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: Effects of low tide rainfall on the erodibility of intertidal cohesive sediments

authors: Pilditch, Conrad A.

subjects: sediment transport

abstract: Low tide rainfall may represent an important but little studied process affecting sediment fluxes on intertidal mudflats. In this study, we simulated rainfall events on an intertidal mudflat (median grain size=18.4 μm) of low slope (1 in 300) then quantified effects on sediment erodibility. Treatments consisted of a high (4.1 mm min⁻¹ for 6 min) and low (0.36 mm min⁻¹ for 60 min) rain intensity, chosen to match naturally occurring events and experiments were conducted seasonally (May and August) to encompass variations in ambient sediment stability. Changes in bed elevation due to rainfall were estimated using marked rods and sediment erodibility parameters (mass of sediment eroded at a flow velocity of 0.3 m s⁻¹ (ME-30, g m⁻²) and critical erosion velocity (Ucrit, m s⁻¹)) were determined in annular flumes (bed area=0.17 m²). Ambient/control sediment erodibility in May (ME-30=211 g m⁻², Ucrit=0.18 m s⁻¹) was higher than in August (ME-30=30 g m⁻², Ucrit=0.26 m s⁻¹) and was correlated with changes in biological activity. In May, surface sediment was influenced by high densities of the bioturbating snail Hydrobia ulvae (1736 ind. m⁻²) and low biomass of the sediment stabilising microphytobenthos (5.7 μg chlorophyll a cm⁻²). In contrast, in August H. ulvae densities were low (52 ind. m⁻²) and microphytobenthic biomass higher (9.2 μg chlorophyll a cm⁻²). The high rain treatment caused a decrease in bed elevation of between 1.5 mm (May) and 4.4 mm (August) and significantly reduced sediment organic content and microphytobenthic biomass. Rainfall increased sediment erodibility; compared to ambient sediments ME-30 increased by a factor of 1.4× in May and 8.8× in August and caused a 10–30% decline in Ucrit. The seasonal difference in treatment effect was due to the change in ambient sediment stability. The low rain treatment in August had no effect on bed elevation, microphytobenthic biomass or sediment erodibility. In May, the same treatment caused a reduction in bed elevation (0.5 mm) and microphytobenthic biomass but counter-intuitively, a decrease in sediment erodibility (ME-30 was reduced by 40%, Ucrit increased by 5%) compared to controls. We attribute this result to removal by rainfall of easily eroded surface flocs and biogenic roughness which resulted in an underlying sediment with a smoother surface and greater resistant to erosion. Results suggest that high intensity rain events may destabilise intertidal sediments making them more susceptible to erosion by returning tidal currents and that the sediment eroded during such events may represent a considerable fraction (up to 25%) of the seasonal variation in shore elevation. The impact of natural rain events are likely to vary considerably due to variations in droplet size, intensity and duration and the interaction with ambient sediment stability

text: Effects of low tide rainfall on the erodibility of intertidal cohesive sediments Low tide rainfall may represent an important but little studied process affecting sediment fluxes on intertidal mudflats. In this study, we simulated rainfall events on an intertidal mudflat (median grain size=18.4 μm) of low slope (1 in 300) then quantified effects on sediment erodibility. Treatments consisted of a high (4.1 mm min⁻¹ for 6 min) and low (0.36 mm min⁻¹ for 60 min) rain intensity, chosen to match naturally occurring events and experiments were conducted seasonally (May and August) to encompass variations in ambient sediment stability. Changes in bed elevation due to rainfall were estimated using marked rods and sediment erodibility parameters (mass of sediment eroded at a flow velocity of 0.3 m s⁻¹ (ME-30, g m⁻²) and critical erosion velocity (Ucrit, m s⁻¹)) were determined in annular flumes (bed area=0.17 m²). Ambient/control sediment erodibility in May (ME-30=211 g m⁻², Ucrit=0.18 m s⁻¹) was higher than in August (ME-30=30 g m⁻², Ucrit=0.26 m s⁻¹) and was correlated with changes in biological activity. In May, surface sediment was influenced by high densities of the bioturbating snail Hydrobia ulvae (1736 ind. m⁻²) and low biomass of the sediment stabilising microphytobenthos (5.7 μg chlorophyll a cm⁻²). In contrast, in August H. ulvae densities were low (52 ind. m⁻²) and microphytobenthic biomass higher (9.2 μg chlorophyll a cm⁻²). The high rain treatment caused a decrease in bed elevation of between 1.5 mm (May) and 4.4 mm (August) and significantly reduced sediment organic content and microphytobenthic biomass. Rainfall increased sediment erodibility; compared to ambient sediments ME-30 increased by a factor of 1.4× in May and 8.8× in August and caused a 10–30% decline in Ucrit. The seasonal difference in treatment effect was due to the change in ambient sediment stability. The low rain treatment in August had no effect on bed elevation, microphytobenthic biomass or sediment erodibility. In May, the same treatment caused a reduction in bed elevation (0.5 mm) and microphytobenthic biomass but counter-intuitively, a decrease in sediment erodibility (ME-30 was reduced by 40%, Ucrit increased by 5%) compared to controls. We attribute this result to removal by rainfall of easily eroded surface flocs and biogenic roughness which resulted in an underlying sediment with a smoother surface and greater resistant to erosion. Results suggest that high intensity rain events may destabilise intertidal sediments making them more susceptible to erosion by returning tidal currents and that the sediment eroded during such events may represent a considerable fraction (up to 25%) of the seasonal variation in shore elevation. The impact of natural rain events are likely to vary considerably due to variations in droplet size, intensity and duration and the interaction with ambient sediment stability

year: 2008

title: Dying to research: An autoethnographic exploration of researching Māori and whānau experiences of end-of-life care

authors: Moeke-Maxwell, Tess

subjects: indigenous

abstract: The authors critically reflect on the autoethnographic process involved in navigating a smooth pathway towards investigating dying, death and bereavement for Māori whānau (families) in a way that supports and gives voice to their experience. This study, based in the Māori & Psychology Research Unit at The University of Waikato, is supported by a Health Research Council Erihapeti Rehu-Murchie Career Development Award. It explores the “end-of-life” journeys of Māori and their whānau in South Auckland and Waikato, through the dying process and subsequent challenges of bereavement. The researcher’s journey from novice to someone fully enmeshed in the struggles and triumphs of conducting research with Māori is examined. There is reflection on the challenges and issues that have emerged since settling on this research topic. These include ethical concerns, and the processes and outcomes associated with negotiating tensions between a shifting academic objectivity and the development of a methodology requiring subjective reflexivity.

text: Dying to research: An autoethnographic exploration of researching Māori and whānau experiences of end-of-life care The authors critically reflect on the autoethnographic process involved in navigating a smooth pathway towards investigating dying, death and bereavement for Māori whānau (families) in a way that supports and gives voice to their experience. This study, based in the Māori & Psychology Research Unit at The University of Waikato, is supported by a Health Research Council Erihapeti Rehu-Murchie Career Development Award. It explores the “end-of-life” journeys of Māori and their whānau in South Auckland and Waikato, through the dying process and subsequent challenges of bereavement. The researcher’s journey from novice to someone fully enmeshed in the struggles and triumphs of conducting research with Māori is examined. There is reflection on the challenges and issues that have emerged since settling on this research topic. These include ethical concerns, and the processes and outcomes associated with negotiating tensions between a shifting academic objectivity and the development of a methodology requiring subjective reflexivity.

year: 2010