Special relativity — An exoteric narrative

Some time earlier¹ we treated our readers to an exoteric narrative of special relativity’s kinematics in which we shunned the use of mathematical formulas. However, the simple and concise account presented then has left quite a few questions open, and we now present the promised sequel to supply the requisite answers.     

Spacing extinction trials alleviates renewal and spontaneous recovery

Studies of extinction in classical conditioning situations can reveal techniques that maximize the effectiveness of exposure-based behavior therapies. In three experiments, we investigated the effect of varying the intertrial interval during an extinction treatment in a fear-conditioning preparation with rats as subjects. In Experiment 1, we found less fear at test (i.e., more effective extinction) when extinction trials were widely spaced, relative to intermediate or massed extinction trials. In Experiment 2, we used an ABA renewal procedure and observed that spaced trials attenuated renewal of conditioned fear relative to massed trials. In Experiment 3, we used a similar design, but instead of changing the physical context at the time of testing, we interposed a retention interval after the extinction treatment to produce a change in the temporal context. The results showed less spontaneous recovery of fear after spaced than after massed extinction trials. These results suggest that extinction is more enduring when the extinction trials are spaced rather than massed. Although the benefits of spacing trials are small when there is no contextual change from extinction to testing, a change in either physical or temporal context following massed extinction trials leads to a recovery from extinction, which is reduced when the trials are spaced.     

Comparisons of Four Methods for Estimating a Dynamic Factor Model

Four methods for estimating a dynamic factor model, the direct autoregressive factor score (DAFS) model, are evaluated and compared. The first method estimates the DAFS model using a Kalman filter algorithm based on its state space model representation. The second one employs the maximum likelihood estimation method based on the construction of a block-Toeplitz covariance matrix in the structural equation modeling framework. The third method is built in the Bayesian framework and implemented using Gibbs sampling. The fourth is the least squares method, which also employs the block-Toeplitz matrix. All 4 methods are implemented in currently available software. The simulation study shows that all 4 methods reach appropriate parameter estimates with comparable precision. Differences among the 4 estimation methods and related software are discussed.     

Studies of visual information processing in schizophrenic children

11 children meeting DSM III criteria for schizophrenia (mean age approximately 12 years), a group of normal children matched in mean mental age to the schizophrenic children, and a group of younger normal children (mean age 6.6 years) were administered a series of visual information-processing tasks in order to isolate core information-processing impairments in childhood onset schizophrenia. In Experiment 1, the schizophrenic children showed impairment relative to the MA-matched normals and performed at the level of the younger normal children on a forced-choice partial-report version of the span-of-apprehension task. Previous research has shown that this task is sensitive to dysfunction in both actively and partially recovered schizophrenic adults as well as a subset of foster children at risk for schizophrenia. Experiment 2 delimited the source of the information-processing impairment in schizophrenic children by ruling out a number of possible causes of impairment and suggesting that schizophrenic children use the same information-acquisition strategies as MA-matched children but less efficiently. Experiment 3 revealed that, consistent with the previous research, the schizophrenic children were comparable with the MA-matched controls on a full-report span-of-apprehension task that placed heavy demands on iconic and short-term memory. Both the schizophrenic and MA-matched normals performed significantly better than the younger normal children. Taken collectively, the results of the three experiments suggest that all groups of children engaged in a serial information-processing strategy while performing on the partial-report version of the span-of-apprehension task. The differential impairment of the schizophrenic children on the partial-report versions but not the full-report version of the span-of-apprehension task seems to reflect inefficiencies in controlled attentional processes that normally develop during middle childhood.     

The Effect of Hearing Impairment on the Quality of Attachment and Mother-Toddler Interaction

In the present study, 41 hearing impaired and 41 hearing toddlers together with their hearing mothers were observed in Ainsworth's Strange Situation and during free play. Both security of attachment and ratings of maternal and toddler behavior during free play were remarkably similar for the hearing impaired and hearing dyads. In addition, security of attachment was related to the ratings of maternal and toddler behavior in a similar way for the hearing impaired and hearing toddlers. The results suggest that development of a secure attachment and maintaining a good mother-toddler relationship does not depend on normal language development during the toddler years.