Stimulus Equivalence: A Comparison of Operant and Associative Procedures

Previous studies comparing the effectiveness of the stimulus-pairing-observation and matching-to-sample procedures in facilitating the formation of equivalence relations have had conflicting findings. In an attempt to clarify the reasons for this, Experiment 1 replicated one of the experiments from Leader and Barnes-Holmes (2001b) but with the Chinese characters used by Clayton and Hayes (2004) as stimuli. The adult participants completed both the stimulus-pairing-observation and matching-to-sample procedures. Neither procedure was found to be more effective than the other, with few of the participants demonstrating equivalence after either procedure. Due to the failure of most participants to demonstrate equivalence, Experiment 2 replicated Experiment 1 but with the original nonsense syllables used by Leader and Barnes-Holmes (2001b). Equivalence was not demonstrated by any of the participants in Experiment 2. Therefore, the failures in Experiment 1 were not the result of the stimuli used. The use of the same stimuli in conflicting relations was identified as the most likely cause. Experiment 3 addressed this by using different nonsense syllables with each procedure. This resulted in greater accuracy on both the symmetry and equivalence tests compared to the earlier experiments; however, none of the participants demonstrated equivalence, and the procedures did not differ in their effectiveness. In Experiments 4 to 6 participants experienced either the stimulus-pairing observation or matching-to-sample procedures. These three experiments examined the effect of instructional specificity, stimulus arrangement, and the number of training trials on the effectiveness of these two procedures. Experiment 4 found that instructions which outlined the task required more specifically increase the effectiveness of both procedures marginally, and that a larger number of training and testing cycles (compared to e 1-3) did not aid in the development of equivalence. Experiment 5 examined the effectiveness of the many-to-one or one-to-many stimulus arrangements (compared to the linear arrangement used in the earlier experiments). The many-to-one and one-to-many arrangements resulted in more participants demonstrating equivalence than the linear arrangement for both the stimulus-pairing-observation and matching-to-sample procedures. Experiment 6 replicated E 5 but with more training trials prior to each equivalence test. This resulted in more participants demonstrating equivalence across both procedures and all stimulus arrangements. The stimulus-pairing-observation and matching-to-sample procedures were found to be equally effective in terms of accuracy achieved on the equivalence tests; however, the matching-to-sample procedure resulted in the development of equivalence within fewer training trials than the stimulus-pairing-observation procedure. When the stimulus-pairing-observation procedure was used, more participants demonstrated equivalence with the one-to-many arrangement than with the many-to-one or linear arrangements. When the matching-to-sample procedure was used, the one-to-many and many-to-one arrangements resulted in more participants demonstrating equivalence than the linear arrangement. Comparisons across the experiments suggested that the number of training trials completed prior to each equivalence test, but not the total number of training trials completed, affected performance. The effectiveness of the stimulus arrangements differed across the procedures, but one-to-many arrangement was more effective than the linear arrangement for both procedures. Overall, these experiments suggest that there is little difference in the effectiveness of the MTS and SPO procedures in facilitating the formation of equivalence relations, and that the development of equivalence is made more likely for both procedures by the addition of more training trials prior to each test, and the use of a one-to-many stimulus arrangement

Extinction-induced variability in human behavior

Participants earned points by pressing a computer space bar (Experiment 1) or forming rectangles on the screen with the mouse (Experiment 2) under differential-reinforcement-of-low-rate schedules, followed by extinction. Variability in interresponse time (the contingent dimension) increased during extinction, as for Morgan and Lee (1996); variability in diagonal length (the noncontingent dimension, Experiment 2) did not. In Experiment 3, points were contingent on rectangle size. Rectangle size and interresponse-time (the noncontingent dimension) variability increased in extinction. There was greater variability in the contingent dimension during extinction for participants with the more varied history of reinforcement in Experiment 2 but not in Experiment 3. Overall, variability in the contingent dimension increased in extinction, but the degree of increase was affected by reinforcement history

