Metronome LKM: An open source virtual keyboard driver to measure experiment software latencies

Experiment software is often used to measure reaction times gathered with keyboards or other input devices. In previous studies, the accuracy and precision of time stamps has been assessed through several means: (a) generating accurate square wave signals from an external device connected to the parallel port of the computer running the experiment software, (b) triggering the typematic repeat feature of some keyboards to get an evenly separated series of keypress events, or (c) using a solenoid handled by a microcontroller to press the input device (keyboard, mouse button, touch screen) that will be used in the experimental setup. Despite the advantages of these approaches in some contexts, none of them can isolate the measurement error caused by the experiment software itself. Metronome LKM provides a virtual keyboard to assess an experiment’s software. Using this open source driver, researchers can generate keypress events using high-resolution timers and compare the time stamps collected by the experiment software with those gathered by Metronome LKM (with nanosecond resolution). Our software is highly configurable (in terms of keys pressed, intervals, SysRq activation) and runs on 2.6–4.8 Linux kernels.     

A solution for measuring accurate reaction time to visual stimuli realized with a programmable microcontroller

This article presents a new solution for measuring accurate reaction time (SMART) to visual stimuli. The SMART is a USB device realized with a Cypress Programmable System-on-Chip (PSoC) mixed-signal array programmable microcontroller. A brief overview of the hardware and firmware of the PSoC is provided, together with the results of three experiments. In Experiment 1, we investigated the timing accuracy of the SMART in measuring reaction time (RT) under different conditions of operating systems (OSs; Windows XP or Vista) and monitor displays (a CRT or an LCD). The results indicated that the timing error in measuring RT by the SMART was less than 2 msec, on average, under all combinations of OS and display and that the SMART was tolerant to jitter and noise. In Experiment 2, we tested the SMART with 8 participants. The results indicated that there was no significant difference among RTs obtained with the SMART under the different conditions of OS and display. In Experiment 3, we used Microsoft (MS) PowerPoint to present visual stimuli on the display. We found no significant difference in RTs obtained using MS DirectX technology versus using the PowerPoint file with the SMART. We are certain that the SMART is a simple and practical solution for measuring RTs accurately. Although there are some restrictions in using the SMART with RT paradigms, the SMART is capable of providing both researchers and health professionals working in clinical settings with new ways of using RT paradigms in their work.     

Adobe Flash as a medium for online experimentation: A test of reaction time measurement capabilities

Adobe Flash can be used to run complex psychological experiments over the Web. We examined the reliability of using Flash to measure reaction times (RTs) using a simple binary-choice task implemented both in Flash and in a Linux-based system known to record RTs with millisecond accuracy. Twenty-four participants were tested in the laboratory using both implementations; they also completed the Flash version on computers of their own choice outside the lab. RTs from the trials run on Flash outside the lab were approximately 20 msec slower than those from trials run on Flash in the lab, which in turn were approximately 10 msec slower than RTs from the trials run on the Linux-based system (baseline condition). RT SDs were similar in all conditions, suggesting that although Flash may overestimate RTs slightly, it does not appear to add significant noise to the data recorded.     

Speed of information-processing in an inductive reasoning task and its relationship to psychometric intelligence

The relationship between psychometric intelligence (measured by means of Raven's Advanced Progressive Matrices and two verbal subtests of the “Intelligenz-Struktur-Test-70”) and speed of information-processing in a newly developed computerized reaction time (RT) task called the Concept-Verification-Test (CVT) was investigated in a sample of 104 undergraduates. In this CVT, first, one of five possible conceptual rules is presented on a computer monitor. After reading the rule, the subject has to press a button and then one of 27 possible simple geometrical figures is presented, which either is an example of the concept or not. The subject has to press the true button if the presented figure is a positive instance of the rule or the false button if it is not. Two RTs were measured: The Comprehension Reaction Time (CRT) from the onset of the rule to the first button press and the Verification Reaction Time (VRT) from the onset of the figure until the response is given. The different complexity of the conceptual rules used also allowed us to examine the “complexity hypothesis” (i.e. correlations with intelligence should be higher for more complex RT tasks). As predicted, both CRTs and VRTs correlated negatively with intelligence, but we found no evidence for the validity of the complexity hypothesis.     

