Progressive Time Delay Research Articles

Promoting multistep requesting through systematic instruction and facilitated iPad-based intervention with children with intellectual disability

A lack of multistep requesting among children with intellectual disability can be an indicator of complex communication and social challenges. This study aims to determine the effect of a systematic instruction (differential reinforcement, progressive time delay, and least-to-most prompting) using an iPad with the “GoTalk Now” app on the acquisition and maintenance of multistep requesting. Using a multiple-probe across-participants design, three children between the ages of nine and 10 diagnosed with intellectual disability participated in this study. The findings revealed that the intervention was effective in both the intervention and maintenance phases. In two participants, the change in performance occurred immediately, while in the other participant, it took more sessions to reach the acquisition criteria. Social validity data were obtained from participants’ teachers. Implications and future directions are discussed according to the findings.

Sequential and directional insulation by conserved CTCF sites underlies the Hox timer in stembryos

During development, Hox genes are temporally activated according to their relative positions on their clusters, contributing to the proper identities of structures along the rostrocaudal axis. To understand the mechanism underlying this Hox timer, we used mouse embryonic stem cell-derived stembryos. Following Wnt signaling, the process involves transcriptional initiation at the anterior part of the cluster and a concomitant loading of cohesin complexes enriched on the transcribed DNA segments, that is, with an asymmetric distribution favoring the anterior part of the cluster. Chromatin extrusion then occurs with successively more posterior CTCF sites acting as transient insulators, thus generating a progressive time delay in the activation of more posterior-located genes due to long-range contacts with a flanking topologically associating domain. Mutant stembryos support this model and reveal that the presence of evolutionary conserved and regularly spaced intergenic CTCF sites controls the precision and the pace of this temporal mechanism.

Design of Channel Estimation for Hybrid Beamforming Millimeter-Wave Systems in the Presence of Beam Squint

In this article, channel estimation for millimeter-wave massive multiple-input–multiple-output (MIMO) systems with hybrid beamforming is considered. With a large number of antenna elements, a progressive time delay across antenna elements incurs a change in the beam direction as a function of subcarriers in an orthogonal frequency-division multiplexing system. Considering the difference in delay across the entire array, a new channel estimation framework is proposed by using a maximum likelihood criterion as a function of the analog training beam and pilot subcarrier assignment. The resulting design achieves asymptotic orthogonality among the channel paths and minimizes the mean squared error. An extension of the proposed design to a uniform planar array is discussed. The Cramér–Rao lower bound for joint channel estimation with hybrid beamforming is derived to verify the effectiveness of the proposed design.

Teaching and Promoting Generalization of Peer Imitation With Preschoolers With Disabilities

Researchers have identified effective instructional strategies for teaching peer imitation, including embedded classroom-based interventions. However, there is a dearth of strategies that have been effective for teaching generalization of imitation skills to novel contexts. Building on previous research, we examined the use of progressive time delay to increase peer imitation in the context of a play activity for four preschoolers with disabilities. We conducted preference and reinforcer assessments to identify effective reinforcers for each child prior to intervention. We conducted a multiple baseline across participants design meeting contemporary single case standards and used visual analysis to identify a functional relation: the intervention package was associated with an increase in the participants’ peer imitation in training contexts. The intervention also led to levels of peer imitation comparable to those of typically developing peers, as measured by a normative peer sample, and generalization to novel contexts.

The Effects of Progressive Time Delay to Teach Social Problem-Solving to Preschoolers

A multiple probe design across participants was used to evaluate the effectiveness of progressive time delay (PTD) during small group instruction to teach social problem-solving to preschoolers and to assess generalization to novel contexts. PTD was used to teach children to both name and use a variety of problem-solving solutions. Target participants, all of whom exhibited challenging behavior or were at risk for social skill deficits, were paired with a typically developing peer for small group instructional sessions. During sessions, children were presented with scenarios involving simple social problems and were asked, “What could you do?” After naming an appropriate solution, participants were prompted to use the solution. Results indicate the use of PTD during small group instruction was effective for teaching social problem-solving to preschoolers, generalized to novel contexts and maintained following the withdrawal of the intervention. Limitations, areas for future research, and implications for practice are discussed.

