A major issue when testing children using a behavioural task is that they be- come bored with the task and stop responding. For this study a large set of data was required so that localisation ability could be investigated. For this reasons it was understood that to increase the number of responses, the testing must be divided into a number of different visits (with time between each visit) and each visit divided into a number of different blocks (with breaks of at least ten minutes between each block).
Responses Over Three Visits
The statistical tests used in this section are the Friedman test and also the Wilcoxon signed-rank test. The Friedman test is used to look at the differences between the age groups when they have repeated measures i.e. multiple visits or blocks. The Wilcoxon signed-rank test is used as a post hoc test used to look for dif- ferences between individual measures e.g. the difference between visits one and two. Table 3.5 shows the total number of responses, total number of cor- rect responses and the number of correct head turn responses averaged over all blocks and reward types. Table 3.6 shows the total number of incorrect trials,
Total Number of Responses M(SD) Total No. Correct Responses M(SD) No. Correct Head Turns M(SD) Visit 1 2 3 1 2 3 1 2 3 Age 1.0-2.2 20.3 (5.6) 20.7 (8.3) 20.3 (5.3) 13.8 (5.5) 12.0 (7.6) 11.8 (6.1) 10.1 (5.1) 9.5 (7.0) 8.0 (5.6) 2.2-4.0 24.0 (9.3) 23.7 (5.3) 22.3 (5.6) 17.6 (9.0) 14.7 (5.9) 12.4 (5.1) 13.1 (7.1) 9.6 (5.2) 8.5 (4.8) 4.0-5.0 27.3 (4.1) 27.7 (4.6) 25.5 (5.2) 12.9 (6.2) 20.2 (6.9) 17.2 (6.3) 15.1 (4.5) 12.1 (5.2) 10.4 (3.8)
Table 3.5:Total and correct number of responses obtained during each visit for each age group. Averaged over blocks and reward types.
Total No. of incorrect responses M(SD) No. incorrect head turns M(SD) No. Null M(SD) Visit 1 2 3 1 2 3 1 2 3 Age 1.0-2.2 6.5(2.9) 8.7(2.6) 8.4(2.9) 0.2(0.4) 0.5(0.7) 0.6(0.5) 6.2(2.5) 7.8(4.0) 7.7(3.7) 2.2-4.0 6.5(4.3) 9.0(2.8) 9.9(2.3) 0.4(0.5) 0.7(0.9) 1.5(2.6) 5.8(4.3) 7.1(3.4) 7.8(3.5) 4.0-5.0 5.4(3.0) 7.5(4.4) 8.3(2.8) 0.5(0.9) 0.9(1.0) 0.3(0.4) 4.7(2.8) 5.5(3.6) 7.5(2.6)
Table 3.6:Total number of incorrect, incorrect head turns and null responses obtained during each visit for each age group. Averaged over
blocks and reward types.
coming boring to the children and the number of responses dropping between visits, this was particularly important for the number of correct head turns. The oldest age group (4.0-5.0 years) shows a significant difference between the three visits (Friedman, χ2(2) = 7.0, p < 0.05). Post hoc tests were only significant for visits one and three (Wilcoxon signed-rank test with Bonferroni correction, z =0, p<0.017).
The other response types show no significances between visits for all age groups.
