Using hardware interrupts for timing visual displays and reaction-time key interfacing on the Commodore 64

The use of hardware interrupts for presenting and timing visual displays and for controlling reaction timing on the Commodore 64 is described. The three sources of interrupts discussed are reaction-time keys interfaced through the user port to on-board hardware timers, the alarm of the 60-Hz real-time clocks, and the video raster. In a demonstration program, these interrupts are used to measure display durations, to change screen displays, and to coordinate the onset of reaction timing with the onset of screen changes. In addition, an externally generated interrupt caused by a keypress is used to control reaction timing independently of CPU operations.     

A simple system for monitoring the timing of infant gaze to stimuli at specific locations

A system for monitoring the timing of infant gazes to specific locations is described. Infants sit on a parent’s lap in a dark room and observe videotaped stimuli presented on one of four monitors. Infrared (IR) light sources provide illumination for an IR-sensitive video camera and are positioned so that the infant’s direction of gaze can be readily apprehended on the basis of the reflections of the IR light sources relative to the infant’s pupil. The parent monitors the infant’s eyes through a headmounted display and keeps the infant in view of the video camera. Direction and timing of gaze shifts can be coded from frame-by-frame inspection of the videotape. We demonstrate that this coding is relatively accurate and that the present system provides some advantages over coding gaze direction on the basis of an unembellished video recording.     

What attracts attention during police pursuit driving?

Efficient deployment of attention is important to the safe execution of tasks with a high content of visual information, such as driving. Chasing a lead vehicle is an extremely demanding and dangerous task, though little is known of the visual skills required. A study is reported that recorded the eye movements of police drivers and two control groups (novices and age‐ and experienced‐ matched controls) while watching a series of video clips of driving. The clips included pursuits, emergency response drives, and control drives (at normal speeds) around Nottinghamshire, UK. Analysis of gaze durations within certain categories of stimuli revealed that daytime pursuit drives correspond with an increase in gaze durations on a lead car (controlled for exposure), though police drivers direct their attention to other sources of potential hazards, such as pedestrians, more so than other drivers. Copyright © 2005 John Wiley & Sons, Ltd.     

A simple and sensitive method to measure timing accuracy

Timing accuracy in presenting experimental stimuli (visual information on a PC or on a TV) and responding (keyboard presses and mouse signals) is of importance in several experimental paradigms. In this article, a simple system for measuring timing accuracy is described. The system uses two PCs (at least Pentium II, 200 MHz), a photocell, and an amplifier. No additional boards and timing hardware are needed. The first PC, a SlavePC, monitors the keyboard presses or mouse signals from the PC under test and uses a photocell that is placed in front of the screen to detect the appearance of visual stimuli on the display. The software consists of a small program running on the SlavePC. The SlavePC is connected through a serial line with a second PC. This MasterPC controls the SlavePC through an ActiveX control, which is used in a Visual Basic program. The accuracy of our system was investigated by using a similar setup of a SlavePC and a MasterPC to generate pulses and by using a pulse generator card. These tests revealed that our system has a 0.01-msec accuracy. As an illustration, the reaction time accuracy of INQUISIT for a few applications was tested using our system. It was found that in those applications that we investigated, INQUISIT measures reaction times from keyboard presses with millisecond accuracy.     

Gaze allocation in a dynamic situation: effects of social status and speaking

Human visual attention operates in a context that is complex, social and dynamic. To explore this, we recorded people taking part in a group decision-making task and then showed video clips of these situations to new participants while tracking their eye movements. Observers spent the majority of time looking at the people in the videos, and in particular at their eyes and faces. The social status of the people in the clips had been rated by their peers in the group task, and this status hierarchy strongly predicted where eye-tracker participants looked: high-status individuals were gazed at much more often, and for longer, than low-status individuals, even over short, 20-s videos. Fixation was temporally coupled to the person who was talking at any one time, but this did not account for the effect of social status on attention. These results are consistent with a gaze system that is attuned to the presence of other individuals, to their social status within a group, and to the information most useful for social interaction.     

Reading your own lips: Common-coding theory and visual speech perception

Common-coding theory posits that (1) perceiving an action activates the same representations of motor plans that are activated by actually performing that action, and (2) because of individual differences in the ways that actions are performed, observing recordings of one’s own previous behavior activates motor plans to an even greater degree than does observing someone else’s behavior. We hypothesized that if observing oneself activates motor plans to a greater degree than does observing others, and if these activated plans contribute to perception, then people should be able to lipread silent video clips of their own previous utterances more accurately than they can lipread video clips of other talkers. As predicted, two groups of participants were able to lipread video clips of themselves, recorded more than two weeks earlier, significantly more accurately than video clips of others. These results suggest that visual input activates speech motor activity that links to word representations in the mental lexicon.     

The effect of display timing on change blindness in pigeons (Columba livia)

Change blindness is a phenomenon in which even obvious changes in a visual scene may go unnoticed. Recent research has indicated that this phenomenon may not be exclusive to humans. Two experiments investigated change blindness in pigeons, using a variant of the widely‐used flicker task to investigate the influence of display timing on change blindness. Results indicate that the duration of time during which a stimulus display is visible influences change detection accuracy, with the effect due to additional search time. The results are discussed in relation to the value of comparative cognition and cross‐species investigations of behavior.     

Millisecond timing on PCs and Macs

A real-time, object-oriented solution for displaying stimuli on Windows 95/98, MacOS and Linux platforms is presented. The program, written in C++, utilizes a special-purpose window class (GLWindow), OpenGL, and 32-bit graphics acceleration; it avoids display timing uncertainty by substituting the new window class for the default window code for each system. We report the outcome of tests for real-time capability across PC and Mac platforms running a variety of operating systems. The test program, which can be used as a shell for programming real-time experiments and testing specific processors, is available at http://www.cs.dal.ca/~macinnwj. We propose to provide researchers with a sense of the usefulness of our program, highlight the ability of many multitasking environments to achieve real time, as well as caution users about systems that may not achieve real time, even under optimal conditions.     

