Two-Stage maximum likelihood estimation in the misspecified restricted latent class model

The maximum likelihood classification rule is a standard method to classify examinee attribute profiles in cognitive diagnosis models (CDMs). Its asymptotic behaviour is well understood when the model is assumed to be correct, but has not been explored in the case of misspecified latent class models. This paper investigates the asymptotic behaviour of a two-stage maximum likelihood classifier under a misspecified CDM. The analysis is conducted in a general restricted latent class model framework addressing all types of CDMs. Sufficient conditions are proposed under which a consistent classification can be obtained by using a misspecified model. Discussions are also provided on the inconsistency of classification under certain model misspecification scenarios. Simulation studies and a real data application are conducted to illustrate these results. Our findings can provide some guidelines as to when a misspecified simple model or a general model can be used to provide a good classification result.     

Direct remembering,mediated remembering,and atypical forgetting functions

Atypical forgetting functions have been demonstrated in several recent studies of delayed matching to sample, in which experimental conditions are altered partway through the retention interval. The forgetting functions are atypical in that accuracy or discriminability is not always a negatively accelerated monotonic function of increasing retention interval duration, but may increase at later times in the retention interval. Atypical forgetting functions reflect changes in levels of discrimination. A switch from a lower level to a higher level of discrimination, or vice versa, can occur at any time in the retention interval. The behavioral theories of remembering proposed by Nevin, Davison, Odum, and Shahan (2007), and White and Brown (2014), offer quantitative predictions of forgetting functions that differ in intercept or slope. Both theories are able to account for atypical forgetting functions, by assuming time‐independent changes in the mediating effect of attending to sample and comparison stimuli (in Nevin et al.'s model) or in the direct effect of the context of reinforcement of the conditional discrimination (in White & Brown's model). Despite differences in their main assumptions, the theories have an edge over any theory that assumes that forgetting is time‐dependent.     

An evaluation of a visual–visual successive matching‐to‐sample procedure to establish equivalence classes in adults

Traditionally, behavior analysts have studied stimulus equivalence using a matching‐to‐sample (MTS) preparation. Although researchers have shown the utility of MTS to yield equivalence classes, the procedure requires several prerequisite skills for a learner to accurately respond. Previous research with humans and nonhumans has shown that relational responding can be produced via compound stimulus discrimination and successive matching‐to‐sample (S‐MTS). We conducted four experiments with college students to further evaluate the effectiveness of S‐MTS in the establishment of stimulus relations. S‐MTS trials consisted of the presentation of a single sample stimulus followed by one comparison in a fixed location on a computer screen. Depending upon the sample–comparison relation, participants touched (i.e., go) or did not touch (i.e., no‐go) the comparison stimulus. Following training of the baseline relations (AB/BC), we assessed the emergence of symmetry, transitivity, and equivalence performances (i.e., BA/CB and AC/CA). Results support the utility of the S‐MTS procedure as a possible alternative to traditional MTS. This study has direct implications for participants for whom traditional three‐array MTS procedures may be challenging.     

Equivalence class formation as a function of preliminary training with pictorial stimuli

The present experiment investigated the effects of preliminary training with pictorial stimuli on the subsequent formation of three 5‐member equivalence classes (A?B?C?D?E) in 84 university students assigned to seven groups of 12. In the Abstract (ABS) group, all stimuli were abstract shapes. In the Picture (PIC) group, the C stimuli were pictures, and the remaining stimuli were the same abstract shapes as in the ABS group. For the remaining five groups, all stimuli were the same abstract shapes as in the ABS group. However, across groups, preliminary training involved either the establishment of conditional relations with simultaneous (SMTS) or delayed (DMTS) matching‐to‐sample with 0 s, 3 s, 6 s, or 9 s between the abstract C stimuli and the meaningful pictures. For the ABS and the PIC groups, 16.7% and 83.3% of participants formed classes, respectively. Preliminary training with SMTS and DMTS with 0 s, 3 s, and 6 s produced a linear increase in the likelihood of equivalence class formation, 41.7%, 50%, and 75%, respectively. Increasing the duration of delay further from 6 s to 9 s produced a substantial decline, 50%. This experiment extends knowledge about how including meaningful pictures enhances equivalence class formation.     

