title: Variables controlling the resurgence of previously reinforced behaviour in hens

authors: Cleland, Bryce Steven

abstract: Resurgence is defined as the occurrence of previously reinforced behaviours when reinforcer delivery ceases for a recently reinforced behaviour. In five experiments, variables suggested to control the degree of occurrence of a first-trained behaviour during the extinction of a second-trained behaviour (resurgence) were investigated. All experiments used hens and behaviours were selected from door push, key peck, and head bob. In Experiment 1, using 6 naive hens, Behaviour 1 was reinforced on a random-interval (RI) 60-s schedule followed by two sessions of extinction. Each occurrence of Behaviour 2 was then reinforced followed by another period of extinction. The degree of occurrence of Behaviour 1 during the final extinction was less than that which occurred during the period of Behaviour 1 extinction, suggesting that the extinction of Behaviour 2 did not increase the occurrence of Behaviour 1. This result failed to support the idea that resurgence is induced by the extinction of Behaviour 2. In Experiment 2, using the same hens and an additional hen, Experiment 1 was repeated five times and then there were either 0 or 9 sessions of Behaviour 1 extinction in a further five conditions. The degree of resurgence was generally less when there were 9 sessions than when there were no sessions but not consistently different from either when there were 2 sessions. Experiment 3 used six naive hens. Two first-trained behaviours were initially reinforced on RI 45-s schedules under a multiple schedule. One first behaviour then received a period of extinction and then each occurrence of two second behaviours was reinforced under the multiple schedule followed by extinction. The sequence from training of the first behaviours to the extinction of the second behaviours was repeated 10 times with the number of occurrences of the component for which extinction was in effect for the first behaviour varying across conditions from 12 to 0. The degree of resurgence was an inverse function of the amount of Behaviour 1 extinction. Experiment 4 used six naive hens. In a multiple schedule two first behaviours were reinforced on RI 20-s schedules and then two second behaviours were reinforced followed by extinction. This was repeated 8 times with the RI schedule in effect for one of the second behaviours varying from 80 s to 10 s across conditions while the other remained at 40 s. The degree of occurrence of Behaviour 1 when Behaviour 2 was reinforced was a direct function of the varied RI schedule of Behaviour 2. The degree of resurgence of Behaviour 1 in extinction was an inverse function of the varied RI schedule of Behaviour 2. The degree of resurgence was also inversely related to the degree of occurrence of this Behaviour 1 when Behaviour 2 was reinforced. Experiment 5 used five naive hens and one hen from Experiment 3 in a multiple-schedule design where the length of training of the second behaviours varied from 124 to O occurrences of a component over three conditions. No effect of this was found on the degree of resurgence. The results are consistent with the hypothesis that resurgence is the result of the prevention of extinction of Behaviour 1 by the reinforcement of Behaviour 2, but they are not definitive proof that this hypothesis is correct. Models derived from the Generalised Matching Law and Behavioural Momentum are also proposed as descriptions of resurgence.

text: Variables controlling the resurgence of previously reinforced behaviour in hens Resurgence is defined as the occurrence of previously reinforced behaviours when reinforcer delivery ceases for a recently reinforced behaviour. In five experiments, variables suggested to control the degree of occurrence of a first-trained behaviour during the extinction of a second-trained behaviour (resurgence) were investigated. All experiments used hens and behaviours were selected from door push, key peck, and head bob. In Experiment 1, using 6 naive hens, Behaviour 1 was reinforced on a random-interval (RI) 60-s schedule followed by two sessions of extinction. Each occurrence of Behaviour 2 was then reinforced followed by another period of extinction. The degree of occurrence of Behaviour 1 during the final extinction was less than that which occurred during the period of Behaviour 1 extinction, suggesting that the extinction of Behaviour 2 did not increase the occurrence of Behaviour 1. This result failed to support the idea that resurgence is induced by the extinction of Behaviour 2. In Experiment 2, using the same hens and an additional hen, Experiment 1 was repeated five times and then there were either 0 or 9 sessions of Behaviour 1 extinction in a further five conditions. The degree of resurgence was generally less when there were 9 sessions than when there were no sessions but not consistently different from either when there were 2 sessions. Experiment 3 used six naive hens. Two first-trained behaviours were initially reinforced on RI 45-s schedules under a multiple schedule. One first behaviour then received a period of extinction and then each occurrence of two second behaviours was reinforced under the multiple schedule followed by extinction. The sequence from training of the first behaviours to the extinction of the second behaviours was repeated 10 times with the number of occurrences of the component for which extinction was in effect for the first behaviour varying across conditions from 12 to 0. The degree of resurgence was an inverse function of the amount of Behaviour 1 extinction. Experiment 4 used six naive hens. In a multiple schedule two first behaviours were reinforced on RI 20-s schedules and then two second behaviours were reinforced followed by extinction. This was repeated 8 times with the RI schedule in effect for one of the second behaviours varying from 80 s to 10 s across conditions while the other remained at 40 s. The degree of occurrence of Behaviour 1 when Behaviour 2 was reinforced was a direct function of the varied RI schedule of Behaviour 2. The degree of resurgence of Behaviour 1 in extinction was an inverse function of the varied RI schedule of Behaviour 2. The degree of resurgence was also inversely related to the degree of occurrence of this Behaviour 1 when Behaviour 2 was reinforced. Experiment 5 used five naive hens and one hen from Experiment 3 in a multiple-schedule design where the length of training of the second behaviours varied from 124 to O occurrences of a component over three conditions. No effect of this was found on the degree of resurgence. The results are consistent with the hypothesis that resurgence is the result of the prevention of extinction of Behaviour 1 by the reinforcement of Behaviour 2, but they are not definitive proof that this hypothesis is correct. Models derived from the Generalised Matching Law and Behavioural Momentum are also proposed as descriptions of resurgence.

