title: Comparing static Gantt and mosaic charts for visualization of task schedules

authors: Luz, Saturnino

subjects: computer science

abstract: A mosaic chart has been proposed for representation of events on a timeline. While early studies demonstrated the effectiveness of mosaics in supporting visualization of multimedia records on a meeting browser, the usability of mosaics as a static timeline visualization has not been studied in more general settings. This paper investigates the use of the mosaic charts for visualization of project schedules. A user study was conducted to compare a building project schedule encoded alternatively as a mosaic or as a Gantt chart. Although the study focused on static graphs, for which the Gantt technique is usually very effective, results showed that the users were as fast and accurate at answering the questions using the mosaic representation as they were using Gantt charts. The analysis and experiment indicated algorithmic, space-filling and interpretation limitations of the mosaic technique. We suggest possible design improvements to overcome some of these limitations.

text: Comparing static Gantt and mosaic charts for visualization of task schedules A mosaic chart has been proposed for representation of events on a timeline. While early studies demonstrated the effectiveness of mosaics in supporting visualization of multimedia records on a meeting browser, the usability of mosaics as a static timeline visualization has not been studied in more general settings. This paper investigates the use of the mosaic charts for visualization of project schedules. A user study was conducted to compare a building project schedule encoded alternatively as a mosaic or as a Gantt chart. Although the study focused on static graphs, for which the Gantt technique is usually very effective, results showed that the users were as fast and accurate at answering the questions using the mosaic representation as they were using Gantt charts. The analysis and experiment indicated algorithmic, space-filling and interpretation limitations of the mosaic technique. We suggest possible design improvements to overcome some of these limitations.

year: 2011

title: An Analysis of the Impact of Reinforcement on Response Variability on Multiple Behavioural Dimensions

authors: Kong, Xiuyan

subjects: Reinforcing behavioural variability

abstract: A series of four experiments were carried out to examine whether increases in variability in responding on some dimensions of a behaviour as a result of reinforcement generalised to other dimensions of the same behaviour. In Experiment 1, adult participants drew 300 rectangles on a computer screens; variability in the Area, Shape and Location dimensions of the rectangles drawn was measured. One group of participants received reinforcement when they drew rectangles varying on all three dimensions (VAR) using a threshold contingency to determine reinforcement while another group received reinforcement regardless whether they varied on any of the dimensions of the rectangles drawn (YOKE). Results showed that the variability of each dimension, as measured by the U-value, was higher for the VAR group than for the YOKE group. In Experiment 2, three groups of adult participants received reinforcement when they varied on two of the three dimensions of the rectangles drawn. Results showed that reinforcing variability in the Shape and Location dimensions and in the Area and Location dimensions resulted in higher variability in these dimensions compared to the dimension where variability was not directly reinforced, as measured by U-values. However, for the group who received reinforcement when varying in the Area and Shape dimensions, the variability across the three dimensions did not differ. Generalisation of reinforced variability was examined by comparing the variability in dimensions that were not subject to reinforcement for varying from Experiment 1 and Experiment 2. For the Shape and Location dimensions, results showed that the variability was higher when the two dimensions occurred with other dimensions that were subject for reinforcement for varying compared to when they occurred with other dimensions that were not required to vary. However, no significant difference was found for the Area dimension. Therefore, there appeared to be generalisation of reinforced variability for only two of these three groups of participants, suggesting the dimensions were not orthogonal. The non-orthogonality of the three dimensions of the rectangles was suggested as a possible confounding variable so that it not be concluded that generalisation of reinforced variability across dimensions had been obtained. Experiment 3 used a task with more independent dimensions (Shape, Colour and Pattern) to control for the non-orthogonality issue found in Experiment 2. Adult participants created objects by selecting elements from three dimensions on the computer screen. One group of participants received reinforcement when they varied on the use of elements on all three dimensions using a threshold contingency while the other group received reinforcement independent of the elements chosen. Results showed that the variability in using the elements for all three dimensions was similar between the two groups; whether the group received reinforcement when the dimensions varied did not make a difference. Inspection of the elements selected on each trial revealed that participants from both groups, in general, responded in stereotypic patterns; however, the stereotypy in the responses was not picked up by the measure of U-value. In Experiment 4, a new task asking participants to colour t-shirts on the computer screen was created to examine the effect of reinforcement on the variability in colours used. Adult and adolescent participants were instructed to colour t-shirts on the computer screen in three phases. In Phase 1, no feedback was provided; in Phase 2, positive feedback was provided when participants used a colour they had not used before (including those used in Phase 1); and in Phase 3, no feedback was provided. Results showed that, after reinforcement for using novel colours, participants who used only a small number of colours initially used more colours; however, the increase was not found for participants who initially used a moderate or high number of colours. U-value as the measure of variability was examined by using two sets of simulated data. It was found that highly stereotypic response patterns can result in extremely high U-values. Also, the number of options/categories used affects the values of U, which makes comparisons between groups difficult. Overall, results from these experiments support the notion that the level of variability in responses can be controlled by reinforcement. It is possible that learned variability can generalise over unreinforced dimensions. However, the examination of generalisation of reinforced variability across dimensions is not conclusive when the dimensions are interdependent. The results and simulation showed that U-value as a measure of variability needs to be used with caution because it does not capture potential stereotypy in responses and the values of U can be ambiguous.

