Computer Technology Audio tape storage of experimental data: An application to tachistoscopic research with children

An inexpensive portable system is described for storing digital data on audio tape for later computer processing. The technique involves the use of integrated circuits and an ordinary stereo tape recorder. Each datum is converted to a binary-coded voltage level that, through a sampling device, controls the phase of a square-wave signal. Depending on whether the bit being coded is \ld0\rd or \ld1,\rd the signal recorded on one tape track is either in phase or 180 deg out of phase with a reference signal recorded on the other track. Later, the recorded tape may be played back into a computer for data analysis. An application of this technique for tachistoscopic research is described.     

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.     

Binaural interaction in backward masking

The binaural auditory system exhibits certain advantages over the monaural system when detecting a tonal signal in a background of masking noise. These advantages have been described in detail and are referred to as masking-level differences, or MLDs. It has been demonstrated, for example, that performance in detecting a tonal signal that has been reversed in phase at one ear relative to the other ear is about 15–17 dB better than detection of the same signal in-phase at the two ears when masked by moderately intense masking noise that is in-phase at the two ears. The explanations for this phenomenon fall into two general categories, and both types of explanations are based upon the interaction of the tonal signal and masker when they are added together. In the present paper, data are presented which indicate that an MLD of at least 4–5 dB can be obtained in a binaural masking experiment in which the offset of the tonal signal precedes the onset of the noise masker.     

APE: average potential evaluation software for the LAB-8 system

A paper-tape software system is described which allows the addition and/or subtraction of signal averaging data from the DEC advanced averager program. This pooled averaging data may be plotted, printed, or punched. A DEC LAB-8 system with 4K memory and high-speed reader/punch are required. Several examples of the application of the system to human evoked brain response data are presented, and the application of the system to other problems is discussed.     

Recording and analyzing eye-position data using a microcomputer workstation

This paper presents a PC-based eye-position data collection and analysis system. Software routines are described that supplement hardware calibration procedures, improving data-collection accuracy and reducing the number of unusable trials. Collected eye-position data can be remapped over a displayed stimulus image and spatially and temporally represented by parameters such as individual fixations, clusters of fixations (Nodine, Carmody, & Kundel, 1978), cumulative clusters, and gaze durations. An important feature of the system is that the software routines preserve scan-path information that provides a sequential dimension to the analysis of eye-position data. A “hotspot” analysis is also described, which cumulates, across 1 or more observers, the frequency of eye-position landings or “hits” on designated areas of interest for a given stimulus. Experimental applications in the fields of radiology, psychology, and art are provided, illustrating how eye-position data can be interpreted both in signal detection and in information-processing frameworks using the present methods of analysis.     

Adding the dimension of color to computer-generated displays

A low-cost system that permits existing computer-generated displays on a black and white CRT display to be reproduced in one of several colors on a color TV receiver is described. A black and white TV camera monitors the computer display, and the camera RF signal is sent to the color TV receiver, which has its three color guns under computer control through an interface unit described herein. In a simple on or off arrangement using three computer output relays, seven distinct and readily identifiable colors are available. With the use of D/A converters, the interface unit is voltage controlled, permitting both faster control and many more hues to be obtained.     

A vocal response time system for use with sentence verification tasks

A software system for the reliable detection of vocal response onset is described. The system was designed specifically for the measurement of vocal response times to speech stimuli presented aurally in a sound field in the presence of some background noise. The response time extraction method described here is robust to masking noise and extraneous sounds that may be included in the subject’s recorded response. In addition, the response words do not have to be limited to a small set because the system is able to differentiate the onset of any speech sounds, including low-energy fricatives. The method described here may be implemented with any computer sound system because it relies only on the sound conversion clock for timing accuracy and uses postprocessing of the signal after acquisition for response extraction. The response time extraction technique as currently implemented does not recognize subject’s responses but could be incorporated into an automatic speech recognition system.     

