the DCD children were better than the TDC group but high intra group variability meant that there were no significant differences between the groups in their estimation of length with any rod placement. Procedure The children were asked to wield unseen, 5 rods of differing lengths 30-90 cms (steps of 15cms), in random order and estimate their length by a marker on a trolley rolled by the other hand to where they thought the end of the rod was located. The children were given a practice trial with a rod length that was not used in the actual testing. The instructions were as follows
“
We are going to play a ‘rod’ game with you. We will give you different length rods and get you to try and estimate the length of the rods without you seeing them. You will sit on a stool and put your arm through a small window and we will then pass you the rod. With your other hand you will hold a handle on a trolley and you have to move it to show us how long you think the rod is .
”
REFERENCES
Beak, S.L. (2001). In search of haptic information: How perception supports action during wielding. Unpublished PhD Thesis, Manchester Metropolitan University. Carello, C. & Turvey, M.T. (2000). Rotational dynamics and dynamic touch. In M. Helleer (Ed.), Touch, representation and blindness. Oxford: Oxford University Press, pp. 22-66. Hill, E.L. (2005). Cognitive explanations of the planning and organization of movement. In D.A. Sugden & M.E. Chambers (Eds.), Children with developmental coordination disorder. London: Whurr. Pegano, C.C. & Turvey, M.T. (1995). The inertia tensor as a basis for the perception of limb orientation. Journal of Experimental Psychology: Human Perception and Performance, 21, 1070-1087. Solomon, H.Y. & Turvey, M.T. (1988). Haptically perceiving the distances reachable with hand-held objects. Journal of Experimental Psychology: Human Perception and Performance, 14, 404-427.
COMMENT This is an exploratory investigation with the interesting result that no differences were found between a group of children who are typically developing and one with identified motor difficulties. This is unusual and we can currently only speculate as to the reasons. The results are more puzzling because with the same group of children, major differences were found between the two groups on a multicomponent movement task that involved both solving a movement problem and movement execution. Our preliminary thoughts surround the nature of the task. The wielding is a purely psychophysical task and one could argue that it has little meaning or real ecological validity. It involves estimation of length of an unseen rod and it may be that in tasks such as this many children with DCD do not show problems. The other task in which we found great differences between the groups is a real motor problem which involved crossing a ‘river’ using mats as stepping stones and included such challenges as estimating distance and their stride length together with the execution of the act. This is altogether a more ecological and complex task drawing upon a range of abilities that we normally use in our everyday lives. We are moving forward in a number of directions. First, we will complete more work with rods and other objects using different hand positions on the rods. In addition, we will start to work with variables that involve more than estimation of rods such as wielding tennis rackets and gauging their comfort and usefulness before actually trying them with full vision.