Mathematica: A flexible design environment for neural networks

Several neural networks were developed inMathematica in order to explore the role of “spiky” neurons in neural network memory simulations. UsingMathematica for this task confirmed its value as a powerful tool for neural network development: It exhibited distinct advantages over other environments in programming ease, flexibility of data structures, and the graphical assessment of network performance.     

COGENT: A visual design environment for cognitive modeling

COGENT is a design environment for modeling cognitive processes and systems. It permits psychologists to construct and test information-processing models of cognition based on traditional box-and-arrow diagrams. COGENT provides a graphical model editor, together with a set of standard types of cognitive module based on familiar theoretical constructs from psychological theory. Models are constructed by selecting appropriate box types, connecting them with appropriate communication links, and configuring the various boxes according to the requirements of the investigator. Once a model has been constructed, it may be executed to examine and analyze its behavior.     

Hypotheses in perception: their development about unambiguous stimuli in the environment

A series of seven photographs which depict a real scene as it is approached by an observer were shown, in sequence, to ninety-six university students. The photographs were either projected colour transparencies or black-and-white prints. Two sixes of photographs were used in each set and the series was presented with or without the first photograph. In earlier studies in which blurred photographs were used as stimuli, observers were unsure about their hypotheses. That was not the case in this study. Although individual observers differed widely in their initial hypotheses, the initial photographs were not perceived as ambiguous. It required on average from 2.9 photographs (large, black-and-white, full series) to 4.5 photographs (small, colour, full series) for correct identification. In general, colour is a hindrance to correct identification. For the full series approximately three hypotheses are put forward before the scene is correctly identified.     

Rapid-REM: A MATLAB simulator of the replaced-elements model

A recent proposal for an elemental account of associative learning phenomena is the replaced-elements model (REM) put forward by Wagner (2003). Although the ideas underlying this model are comparatively simple, implementation of the model is rather complex. In this article, we present Rapid-REM, a MATLAB simulator of Wagner's model. Rapid-REM features a graphical user interface for manipulating all essential parameter values and for control of the simulation process, graphical visualization of the simulation course and the results, and the alternative possibility of simulating the replaced-elements model as it was originally proposed (Wagner & Brandon, 2001). Rapid-REM is available free of charge from www.staff.uni-marburg.de/(tilde)lachnit/Rapid-REM/. This simulator makes it easy to derive predictions for REM and evaluate them, and it will therefore facilitate insights into the mechanisms of associative learning.     

An economical microcomputer design for the generation and display of timed visual stimuli: The TDL VDB

Recent developments in microprocessor-based technology should be of particular interest to psychologists concerned with perceptual and cognitive processes. This paper describes the advantages of a Z-80-based system that uses the Technical Design Labs video display board (VDB) for the generation and control of visual stimuli.     

ALTSim: A MATLAB simulator for current associative learning theories

ALTSim is a MATLAB-based simulator of several associative learning models, including Pearce’s configural model, the extended configural model, the Rescorla-Wagner model, the unique cue hypothesis, the modified unique cue hypothesis, the replaced elements model, and Harris’s elemental model. It allows for specifying all relevant parameters, as well as exact stimulus sequences by graphical user interfaces. It is an easy-to-use tool that facilitates evaluating and comparing the featured associative learning models. ALTSim is available free of charge from www.staff.uni-marburg.de/~lachnit/ALTSim/.     

TwoMP: A MATLAB graphical user interface for two-mode partitioning

Two-way two-mode data occur in almost every domain of scientific psychology. The information present in such data, however, may be hard to grasp because of the dimensions of one or both modes. Two-mode partitioning addresses this problem by breaking down both modes into a number of mutually exclusive and exhaustive subsets. Although such a technique may be very useful, up to now, software—and consequently, two-mode partitioning—has been available only to a handful of specialists in the field. In this article, we present a free, easy-to-use MATLAB graphical user interface (TwoMP) for two-mode partitioning models, specifically developed for nonspecialist users. A short formal introduction is given on the statistics of the method, and the basic use of TwoMP is demonstrated with an example.     

Signal evaluation environment: a new method for the design of peripheral in-vehicle warning signals

An evaluation method called the Signal Evaluation Environment (SEE) was developed for use in the early stages of the design process of peripheral warning signals while driving. Accident analyses have shown that with complex driving situations such as intersections, the visual scan strategies of the driver contribute to overlooking other road users who have the right of way. Salient peripheral warning signals could disrupt these strategies and direct drivers’ attention towards these road users. To select effective warning signals, the SEE was developed as a laboratory task requiring visual–cognitive processes similar to those used at intersections. For validation of the SEE, four experiments were conducted using different stimulus characteristics (size, colour contrast, shape, flashing) that influence peripheral vision. The results confirm that the SEE is able to differentiate between the selected stimulus characteristics. The SEE is a useful initial tool for designing peripheral signals, allowing quick and efficient preselection of beneficial signals.     

