Commentary on “Mediation analysis and categorical variables: The final frontier” by Dawn Iacobucci

The commentary discusses several topics in Dr. Iacobucci's article on mediation analysis with categorical variables including the lack of equivalency of mediated effect measures, ab, and c–c′, that are algebraically equivalent in ordinary least squares regression models. The commentary raises the issue of correlated mediation coefficients and presents formulas to include the correlation in the test of significance. References to new developments in causal mediation analysis for categorical variables are given and the importance of programs of research to establish a mediation theory is emphasized.     

Effects of a meaningful, a discriminative, and a meaningless stimulus on equivalence class formation

Thirty college students attempted to form three 3-node 5-member equivalence classes under the simultaneous protocol. After concurrent training of AB, BC, CD, and DE relations, all probes used to assess the emergence of symmetrical, transitive, and equivalence relations were presented for two test blocks. When the A-E stimuli were all abstract shapes, none of 10 participants formed classes. When the A, B, D, and E stimuli were abstract shapes and the C stimuli were meaningful pictures, 8 of 10 participants formed classes. This high yield may reflect the expansion of existing classes that consist of the associates of the meaningful stimuli, rather than the formation of the ABCDE classes, per se. When the A-E stimuli were abstract shapes and the C stimuli became S(D)s prior to class formation, 5 out of 10 participants formed classes. Thus, the discriminative functions served by the meaningful stimuli can account for some of the enhancement of class formation produced by the inclusion of a meaningful stimulus as a class member. A sorting task, which provided a secondary measure of class formation, indicated the formation of all three classes when the emergent relations probes indicated the same outcome. In contrast, the sorting test indicated "partial" class formation when the emergent relations test indicated no class formation. Finally, the effects of nodal distance on the relatedness of stimuli in the equivalence classes were not influenced by the functions served by the C stimuli in the equivalence classes.     

Hemispheric differences in the effects of context on vowel perception

Listeners perceive speech sounds relative to context. Contextual influences might differ over hemispheres if different types of auditory processing are lateralized. Hemispheric differences in contextual influences on vowel perception were investigated by presenting speech targets and both speech and non-speech contexts to listeners’ right or left ears (contexts and targets either to the same or to opposite ears). Listeners performed a discrimination task. Vowel perception was influenced by acoustic properties of the context signals. The strength of this influence depended on laterality of target presentation, and on the speech/non-speech status of the context signal. We conclude that contrastive contextual influences on vowel perception are stronger when targets are processed predominately by the right hemisphere. In the left hemisphere, contrastive effects are smaller and largely restricted to speech contexts.     

Is the go/no-go lexical decision task preferable to the yes/no task with developing readers?

The lexical decision task is probably the most common laboratory visual word identification task together with the naming task. In the usual setup, participants need to press the “yes” button when the stimulus is a word and the “no” button when the stimulus is not a word. A number of studies have employed this task with developing readers; however, error rates and/or response times tend to be quite high. One way to make the task easier for young readers is by employing a go/no-go procedure: “If word, press ‘yes’; if not, refrain from responding.” Here we conducted a lexical decision experiment that systematically compared the yes/no and go/no-go variants of the lexical decision task with developing readers (second- and fourth-grade children). Results showed that (a) error rates for words and nonwords were much lower in the go/no-go task than in the yes/no task, (b) lexical decision times were substantially faster in the go/no-go task, and (c) there was less variability in the latency data of the go/no-go task for high-frequency words. Thus, the go/no-go lexical decision task is preferable to the “standard” yes/no task when conducting experiments with developing readers.     

Exploring the enactment effect from an information processing view: What can we learn from serial position analyses?

The focus of the present article was to analyze processes that determine the enactment and age effect in a multi-trial free recall paradigm by looking at the serial position effects. In an experimental study (see Schatz et al 2010), the performance-enhancing effect of enactive encoding and repeated learning was tested with older and younger participants. As expected, there was a steady improvement of memory performance as a function of repeated learning regardless of age. In addition, enactive encoding led to a better memory performance than verbal encoding in both age groups. Furthermore, younger adults outperformed the elderly regardless of type of encoding. Analyses in the present article show that encoding by enacting seems to profit especially from remembering the last items of a presented list. Regarding age differences, younger outperformed older participants in nearly all item positions. The performance enhancement after task repetition is due to a higher amount of recalled items in the middle positions in a subject performed task (SPT) and a verbal task (VT) as well as the last positions of a learned list in VT.     

Exposure to music with prosocial lyrics reduces aggression: First evidence and test of the underlying mechanism

Previous research has predominantly focused on negative effects of music exposure by demonstrating that listening to antisocial music increases aggression and aggression-related variables. The present research tests the idea that listening to prosocial (relative to neutral) music decreases aggressive outcomes. In fact, five studies revealed that prosocial music exposure decreased aggressive cognition, affect, and behavior. Mediational analyses showed that the effect of music condition on aggressive behavior was accounted for by differences in aggressive affect. Implications of these results for the predictive validity of the general learning model (Buckley & Anderson, 2006) for the effects of media exposure on social tendencies are discussed.     

Individuals differ in the attentional blink: Mental speed and intra-subject stability matter

The failure to correctly report two targets (“T₁”, “T₂”) that follow each other in close temporal proximity has been called the “attentional blink” (AB). The AB has, so far, mainly been studied using experimental approaches. The present studies investigated individual differences in AB performance, revealing (among further findings) a high positive correlation between the accuracies of detecting the two targets correctly (r = 0.69); and between T₂∣T₁ accuracy and psychometric intelligence (0.41 ≤ r ≤ 0.43) and RT variability in short-term and working memory (− 0.38 ≤ r ≤ − 0.45). Together, these results support important aspects of major theoretical accounts of the AB from an individual differences perspective and introduce intelligence and intra-subject stability as contributing factors in AB performance.     

城镇化进程中离乡农民心理健康特点调查及心理素质、相对剥夺感的影响机制

为探讨城镇化进程中离乡农民的心理健康特点以及心理素质、相对剥夺感对其的影响,通过量表对1339名城乡居民进行调查。结果发现:离乡与留乡农民在幸福感、拥有生命意义感、感知控制感、心理素质方面显著低于城镇居民,在状态焦虑方面显著高于城镇居民; 离乡农民在抑郁上显著高于城镇居民,在感知控制感上显著高于留乡农民,在心理素质上显著低于留乡农民; 留乡农民在相对剥夺感上显著高于城镇居民; 离乡农民的幸福感、拥有生命意义感、感知控制感态与相对剥夺感呈显著负相关,与心理素质呈显著正相关; 离乡农民的抑郁、状态焦虑与相对剥夺感呈显著正相关,与心理素质呈显著负相关; 离乡农民的相对剥夺感与心理素质之间呈显著负相关。心理素质除了可以直接预测心理健康各项指标,还可以通过相对剥夺感的中介作用,间接预测幸福感、抑郁及状态焦虑。提升心理素质和降低相对剥夺感是离乡农民心理健康服务的重要切入点。     

Perceiving by proxy: Effect-based action control with unperceivable effects

Anticipations of future sensory events have the potential of priming motor actions that would typically cause these events. Such effect anticipations are generally assumed to rely on previous physical experiences of the contingency of own actions and their ensuing effects. Here we propose that merely imagined action effects may influence behaviour similarly as physically experienced action effects do. Three experiments in the response–effect compatibility paradigm show that the mere knowledge of action–effect contingencies is indeed sufficient to incorporate these effects into action control even if the effects are never experienced as causally linked to own actions. The experiments further highlight constraints for this mechanism which seems to be rather effortful and to depend on explicit intentions.