Timing and reaction time.

Because reaction time (RT) tasks are generally repetitive and temporally regular, participants may use timing strategies that affect response speed and accuracy. This hypothesis was tested in 3 serial choice RT experiments in which participants were presented with stimuli that sometimes arrived earlier or later than normal. RTs increased and errors decreased when stimuli came earlier than normal, and RTs decreased and errors increased when stimuli came later than normal. The results were consistent with an elaboration of R. Ratcliff's diffusion model (R. Ratcliff, 1978; R. Ratcliff & J. N. Rouder, 1998; R. Ratcliff, T. Van Zandt, & G. McKoon, 1999), supplemented by a hypothesis developed by D. Laming (1979a, 1979b), according to which participants initiate stimulus sampling before the onset of the stimulus at a time governed by an internal timekeeper. The success of this model suggests that timing is used in the service of decision making.     

On timing events in computer-controlled experiments

This paper considers the problem of timing events in computer-controlled experiments. A digital clock is defined as a time-mark generator or “ticker” and a counter. A discussion of time-mark generators commonly used in computers is followed by a consideration of several ways in which computer clocks are implemented and used. A framework for the latter discussion is provided by a classification of clocks in terms of whether the ticker or the counter (either or both) is internal or external to the computer.     

Response time accuracy in Apple Macintosh computers

The accuracy and variability of response times (RTs) collected on stock Apple Macintosh computers using USB keyboards was assessed. A photodiode detected a change in the screen’s luminosity and triggered a solenoid that pressed a key on the keyboard. The RTs collected in this way were reliable, but could be as much as 100 ms too long. The standard deviation of the measured RTs varied between 2.5 and 10 ms, and the distributions approximated a normal distribution. Surprisingly, two recent Apple-branded USB keyboards differed in their accuracy by as much as 20 ms. The most accurate RTs were collected when an external CRT was used to display the stimuli and Psychtoolbox was able to synchronize presentation with the screen refresh. We conclude that RTs collected on stock iMacs can detect a difference as small as 5–10 ms under realistic conditions, and this dictates which types of research should or should not use these systems.     

A “hand-shaking” multiplexer for the IBM 1800

An instrument is described which is used to multiplex the “ready” and “external sync” lines of an IBM 1800’s data channel to 15 external devices. Used with the digital output registers of the computer, the device facilitates the interfacing of non-IBM peripheral devices to the 1800. The multiplexer can be used in any application in which a pair of lines needs to be shared among several devices.     

An external millisecond timer for the Apple Macintosh with applications to cross-modal lexical priming

The circuit and program described in this report allow researchers to use Macintosh personal computers to conduct research that requires timing with millisecond accuracy. This is accomplished with external response keys and an external clock that sends characters through the Macintosh’s serial port. For researchers interested in cross-modal lexical priming tasks, a tachistoscopic slide shutter is incorporated to allow for accurately timed presentation of visual stimuli. Because the visual display and response keys are external to the computer, display and reaction times are not subject to the timing constraints inherent to the keyboard or the Macintosh Event Manager. All circuit diagrams and code are in the public domain.     

Mental chronometry and individual differences: Modeling reliabilities and correlations of reaction time means and effect sizes

We used a general stage-based model of reaction time (RT) to investigate the psychometric properties of mean RTs and experimental effect sizes (i.e., differences in mean RTs). Using the model, formulas were derived for the reliabilities of mean RTs and RT difference scores, and these formulas provide guidance about the number of trials per participant needed to obtain reliable estimates of these measures. In addition, formulas were derived for various different types of correlations computed in RT research (e.g., correlations between a mean RT and an external non-RT measure, between two mean RTs, between a mean RT and an RT effect size). The analysis revealed that observed RT-based correlations depend on many parameters of the underlying processes contributing to RT. We conclude that these correlations often fail to support the inferences drawn from them and that their proper interpretation is far more complex than is generally acknowledged.     

