Participants
Thirty children took part in the study. The children’s parents were briefed about the research goal and procedure and agreed with the participation of their children. Parents signed an informed consent form in accord with the requirements of the Ethics Committee for Research of the University of Sao Paulo, Brazil. All children came from two elementary schools and were eligible to take part in the study once from school records they were considered typically developing children. Exclusion criteria included children who had any developmental disorder such as attention-deficit hyperactivity, autism spectrum disorder or any classical neurological sign such cerebral palsy. The children were randomly assigned to one of two groups defined by the school furniture layout: Group Fixed School Desk (GF) with seven boys and eight girls (n = 15), mean age of 6 years and 9 months, and Group Adjustable School Desk (GA) with nine boys and six girls (n = 15), mean age of 6 years and 7 months.
Experimental task and apparatus
The task involved the reproduction of a graphic pattern similar to a king’s crown (Fig. 1). This graphic pattern was defined after a pilot study and for having two advantages: (a) it was easily recognizable by children who associated it with a kind of a crown; (b) it involved a combination of traces with linear and semicircular shapes that made the task demanding in two dimensions: (a) The spatio-temporal pattern to integrate strokes; (b) The sequence of strokes. The graphic pattern was tested in a pilot study and proved to be easily recognised by children with similar ages.
The reproduction of the graphic pattern was made on a AIPTEC Tablet, model 8000 U, with a cordless sensitive pressure pen. The tablet was connected to a notebook model Hewlett-Packard Pavillion Intel Dual Core. The collected data was treated by a Software MovAlyzer, version 3.2, developed by Neuroscript Group. This software recognized children’s strokes in terms of space and time allowing for the description of the graphic produced in terms of stroke speed, timing and sequence.
Procedure
The study focused on the effect of two kinds of school furniture, one standard and fixed (GF), and another that could to be adjustable (GA) to the child’s physical dimensions (Fig. 2). Children in the GF practiced the graphic pattern in a standard school desk commonly used in most public schools in São Paulo, Brazil. In the other group, GA, children sat in a school furniture in which the height of the chair and the desk could be adjustable to the children’s anthropometrical dimensions. The school desk was adjusted to each child in order for he or she to sit with their hips, knees and ankles at 90°, their feet fully supported on the floor and with their arms being supported comfortably on the table that was slightly inclined. The children’s height was controlled by the use of the individual’s mean height in the sample. The children who exceeded the mean height of 116 cm in more than 6 centimetres were not considered for data analysis.
The study was conducted in a quiet room in the elementary school attended by the children studied, following an authorization given by the School Principal. In accord with the classroom teacher, each child was invited to take part in a graphic task that was going to take place in another room. Once there, the child was asked whether he or she recognized the figure and then whether he or she could drawn it. The child was asked to reproduce the pattern as accurate and fast as possible in 25 trials. The criterion figure was presented at the top of each sheet serving as model to the children. The instructions stated that the king’s crown should present three tips and a rounded base. The experimenter asked the child to perform the task with his or her preferred hand and not the change hands during practice. The child had visual feedback about the spatial features of the patterns produced and also the time taken to perform it.
Measures and hypothesis
From the record of strokes the quality of the graphic skill was assessed by two evaluators who judged the degree of legibility considered from the correspondence between the model and the actual drawing. Graphic reproductions were considered legible when the three tips and the rounded base of the crown could be identified. The agreement between the evaluators judgments was tested by an inter-rater agreement index proposed by Thomas et al. (2011). The values obtained were higher than 0.81 which is considered a very satisfactory agreement. Another qualitative measurement was the posture adopted by the children in each kind of school desk. The categorization was based on four body posture components thought to be adequate to optimize handwriting performance: support on the chair backrest; elbow support in the desk; hand support on the paper and support of the feet.
Legibility was further used as a control to eliminate from the quantitative analysis the drawings that did not correspond to the model. The software MovAlyzer made a recognition analysis of all patterns drawn automatically discarding those that did not match the specifications. The quantitative analysis was based on two measures: total movement time and spatial linear error. Total Movement Time comprehended the time interval from the start of the first stroke to the conclusion of the drawing calculated in seconds. Spatial linear error was calculated as the linear size difference in centimetres between criterion figure (the model) and the actual drawing performed by the children.
The main assumption made in the present study was that the lay out of school desk will interfere with the legibility of the drawing, body posture and also with the spatial and temporal aspects of graphic patterns. Hence, we hypothesized that adjustable school desk will provide better conditions for practicing the drawing. This benefit will be manifested in the children’s performance with the GA doing better than GF in every account.
Statistical analysis
For the purpose of the descriptive and inferential statistics, the 25 trials of the practice session were grouped in five blocks with five trials each. The Univariate Cochran’s C and Brown-Forsythe tests were used to test for normality of the resulting data. The differences in pattern legibility and spatio-temporal parameters between the two layouts of school furniture during the practice of the task were tested by a Two-Way ANOVA, Group (2) × Blocks (5) with repeated measures in the second factor. Whenever a significant F-ratio was obtained, the Tukey post hoc test with Bonferroni correction was used to locate the differences. For all statistical analyses, significance was accepted at p < 0.05. The Contingency Correlation test was also calculated to search for significant associations between body postures components and legibility of patterns. This type of test is recommended to verify the existence of associations between nominal variables. The statistical analysis was performed using Statistical Package for Social Sciences (SPSS, version 22.0).