Logarithmic Versus Linear Change in Step Size When Using an Adaptive Threshold-Seeking Procedure in a Frequency Discrimination Task: Does It Matter?

2019 ◽  
Vol 62 (10) ◽  
pp. 3887-3900
Author(s):  
Yael Zaltz ◽  
Daphne Ari-Even Roth ◽  
Noam Amir ◽  
Liat Kishon-Rabin
Keyword(s):  
Young Adults ◽  
Computer Simulations ◽  
Human Subjects ◽  
Frequency Discrimination ◽  
Adaptive Threshold ◽  
Group Method ◽  
Step Size ◽  
Linear Change ◽  
Subject Design ◽  
Linear Rule

Different rules for changing step sizes (e.g., logarithmic, linear) are alternately used in adaptive threshold-seeking procedures, with no clear justification. We hypothesized that the linear rule may yield more accurate thresholds for poor performers because the step sizes are predetermined and fixed across listeners and thus can be small, in contrast to the logarithmic rule, in which step sizes are changed with respect to the listener's performance. Purpose The aim of this study was to test the effect of logarithmic and linear rules on frequency discrimination (FD) thresholds. Method Three experiments involving human subjects and Monte Carlo computer simulations were designed and conducted. In the 1st experiment, FD thresholds were estimated in 40 young adults with either 3-interval 2-alternative forced choice (3I2AFC; n = 19) or 2-interval 2AFC ( n = 21) in a within-subject design. In the 2nd experiment, thresholds were estimated in 16 children (7–8 years old) in a within-subject design, using 3I2AFC. In the 3rd experiment, thresholds were estimated in 30 young adults in a between-subjects design using 3I2AFC. Results No significant differences were shown between the 2 rules, regardless of age group, method, or level of FD performance. Computer simulations supported the empirical findings, predicting similar FD thresholds for both rules in the majority of runs. However, they also yielded more accurate thresholds with the linear rule, but with a larger number of outliers, which increased as the listener's attention level decreased. Conclusion Overall, the use of a particular rule has little influence on FD thresholds. Possible outliers may be minimized by monitoring the participant's attention at the beginning of the run.

scholarly journals Sensory attributes of e-cigarette flavours and nicotine as mediators of interproduct differences in appeal among young adults

2019 ◽  
pp. tobaccocontrol-2019-055172 ◽  
Author(s):  
Adam Leventhal ◽  
Junhan Cho ◽  
Jessica Barrington-Trimis ◽  
Raina Pang ◽  
Sara Schiff ◽  
...  
Keyword(s):  
Young Adults ◽  
Interaction Effects ◽  
Sensory Attributes ◽  
Electronic Cigarette ◽  
Free Products ◽  
Nicotine Content ◽  
Visual Analogue Scales ◽  
Subject Design ◽  
Aversive Taste ◽  
Analogue Scales

ObjectiveTo estimate the extent to which specific sensory attributes, for example, smoothness, mediate differences in electronic cigarette (e-cigarette) appeal between products in non-tobacco versus tobacco flavours and varying nicotine content in young adults.MethodE-cigarette users (n=100; aged 18–34 years) administered standardised two-puff e-cigarette doses of different products varying in a flavour (fruit, menthol, tobacco) × nicotine (nicotine-containing (6 mg/mL freebase), nicotine-free) within-subject design. Participants rated sensory attributes (sweetness, bitterness, smoothness and harshness) and appeal on 100-unit visual analogue scales after administering each product. Sensory ratings were tested as simultaneous mediators of flavour, nicotine and flavour × nicotine effects on appeal.ResultsAppeal preferences for fruit versus tobacco flavours were mediated by sweetness-enhancing (βindirect=0.092), smoothness-enhancing (βindirect=0.045) and bitterness-reducing (βindirect=0.072) effects of fruit flavours. Appeal preferences for menthol versus tobacco flavours were mediated by menthol’s smoothness-enhancing (βindirect=0.039) and bitterness-reducing (βindirect=0.034) effects. Lower appeal of nicotine-containing versus nicotine-free products was mediated by nicotine’s sweetness-reducing (βindirect=–0.036), smoothness-reducing (βindirect=–0.156) and bitterness-increasing (βindirect=0.045) effects. Flavour × nicotine interaction effects on appeal were explained by menthol-related suppression of nicotine’s bitterness-enhancing and sweetness-reducing mediation pathways and fruit-related suppression of nicotine’s bitterness-enhancing mediation pathway. Harshness did not mediate appeal after adjusting for other sensory attributes.ConclusionBitterness and smoothness may be cross-cutting mediators of interproduct variation in the effects of types of non-tobacco flavours and nicotine on e-cigarette appeal in young adults. Sweetness may also mediate appeal-enhancing effects of fruit and appeal-reducing effects of nicotine. Non-tobacco flavours may suppress appeal-reducing effects of nicotine in e-cigarettes through attenuation of nicotine’s aversive taste attributes.