The Effects of Mastery Criteria on Maintenance: A Replication With Most-to-Least Prompting.

Previous research has suggested that skills taught with a least-to-most prompting procedure to 80% and 90% accuracy did not always maintain high levels of performance maintenance. The present study replicates and extends previous research by evaluating the effects of various mastery criteria (i.e.,80%, 90%, and 100% accuracy across three consecutive sessions) on the maintenance of tacting skills taught with a most-to-least prompting procedure combined with a progressive time delay. Results of this study support previous research and further demonstrate that the highest levels of maintenance are achieved with 100% and 90% accuracy criteria for up to a month. For the 80% criterion, performance deteriorated during follow-up probes. Contrary to previous research suggesting a 90% criterion combined with least-to-most prompting procedures was not always sufficient for producing skill maintenance, the current study may provide preliminary support for the use of a 90% accuracy mastery criterion when combined with a most-to-least prompting procedure with a progressive time delay.

Insights Into Cerebral Tissue-Specific Response to Respiratory Challenges at 7T: Evidence for Combined Blood Flow and CO2-Mediated Effects

Cerebrovascular reactivity (CVR) mapping is finding increasing clinical applications as a non-invasive probe for vascular health. Further analysis extracting temporal delay information from the CVR response provide additional insight that reflect arterial transit time, blood redistribution, and vascular response speed. Untangling these factors can help better understand the (patho)physiology and improve diagnosis/prognosis associated with vascular impairments. Here, we use hypercapnic (HC) and hyperoxic (HO) challenges to gather insight about factors driving temporal delays between gray-matter (GM) and white-matter (WM). Blood Oxygen Level Dependent (BOLD) datasets were acquired at 7T in nine healthy subjects throughout BLOCK- and RAMP-HC paradigms. In a subset of seven participants, a combined HC+HO block, referred as the “BOOST” protocol, was also acquired. Tissue-based differences in Rapid Interpolation at Progressive Time Delays (RIPTiDe) were compared across stimulus to explore dynamic (BLOCK-HC) versus progressive (RAMP-HC) changes in CO2, as well as the effect of bolus arrival time on CVR delays (BLOCK-HC versus BOOST). While GM delays were similar between the BLOCK- (21.80 ± 10.17 s) and RAMP-HC (24.29 ± 14.64 s), longer WM lag times were observed during the RAMP-HC (42.66 ± 17.79 s), compared to the BLOCK-HC (34.15 ± 10.72 s), suggesting that the progressive stimulus may predispose WM vasculature to longer delays due to the smaller arterial content of CO2 delivered to WM tissues, which in turn, decreases intravascular CO2 gradients modulating CO2 diffusion into WM tissues. This was supported by a maintained ∼10 s offset in GM (11.66 ± 9.54 s) versus WM (21.40 ± 11.17 s) BOOST-delays with respect to the BLOCK-HC, suggesting that the vasoactive effect of CO2 remains constant and that shortening of BOOST delays was be driven by blood arrival reflected through the non-vasodilatory HO contrast. These findings support that differences in temporal and magnitude aspects of CVR between vascular networks reflect a component of CO2 sensitivity, in addition to redistribution and steal blood flow effects. Moreover, these results emphasize that the addition of a BOOST paradigm may provide clinical insights into whether vascular diseases causing changes in CVR do so by way of severe blood flow redistribution effects, alterations in vascular properties associated with CO2 diffusion, or changes in blood arrival time.

Effects of time delay and requiring echoics on answering questions about visual stimuli

An important communication skill for children with autism is answering multiple questions about visual stimuli (e.g., "What is it?" "What color is it?"). We targeted answering "What number?" and "What shape?" in the presence of numbers inside shapes, and "What is it?" and "What color?" in the presence of colored objects (e.g., a yellow cat) with 3 preschoolers with autism. In addition to a progressive time delay, we required the participants to answer the questions by echoing a keyword from the questions. For example, we taught them to answer, "What color?" with "color blue." In the context of a multiple-probe design across behaviors within a multiple-probe design across participants, the procedure was effective in increasing trained responses and producing within- and across-category generalization. The echoic may have facilitated the responses by increasing the salience of the auditory stimuli and strengthening intraverbals within autoclitic frames.