PSARP,a programmable signal and response processor

Experiments on perceptual-motor skills often ask for complex application of standard devices. Combinations of the usual electric or electronic instruments such as signal generators, simple time counters and response recorders cannot always be used to form a sufficiently flexible system for a particular set of experiments. In general, an apparatus specially built for a specific experiment does not satisfy the requirements of related investigations and the same device is seldom used again. This paper gives an outline of the principles of a flexible and programmable system which meets the requirements of a considerable number of variables. Some first applications of the system are described.     

Independent control of dual video subsystems on the IBM PC and compatibles

Two methods for generating video output on multiple video monitors are described. The first method involves splitting the signal from a single video adaptor card-so that multiple video monitors may be attached. Although this method is simple and relatively cost-effective, it is limited to adaptors that produce only digital video signals, thus precluding the use of VGA systems and composite displays. The second method involves the installation and programming of video adaptors: Two sample programs, which control a secondary adaptor by means of either BIOS routines or direct commands via C code, are described. Although more complex, this second method allows output to each display to be controlled independently. Furthermore, output to one screen may consist of graphics information while output to the second screen consists of text. Together, both methods can be used to create an experimental system composed of multiple data-collection stations and an independent experimenter console.     

Saccadic eye movement programming: sensory and attentional factors

The relationship between attention and eye movements is explored by consideration of the variety of ways attention may affect saccade programming. Four forms of attention are distinguished: one exogenous and three endogenous through either locations or objects or features. Each of these can control or influence the saccadic generation process. Visual onsets generate a rapid transient signal with low resolution that travels from the visual system to the oculomotor system. Generation of an eye movement is associated with an attentional signal, probably also with low resolution, travelling from the oculomotor system to the visual system. A high-resolution attentional signal, which appears to require voluntary effort, can also select saccadic targets.     

Form emergence and fixation of head bobbing displays in the green anole lizard (Anolis carolinensis): a reptilian model of signal ontogeny

Signal ontogeny was examined in green anoles (Anolis carolinensis). From 1,246 head bob displays given by 114 juveniles, it was found that juveniles possessed all 3 display types (A, B, and C) described for adults and that C displays were present at hatching, but A and B displays appeared to emerge gradually from a common precursor. Durations of the head bobs and pauses that make up juvenile displays tended to be more variable (i.e., less stereotyped) than those of adult displays. However, within the juvenile class, sex, age (or size), social context, and rearing environment (field or lab) had no effect on display structure or stereotypy. Thus, in contrast to typical signal ontogeny in songbirds and mammals, components of the green anole signal repertoire are expressed from early development. Similar to signal ontogeny in altricial species, maturation is nevertheless important for the complete and stereotyped expression of the adult signal repertoire.     

A method for the precise switching of speech

A simple procedure by which a speech signal may be switched on or off (or from one ear to the other) at a precise instant of time is described. The speech sample is first recorded on a magnetic tape loop. A reference pulse is then recorded preceding the speech signal. This reference pulse triggers an adjustable time delay which in tum operates an electronic switch at an appropriate time.     

Latency of autokinesis and convergence of the eyes

It is suggested that one of the determinants of autokinesis is noise associated with a hypothesized eye-in-head position monitor within the oculomotor system. It is argued that a decrease in convergence of the eyes is associated with a decrease in the magnitude of the signal relating to eye position. The prediction is that this will thereby produce an increase in the effectiveness of noise as a spurious signal. An experiment is described in which a just-visible oscilloscope spot was viewed in a dark room at four distances along the subject's median sagittal plane. The latency of appearance of autokinetio movement was measured in each of these conditions. It was found that as distance increased, i.e. as convergence decreased, latency decreased also. This result is consistent with the prediction.     

Apparatus for bisensory presentation of coded signals

Apparatus capable of transmitting signals to either a vibrator or to a light, or to both vibrator and light simultaneously, is described. The basis for encoding vibrotactile and visual stimuli is varying intensities and durations of signal.     