Computer simulations of motoneuron firing rate modulation

1993 ◽  
Vol 69 (4) ◽  
pp. 1005-1008 ◽  
Author(s):  
C. J. Heckman ◽  
M. D. Binder
Keyword(s):  
Computer Simulations ◽  
Synaptic Input ◽  
Human Subjects ◽  
Motor Units ◽  
High Threshold ◽  
Synaptic Organization ◽  
Opposite Pattern ◽  
Discharge Rates ◽  
Low Threshold ◽  
Rate Limiting

1. As a human subject slowly increases the amount of force exerted by a muscle, the discharge rates of low-threshold motor units saturate at a rather low level, whereas higher-threshold units continue to be recruited and undergo increases in their discharge rates. The presently known intrinsic properties of motor units do not produce this "rate limiting." 2. Using computer simulations of a model motoneuron pool, we tested the hypothesis that rate limiting can be accounted for on the basis of the known distributions of synaptic input from different sources. The properties of the simulated motor units and their synaptic inputs were based as closely as possible on the available experimental data. A variety of simulated synaptic input organizations were applied to the pool, and the resulting outputs were compared with the data on rate limiting in human subjects. 3. We found that the data on rate limiting in human subjects greatly constrained the possible organizations of characterized synaptic input systems. Only when the synaptic organization included a gradual "crossover" between two specific types of input systems could the human data be accurately reproduced. Low input/output levels relied on a system organized like the monosynaptic Ia input, which produces greater effective synaptic currents in low- than in high-threshold motor units. Above a sharply defined crossover level, all further increases in output were produced by a system organized like the oligosynaptic rubrospinal input, which generates the opposite pattern.

scholarly journals Effects of stimulus level on nonspectral frequency discrimination by human subjects

1994 ◽  
Vol 78 (2) ◽  
pp. 197-209 ◽  
Author(s):  
Bryan E. Pfingst ◽  
Lisa A. Holloway ◽  
Natee Poopat ◽  
Arohan R. Subramanya ◽  
Melissa F. Warren ◽  
...  
Keyword(s):  
Human Subjects ◽  
Frequency Discrimination ◽  
Stimulus Level

Association between sexually transmissible infection testing, numbers of partners and talking to partners and friends about sexual health: survey of young adults

Sexual Health ◽  
2017 ◽  
Vol 14 (4) ◽  
pp. 378 ◽  
Author(s):  
Natalie A. Hendry ◽  
Graham Brown ◽  
Gary W. Dowsett ◽  
Marina Carman
Keyword(s):  
At Risk ◽  
Young Adults ◽  
Sexual Health ◽  
Health Knowledge ◽  
Sexual Partners ◽  
Group Method ◽  
Friendship Networks ◽  
Sti Testing ◽  
Sexually Transmissible Infection ◽  
Transmissible Infection