VIDEOLOGGER: A computerized multichannel event recorder for analyzing videotapes

A microcomputer-assisted system that permits multiple events to be coded from videotape to a common time base is described. The system allows an operator, by pressing a button, to record the onset and offset times of any number of events. It requires a video recorder, an Apple II microcomputer, a John Bell 6522 timing card, and a pair of switches. The software package consists of five programs: one to make timing signals on the videotape, one to record the onset time and duration of the operator’s buttonpresses, one to read and print the coding data from disk, one to operate the timer, and one to process the compiled code used in the software package. All necessary wiring diagrams are shown. Software is available gratis from the authors on request.     

Identification of the eye-brain-hand system with point processes: a new approach to simple reaction time

By presenting a Poisson process of flashes to observers who hit a button as quickly as possible after each, the authors identified the system involved in simple reaction time (RT). The nonlinear kernels up to 2nd order were measured from the stimulus and response point processes. The 1st-order kernel is analogous to a histogram of simple RTs. The 2nd-order kernel shows complex patterns of nonlinear suppression and facilitation between pairs of flashes. Simple RT measured as the lag of the 1st-order kernel's peak agrees with RT from conventional discrete trial experiments. RTs are shorter and less variable when the flashes are separated by uniform rather than exponential delays, which shows that observers use the stimulus hazard function to become prepared to detect and respond to the flash.     

Timing accuracy under Microsoft Windows revealed through external chronometry

Recent studies by Myors (1998, 1999) have concluded that the Microsoft Windows operating system is unable to support sufficient timing precision and resolution for use in psychological research. In the present study, we reexamined the timing accuracy of Windows 95/98, using (1) external chronometry, (2) methods to maximize the system priority of timing software, and (3) timing functions with a theoretical resolution of 1 msec or better. The suitability of various peripheral response devices and the relative timing accuracy of computers with microprocessors with different speeds were also explored. The results indicate that if software is properly controlled, submillisecond timing resolution is achievable under Windows with both old and new computers alike. Of the computer input devices tested, the standard parallel port was revealed as the most precise, and the serial mouse also exhibited sufficient timing precision for use in single-interval reaction time experiments.     

Combining EEG,MIDI, and motion capture techniques for investigating musical performance

This article describes a setup for the simultaneous recording of electrophysiological data (EEG), musical data (MIDI), and three-dimensional movement data. Previously, each of these three different kinds of measurements, conducted sequentially, has been proven to provide important information about different aspects of music performance as an example of a demanding multisensory motor skill. With the method described here, it is possible to record brain-related activity and movement data simultaneously, with accurate timing resolution and at relatively low costs. EEG and MIDI data were synchronized with a modified version of the FTAP software, sending synchronization signals to the EEG recording device simultaneously with keypress events. Similarly, a motion capture system sent synchronization signals simultaneously with each recorded frame. The setup can be used for studies investigating cognitive and motor processes during music performance and music-like tasks—for example, in the domains of motor control, learning, music therapy, or musical emotions. Thus, this setup offers a promising possibility of a more behaviorally driven analysis of brain activity.     

项目反应时间的对数偏正态模型

近年来,项目反应时间数据的建模是心理和教育测量领域的热门方向之一。针对反应时间的对数正态模型和Box-Cox正态模型的不足,本文在van der Linden的分层模型框架下基于偏正态分布建立一个反应时间的对数线性模型,并成功给出模型参数估计的马尔科夫链蒙特卡罗（Markov Chain Monte Carlo, MCMC）算法。模拟研究和实例分析的结果均表明,与对数正态模型和Box-Cox正态模型相比,对数偏正态模型表现出更加优良的拟合效果,具有更强的灵活性和适用性。     

The EZ diffusion method: Too EZ?