Communication Intervention Implementation via Telepractice Parent Coaching: Parent Implementation Outcomes

Telepractice coaching may be a viable alternative technology tool to deliver services to parents of children with autism spectrum disorder. Using a multiple probe design across participants, we examined the effectiveness of telepractice parent coaching in a communication intervention on parents’ implementation of strategies to improve their children’s communication skills. Project coaches instructed parents on strategies to teach communication skills to their child, including incentivizing communication, modeling, prompting, progressive time delay, and expanding. Results indicated a functional relation between the telepractice parent coaching intervention and parent use of strategies. Effect sizes for each participant are compatible with visual analysis results that show a very low effect to very strong effect depending on the intervention component examined.

Improving energy efficiency in massive MIMO: joint digital beam‐steering and tone‐reservation PAPR reduction

In this study, the authors propose a novel architecture based on the combination of peak-to-average power ratio (PAPR) reduction with digital beamforming (BF) for mm-wave massive multiple-input multiple-output (MIMO) systems. In order to keep the power amplifiers (PAs) working at the same input back-off thus maximising the system power efficiency, they propose to perform time-domain transmit beam-steering by adding progressive time delays to the signals at each antenna element, while keeping the amplitude weights unitary. They show that these time delays can be obtained with a finite impulse response filter implementation of time-domain fractional delay filter structures such as Lagrange interpolation polynomials. They also introduce an analysis on the PAPR of the interpolated signals, where they derive an upper bound to it and show that its value is similar to that of the signal at the input of the interpolation filters, showing the feasibility of the proposed method. In addition, they present a detailed analysis where they show that a significant reduction in computational complexity is obtained when compared to frequency-domain BF. Simulation results validate that the novel proposed scheme combining PAPR reduction and digital BF offers high-precision beam-steering maintaining reduced PAPR in the delayed signals fed to the antennas.

Transitioning from a low- to high-tech Augmentative and Alternative Communication (AAC) system: effects on augmented and vocal requesting

A considerable number of studies have demonstrated that augmentative and alternative communication (AAC) is effective in increasing speech production in some children with autism spectrum disorder (ASD). Thus, this study aimed to (a) investigate the effects of a Picture Exchange Communication System (PECS) Phase IV protocol on the acquisition of spontaneous augmented requests, (b) evaluate the impact of progressive time delay and synthetic speech output on the development of vocal requests, and (c) determine the participants’ preferences for each modality after reaching mastery. A multiple-baseline design across four children with ASD was used to measure the acquisition of augmented and vocal requests during the transition from low-tech to high-tech AAC systems. During a natural condition (i.e., playtime), a modified PECS Phase IV protocol was applied to teach the participants to request by producing multisymbol messages (e.g., I WANT + names of a preferred item) using an iPad as well as vocalizations. After mastery, the participants’ preference for using the modified PECS Phase IV app or the communication book was assessed by comparing the response allocations. The preliminary results suggest that the modified PECS protocol can be used to transition from a low- to high-tech communication modality.

The Effectiveness of Progressive Time Delay on Teaching Pedestrian Skill to Individuals with Intellectual Disability

The purpose of the study was to examine the effectiveness of progressive time delay teaching method on teaching a pedestrian skill to individuals with intellectual disabilities. The study was conducted with three participants with mild intellectual disabilities who were 10-11 years old. Multiple probe design across participants was used in the study. The results of the study revealed that the participants of the study acquired the targeted pedestrian skill, the first participant maintained the acquired skill one, three and five weeks after the implementation was completed whereas the third participant maintained the skill one, two and four weeks after the implementation was completed. Besides, all participants generalized the skill which they acquired on a simulation material to a real environment. Social validity results of the study revealed that the parents of the participants and the policeman who took part in the generalization session had positive opinions about the study.

Using Progressive Time Delay to Increase Levels of Peer Imitation During Play With Preschoolers With Disabilities.

