Simulating multivariate nonnormal distributions

A method for generating multivariate nonnormal distributions with specified intercorrelations and marginal means, variances, skews, and kurtoses is proposed. As an example, the method is applied to the generation of simulated scores on three psychological tests administered to a single group of individuals.     

TEACHING SAFETY SKILLS TO HIGH SCHOOL STUDENTS WITH MODERATE DISABILITIES

Teaching students with disabilities to respond appropriately to potentially dangerous situations is a useful skill that has received little research attention. This investigation taught 3 students with moderate mental retardation to remove and discard broken materials (plates, glasses) safely from (a) a sink containing dishwater, (b) a countertop, and (c) a floor. A 4th student was instructed on the sink task only. A multicomponent treatment package was used to teach the skills. Simulated materials were used initially and were replaced with broken plates and glasses. A multiple probe design was used to evaluate the effectiveness of the treatment package. The results indicated that the treatment package was effective in teaching the skills. Data were collected 1 week and 1 month following the completion of training, and indicated mixed results. No student was injured during any phase of training. Issues pertinent to teaching safety skills to students with moderate disabilities are discussed.     

Visual dominance in inhibitory conditioning in the pigeon

In a conditioned inhibition paradigm (A+, B+, AX?_, pigeons received either of two keylight stimuli reliably followed by food (A+, B+). However, when one of these keylights was accompanied by another stimulus, food did not follow (AX?). For some groups, the putative inhibitor was a tone, whereas for others it was illumination of a red houselight. The birds pecked the A and B stimuli at a high rate. When X was red houselight, the birds pecked A at a much lower rate in the presence of X. When X was a tone, discrimination between A and AX was much poorer. Moreover, in a transfer test, red houselight inhibited responding to the other keylight, B, but tone did not. These results indicate that red houselight becomes a conditioned inhibitor more quickly than tone in appetitive situations, just as red houselight becomes a conditioned excitor more quickly in those situations. These results contradict the assertion that the latter outcome occurs because red houselight is a stronger appetitive excitor than tone at the start of the experiment (the “head start” hypothesis).     

The attentional blink is not affected by backward masking of T2, T2-mask SOA, or level of T2 impoverishment

Identification of the second of two targets (T2) is impaired when presented shortly after the first (T1). This attentional blink (AB) is thought to arise from a delay in T2 processing during which T2 is vulnerable to masking. Conventional studies have measured T2 accuracy which is constrained by the 100% ceiling. We avoided this problem by using a dynamic threshold-tracking procedure that is inherently free from ceiling constraints. In two experiments we examined how AB magnitude is affected by three masking-related factors: (a) presence/absence of T2 mask, (b) T2-mask stimulus onset asynchrony (SOA), and (c) level of T2 impoverishment (signal-to-noise ratio [SNR]). In Experiment 1, overall accuracy decreased with T2-mask SOA. The magnitude of the AB, however, was invariant with SOA and with mask presence/absence. Experiment 2 further showed that the AB was invariant with T2 SNR. The relationship among mask presence/absence, SOA, and T2 SNR and the AB is encompassed in a qualitative model.     

When moderation is mediated and mediation is moderated

Procedures for examining whether treatment effects on an outcome are mediated and/or moderated have been well developed and are routinely applied. The mediation question focuses on the intervening mechanism that produces the treatment effect. The moderation question focuses on factors that affect the magnitude of the treatment effect. It is important to note that these two processes may be combined in informative ways, such that moderation is mediated or mediation is moderated. Although some prior literature has discussed these possibilities, their exact definitions and analytic procedures have not been completely articulated. The purpose of this article is to define precisely both mediated moderation and moderated mediation and provide analytic strategies for assessing each.     

The nature of hemispheric specialization for prosody perception

Recent evidence suggests a relative right-hemispheric specialization for emotional prosody perception, whereas linguistic prosody perception is under bilateral control. It is still unknown, however, how the hemispheric specialization for prosody perception might arise. Two main hypotheses have been put forward. Cue-dependent hypotheses, on the one hand, propose that hemispheric specialization is driven by specialization for the non-prosody-specific processing of acoustic cues. The functional lateralization hypothesis, on the other hand, proposes that hemispheric specialization is dependent on the communicative function of prosody, with emotional and linguistic prosody processing being lateralized to the right and left hemispheres, respectively. In the present study, the functional lateralization hypothesis of prosody perception was systematically tested by instructing one group of participants to evaluate the emotional prosody, and another group the linguistic prosody dimension of bidimensional prosodic stimuli in a dichotic-listening paradigm, while event-related potentials were recorded. The results showed that the right-ear advantage was associated with decreased latencies for an early negativity in the contralateral hemisphere. No evidence was found for functional lateralization. These findings suggest that functional lateralization effects for prosody perception are small and support the structural model of dichotic listening.     

Authoritarianism, social dominance orientation and prejudice: Effects of various self-categorization conditions

One hundred and seventy nine students first answered RWA and SDO scales were assigned to experimental conditions that primed different forms of self-categorization, and finally responded for prejudice scales for three target ethnic groups. The results showed first, that RWA and SDO correlate with prejudice in a control condition. Second, RWA and SDO correlated differently with prejudice depending on the way in which membership to social group was primed. When a prime as member of a group oriented to devotion to the in-group norms and values was used, the correlation of RWA and in-group identification with prejudice was significant, but when a prime as member of a competitive group was used, only SDO correlated significantly with prejudice. The results were discussed as identifying two different schemas of social categorization according to which RWA and SDO expressed sets of social beliefs and attitudes relevant for inter-group relations.