Comparing Tangible Symbols, Picture Exchange and a Direct Selection Response when Teaching Requesting to Two Children with Autism Spectrum Disorder

<p>Children diagnosed with Autism Spectrum Disorder (ASD) who fail to develop functional speech are candidates for augmentative and alternative communication (AAC) systems. One of the primary intentions of AAC is to provide an alternative method of communicating in the absence of speech (Mirenda, 2003). In order to select the most beneficial AAC system for a user, in regards to the ease of acquisition and successfully communicating with AAC systems, it is considered important to undertake research comparing various AAC systems and to assess users’ preferences for using one system over another. Empirical evidence from previous studies comparing AAC indicates that users often learn to use AAC systems with varying degrees of proficiency and at various acquisition rates. Additionally, assessing users’ preferences for different AAC systems has been shown to influence acquisition rates and long term maintenance of AAC systems and is suggested to be an important component when carrying out AAC intervention. In the present study a tangible symbol (TS) communication system was compared, in terms of acquisition rates and preference, with Picture Exchange (PE) and an additional direct selection (DS) method of gaining access to desired stimuli in two young boys with ASD. Two male participants diagnosed with ASD were taught via systematic instructional procedures to request/gain access to the continuation of preferred cartoon movies by using TS, PE, and DS. Additionally, preference assessments were implemented during intervention and follow-up phases to determine whether the participants showed a preference for using one of these three requesting/access methods over the other two, and whether any such preferences remained stable throughout follow-up sessions. Results indicated that both participants successfully learned to request each of the six cartoon movies using each of the three methods. Specifically, acquisition rates for TS and PE were comparable across both participants, and overall both participants preferred to request using the TS. During intervention sessions, one participant preferred to use DS, however this preference changed during follow-up where he chose to use TS more overall. These data suggest that TS is a viable AAC option for children with ASD who do not speak, and can be learned to a high proficiency after receiving systematic teaching procedures as used in the present study.</p>

Comparing Tangible Symbols, Picture Exchange and a Direct Selection Response when Teaching Requesting to Two Children with Autism Spectrum Disorder

<p>Children diagnosed with Autism Spectrum Disorder (ASD) who fail to develop functional speech are candidates for augmentative and alternative communication (AAC) systems. One of the primary intentions of AAC is to provide an alternative method of communicating in the absence of speech (Mirenda, 2003). In order to select the most beneficial AAC system for a user, in regards to the ease of acquisition and successfully communicating with AAC systems, it is considered important to undertake research comparing various AAC systems and to assess users’ preferences for using one system over another. Empirical evidence from previous studies comparing AAC indicates that users often learn to use AAC systems with varying degrees of proficiency and at various acquisition rates. Additionally, assessing users’ preferences for different AAC systems has been shown to influence acquisition rates and long term maintenance of AAC systems and is suggested to be an important component when carrying out AAC intervention. In the present study a tangible symbol (TS) communication system was compared, in terms of acquisition rates and preference, with Picture Exchange (PE) and an additional direct selection (DS) method of gaining access to desired stimuli in two young boys with ASD. Two male participants diagnosed with ASD were taught via systematic instructional procedures to request/gain access to the continuation of preferred cartoon movies by using TS, PE, and DS. Additionally, preference assessments were implemented during intervention and follow-up phases to determine whether the participants showed a preference for using one of these three requesting/access methods over the other two, and whether any such preferences remained stable throughout follow-up sessions. Results indicated that both participants successfully learned to request each of the six cartoon movies using each of the three methods. Specifically, acquisition rates for TS and PE were comparable across both participants, and overall both participants preferred to request using the TS. During intervention sessions, one participant preferred to use DS, however this preference changed during follow-up where he chose to use TS more overall. These data suggest that TS is a viable AAC option for children with ASD who do not speak, and can be learned to a high proficiency after receiving systematic teaching procedures as used in the present study.</p>

Derivation of Predator Functional Responses Using a Mechanistic Approach in a Natural System