Background Young adults, aged 18–30 years, comprise the largest proportion of sexually transmissible infection (STI) notifications in Australia compared with other age groups. Understanding the influence of partner and friendship networks on their STI testing practices may enhance health promotion efforts to increase testing for this group. Method: Participants aged 21–30 years, living in Australia for ≥3 years, were recruited within nightlife precincts in Melbourne, Australia. They completed a survey on demographic items, sexual health attitudes, sexual health knowledge and STI testing experiences and perceptions. Responses to items related to talking to partners and friends about STI testing were allocated partner and friend communication scores. Analyses included χ2 tests of independence and independent sample t-tests. Results: Overall, 36.5% (61/167) of participants had tested for STIs in the previous 12 months. Of those who had tested for STIs, most had significantly higher numbers of sexual partners in the same period (P < 0.05), and were significantly more likely to have felt at risk of STI acquisition (P < 0.05). Significantly greater mean partner and friend communication scores were associated with higher numbers of sexual partners, feeling at risk of STIs, and testing for STIs in the previous 12 months (all P < 0.05). There were no significant differences when participants were stratified by gender or age. Conclusion: Talking to partners and friends about STI testing is associated with testing rates for young adults. Feeling at risk and increased numbers of sexual partners may be associated with the promotion of STI testing among friends and partners.

scholarly journals Human Challenge Studies with Wild Type SARS-CoV-2 Violate Longstanding Codes of Human Subjects Research

2020 ◽  
Author(s):  
Stanley M Spinola ◽  
Camilla Broderick ◽  
Gregory D Zimet ◽  
Mary A Ott
Keyword(s):  
Young Adults ◽  
Vaccine Efficacy ◽  
Human Subjects ◽  
Severe Disease ◽  
Infectious Agents ◽  
Wild Type ◽  
Human Subjects Research ◽  
Nuremberg Code ◽  
Curative Therapy ◽  
Societal Pressure

Abstract This manuscript explores the ethics of human inoculation experiments in young healthy adults with wild type SARS-CoV-2 as a tool to evaluate vaccine efficacy in the context of the Nuremberg Code, the Declaration of Helsinki, and the Belmont Report and in the context of dose response relationships with infectious agents. Despite societal pressure to develop a SARS-CoV-2 challenge model to evaluate vaccines, we argue that there are substantial risks that cannot be adequately defined because the dose of SARS-CoV-2 that causes severe disease in young adults is unknown. In the absence of curative therapy, even if a volunteer consents, longstanding ethical codes governing human subjects research preclude the conduct of such experiments.

scholarly journals The anabolic response to a meal containing different amounts of protein is not limited by the maximal stimulation of protein synthesis in healthy young adults

2016 ◽  
Vol 310 (1) ◽  
pp. E73-E80 ◽  
Author(s):  
Il-Young Kim ◽  
Scott Schutzler ◽  
Amy Schrader ◽  
Horace J. Spencer ◽  
Gohar Azhar ◽  
...  
Keyword(s):  
Young Adults ◽  
Protein Synthesis ◽  
Protein Intake ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Human Subjects ◽  
Whole Body ◽  
Protein Kinetics ◽  
Body Protein ◽  
Stimulation Of

We have determined whole body protein kinetics, i.e., protein synthesis (PS), breakdown (PB), and net balance (NB) in human subjects in the fasted state and following ingestion of ∼40 g [moderate protein (MP)], which has been reported to maximize the protein synthetic response or ∼70 g [higher protein (HP)] protein, more representative of the amount of protein in the dinner of an average American diet. Twenty-three healthy young adults who had performed prior resistance exercise (X-MP or X-HP) or time-matched resting (R-MP or R-HP) were studied during a primed continuous infusion of l-[2H5]phenylalanine and l-[2H2]tyrosine. Subjects were randomly assigned into an exercise (X, n = 12) or resting (R, n = 11) group, and each group was studied at the two levels of dietary protein intake in random order. PS, PB, and NB were expressed as increases above the basal, fasting values (mg·kg lean body mass−1·min−1). Exercise did not significantly affect protein kinetics and blood chemistry. Feeding resulted in positive NB at both levels of protein intake: NB was greater in response to the meal containing HP vs. MP ( P < 0.00001). The greater NB with HP was achieved primarily through a greater reduction in PB and to a lesser extent stimulation of protein synthesis (for all, P < 0.0001). HP resulted in greater plasma essential amino acid responses ( P < 0.01) vs. MP, with no differences in insulin and glucose responses. In conclusion, whole body net protein balance improves with greater protein intake above that previously suggested to maximally stimulating muscle protein synthesis because of a simultaneous reduction in protein breakdown.

