Do chickens (Gallus gallus f. domestica) decompose visual figures?

To investigate whether learning to discriminate between visual compound stimuli depends on decomposing them into constituting features, hens were first trained to discriminate four features (red, green, horizontal, vertical) from two dimensions (colour, line orientation). After acquisition, hens were trained with compound stimuli made up from these dimensions in two ways: a separable (line on a coloured background) stimulus and an integral one (coloured line). This compound training included a reversal of reinforcement of only one of the two dimensions (half-reversal). After having achieved the compound stimulus discrimination, a second dimensional training identical to the first was performed. Finally, in the second compound training the other dimension was reversed. Two major results were found: (1) an interaction between the dimension reversed and the type of compound stimulus: in compound training with colour reversal, separable compound stimuli were discriminated worse than integral compounds and vice versa in compound training with line orientation reversed. (2) Performance in the second compound training was worse than in the first one. The first result points to a similar mode of processing for separable and integral compounds, whereas the second result shows that the whole stimulus is psychologically superior to its constituting features. Experiment 2 repeated experiment 1 using line orientation stimuli of reversed line and background brightness. Nevertheless, the results were similar to experiment 1. Results are discussed in the framework of a configural exemplar theory of discrimination that assumes the representation of the whole stimulus situation combined with transfer based on a measure of overall similarity.     

Inferring the structure of latent class

Present optimization techniques in latent class analysis apply the expectation maximization algorithm or the Newton-Raphson algorithm for optimizing the parameter values of a prespecified model. These techniques can be used to find maximum likelihood estimates of the parameters, given the specified structure of the model, which is defined by the number of classes and, possibly, fixation and equality constraints. The model structure is usually chosen on theoretical grounds. A large variety of structurally different latent class models can be compared using goodness-of-fit indices of the chi-square family, Akaike’s information criterion, the Bayesian information criterion, and various other statistics. However, finding the optimal structure for a given goodness-of-fit index often requires a lengthy search in which all kinds of model structures are tested. Moreover, solutions may depend on the choice of initial values for the parameters. This article presents a new method by which one can simultaneously infer the model structure from the data and optimize the parameter values. The method consists of a genetic algorithm in which any goodness-of-fit index can be used as a fitness criterion. In a number of test cases in which data sets from the literature were used, it is shown that this method provides models that fit equally well as or better than the models suggested in the original articles.     

A Web-based program for coding open-ended response protocols

A Web-based coding application was designed to improve coding efficiency and to provide a systematic means of evaluating responses to open-ended assessments. The system was developed for use by multiple raters to assign open-ended responses to predetermined categories. The application provides a software environment for efficiently supervising the work of coders and evaluating the quality of the coding by (1) systematically presenting open-ended responses to coders, (2) tracking each coder’s categorized responses, and (3) assessing interrater consistency at any time in order to identify coders in need of further training. In addition, the application can be set to automatically assign repeated responses to categories previously identified as appropriate for those responses. To evaluate the efficacy of the coding application and to determine the statistical reliability of coding open-ended data within this application, we examined data from two empirical studies. The results demonstrated substantial interrater agreement on items assigned to various categories across free and controlled association tasks. Overall, this new coding application provides a feasible method of reliably coding open-ended data and makes the task of coding these data more manageable.     

Generating complex three-dimensional stimuli (Greebles) for haptic expertise training

An apparatus is described that accurately measures response times and video records hand movements during haptic object recognition using complex three-dimensional (3-D) forms. The apparatus was used for training participants to become expert at perceptual judgments of 3-D objects (Greebles) using only their sense of touch. Inspiration came from previous visual experiments, and therefore training and testing protocols that were similar to the earlier visual procedures were used. Two sets of Greebles were created. One set (clay Greebles) was hand crafted from clay, and the other (plastic Greebles) was machine created using rapid prototyping technology. Differences between these object creation techniques and their impact on perceptual expertise training are discussed. The full set of these stimuli may be downloaded from www.psychonomic.org/archive/.     

WebDiP: A tool for information search experiments on the World-Wide Web

We describe WebDiP (Web Decision Processes)—an open-source, online tool—which enables a researcher to track participants while they search for information in a database, available through the Internet. After various instructions on setup and configuration are given, a detailed view of WebDiP explains the system’s technical features. Furthermore, other open-source tools are mentioned that helped in programming WebDiP, running it, or analyzing data gathered with it. We present new approaches of how open-source thinking can be incorporated into a research process and discuss future perspectives of WebDiP.     

Objective versus estimated age of word acquisition: A study of 202 Italian children

We provide objective data concerning the age of acquisition (AoA) of words from 202 Italian children 34–69 months of age. We investigated picture naming with 80 concrete words belonging to eight semantic categories that are included in a widely used battery for the study of naming and semantic memory. For each word, we calculated three different indices: two directly expressing the age at which a picture was given the correct name by at least 75% of the subjects, and one expressing the overall percentage of our children who were correct in the task. (For the latter index, we provide separate values for boys and girls.) The correlation between objective indices of AoA and adult estimates culled from the literature was not very high. Moreover, objective indices showed low correlations with frequency and familiarity, in contrast to adult ratings. We conclude that adult estimates of AoA present validity problems and should be used with caution. The full set of stimuli is available at www.psychonomic.org/archive.     

The functional significance of theta and upper alpha oscillations

Recent findings are reviewed indicating that upper alpha oscillations - when analyzed with appropriate time/ frequency resolution - show a similar physiological reactivity as theta in working memory tasks. Comparable to theta, a load dependent increase in power can be observed during retention and increased evoked activity during retrieval. During retrieval attempts theta behaves like a traveling wave spreading from anterior to posterior sites. During actual retrieval, however, evoked upper alpha becomes transiently nested in theta. We suggest that theta reflects working memory functions whereas upper alpha may be important for the reactivation of long-term memory codes in short-term memory.     

Social dominance orientation,prejudice, and discrimination: A new computer-based method for studying discriminatory behaviors

A number of studies have shown that the scale of social dominance orientation (SDO), used to measure the degree of preference for inequality among social groups, is a predictive measure of social and political attitudes toward stigmatized outgroups. However, the relationship between SDO and discrimination has received little attention. The main goal of this study was to assess the validity of a new computer-based method used to measure discriminatory behaviors in a laboratory setting. An additional goal was to test the mediating role of prejudice in the relation between SDO and discrimination. The results provide a first validation of this new method and demonstrate that the effect of SDO on discrimination is mediated by prejudice.