The functional response is at the core of any predator-prey interactions as it establishes the link between trophic levels. The use of inaccurate functional response can profoundly affect the outcomes of population and community models. Yet most functional responses are evaluated using phenomenological models which often fail to discriminate among functional response shapes and cannot identify the proximate mechanisms regulating predator acquisition rates. Using a combination of behavioral, demographic, and experimental data collected over 20 years, we develop a mechanistic model based on species traits and behavior to assess the functional response of a generalist mammalian predator, the arctic fox (Vulpes lagopus), to various tundra prey species (lemmings and the nests of geese, passerines, and sandpipers). Predator acquisition rates derived from the mechanistic model were consistent with field observations. Although acquisition rates slightly decrease at high goose nest and lemming densities, none of our simulations resulted in a saturating response in all prey species. Our results highlight the importance of predator searching components in predator-prey interactions, especially predator speed, while predator acquisition rates were not limited by handling processes. By combining theory with field observations, our study provides support that the predator acquisition rate is not systematically limited at the highest prey densities observed in a natural system. Our study also illustrates how mechanistic models based on empirical estimates of the main components of predation can generate functional response shapes specific to the range of prey densities observed in the wild. Such models are needed to fully untangle proximate drivers of predator-prey population dynamics and to improve our understanding of predator-mediated interactions in natural communities.

Derivation of predator functional responses using a mechanistic approach in a natural system

The functional response is central to our understanding of any predator–prey system as it establishes the link between trophic levels. Most functional responses are evaluated using phenomenological models linking predator acquisition rate and prey density. However, our ability to measure functional responses using such an approach is often limited in natural systems and the use of inaccurate functions can profoundly affect the outcomes of population and community models. Here, we develop a mechanistic model based on extensive data to assess the functional response of a generalist predator, the arctic fox (Vulpes lagopus), to various tundra prey species (lemmings and the nests of geese, passerines and sandpipers). We found that predator acquisition rates derived from the mechanistic model were consistent with field observations. Although sigmoidal functional responses were previously used to model fox-prey population dynamics, none of our simulations resulted in a saturating response in all prey species. Our results highlight the importance of predator searching components in predator-prey interactions, especially predator speed, while predator acquisition rates were not limited by handling processes. By combining theory with field observations, our study provides evidences that predator acquisition rate is not systematically limited at the highest prey densities observed in a natural system. We reinforce the idea that functional response categories, typically types I, II, and III, should be considered as particular cases along a continuum. Specific functions derived with a mechanistic approach for a range of densities observed in natural communities should improve our ability to model and understand predator-prey systems.

Assessing the Potential Impact of a Long-Acting Skin Disinfectant in the Prevention of MRSA

Background: Healthcare-associated transmission of methicillin-resistant Staphylococcus aureus (MRSA) remains a persistent problem despite advances in prevention. The use of chlorhexidine gluconate (CHG) as a means of decolonizing patients, either through targeted decolonization or daily bathing, is a frequently used measure to supplement other MRSA reduction interventions. However, there is room for new and innovative decolonizing agents. We explored the potential utility of a long-acting CHG-like disinfectant with a persistent protective effect as well as an immediate decolonizing action in the prevention of MRSA acquisition as well as the subsequent development of clinical illness and MRSA-related mortality. Methods: We modeled MRSA transmission throughout an 18-bed intensive care unit, based on previously published models. A baseline model with no daily decolonizing protocol was used as a baseline and was compared to a scenario assuming that patients were bathed with CHG, which decolonizes them but provides no ongoing protection, as well as a scenario involving a hypothetical treatment that both decolonizes and provides ongoing protection from subsequent colonization. We varied the duration and efficacy of this protection to fully explore the potential utility of such a treatment. Results: The results of the simulations are shown in Fig. 1, where duration and efficacy of protection varied. The number of MRSA acquisitions from each combination is depicted as a single point, with blue points indicating correspondingly fewer MRSA acquisitions. Overall, improved efficacy of the hypothetical disinfectant resulted in immediate improvements in MRSA acquisition rates when compared to the baseline. To see major improvements in the MRSA acquisition rate due to the duration of infection, that duration must be well above 10 hours in many scenarios. There is also little evidence of synergy between the two. Conclusions: Based on recent results suggesting CHG has a relatively modest per-use efficacy (<.20), there is room for improvement in the formulation and administration of decolonizing agents. Although there has been considerable excitement about the possibility of long-acting agents that not only decolonize but provide long-acting protection against colonization, these results suggest that such protection would only result in markedly decreased acquisition rates only if that duration of protection was extremely long, or if the agent itself was also considerably more efficacious than CHG. These results may be used to help consider the necessary study size for clinical studies of these agents in the future, or to set research priorities and properly calibrate expectations.Funding: NoneDisclosures: None