year: 2000

title: Book review: The material child: Growing up in consumer culture

authors: Lealand, Geoff

abstract: This article reviews the book: “The material child: Growing up in consumer culture”, by David Buckingham.

text: Book review: The material child: Growing up in consumer culture This article reviews the book: “The material child: Growing up in consumer culture”, by David Buckingham.

year: 2012

title: A core phyllosphere microbiome exists across distant populations of a tree species indigenous to New Zealand

authors: Noble, Anya S.

subjects: Science & Technology

abstract: The phyllosphere microbiome is increasingly recognised as an influential component of plant physiology, yet it remains unclear whether stable host-microbe associations generally exist in the phyllosphere. Leptospermum scoparium (mānuka) is a tea tree indigenous to New Zealand, and honey derived from mānuka is widely known to possess unique antimicrobial properties. However, the host physiological traits associated with these antimicrobial properties vary widely, and the specific cause of such variation has eluded scientists despite decades of research. Notably, the mānuka phyllosphere microbiome remains uncharacterised, and its potential role in mediating host physiology has not been considered. Working within the prevailing core microbiome conceptual framework, we hypothesise that the phyllosphere microbiome of mānuka exhibits specific host association patterns congruent with those of a microbial community under host selective pressure (null hypothesis: the mānuka phyllosphere microbiome is recruited stochastically from the surrounding environment). To examine our hypothesis, we characterised the phyllosphere and associated soil microbiomes of five distinct and geographically distant mānuka populations across the North Island of New Zealand. We identified a habitat-specific and relatively abundant core microbiome in the mānuka phyllosphere, which was persistent across all samples. In contrast, non-core phyllosphere microorganisms exhibited significant variation across individual host trees and populations that was strongly driven by environmental and spatial factors. Our results demonstrate the existence of a dominant and ubiquitous core microbiome in the phyllosphere of mānuka, supporting our hypothesis that phyllosphere microorganisms of mānuka exhibit specific host association and potentially mediate physiological traits of this nationally and culturally treasured indigenous plant. In addition, our results illustrate biogeographical patterns in mānuka phyllosphere microbiomes and offer insight into factors contributing to phyllosphere microbiome assembly.

text: A core phyllosphere microbiome exists across distant populations of a tree species indigenous to New Zealand The phyllosphere microbiome is increasingly recognised as an influential component of plant physiology, yet it remains unclear whether stable host-microbe associations generally exist in the phyllosphere. Leptospermum scoparium (mānuka) is a tea tree indigenous to New Zealand, and honey derived from mānuka is widely known to possess unique antimicrobial properties. However, the host physiological traits associated with these antimicrobial properties vary widely, and the specific cause of such variation has eluded scientists despite decades of research. Notably, the mānuka phyllosphere microbiome remains uncharacterised, and its potential role in mediating host physiology has not been considered. Working within the prevailing core microbiome conceptual framework, we hypothesise that the phyllosphere microbiome of mānuka exhibits specific host association patterns congruent with those of a microbial community under host selective pressure (null hypothesis: the mānuka phyllosphere microbiome is recruited stochastically from the surrounding environment). To examine our hypothesis, we characterised the phyllosphere and associated soil microbiomes of five distinct and geographically distant mānuka populations across the North Island of New Zealand. We identified a habitat-specific and relatively abundant core microbiome in the mānuka phyllosphere, which was persistent across all samples. In contrast, non-core phyllosphere microorganisms exhibited significant variation across individual host trees and populations that was strongly driven by environmental and spatial factors. Our results demonstrate the existence of a dominant and ubiquitous core microbiome in the phyllosphere of mānuka, supporting our hypothesis that phyllosphere microorganisms of mānuka exhibit specific host association and potentially mediate physiological traits of this nationally and culturally treasured indigenous plant. In addition, our results illustrate biogeographical patterns in mānuka phyllosphere microbiomes and offer insight into factors contributing to phyllosphere microbiome assembly.

year: 2020