scholarly journals Revisiting pest sampling plans in light of economic uncertainty and risk aversion.

2020 ◽  
Author(s):  
Diego F. Rincon ◽  
Hugo Fernando Rivera-Trujillo ◽  
Lorena Mojica-Ramos ◽  
Felipe Borrero-Echeverry
Keyword(s):  
Decision Making ◽  
Risk Aversion ◽  
Computer Simulations ◽  
Binary Data ◽  
Human Subjects ◽  
Decision Threshold ◽  
Market Uncertainty ◽  
Economic Threshold ◽  
Tomato Crop ◽  
Sampling Plans

Abstract Decision-making for pest management in agriculture is often assisted by sampling plans that guide users in determining the need for an intervention. Even though Tuta absoluta is easily recognizable by most tomato growers and that several sampling plans have been developed, adoption of decision-making systems for this pest is still incipient. Two potential obstacles for adoption are market uncertainty and farmer's risk aversion. Both obstacles could be tackled by adopting sampling plans that allow farmers to plan interventions according to rough estimations of economic thresholds and the intuition and experience gained by farmers. In this study, we evaluated four sampling plans using computer simulations and field trials. We compared the efficiency and the ability of each plan to both estimate the actual mean number of larvae per plant and to classify pest populations according to a predefined economic threshold. We also analyzed the time spent, and plants examined by human subjects applying each plan on a tomato crop with a T. absoluta infestation slightly over a predefined economic threshold. We show that sampling plans that deliver the most precise classifications, are poorest in delivering pest density estimations and vice versa. Our findings are consistent for both human subjects and computer simulations. However, the average number of samples required by sampling plans does not reflect the time spent by humans sampling real plants. Our results show that sampling plans based on counts, as opposed to those based on binary data, can efficiently provide reliable information on a current level of T. absoluta infestation relative to an estimated decision threshold. We suggest that sampling plans that promote the creation of farmer's memory, such as those based on counts, may be more suitable to both reduce risk aversion and increase adaptability to market uncertainty.

Nonlinear Adaptive Filtering with a Family of Kernel Affine Projection Algorithms

2015 ◽  
pp. 61-83 ◽  
Author(s):  
Felix Albu ◽  
Kiyoshi Nishikawa
Keyword(s):  
Nonlinear System ◽  
Computer Simulations ◽  
Nonlinear System Identification ◽  
Projection Algorithm ◽  
Projection Algorithms ◽  
Step Size ◽  
Affine Projection ◽  
The Family ◽  
Nonlinear Adaptive Filtering ◽  
Proportionality Principle

In this chapter, the family of kernel affine projection algorithms with coherence criterion is presented. The proportionality principle is translated to the kernel-based version. A new algorithm called Kernel Proportionate Affine Projection Algorithm (KPAPA) is proposed. It is proved that the additional computational increase burden is independent of the order of the algorithm, being dependent only on the order of the kernel expansion. The Dichotomous Coordinate Descent (DCD) method and an example of an efficient implementation of KAPA using DCD are presented. This chapter also discusses the influence of the coherence value, the step size value, and the dictionary size on the performance of KAPA and KPAPA algorithms. The effectiveness of the proposed algorithms and the effect of different parameters are confirmed by computer simulations for nonlinear system identification application.

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