text: An Analysis of the Impact of Reinforcement on Response Variability on Multiple Behavioural Dimensions A series of four experiments were carried out to examine whether increases in variability in responding on some dimensions of a behaviour as a result of reinforcement generalised to other dimensions of the same behaviour. In Experiment 1, adult participants drew 300 rectangles on a computer screens; variability in the Area, Shape and Location dimensions of the rectangles drawn was measured. One group of participants received reinforcement when they drew rectangles varying on all three dimensions (VAR) using a threshold contingency to determine reinforcement while another group received reinforcement regardless whether they varied on any of the dimensions of the rectangles drawn (YOKE). Results showed that the variability of each dimension, as measured by the U-value, was higher for the VAR group than for the YOKE group. In Experiment 2, three groups of adult participants received reinforcement when they varied on two of the three dimensions of the rectangles drawn. Results showed that reinforcing variability in the Shape and Location dimensions and in the Area and Location dimensions resulted in higher variability in these dimensions compared to the dimension where variability was not directly reinforced, as measured by U-values. However, for the group who received reinforcement when varying in the Area and Shape dimensions, the variability across the three dimensions did not differ. Generalisation of reinforced variability was examined by comparing the variability in dimensions that were not subject to reinforcement for varying from Experiment 1 and Experiment 2. For the Shape and Location dimensions, results showed that the variability was higher when the two dimensions occurred with other dimensions that were subject for reinforcement for varying compared to when they occurred with other dimensions that were not required to vary. However, no significant difference was found for the Area dimension. Therefore, there appeared to be generalisation of reinforced variability for only two of these three groups of participants, suggesting the dimensions were not orthogonal. The non-orthogonality of the three dimensions of the rectangles was suggested as a possible confounding variable so that it not be concluded that generalisation of reinforced variability across dimensions had been obtained. Experiment 3 used a task with more independent dimensions (Shape, Colour and Pattern) to control for the non-orthogonality issue found in Experiment 2. Adult participants created objects by selecting elements from three dimensions on the computer screen. One group of participants received reinforcement when they varied on the use of elements on all three dimensions using a threshold contingency while the other group received reinforcement independent of the elements chosen. Results showed that the variability in using the elements for all three dimensions was similar between the two groups; whether the group received reinforcement when the dimensions varied did not make a difference. Inspection of the elements selected on each trial revealed that participants from both groups, in general, responded in stereotypic patterns; however, the stereotypy in the responses was not picked up by the measure of U-value. In Experiment 4, a new task asking participants to colour t-shirts on the computer screen was created to examine the effect of reinforcement on the variability in colours used. Adult and adolescent participants were instructed to colour t-shirts on the computer screen in three phases. In Phase 1, no feedback was provided; in Phase 2, positive feedback was provided when participants used a colour they had not used before (including those used in Phase 1); and in Phase 3, no feedback was provided. Results showed that, after reinforcement for using novel colours, participants who used only a small number of colours initially used more colours; however, the increase was not found for participants who initially used a moderate or high number of colours. U-value as the measure of variability was examined by using two sets of simulated data. It was found that highly stereotypic response patterns can result in extremely high U-values. Also, the number of options/categories used affects the values of U, which makes comparisons between groups difficult. Overall, results from these experiments support the notion that the level of variability in responses can be controlled by reinforcement. It is possible that learned variability can generalise over unreinforced dimensions. However, the examination of generalisation of reinforced variability across dimensions is not conclusive when the dimensions are interdependent. The results and simulation showed that U-value as a measure of variability needs to be used with caution because it does not capture potential stereotypy in responses and the values of U can be ambiguous.

year: 2016

title: ‘Revolting murder at Te Aroha’ in 1881

authors: Hart, Philip

abstract: The brutal murder of Hamiona Haira, who had been mining with his two brothers and his father-in-law, shocked the new settlement. Being a member of Ngati Koi and Ngati Hako, these hapu threatened utu on the Pakeha responsible, causing both Maori and Pakeha miners to abandon their claims at Tui. Suspicion immediately fell on John Procoffy, a Finn, and evidence was quickly collected, officials being anxious to obtain a speedy conviction to avoid an innocent Pakeha being killed in revenge. Rangatira agreed to let the courts deal with the case, although some Pakeha criticized the government for being too anxious to appease Maori.
After a coroner’s inquest, which included Maori as members of the jury, returned a verdict of murder by ‘person or persons unknown’, Procoffy faced two trials. As the prosecution was handicapped by the limitations of contemporary forensic skills, its case was largely circumstantial. Although the police were certain they had their murderer, others were not convinced, and there was a reluctance to convict because of the death penalty. The final outcome was a verdict of not guilty, which, as was pointed out, should have been ‘not proven’. 
Procoffy fled the country. His acquittal was accepted by Maori leaders, and calm returned to Te Aroha.

text: ‘Revolting murder at Te Aroha’ in 1881 The brutal murder of Hamiona Haira, who had been mining with his two brothers and his father-in-law, shocked the new settlement. Being a member of Ngati Koi and Ngati Hako, these hapu threatened utu on the Pakeha responsible, causing both Maori and Pakeha miners to abandon their claims at Tui. Suspicion immediately fell on John Procoffy, a Finn, and evidence was quickly collected, officials being anxious to obtain a speedy conviction to avoid an innocent Pakeha being killed in revenge. Rangatira agreed to let the courts deal with the case, although some Pakeha criticized the government for being too anxious to appease Maori.
After a coroner’s inquest, which included Maori as members of the jury, returned a verdict of murder by ‘person or persons unknown’, Procoffy faced two trials. As the prosecution was handicapped by the limitations of contemporary forensic skills, its case was largely circumstantial. Although the police were certain they had their murderer, others were not convinced, and there was a reluctance to convict because of the death penalty. The final outcome was a verdict of not guilty, which, as was pointed out, should have been ‘not proven’. 
Procoffy fled the country. His acquittal was accepted by Maori leaders, and calm returned to Te Aroha.

year: 2016