Responses within Each Visit
With the number of responses decreasing for subsequent visits, in order to in- vestigate how the number of responses changed between blocks (i.e. does ex- posure to the task during a single visit effect the number of the responses) the data will need to be corrected to remove the effect of the visit. Before this can be investigated it was shown that the more visits the children attend we see an overall drop in the number of responses obtained. For analysis of the effect different blocks have within a visit, the effects of the visit must be corrected for. This is to correct for the drop in responses due to each visit and just see the drop in blocks within each visit. The relative number of responses within each block are corrected for by subtracting the mean across the three blocks per visit from the data within each block. The equation for this is shown in Equation 3.1;
where BC is the corrected block, B is the block to be corrected, i is the block number and j is the visit number. ¯V is the mean number of trials during visit j. Table 3.7 shows the total number of relative responses, the total number of relative correct responses and the number of relative correct head turns for each age group and block, averaged over each reward type and corrected for each visit. Table 3.8 shows the total number of relative incorrect responses, the relative number of incorrect head turns and relative null responses for each age group and block, averaged over each reward type and corrected for each visit. All three age groups show a drop in responses across the three blocks on each day’s visit, with block three having the biggest drop in responses for all three age groups. When looking at the correct head responses, age group 1.0-2.2 years shows a significant drop between visits (Friedman, χ2(2) = 14.6, p < 0.05). Post hoc analysis shows significance between visits one and two (Wilcoxon signed-rank test with Bonferroni correction: z = 0, p < 0.017) and also vis- its one and three (Wilcoxon signed-rank test with Bonferroni correction: z = 0, p < 0.017). Age group 1.0-2.2 years also show a significant drop in the total number of correct responses (Friedman:χ2(2) =8.7, p <0.05). Post hoc analy- sis shows a difference between blocks one and two (Wilcoxon signed-rank test with Bonferroni correction: z = 0, p < 0.017) and also blocks one and three (Wilcoxon signed-rank test with Bonferroni correction: z = 0, p < 0.017). Age
Relative No. Total Relative No. Correct Relative No. Correct head Blocks 1 2 3 1 2 3 1 2 3 Age Group 1.0-2.2 4.0 (6.9) -0.8 (8.7) -3.0 (8.8) 6.5 (7.5) -2.4 (7.2) -4.3 (7.3) 3.2 (6.3) -0.4 (6.0) -2.9 (4.3) 2.2-4.0 3.3 (4.5) 0.5 (5.6) -3.7 (6.9) 4.0 (5.2) -0.1 (6.4) -3.9 (7.0) 3.1 (4.3) -0.4 (4.6) -2.7 (6.1) 4.0-5.0 1.2 (2.4) 0.3 (6.8) -1.4 (6.7) 1.9 (5.1) -0.1 (7.0) -1.7 (7.2) 1.4 (3.0) 0.3 (4.8) -1.7 (4.3)
Table 3.7:Relative total number of responses per block (30 trials per block) and correct head turns per block corrected for visits using
Equation 3.1. Signs are kept to show an increase (positive) or decrease (negative) in the number of responses per block.
Relative No. Incorrect Relative No. Incorrect Head Relative No. Null Blocks 1 2 3 1 2 3 1 2 3 Age Group 1.0-2.2 -1.2(2.6) +0.5(2.4) +0.7(3.4) +0.1(0.5) 0.0(0.6) -0.1(0.4) -1.0(2.8) +0.5(3.6) +0.5(3.3) 2.2-4.0 -0.8(3.8) +0.6(4.4) +0.2(1.7) 0.0(1.1) 0.0(1.3) 0.0(1.0) -1.1(2.8) +0.5(3.6) +0.5(3.3) 4.0-5.0 -0.7(3.6) +0.4(4.5) +0.3(3.7) 0.0(0.8) 0.0(0.8) 0.0(0.6) -0.7(2.9) +0.2(3.0) +0.6(2.7)
Table 3.8:Relative number of total incorrect responses per block (30 trials per block), relative number of incorrect head turns per block
and relative number of null responses, corrected for visits using Equation 3.1. Signs are kept to show an increase (positive) or decrease (negative) in the number of responses per block.
tion: z =0, p<0.017) and also visits one and three (Wilcoxon signed-rank test with Bonferroni correction: z =0, p<0.017).
Age group 4.0-5.0 years also shows a significant drop in correct head turns be- tween visits (Friedman:χ2(2) =6.7, p <0.05). Post hoc analysis shows a differ- ence between blocks one and three (Wilcoxon signed-rank test with Bonferroni correction: z=0, p<0.017).
The results suggest for all of the children, the total number of responses and the number of correct head turns is highest during block one and the number of incorrect responses lowest during block one. The drop in total and correct responses and increase in incorrect responses is seen to affect the younger age groups more (1.0-2.2 years and 2.2-4.0 years). Age group 4.0-5.0 years does show a change in the number of responses, however, this change is more grad- ual compared to the other two age groups.
Overall we see that increasing exposure to the task leads to a reduction in the number of responses and increase in the number of incorrect responses. This can be seen in terms of visits and also within blocks. It was hoped that by spreading testing over a number of visits and having breaks between blocks that this could be eliminated. However, the results that even with such breaks and visits, the children still become bored with the task.