Reinforcer magnitude and demand under fixed-ratio schedules with domestic hens

This study compared three methods of normalizing demand functions to allow comparison of demand for different commodities and examined how varying reinforcer magnitudes affected these analyses. Hens responded under fixed-ratio schedules in 40-min sessions with response requirement doubling each session and with 2-s, 8-s, and 12-s access to wheat. Over the smaller fixed ratios overall response rates generally increased and were higher the shorter the magazine duration. The logarithms of the number of reinforcers obtained (consumption) and the fixed ratio (price) were well fitted by curvilinear demand functions (Hursh et al., 1988. Journal of the Experimental Analysis of Behavior 50, 419–440) that were inelastic (b negative) over small fixed-ratios. The fixed ratio with maximal response rate (Pmax) increased, and the rate of change of elasticity (a) and initial consumption (L) decreased with increased magazine duration. Normalizing consumption using measures of preference for various magazine durations (3-s vs. 3-s, 2-s vs. 8-s, and 2-s vs. 12-s), obtained using concurrent schedules, gave useful results as it removed the differences in L. Normalizing consumption and price (Hursh and Winger, 1995. Journal of the Experimental Analysis of Behavior 64, 373–384) unified the data functions as intended by that analysis. The exponential function (Hursh and Silberberg, 2008. Psychological Review, 115, 186–198) gave an essential value that increased (i.e., α decreased significantly) as magazine duration decreased. This was not as predicted, since α should be constant over variations in magazine duration, but is similar to previous findings using a similar procedure with different food qualities (hens) and food quantities (rats)

Avoidable Waste in Ophthalmic Epidemiology: A Review of Blindness Prevalence Surveys in Low and Middle Income Countries 2000–2014

Purpose:- Sources of avoidable waste in ophthalmic epidemiology include duplication of effort, and survey reports remaining unpublished, gaining publication after a long delay, or being incomplete or of poor quality. The aim of this review was to assess these sources of avoidable waste by examining blindness prevalence surveys undertaken in low and middle income countries (LMICs) between 2000 and 2014. Methods:- On December 1 2016 we searched MEDLINE, EMBASE and Web of Science databases for cross-sectional blindness prevalence surveys undertaken in LMICs between 2000–2014. All surveys listed on the Rapid Assessment of Avoidable Blindness (RAAB) Repository website (“the Repository”) were also considered. For each survey we assessed i) availability of scientific publication, survey report, summary results tables and/or datasets; ii) time to publication from year of survey completion and journal attributes; iii) extent of blindness information reported; and iv) rigour when information was available from two sources (i.e. whether it matched). Results:- Of the 279 included surveys (from 68 countries) 186 (67%) used RAAB methodology; 146 (52%) were published in a scientific journal, 57 (20%) were published in a journal and on the Repository, and 76 (27%) were on the Repository only (8% had tables; 19% had no information available beyond registration). Datasets were available for 50 RAABs (18% of included surveys). Time to publication ranged from <1–11 years (mean, standard deviation 2.8±1.8 years). The extent of blindness information reported within studies varied (e.g. presenting and best-corrected, unilateral and bilateral); those with both a published report and Repository tables were most complete. For surveys published and with RAAB tables available, discrepancies were found in reporting of participant numbers (14% of studies) and blindness prevalence (15%). Conclusion:- Strategies are needed to improve the availability, consistency and quality of information reported from blindness prevalence surveys, and hence reduce avoidable waste

Primary HIV-1 Infection Among Infants in sub-Saharan Africa: HPTN 024.