Research suggests peer imitation can be taught using systematic procedures and can be embedded into ongoing play contexts with preschool-age children. However, additional research is needed to test procedures that may increase levels of peer imitation with toddlers with disabilities and in generalized contexts. We used a multiple probe across participants research design to evaluate the effectiveness of progressive time delay (PTD) to teach peer imitation to preschoolers with disabilities during a play activity with a peer. We also examined the efficacy of PTD in a generalized context (i.e., new peers, implementer, and materials). Visual analysis indicated a functional relation between PTD and unprompted peer imitation; however, generalization was variable across participants. Our results support previous research indicating PTD is effective in teaching children with disabilities to imitate their peers.

A comparison of prompting methods to teach sight words to students with autism spectrum disorder

Time delay procedures are one of the most commonly used and effective strategies for teaching sight words to learners with disabilities. However, less is known about whether they are differentially effective and efficient with learners. This study compared the effectiveness and efficiency of progressive time delay and simultaneous prompting on sight word acquisition among three learners with autism spectrum disorder using an adapted alternating treatments design across word sets. For two participants, both procedures led to skill acquisition with no clear differences in efficiency. For the remaining participant, neither procedure was effective; therefore, the reading task was changed to a receptive one, and a stimulus fading intervention package was implemented.

Providing Small Group Instruction to Children With Disabilities and Same-Age Peers

Small group instruction in classrooms provides children opportunities to collaborate on academic tasks, as well as opportunities for social interactions. Although such arrangements are common for children with typical development, children with moderate to severe disabilities (MSD) may receive few or no opportunities to participate meaningfully in small group instruction with same-age peers with typical development. The purpose of this study was to evaluate the use of a progressive time delay procedure for teaching children with MSD (autism spectrum disorder and/or intellectual disability) and those with typical social development, but at-risk for academic failure, to name sight words during small group instruction. In addition, children had multiple opportunities per session to provide tokens to peers, praise peers for correct responses, and initiate conversations and respond to a peer’s conversation initiations. Results indicated that children with and without disabilities can learn to name sight words, as well as learn to initiate conversation when tokens include pictures or photographs of each child’s preferred items or activities. Implications for teachers and future studies are provided.

فعالیة استخدام إجراء التأخیر الزمنی المتدرج فی إکساب مهارة قراءة بعض الکلمات الوظیفیة للتلمیذات ذوات الإعاقة الفکریة البسیطة والمتوسطة (دراســـــة مقـــارنــــة) The Efficiency of Using Progressive Time Delay Procedure (PTD) in Teaching Reading Skill of Some Functional Words to Female Students of Mild and Moderate Intellectual Disabilities ( A Compara

هدفت الدراسة الحالية إلى التعرف على فاعلية استخدام إجراء التأخير الزمني المتدرج في إکساب مهارة قراءة بعض الکلمات الوظيفية للتلميذات ذوات الإعاقة الفکرية البسيطة والمتوسطة، إضافة إلى احتفاظهن بالکلمات المکتسبة، وتعميمهن لها، وأخيرا المقارنة بين الفئتين التلميذات من حيث عدد محاولات اکتساب المهارة، الفترة الزمنية المستغرقة لاکتسابها، ونسبة الأخطاء . تکونت عينة الدراسة من (6) تلميذات ملتحقات بمعهد التربية الفکرية بشرق الرياض، وقد تم تقسيمهن إلى مجموعتين، وتدريبهن على قراءة بعض الکلمات الوظيفية باستخدام إجراء التأخير الزمني المتدرج، وقد استخدمت هذه الدراسة المنهج التجريبي. أظهرت نتائج الدراسة فعالية إجراء التأخير الزمني المتدرج، حيث اکتسبت تلميذات المجموعة الأولى مهارة قراءة بعض الکلمات الوظيفية بها بنسبة نجاح (100%). وتعميمها في المواقف الأخرى بنسبة نجاح تتراوح ما بين (89% - 100%). کذلک ظهرت اکتسبت تلميذات المجموعة الثانية مهارة قراءة بعض الکلمات الوظيفية واحتفظن بها بنسبة نجاح (100%)، وتعميمها في المواقف الأخرى بنسبة نجاح تتراوح ما بين (72% - 100%). توصلت نتائج الدراسة باستخدام إجراء التأخير الزمني المتدرج إلى أنه توجد فروق لا تذکر بين المجموعتين (فئة الإعاقة الفکرية البسيطة، وفئة الإعاقة الفکرية المتوسطة) من حيث عدد المحاولات، الفترة الزمنية المستغرقة لاکتساب المهارة، وتدني نسب الأخطاء The present study aimed to determine Progressive Time Delay (PTD) procedure efficiency in teaching reading skill of some functional to female students with mild and moderate intellectual disabilities. The efficiency of this procedure was also studied maintenance and generalization of acquired words. A comparison was also drawn between mild and moderate intellectual disabilities female students in terms of number of attempts to acquire skill, time span of acquiring skill and error percentage. The study employed single subject method in determining these factors. The study sample comprised (6) female students enrolled in intellectual Education Institute in Eastern Riyadh. It was subdivided into two groups; first one contained (3) students who had mild intellectual disabilities; while second contained (3) students who had moderate intellectual disabilities. The students of both groups were trained on reading some functional using Progressive Time Delay procedure. The study revealed efficiency of PTD procedure in teaching students of both groups the skill of reading functional words in addition to their ability to maintain acquired and generalize them to other situations. The study also revealed that there were no significant differences between two groups (the mild and moderate mentally retarded) in terms of number of attempts, time span used to acquire skill and low number of errors.

