A PC parallel port button box provides millisecond response time accuracy under Linux

For psychologists, it is sometimes necessary to measure peoples reaction times to the nearest millisecond. This article describes how to use the PC parallel port to receive signals from a button box to achieve millisecond response time accuracy. The workings of the parallel port, the corresponding port addresses, and a simple Linux program for controlling the port are described. A test of the speed and reliability of button box signal detection is reported. If the reader is moderately familiar with Linux, this article should provide sufficient instruction for him or her to build and test his or her own parallel port button box. This article also describes how the parallel port could be used to control an external apparatus     

A microcomputer-based cardiotachometer with video display

A KIM-1 single board microcomputer implementation of a cardiotachometer that provides a low-cost versatile heart-rate data acquisition system is described. Unique features include telemetry, a composite video output signal of a video frame displaying elapsed time and heart-rate, and a TV camera signal of the behavior. Data is videotape- and/or audiotape-recorded for further analysis with a larger computer.     

Tachistoscopic display using color-lookup-table display devices

In this article, I describe a method for presenting multiple bit-mapped images on video displays under precise temporal control. The method makes use of the color-table animation technique that can be used with color-lookup-table display devices. The principal challenge in applying this technique to the display of multiple stimuli lies in dealing efficiently with the problem of overlapping displays. The solution described here is to allocate separate bit slices of screen memory to stimuli that overlap and to allocate sequential color-table indices to stimuli that are disjoint. Software is described that automatically computes the location of a stimulus on the screen, allocates color indices appropriately, transfers bit images to screen memory efficiently, and manipulates the color lookup table to present a given stimulus to the viewer. These operations are handled transparently; the user simply draws the stimuli and then turns them on or off under program control.     

DMDX: A Windows display program with millisecond accuracy

DMDX is a Windows-based program designed primarily for language-processing experiments. It uses the features of Pentium class CPUs and the library routines provided in DirectX to provide accurate timing and synchronization of visual and audio output. A brief overview of the design of the program is provided, together with the results of tests of the accuracy of timing. The Web site for downloading the software is given, but the source code is not available.     

Visual display in the multipurpose laboratory: The benefits of video scan-conversion

A visual display system, based upon the PEP-400 video scan-converter, is described. For a cost of about $5,600, including nine video monitors, a laboratory can provide flexible, computer-generated, alpha-meric, and graphic displays simultaneously to eight subjects. Some performance results are given, as is discussion of interfacing and software required for a DEC lab system.     

Effects of word spacing on reading Chinese text from a video display terminal

This study investigated the effects of designing space between words in Chinese text, i.e., whether using a "word" instead of a "character" as a presentation unit, will facilitate the performance of reading from a video display terminal. Experimental results indicated that the main effect of word spacing significantly affected the reading time and the number of questions answered correctly. Subjects spent less time on the text with half-character word spacing or with whole-character word spacing than with conventional type (without word spacing). We also discovered that the number of questions answered correctly for stimuli with half-character spacing is significantly greater than that for stimuli with whole-character spacing, while both are smaller than for stimuli with conventional type. The additional variables, such as text difficulty and display control have significant effects as well. Our results suggested that the optimal word spacing in Chinese text should be greater than that in the traditional layout and less than a whole-character spacing. Apparently, in Chinese text, using a "word" as a presentation unit is more favorable than the traditional layouts that do not have any explicit word boundaries. The word spacing design may benefit in reading difficult or unfamiliar materials and further apply in emergency situations or in reading ambiguous sentences.     

Measuring reaction time and controlling the video display in experiments on an IBM PC

The problems of using the IBM PC XT/AT or their clones in experiments are recognized because of the slow, inadequate and awkward timing procedures of these microcomputers. Some specific solutions to these problems are described, including a compiled BASIC approach using real time procedures accurate to 1 millisecond (although resolution to 1 microsecond can be achieved) and synchronization of the video display with the program. Programs are available from the authors on receipt of a 5 1/4 inch floppy disc or $10.     

A method for calibrating the spatial coordinates of a visual display to high accuracy

High-resolution CRT displays are subject togeometric distortion: lines that are straight in the internal coordinates of the graphics software and hardware are curved when projected onto a plane in the observer’s line of sight. As the available resolution of CRT screens increases, it becomes more difficult to measure and correct for this distortion. We present a simple, highly accurate method for determining the mapping between internal coordinates and the viewing plane. It requires that an observer, using a calibration program, adjust triples of displayed points until they are collinear. A metal straightedge placed between the observer and the screen aids in this judgment. We describe the calibration of an IBM Enhanced Graphics Display in high-resolution mode (350 × 640 pixels), and illustrate how to use the estimated mapping to choose internal coordinates to draw undistorted figures that are accurate to within 0.5 pixel. The method can be used to assess or to correct the accuracy of visual displays. The method is relevant to experiments in spatial vision, spatial perception, perception of dot patterns, and any application in which geometrically accurate stimuli are required.     

Image quality of a mobile display under different illuminations

This study constructed the image quality models for a small mobile display under different ambient illumination levels using Group Method and Data Handling (GMDH) and described the relationship between perceived image quality and physical measurements. 33 college students took part in this experiment and were asked to evaluate the image quality under 1500 lux (typical indoor office illumination) and 7000 lux (simulated outdoor environment) in Stage One and Stage Two, respectively. In each stage, the participants had to evaluate 21 images. 17 sets of the data as a training set were used to build the model and four sets of the data as a testing set were used to verify the model. The results indicated that the effects of luminance, contrast, correlated color temperature (CCT), and resolution were significant on perceived image quality under 1500 lux. However, color temperature was not a significant physical characteristic, and an interaction between luminance and contrast was found below 7000 lux. From the results of the experiment, it is considered that the outdoor environment (7000 lux) is not suitable for using mobile displays. Finally, once a valid image quality model is built, the subjective image quality can be established when the measurements of significant physical characteristics are provided. The results of subjective ratings can also be provided for mobile display manufacturers to improve the product quality so that their products can meet customers' requirements.     