The (Non) Religion of Mechanical Turk Workers

Social science researchers have increasingly come to utilize Amazon's Mechanical Turk (MTurk) to obtain adult, opt‐in samples for use with experiments. Based on the demographic characteristics of MTurk samples, studies have provided some support for the representativeness of MTurk. Others have warranted caution based on demographic characteristics and comparisons of reliability. Yet, what is missing is an examination of the most glaring demographic difference in MTurk—religion. We compare five MTurk samples with a student convenience sample and the 2012 General Social Survey, finding that MTurk samples have a consistent bias toward nonreligion. MTurk surveys significantly overrepresent seculars and underrepresent Catholics and evangelical Protestants. We then compare the religiosity of religious identifiers across samples as well as relationships between religiosity and partisanship, finding many similarities and a few important differences from the general population.     

Fix and sample with rats in the dynamics of choice

The generality of the molar view of behavior was extended to the study of choice with rats, showing the usefulness of studying order at various levels of extendedness. Rats' presses on two levers produced food according to concurrent variable-interval variable-interval schedules. Seven different reinforcer ratios were arranged within each session, without cues identifying them, and separated by blackouts. To alternate between levers, rats pressed on a third changeover lever. Choice changed rapidly with changes in component reinforcer ratio, and more presses occurred on the lever with the higher reinforcer rate. With continuing reinforcers, choice shifted progressively in the direction of the reinforced lever, but shifted more slowly with each new reinforcer. Sensitivity to reinforcer ratio, as estimated by the generalized matching law, reached an average of 0.9 and exceeded that documented in previous studies with pigeons. Visits to the more-reinforced lever preceded by a reinforcer from that lever increased in duration, while all visits to the less-reinforced lever decreased in duration. Thus, the rats' performances moved faster toward fix and sample than did pigeons' performances in previous studies. Analysis of the effects of sequences of reinforcer sources indicated that sequences of five to seven reinforcers might have sufficed for studying local effects of reinforcers with rats. This study supports the idea that reinforcer sequences control choice between reinforcers, pulses in preference, and visits following reinforcers.     

USING COMPLEX AUDITORY—VISUAL SAMPLES TO PRODUCE EMERGENT RELATIONS IN CHILDREN WITH AUTISM

Six participants with autism learned conditional relations between complex auditory‐visual sample stimuli (dictated words and pictures) and simple visual comparisons (printed words) using matching‐to‐sample training procedures. Pre‐ and posttests examined potential stimulus control by each element of the complex sample when presented individually and emergence of additional conditional relations and oral labeling. Tests revealed class‐consistent performance for all participants following training.     

Observing behavior and atypically restricted stimulus control

Restricted stimulus control refers to discrimination learning with atypical limitations in the range of controlling stimuli or stimulus features. In the study reported here, 4 normally capable individuals and 10 individuals with intellectual disabilities (ID) performed two-sample delayed matching to sample. Sample-stimulus observing was recorded with an eye-tracking apparatus. High accuracy scores indicated stimulus control by both sample stimuli for the 4 nondisabled participants and 4 participants with ID, and eye tracking data showed reliable observing of all stimuli. Intermediate accuracy scores indicated restricted stimulus control for the remaining 6 participants. Their eye-tracking data showed that errors were related to failures to observe sample stimuli and relatively brief observing durations. Five of these participants were then given interventions designed to improve observing behavior. For 4 participants, the interventions resulted initially in elimination of observing failures, increased observing durations, and increased accuracy. For 2 of these participants, contingencies sufficient to maintain adequate observing were not always sufficient to maintain high accuracy; subsequent procedure modifications restored it, however. For the 5th participant, initial improvements in observing were not accompanied by improved accuracy, an apparent instance of observing without attending; accuracy improved only after an additional intervention that imposed contingencies on observing behavior. Thus, interventions that control observing behavior seem necessary but may not always be sufficient for the remediation of restricted stimulus control.     

Victimization and PTSD in a Faroese youth total-population sample

Petersen, T., Elklit, A. & Olesen, J. G. (2010). Victimization and PTSD in a Faroese youth total-population sample. Scandinavian Journal of Psychology, 51, 56–62.
The prevalence of twenty traumatic events and negative life events in relation to posttraumatic stress disorder (PTSD) was studied in a Faroese total-population sample of 687 eighth-grade students with a mean age of 14.2 years. Ninety-four percent of the females and 89% of the males were directly exposed to or had witnessed at least one traumatic event or a negative life event. The odds ratios for PTSD after direct and indirect exposure to specific events are described. The lifetime prevalence of PTSD was 20%, whereas another 14% reached a subclinical level of PTSD. After exposure, females had PTSD more than twice as often as males. Being exposed to multiple traumatic events, living with a single parent, and having experienced a traumatic event or a negative life event within the last year were all associated with PTSD and its subscales.