Initiation and Generalization of Self-Instructed Video Activity Schedules for Elementary Students With Intellectual Disability

This study evaluated the effects of progressive time delay (PTD) to teach four elementary students with intellectual disability on how to self-instruct using a video activity schedule. A single-case multiple probe across participants design with a multiple probe across environments design for each participant was used to assess the generalization of the self-instruction behavior to novel environments. All participants acquired the self-instruction behavior in their target environments. One participant generalized this behavior to a novel environment by the completion of the study, and the other three participants required introduction of the independent variable (PTD) to master acquisition in the two generalization environments. Implications for practitioners and suggestions for effective programming of generalization in future research are discussed.

Effects of a Lag Schedule with Progressive Time Delay on Sign Mand Variability in a Boy with Autism.

For some children with autism, mand training can produce highly repetitive manding unless the environment is arranged in a manner that promotes mand variability. Prior research demonstrated that mand training using a lag schedule and progressive time delay increased variability in vocal manding in children with autism. Whether lag schedules have similar effects on sign mand topographies is unknown. The current study evaluated the effects of mand training with a Lag 1 schedule of reinforcement and progressive time delay (TD) on topographical variability and the development of a sign mand response class hierarchy in a boy with autism. The results suggest independent use of all sign mand topographies occurred, a mand response class hierarchy was developed, and topographically variant sign manding increased under the Lag 1 + TD schedule compared to a Lag 0 schedule of reinforcement. Implications for practitioners, limitations, and directions for future research are discussed.

Using Progressive Time Delay to Increase Levels of Peer Imitation During Sculpting Play.

A multiple probe across participants with an embedded withdrawal single case research design was used to examine the effectiveness of a progressive time delay (PTD) procedure to teach preschoolers with disabilities to imitate their peers during a sculpting play activity. Data indicated the presence of a functional relation between the use of PTD and contingent reinforcement on increased levels of peer imitation across participants; levels also decreased when PTD was withdrawn, although not to baseline levels. Overall levels of peer imitation had a greater magnitude of change than demonstrated in previous research.

Effects of a lag schedule of reinforcement with progressive time delay on topographical mand variability in children with autism

ABSTRACTObjective: Evaluate the effects of a Lag 1 schedule of reinforcement and progressive time delay (TD) on topographical mand variability in children with autism. Methods: Using single-subject design methodology, a multiple baseline across behaviors with embedded reversal design was employed. During Lag 0, reinforcement was delivered contingent on any independent instances of manding. During Lag 1 + TD, prompts were faded and reinforcement was delivered contingent on independent or prompted variant mand topographies. Results: Higher levels of topographical mand variability were observed during Lag 1 + TD for both participants. Conclusions: A Lag 1 schedule of reinforcement with progressive TD increased variability across functionally equivalent vocal mand topographies for both participants. This finding extends prior literature by providing a novel model for studying reinforced mand variability in children, and by demonstrating how practitioners could use prompts and differential reinforcement to increase topographical mand variability in children with autism.