A microcomputer-controlled laboratory: Software

The software used in a microcomputer-controlled laboratory is described. Primary emphasis is placed upon describing the capabilities of a powerful, easy-to-use programming language appropriate for controlling research in a wide variety of applications. It is particularly appropriate for physiological and operant laboratories. Design of the language and accompanying operating system follow a rigorous modular, structured approach, with most coding done in high-level languages. As a result, the code is easy to maintain and expand. In addition, it is not difficult to adapt the programs to other microprocessors to take advantage of a rapidly improving technology.     

A microcomputer-controlled solid-state dark adaptometer

A low-cost microprocessor-controlled light-emitting diode (LED) dark adaptometer is described. The apparent intensities of red and green stimuli are controlled by changing the duty cycles of LED display elements which are operated at constant pulse repetition rates. The psychophysical method of limits is used to obtain threshold data. Stimulus parameters and test procedures are under software control. The design utilizes programmable integrated circuitry that may be used with a variety of microprocessors.     

A microcomputer-controlled laboratory: Hardware

A microcomputer-controlled laboratory designed to incorporate the Motorola 6800 microprocessor unit is described. The microcomputer system is reliable, flexible, and expandable, as well as adaptable to the next generation of Motorola microprocessor components. A modular system design utilizes multiprocessing with separate microprocessor units dedicated to specific functions. This computer, when used with powerful, high-level software, provides a general-purpose psychology laboratory computer system that is easy to use.     

A microprocessor reaction time laboratory

The hardware and software required to implement a multiple-subject microprocessor-based laboratory are described. A basic stimulus-probe reaction time paradigm encompasses a wide range of cognitive psychology experiments and requires little or no sophistication to use.     

A microcomputer-controlled system for measuring reactivity in small animals

A microcomputer-controlled system has been designed for measuring reactivity in small laboratory animals. This system uses a microcomputer to trigger an acoustic signal, which is fed to a loudspeaker through an audio power amplifier. An animal’s acoustic startle response is recorded using a moving-coil loudspeaker as a movement transducer. The transducer output is coupled to a peak-hold circuit that records the maximum voltage generated by the animal’s response. After conversion to digital form, the data for each stimulus presentation are stored and then printed when all trials have been completed.     

A warning about median reaction time

When used with positively skewed reaction time distributions, sample medians tend to over-estimate population medians. The extent of overestimation is related directly to the amount of skew in the reaction time distributions and inversely to the size of the sample over which the median is computed. Simulations indicate that overestimation could approach 50 ms with small samples and highly skewed distributions. An important practical consequence of the bias in median reaction time is that sample medians must not be used to compare reaction times across experimental conditions when there are unequal numbers of trials in the conditions. If medians are used with unequal sample sizes, then the bias may produce an artifactual difference in conditions or conceal a true difference. Some recent studies of cuing and stimulus probability effects provide examples of this potential artifact.     

A transit-signal methodology for studying reaction time

A new general method has been devised for measuring reaction time, which combines the traditional transit and signal methods. Some applications are described. Advantages over the traditional procedures are considered.     

A strategy for microcomputer-controlled measurement of responses in the behavioral laboratory

Problems associated with microcomputer measurement of responses in operant conditioning experiments are discussed. A general strategy that addresses these problems is presented. Although implementation of the strategy requires assembly language programming, the procedures can be used in conjunction with most high-level programming languages. The method ensures that all responses are detected, prevents detection of multiple responses during switch contact bounce, and indicates when responses are being processed at excessive intervals following their occurrences.     

A free, easy-to-use, computer-based simple and four-choice reaction time programme: the Deary-Liewald reaction time task

Reaction time tasks are used widely in basic and applied psychology. There is a need for an easy-to-use, freely available programme that can run simple and choice reaction time tasks with no special software. We report the development of, and make available, the Deary-Liewald reaction time task. It is initially tested here on 150 participants, aged from 18 to 80, alongside another widely used reaction time device and tests of fluid and crystallised intelligence and processing speed. The new task’s parameters perform as expected with respect to age and intelligence differences. The new task’s parameters are reliable, and have very high correlations with the existing task. We also provide instructions for downloading and using the new reaction time programme, and we encourage other researchers to use it.     

Rasch-representable reaction time distributions

This article investigates properties of a representation based on the Rasch test model for reaction times (RT) that was proposed by Micko. Necessary and sufficient conditions for a set of RT distributions to be Rasch-representable are derived. It is shown that independent serial and independent parallel processing models cannot be reconciled with the representation. However, random extreme models compatible with the Reasch-representation exist that assume RT is determined by the longest or he shortest processing time of a random number of independent paraloel channels. Nonparametric properties of Rasch-representable distributions are derived that can be used for testing the model and for estimating its parameters. Conditions are presented for Rasch-representable distributions to form a scale family. Finally, Rasch-represent-able distributions are characterized interms of their hazard functions.For helpful discussions, we are grateful to Hans Irtel, Christoph Micko, Hartmann Scheiblechner, and Hans-Henning Schultz.     