A delivery system for olfactory stimuli

This paper describes the design of a new method for controlling and administering olfactory stimuli—namely, thehood system. The hood system involves a stream of vaporized odor (at known concentrations) mixed with odorless air and pumped (at a constant flow rate) into an oxygen therapy hood. It is designed to be used with odorants in solution, such as essential oils, as the olfactory stimulus. The use of oxygen therapy hoods allows for the precise control of a constant concentration of odorized air over time, while allowing subjects to breathe normally. The hood system provides a natural administration of olfactory stimuli and the exact determination of the stimulus concentration. The use of this system will allow experimental conditions to be completely defined and results and replication studies to be accurately interpreted. The hood system is portable, cost effective, and constructed from readily available components. It is proposed that the hood system could be adopted to suit a wide range of olfactory research, particularly that in which the effects of chronic exposure to olfactory stimuli on cognition are examined.     

Response differentiation: A psychophysical method for response produced stimuli

Twenty-four rats were reinforced for releasing a lever between t and t + .20 sec after pressing it. Response duration differentiation performance decreased monotonically as t was increased in length from .10 sec to 1.60 sec. A response analogue of Weber’s ratio was constant throughout the middle range of duration bandwidth requirements and increased at the ex tremely short bandwidth—a response-differentiation finding analogous to Weber’s law of stimulus discrimination. This finding was interpreted as support for the conceptualization that response differentiation represents a special instance of response discrimination or discrimination based on response-produced stimuli.     

Memory for common and bizarre stimuli: A storage-retrieval analysis

We tested the hypothesis that common stimuli are stored in memory better than bizarre stimuli are. Subjects memorized a series of noun pairs embedded within 20 common or bizarre sentences. By using a between-list design, free and cued recall, and intentional-learning instructions, we were able to obtain a commonness effect (i.e., a recall advantage for the common sentences). Riefer and Rouder’s (1992) multinomial processing-tree model for measuring storage and retrieval was applied to the data, which revealed that the recall advantage for common sentences was due to storage and not retrieval processes. We propose a two-factor theory: that common items are stored better in memory, but that bizarre items are retrieved better from memory. This storage-retrieval explanation does a good job of accounting for a number of findings associated with the bizarreness effect.     

Visual stimuli on the Commodore Amiga: A tutorial

The Commodore Amiga home microcomputer, together withDeLuxePaint, a commercial software package, can generate many useful visual stimuli, including random-dot stereograms, apparent motion, texture edges, aftereffects from dimming and brightening, motion aftereffects, dynamic random noise, and drifting and counterphase gratings. Videotapes can readily be made of these displays. No programming experience is necessary.     

Recognition of maternal environment in piglets: effects of age and some discrete complex stimuli

Ethological evidence suggests that 1-week-old piglets can distinguish between their own mother or home environment and alien ones. The bases for this discrimination were investigated in two series of experiments employing a T-maze. In the first series, the apparatus was placed between two pens each housing a sow and its piglets, with each of the two goal-arms having a wire mesh end protruding into one of the pens. When piglets from each of these pens (as well as controls from other litters) were run individually in the apparatus, piglets of all ages from 1 to 14 days showed preferential responses towards their home environment. In the second series of experiments, various discrete but complex natural stimuli were placed at the end of the goal-arms: in each case, the stimuli in the two goal-arms were indentical in nature except in their derivation from the maternal pen or an alien one. One-week-old piglets showed a significant preference for their own mother (vs. another sow visible and audible through wire mesh), for wood shavings mixed with sow faeces from their own pen (on the floor of the goal-arm), and for air blown over maternal faeces and shavings. But they showed no evidence of distinguishing between a littermate and another piglet (penned at the other side of the wire mesh terminating a goal-arm).     

What we fear most: A developmental advantage for threat-relevant stimuli

Fear is one of our most basic emotions. It is an important social signal and alerts us to when a situation is safe or risky. Interestingly, not all fears are created equal: Several researchers have proposed that humans develop specific fears, such as fear of threatening stimuli, more readily than others. Here we discuss three major theories of fear acquisition, and consider the possibility that some fears are privileged in learning. Second, we review a growing literature that suggests that humans have perceptual biases that quickly draw attention to threatening stimuli in the environment. In particular, we highlight recent developmental work that shows that even infants and young children respond rapidly to the presence of threat well before they acquire any threat-relevant fears. Finally, we argue that such biases may play a causal role in privileging fear learning for certain threats, and we suggest directions for future work that can clarify whether early biases in perception indeed facilitate the development of our most common fears.     

Constructing isoluminant stimuli for word recognition research: A precautionary study

Isoluminant stimuli are used increasingly often to investigate processes underlying visual word recognition. However, construction of isoluminant stimuli is not straightforward, and inappropriate construction may have the result of misinforming theories that relate word recognition to neurological function. To inform the use of isoluminant stimuli in studies of word recognition, the present article details two experiments in which isoluminant stimuli were constructed using physical onscreen luminance matching and heterochromatic flicker photometry (HFP) with four different stimulus types: disks, squares, rectangles, and letter strings. The findings reveal (1) substantial differences between isoluminance determined by physical onscreen luminance matching and HFP, (2) substantial differences in HFP isoluminance across stimulus types, and (3) substantial differences in HFP isoluminance across participants. These findings indicate that, in contrast to common practice in word recognition research, HFP provides a better indication of isoluminance than physical onscreen matching; but HFP stimuli should match those used in the experiment proper and should be used to assess isoluminance individually for each participant.     

A system for computer control of auditory stimuli

A computer system for generation of auditory stimuli is described. The system produces natural-speech or software-generated stimuli for monaural, binaural, or dichotic presentation. Stimuli have been generated for experiments run both on-line and off-line.