The diffusion model (Ratcliff, 1978) for fast two-choice decisions has been successful in a number of domains. Wagenmakers, van der Maas, and Grasman (2007) proposed a new method for fitting the model to data (“EZ”) that is simpler than the standard chisquare method (Ratcliff & Tuerlinckx, 2002). For an experimental condition, EZ can estimate parameter values for the main components of processing using only correct response times (RTs), their variance, and accuracy, not error RTs or the shapes of RT distributions. Wagenmakers et al. suggested that EZ produces accurate parameter estimates in cases in which the chi-square method would fail-specifically, experimental conditions with small numbers of observations or with accuracy near ceiling. In this article, I counter these claims and discuss EZ’s limitations. Unlike the chi-square method, EZ is extremely sensitive to outlier RTs and is usually less efficient in recovering parameter values, and it can lead to errors in interpretation when the data do not meet its assumptions, when the number of observations in an experimental condition is small, or when accuracy in an experimental condition is high. The conclusion is that EZ can be useful in the exploration of parameter spaces, but it should not be used for meaningful estimates of parameter values or for assessing whether or not a model fits data.     

A crossed random effects diffusion model for speeded semantic categorization decisions

Choice reaction times (RTs) are often used as a proxy measure of typicality in semantic categorization studies. However, other item properties have been linked to choice RTs as well. We apply a tailored process model of choice RT to a speeded semantic categorization task in order to deconfound different sources of variability in RT. Our model is based on a diffusion model of choice RT, extended to include crossed random effects (of items and participants). This model retains the interesting process interpretation of the diffusion model’s parameters, but it can be applied to choice RTs even in the case where there are few or no repeated measurements of each participant-item combination. Different aspects of the response process are then linked to different types of item properties. A typicality measure turns out to predict the rate of information uptake, while a lexicographic measure predicts the stimulus encoding time. Accessibility measures cannot reliably predict any component of the decision process.     

Effects of priming, discriminability, and reinforcement on reaction-time components of pigeon visual search

Pigeons searched computer screens for 1 of 4 letter targets among 55 alphanumeric distractors. In Experiment 1, valid-cue trials used distinctive patterns to signal the subsequent appearance of specific targets, whereas ambiguous-cue trials used a signal common to all targets. Search reaction times (RTs) after valid cues were shorter than after the ambiguous cue; increased target discriminability also reduced RT. In Experiment 2, when reinforcement for 2 targets shifted from 10% to 20%, RTs to those targets dropped, whereas RTs to the other 2 targets rose. RT distributions suggested that precues and discriminability both affect the momentary probability of finding a target, as embodied in the decay constant of an underlying exponentially distributed RT component. Reinforcement changes appeared to affect different components of the response process, embodied in changes in the mean of an underlying lognormal distribution.     

Direct measurement of the system latency of gaze-contingent displays

Gaze-contingent displays combine a display device with an eyetracking system to rapidly update an image on the basis of the measured eye position. All such systems have a delay, the system latency, between a change in gaze location and the related change in the display. The system latency is the result of the delays contributed by the eyetracker, the display computer, and the display, and it is affected by the properties of each component, which may include variability. We present a direct, simple, and low-cost method to measure the system latency. The technique uses a device to briefly blind the eyetracker system (e.g., for video-based eyetrackers, a device with infrared light-emitting diodes (LED)), creating an eyetracker event that triggers a change to the display monitor. The time between these two events, as captured by a relatively low-cost consumer camera with high-speed video capability (1,000 Hz), is an accurate measurement of the system latency. With multiple measurements, the distribution of system latencies can be characterized. The same approach can be used to synchronize the eye position time series and a video recording of the visual stimuli that would be displayed in a particular gaze-contingent experiment. We present system latency assessments for several popular types of displays and discuss what values are acceptable for different applications, as well as how system latencies might be improved.