Our objectives were to assess clinical signs and diagnoses associated with primary HIV-1 infection among infants. We analyzed data from a clinical trial (HIV Prevention Trials Network Protocol 024) in sub-Saharan Africa. Study visits were conducted at birth, at 4-6 weeks, and at 3, 6, 9, and 12 months. The study population comprised live born, singleton, first-born infants of HIV-1-infected women with negative HIV-1 RNA assays who were still breastfeeding at 4-6 weeks. Of 1317 HIV-1-exposed infants, 84 became HIV-1 infected after 4-6 weeks and 1233 remained uninfected. There were 102 primary and 5650 nonprimary infection visits. The most common signs were cough and diarrhea, and the most common diagnoses were malaria and pneumonia. Primary infection was associated with significantly increased odds of diarrhea [odds ratio (OR) = 2.4], pneumonia (OR = 3.5), otitis media (OR = 3.1), and oral thrush (OR = 2.9). For the clinical signs and diagnoses evaluated, sensitivity was low (1%-16.7%) and specificity was high (88.2%-99%). Positive predictive values ranged from 0.1%-1.4%. Negative predictive values ranged from 28.0%-51.1%. Certain clinical signs and diagnoses, although more common during primary HIV-1 infection, had low sensitivity and high specificity. Efforts to expand access to laboratory assays for the diagnosis of primary HIV-1 infection among infants of HIV-1-infected women should be emphasized

Recent ASA presidents and ‘top’ journals: observed publication patterns, alleged cartels and varying careers

It has been common for studies presented as about American sociology as a whole to rely on data compiled from leading journals (American Sociological Review [ASR] and American Journal of Sociology [AJS]), or about presidents of the American Sociological Association [ASA], to represent it. Clearly those are important, but neither can be regarded as providing a representative sample of American sociology. Recently, Stephen Turner has suggested that dominance in the ASA rests with a ‘cartel’ initially formed in graduate school, and that it favors work in a style associated with the leading journals. The adequacy of these ideas is examined in the light of available data on the last 20 years, which show that very few of the presidents were in the same graduate schools at the same time. All presidents have had distinguished academic records, but it is shown that their publication strategies have varied considerably. Some have had no ASR publications except their presidential addresses, while books and large numbers of other journals not normally mentioned in this context have figured in their contributions, as well as being more prominent in citations. It seems clear that articles in the leading journals have not been as closely tied to prestigious careers as has sometimes been suggested, and that if there is a cartel it has not included all the presidents

Matching-to-sample and stimulus-pairing-observation procedures in stimulus equivalence: The effects of number of trials and stimulus arrangement

Studies comparing the effectiveness of the stimulus-pairing-observation and matching-to-sample procedures in facilitating equivalence relations have reported conflicting findings. This study compared the effectiveness of these procedures and examined the effect of stimulus arrangement and the number of training trials completed prior to each exposure to tests for symmetry and equivalence. Overall, the matching-to-sample procedure resulted in a greater percentage of participants demonstrating equivalence, and with fewer training trials, than did the stimulus-pairing-observation procedure. The one-to-many stimulus arrangement was more effective than the many-to-one and linear arrangements, overall. However, there was an interaction between the type of training procedure and stimulus arrangement. Participants who completed 120 training trials prior to each test were more likely to demonstrate equivalence than participants who completed 60 trials. This appeared to be the result of completing a greater number of trials prior to each test rather than of the number of training trials completed overall

How do you recruit and retain a prebirth cohort? Lessons learnt from growing up in New Zealand

Growing Up in New Zealand, a longitudinal study following nearly 7,000 children, has faced some unique challenges in identifying, enrolling, and retaining a large and diverse antenatal cohort. Identification of a study region with population demographics that enabled enrollment of an appropriately diverse sample was required as was intensive community and participant engagement in order to promote the study. Complementary methods used included direct engagement with prospective participants and the community and indirect engagement via media. Thus far, retention rates above 95% have been achieved by maintaining a multimethod approach that includes valuing participants and building trusting relationships, strong brand recognition, community engagement, maintenance of participant contact and location records, ensuring high-quality interactions between the participants and the study, pretesting measures and methods prior to the main cohort, and using participant feedback to inform the measures and methods used in future waves of data collection