传统、浮躁、道德及其它--医域随感

多年来我一直从事外科医、教、研和科室管理工作,并兼任一些专业杂志的编辑和审稿工作.记不清楚由什么时候开始,逐渐感觉到平时熟悉的情况出现了一些微妙的变化,特别是近几年,可能是市场经济大环境的影响或是社会上漂浮的灰尘飞落到医院和学术界,不太寻常的现象似有所增多.其中有些情况均为所见所闻,间或偶尔与同道议论过,现结合当前事态发展,重新认识一下,可能有益无害.     

Digitized images: what type of grey scale should one use?

One of the issues faced by engineers when designing a system which records an external event and represents it in the form of a digitized image on VDU screen is which type of grey scale to use. An experiment is described which compares, in a simulated digitized image, the effect of a linear and a logarithmic grey scale on the detectability of a straight-line signal embedded in visual noise. It was found that both bright and dark signals were detected more easily with the linear scale. A signal detection theory analysis was carried out to compare human performance with that of an 'ideal' observer who performed the detection task with a filter spatially matched to the signal. It was found that the model of performance for this ideal observer accounted well for the results provided the assumption of a linear transformation of luminance was made. The analysis showed that the superiority of the linear over the logarithmic grey scale was simply due to the higher signal-to-noise ratio of the signals in the former.     

The refractory period and serial choice-reactions

An experiment is described in which subjects had to make consecutive 2-choice reactions to light and sound stimuli, the interval between signals being fixed for anyone series of presentations. When under these conditions, reaction times to the second signal are compared to those obtained when the first signal is used only as a warning, delays are found for short intervals. These results and the wide individual differences obtained are discussed in relation to theories that have been put forward to account for the delays obtained in serial reaction tasks.     

Studies on sensory feedback: III the effects of display gain on tracking performance

Instrumentation is described which permits study of the effects of different forms of visual feedback display on the patterns of fine movement obtained from the extended human index finger when the subject is attempting to keep his finger at a fixed point in space. The task is a compensatory tracking task in which the only source of input to the system is the subject's own finger movement. The effects of increasing the gain (or amplification) of a proportional error signal on the pattern of finger movement was studied. Gains of 1, 2, 4, 10, 20 and 40 were studied with a group of 24 subjects. Increasing the gain of a proportional error signal resulted in a marked improvement in the ability of subjects to maintain their extended finger at a fixed point in space. As the gain of the error signal was increased, the subject's high-amplitude, low frequency errors were reduced, and there was a progressive appearance of high-frequency activity of low-amplitude, more accurately centred about the reference position in space. A total off-target area measure (integrated absolute error) showed marked decrease in scores as the amplification of the error signal was increased from 1 through 10. Beyond this gain there was no appreciable additional improvement in motor control, however no degradation of control was noted to characterize the group performance.

Exploratory studies were undertaken to permit comparison of the effects of increasing the gain of a proportional visual display with the effects of increasing the gain of non-proportional visual and auditory displays. An increase in the dominant-energy frequency was noted as the error signal gain was increased, independent of whether a proportional visual, or non-proportional visual or auditory display was used. This observation suggests that common mechanisms mediate the processing of the gain parameters of feedback displays, in some measure independent of the display form or the sensory modality used for presentation.     

Motion aftereffects and retinal motion

Two experiments are described in which it was investigated whether the adaptation on which motion aftereffects (MAEs) are based is a response to retinal image motion alone or to the motion signal derived from the process which combines the image motion signal with information about eye movement (corollary discharge). In both experiments observers either fixated a stationary point or tracked a vertically moving point while a pattern (in experiment 1, a grating; in experiment 2, a random-dot pattern) drifted horizontally across the field. In the tracking condition the adapting retinal motion was oblique. In the fixation condition it was horizontal. In every case in both conditions the MAE was horizontal, in the direction opposite to that of pattern motion. These results are consistent with the hypothesis that the adaptation is a response to the motion signal derived from the comparison of eye and image motion rather than to retinal motion per se. An alternative explanation is discussed.