DIS: An n-channel tachistoscope algorithm

DIS is a stand-alone, file-oriented, n-channel tachistoscope simulator. The paper describes the program in terms of both the syntax required to set up a display and the basic operation of the algorithm. Short routines illustrating two experimental paradigms are provided.     

An N-channel stroboscopic tachistoscope for typewritten stimuli

The n-channel tachistoscope described employs the principle of “stopping” a continuously moving list of words by means of stroboscopic flashes of light. It can present as many as 50 stimuli per trial at any rate between 5 and 40 items per second. Stimulus materials can be prepared on an electric typewriter. It provides only partial control over the various time parameters.     

A VGA tachistoscope

A set of tachistoscope-emulation functions for IBM-PC-compatible computers equipped with the VGA display controller is described. C or Pascal programs including these functions can easily produce multifield tachistoscopic presentations of colored text.     

Apple slide tachistoscope

We outline a BASIC program and subsidiary machine language timing routines that enable the Apple II series of computers to be employed as control devices for the tachistoscopic presentation of 35-mm slides and the collection of response latencies. The program is functional for experiments that require pictorial stimuli to be presented in up to three separate fields, with precise display times, precise interstimulus and intertriai intervals, and the collection of manual or vocal reaction times with millisecond accuracy. The major advantages of this system are that initial setup costs are substantially lower than those for other similar systems (e.g., Loftus, Gillispie. Tigre, & Nelson, 1984) and that user customization of the program may be accomplished by anyone possessing rudimentary knowledge of the BASIC programming language.     

A spectacle-mounted liquid-crystal tachistoscope

A spectacle-mounted shuttering device, the Portable Liquid-crystal Apparatus for Tachistoscopy via visual Occlusion, based on light-scattering cholesteric liquid crystals, is introduced. Operating characteristics of the device are discussed with respect to the design objectives of comfort, switching speed, light transmission, light extinction, safety, and reliability. A number of practical research, clinical, and industrial applications of the spectacles as tachistoscope, stroboscope, and stereoscopic viewing apparatus are summarized.     

Measuring projection tachistoscope shutter characteristics

Projection tachistoscopes have shutters that control the presentation of stimuli. Shutter characteristics such as opening times, closing times, and mechanical reliability are important factors in applications of these tachistoscopes. The device described in this report allows the operating characteristics of shutters used in projection tachistoscopes to be evaluated. The use of the device is illustrated by measurements of three commercially available tachistoscope shutters. Each shutter was characterized by five parameters: opening and closing speeds, the lag between shutter activation and operation, the briefest stimulus presentation that the shutter allowed, and the shutter’s ability to repeat exposure durations accurately.     

The word without the tachistoscope

In experiments with an unlimited viewing time, we were able to isolate specific stimulus factors that lead to the word-superiority effect. We discovered that advantages of words over nonwords, and words over single letters, are caused by different factors. The word-nonword effect was found in a variety of circumstances, such as with small type, low contrast, or a simultaneously present mask. The advantage of words over single letters occurs only when the stimuli are embedded in a mask making it difficult to find a single letter. In addition, we obtained a word-detection effect without a brief exposure: Subjects were more accurate detecting the presence of words than nonwords. However, this effect only occurred when subjects were required to discriminate letters from nonletters. Thus, the word-superiority (word-nonword difference) and word-detection effects both involve letter discrimination and can be explained by similar mechanisms.     

A versatile microcomputer-based multiple-field tachistoscope

A newly introduced microcomputer in its most basic form provides a wide variety of stimulus display capabilities at an extremely low price. Several simple illustrative programs demonstrate its ability to present any number of visual stimuli in sequence and record response latencies, thus duplicating the functions of a multiple-field tachistoscope and associated response-recording instrumentation.     

A computer-based programmable tachistoscope for nonprogrammers

A set of programs for on-line control of reaction time experiments is described. These programs allow a wide range of experiments to be coded in a simple form that eliminates the need for any knowledge of programming.     

The PC tachistoscope has 240 pages

Myors (1998) showed how to combine familiar video page switching with bit-plane layering in video mode 0dh to increase the capacity of the PC tachistoscope from 8 to 32 pages. The present article shows how to combine video page switching with color page switching to implement a 240-page tachistoscope, thus producing an almost eightfold increase in the capacity of the PC tachistoscope. The main limitation of this technique is that the images cannot all be located in the same position on the screen. Complete source code in C is included.     

The PC tachistoscope has 32 pages

Page switching is the basis of the PC tachistoscope, and usual accounts of page switching on the PC refer to a maximum of 8 available pages. This article shows how to achieve up to 16 pages in 40-column text mode and up to 32 pages in low-resolution graphics mode using conventional page switching combined with the bit-plane layering technique described by Bokhorst (1995). A high level C program is presented to show how this is done. When 32 pages are in use, the images must be monochrome.     

A simple tachistoscope for student labs

An inexpensive tachistoscope for student labs is described that utilizes a camera shutter to control exposure duration and a potentiometer to vary light intensity. Stimuli can be drawn or typed on 3 x 5 index cards.     

Technical improvements to the projection tachistoscope

Three disadvantages of the usual projection tachistoscope are discussed. Because of low mechanical precision, stimulus alignment is difficult. Because of rather low focal distances of the projection lenses, the stimuli provide visual angles that are often larger than desired, and the photographic shutters are noisy, are relatively inert, and have a limited service life. A new construction is described that avoids these disadvantages with a modified configuration of commercial elements: stable and precise mounting of the single channels, a double-lens projection system, and a noiseless, fast mechanical shutter based on a limited-rotation motor.     

A multichannel PC tachistoscope with high resolution and fast display change capability

The number of channels that PC tachistoscopes can have has increased recently (Bokhorst, 1995; Myors, 1998); however, neither the quality of display nor speed of image switching has been improved. This article shows the capability of VESA’s VBE 3.0 standard (1998) for increasing the number of channels of high-quality images. And the refresh rate can be set to the fastest cathode ray tube (CRT) scanning rate the monitor can tolerate in order to reduce the timing delay of changing display. A PCTSCOPE library was written in C to provide these capabilities, which is compatible with conventional DOS real mode. The PC tachistoscope can have numbers of channels with various resolutions and colors and different refresh rates. For example, 25 images with the resolution of 640 × 480 pixels and 256 colors can be loaded to video memory, and vertical refresh rate can be set to 180 Hz. It takes less than 6 msec to change the display among 25 channels in synchronizing with the start of the video scanning frame. In this library, the number of channels, the resolution of the images, and the speed of changing display all are improved. The multichannel PC tachistoscope with this technique is especially suitable for research requiring high-quality images and rapid successive presentation of stimuli.