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.     

The SYBAR system: Integrated recording and display of video, EMG, and force plate data

A new system—called SYBAR—is introduced, that employs digital video for registration of the movements of a patient while simultaneously recording electromyogram signals of relevant muscles and ground reaction forces (for the lower extremities in gait studies). All information is stored in a multimedia record, which can be viewed by the clinician with a simple user interface. This setup allows an integrated and more detailed view of the movement of the patient and related information (i.e., muscle physiology). It is used by clinicians to assess the causes of movement disorders in their patients. This paper describes the SYBAR system and focuses on the employed methods of data synchronization for both the time and the spatial domains. It is concluded that, although SYBAR was developed for clinical gait studies, the technology can be applied in all situations in which the relation between physiological signals and human or animal behavior is studied.     

Perceiving minimal distinctions in ASL under normal and point-light display conditions

Perceptual confusions within 36 formationally minimal pairs of signs were assessed for native signers under two conditions of video presentation: (1) normally lighted black-and-white displays and (2) point-light displays constructed by affixing 26 points of retroreflective tape on the fingertips, back knuckles, and wrists and 1 point on the nose of the signer. Nine pairs were selected for each of the formational parameters of handshape, location, movement, and orientation. For each minimal pair, a native signer constructed and signed an ASL sentence that was syntactically and semantically appropriate for both members of the pair. Fourteen highly fluent ASL users responded by selecting a picture appropriate to the viewed sentence, thus avoiding contamination by English. For both viewing conditions, subjects discriminated the minimal pairs significantly better than chance. Performance was better (1) when location or orientation differentiated the signs than when movement or handshape did and (2) in normal lighting than in the point-light displays. With the point/light displays, discrimination of location, movement, and orientation was poorer and handshape discrimination was at chance. The discussion considers (1) the confusion of signs in the absence of linguistic redundancy, (2) the effectivenese of the point-light configurations as “minimal cues” for the contrasts, and (3) the efficacy of using these point-light configurations to reduce the information in ASL to a narrow bandwidth.     

Timing accuracy of PC programs running under DOS and Windows

The time in which to press a key and the video retrace interval were measured under various conditions of MS-DOS, Windows 3.1, Windows 3.11, Windows 95, and Windows NT 4.0 Workstation. All the measurements were obtained with the same program running on a single Pentium 300 computer. In all, samples of 1,000 timing measurements were obtained in each of 96 different conditions. Standard deviations of the times ranged from about 0.0006 msec under DOS 6.22 to almost 40 msec under Windows 3.11, representing an increase in timing error of up to 6,000,000%. Researchers requiring millisecond timing accuracy are recommended to use DOS only.     

Psychology of computer use: IV. Effects of video display units on fundamental visual processes: temporal resolution

Measures of two-pulse resolution (2PR) using foveally and peripherally viewed targets were obtained before and after reading videotext and print. Three pulse durations (25, 250, and 300 msec.) were used. The results showed that (a) 2PR on the fovea is about a fourth of that on the periphery, (b) peripheral 2PR increases following reading videotext, and (c) no appreciable effects occur following reading print.     

Scoring accuracy using the comprehensive system for the Rorschach.

The Comprehensive System (CS; Exner, 1974, 1978) for scoring Rorschach responses is the most widely taught and most widely accepted system in use today. The complexity and labor- intensive nature of the CS makes the issue of scoring accuracy a central concern. Twenty-one graduate psychology students and 12 professionals scored 20 Rorschach responses drawn from normal and clinical protocols. In general. accuracy scores for both students and professionals were below acceptable levels. Accuracy scores were clearly better for the code categories of Location, DQ, Pairs, Popular, and Z than for Determinants, FQ, Content, and Special Scores. Responses from clinical protocols were subject to more error. The results suggest that high levels of scoring errors may exist in the field use of the CS. Training standards may need to be devised to insure scoring competence.     

Investigating spatial vision and dynamic attentional selection using a gaze-contingent multiresolutional display

This study examined spatial vision and attentional selection using a gaze-contingent multiresolutional display, with a dynamic, gaze-centered, high-resolution window and lower resolution periphery. Visual search times and eye movements from 15 participants in a 3 x 3 design (Window Radius x Peripheral Resolution) suggest that contrast sensitivity as a function of retinal eccentricity affects attentional selection and visual processing. Smaller windows led to longer search times and shorter saccades; lower peripheral resolution also shortened saccades (all ps < .05) as a result of avoiding fixating degraded areas. Fixation durations, although longer for smaller windows (p < .05), were unaffected by whether the next saccade went within or outside the window. These results are explained through (a) competition among potential saccade targets where above-threshold filtering reduces an object's relative salience and (b) generally disrupted visual processing.     

Accurate display timing using an enhanced BASIC for the Tandy Color Computer

The general suitability of the Tandy Color Computer as an inexpensive laboratory microcomputer is discussed. A program is described that adds several useful timing-related functions to the native BASIC in the Tandy Color Computer, thus allowing BASIC to be used for programming experiments involving tachistoscopic displays and reaction times.     

Measuring reaction time with millisecond accuracy using the TRS-80 microcomputer

A machine language subroutine is proposed for measuring reaction time with millisecond accuracy using the TRS-80 microcomputer. This timer is accurate to 1 msec in the first 30,000 msec and to 5 msec in the first 65,000 msec (1 part in 10,000).