A choice reaction time index of callosal anatomical homotopy

Tachistoscopically presented bilateral stimulus pairs not parallel to the meridian produced significantly longer RTs on a task requiring discrimination of shapes (Go/no-Go) than pairs emplaced symmetrically on each side of the meridian in Desjardins and Braun [Desjardins, S., & Braun, C. M. J. (2006). Homotopy and heterotopy and the bilateral field advantage in the Dimond paradigm. Acta Psychologica, 121,  125–136]. This was explained by the fact that there are more homotopic than heterotopic fibers in the corpus callosum. However: (1) different parts of the visual field were not equiprobably stimulated, possibly causing subtle biases, (2) the predicted cost of vertical asymmetry was tested only with bilateral stimuli, and (3) interstimulus distance was at the outer limit of callosal midline fusion (10.6°). Here, a tachistoscopic experiment with 24 normal participants replicated the between-field vertical symmetry advantage [Desjardins, S., & Braun, C. M. J. (2006). Homotopy and heterotopy and the bilateral field advantage in the Dimond paradigm. Acta Psychologica, 121, 125–136.], but without irrelevant stimulation conditions and with more proximal stimuli. In addition, a significant specific cost of vertical asymmetry of 7 ms was found for between-field integration over within-field integration. As far as we know, this is the first demonstration of an effect of callosal anatomical homotopy with reaction time.     

Payoff: A neglected factor in reaction time measurement

The aim of this paper is to point out some implications of implicit or explicit payoffs in reaction time experiments. In any psychophysical task the subject is given a set of instructions which define the desired performance, as it were the rules of the game. Instructions may be supplemented by knowledge of results which further define the required performance. When performance admits of being “good” or “bad,” however wide these limits, the instructions may be said to define, explicitly or implicitly, a system of payoffs. In reaction time experiments the subject is instructed, amongst other things, to respond as soon as possible after the stimulus but never before it. These instructions could equally well be represented by a system of payoffs and Figure 1 illustrates the kind of payoff system normally implied in these instructions. If S represents the time at which the physical stimulus occurs the graph shows a fixed penalty for anticipations (response before S), maximum positive score for responses immediately following S declining at an arbitrary rate as a function of elapsed time between S and the response until an unacceptably long time involves a constant maximum penalty. Some experimenters choose to treat very short RT's as anticipations. This is represented by the dashed line in Figure 1, but it should be clear that payoff values are, to a certain extent, arbitrary.     

On measuring the minimum detection time: A simple reaction time study in the time estimation paradigm

Kornblum's time estimation paradigm, together with the so‐called ‘race model’, provides an appealing alternative for measuring the ‘cut‐off’ which separates ‘true’ reaction times from anticipatory reaction times. However, the model is not precise enough to reveal the relation between the signal intensity and the ‘cut‐off’. Accordingly, Kornblum's model is extended with an emphasis on the measure of the ‘cut‐off’. Another aspect of the extension is to use a parametric method to analyse the data. In particular, it is assumed that the time estimation‐induced latency is gamma distributed and the signal‐induced latency is Weibull distributed, with the latter shifted by the ‘cut‐off’. The rationale behind the parametric assumption is discussed. For illustrative purposes, two pieces of experimental work are presented. Since the core of the race model is the assumption of an independent race between the time estimation process and the detection process, the first experiment tests whether, for the same signal intensity, the signal‐induced latency distribution is invariant across different time intervals; the second experiment tests whether, for the same time interval, the time estimation‐induced latency distribution is invariant across different signal intensity conditions. The data from the second experiment are also used to test various parametric assumptions in the model, which include the signal effect on the ‘cut‐off’. The new model fits the data well.     

A comparison of sequential sampling models for two-choice reaction time

The authors evaluated 4 sequential sampling models for 2-choice decisions--the Wiener diffusion, Ornstein-Uhlenbeck (OU) diffusion, accumulator, and Poisson counter models--by fitting them to the response time (RT) distributions and accuracy data from 3 experiments. Each of the models was augmented with assumptions of variability across trials in the rate of accumulation of evidence from stimuli, the values of response criteria, and the value of base RT across trials. Although there was substantial model mimicry, empirical conditions were identified under which the models make discriminably different predictions. The best accounts of the data were provided by the Wiener diffusion model, the OU model with small-to-moderate decay, and the accumulator model with long-tailed (exponential) distributions of criteria, although the last was unable to produce error RTs shorter than correct RTs. The relationship between these models and 3 recent, neurally inspired models was also examined.