Differential effect of distractor timing on localizing versus identifying visual changes

When visual changes are accompanied by visual transients, such as in the case of saccades, eye blinks, and brief flickers, they often go unnoticed; this phenomenon is called change blindness (Rensink, R. A. (2002). Change detection. Annual Review of Psychology 53, 245; Simons, D. J., & Levin, D. T. (1997). Change blindness. Trends in Cognitive Sciences 1, 261). Change blindness occurs even when the position of visual transients does not cover the location of the change (as in the 'mudsplash' paradigm) (O'Regan, J. K., Rensink, R. A., & Clark, J. J. (1999). Nature 398, 34). By using a simplified mudsplash display, the present study investigated whether change blindness depends on (a). the timing of visual transients, and (b). the task that observers perform. Eight Gabor elements with random orientations were presented. One element (target) was rotated 45 degrees clockwise or counterclockwise without a temporal gap. High contrast visual transients, not overlapping with the elements, appeared at various times with respect to the target change. Observers reported where the change was (change localization), or in which direction the target rotated (change identification). Change localization was impaired primarily when the onset of the transient was at or after the change. In contrast, change identification was impaired mainly when the transient preceded the change. These results suggest that change localization and change identification are mediated in part by different mechanisms.     

Visual discrimination of delayed self-generated movement reveals the temporal limit of proprioceptive–visual intermodal integration

This study examined the intermodal integration of visual–proprioceptive feedback via a novel visual discrimination task of delayed self-generated movement. Participants performed a goal-oriented task in which visual feedback was available only via delayed videos displayed on two monitors—each with different delay durations. During task performance, delay duration was varied for one of the videos in the pair relative to a standard delay, which was held constant. Participants were required to identify and use the video with the lesser delay to perform the task. Visual discrimination of the lesser-delayed video was examined under four conditions in which the standard delay was increased for each condition. A temporal limit for proprioceptive–visual intermodal integration of 3–5 s was revealed by subjects’ inability to reliably discriminate video pairs.     

Research note: Peak velocity timing invariance

Summary Subjects used arm movements to move a dot on a visual display into a predefined target area. Measures of the peak velocity values and the timing of the peaks were taken for the initial (preplanned) and the immediately subsequent (corrective) phases of movement. In both phases the value of the maximum velocity depended on task parameters such as amplitude. However, the time of the peak of each phase relative to its onset was invariant. Some implications of these observations for the nature of motor programs are discussed.     

Is gaze behaviour in a laboratory context similar to that in real-life? A study in bicyclists

Numerous laboratory-based studies recorded eye movements in participants with varying expertise when watching video projections in the lab. Although research in the lab offers the advantage of internal validity, reliability and ethical considerations, ecological validity is often questionable. Therefore the current study compared visual search in 13 adult cyclists, when cycling a real bicycle path and while watching a film clip of the same road. Dwell time towards five Areas of Interest (AOIs) is analysed. Dwell time (%) in the lab and real-life was comparable only for the low quality bicycle path. Both in real-life and the lab, gaze is predominantly driven towards the road. Since gaze behaviour in the lab and real-life tends to be comparable with increasing task-complexity (road quality), it is concluded that under certain task constraints laboratory experiments making use of video clips might provide valuable information regarding gaze behaviour in real-life.     

Visual display recognition and the duplication of inspection sequences

In a test of Noton and Stark’s 11971) contention that visual display recognition depends upon the duplication of the fixation sequence initially used in viewing the display, recognition performance and reaction times were recorded for six subjects in a visual recognition task. The task involved initial sequential presentation of elements of a display followed by presentation of a recognition probe that either did or did not duplicate the initial presentation sequence. Either performance or reaction times, or both, suffered when the initial presentation sequence was not duplicated, lending some support to Noton and Stark’s position. However, these differences were less pronounced when the recognition probe was displayed for a longer time, indicating that non-sequence-dependent processes may become increasingly important at longer viewing times.     

The need for speed: Scores on a new video-based measure of speeding propensity,suitable for use in online research,correlate with drivers’ on-road speeding behaviour

A video-based measure of drivers’ speeding propensity (the UQ Video Speed Test) was developed for use in both laboratory-based and online research studies. In the test, the respondent is presented with a series of 16 video clips of traffic footage, which were shot from the driver’s perspective using a camera mounted behind the windscreen of a moving car. For each clip, the respondent’s task is to indicate to what extent they would travel faster or slower than the speed of the camera car. Responses to all clips are averaged to determine the respondent’s overall score. In the present study, we investigated associations between drivers’ video speed test scores and five measures of real everyday speeding behaviour obtained over a 5-week period using GPS trackers. There was a significant positive correlation for each of the five on-road speeding measures. In addition, age-related differences in test scores were consistent with observed real-world group differences in speeding behaviour. Test scores also correlated with an established self-report questionnaire measure of speeding (i.e., the Speed Scale from the Driving Style Questionnaire). Overall, the data supported the use of the UQ Video Speed Test as a proxy measure of drivers’ real-world speeding behaviour in laboratory-based and online studies (though it would be inadvisable to use such tests in the assessment of drivers for licensing purposes, due to the potential to “fake good”). The test can be deployed using standard online survey platforms (e.g., Qualtrics), and is available at no cost for use in driving research.     

Facial expressions in common marmosets (Callithrix jacchus) and their use by conspecifics

Facial expressions have been studied mainly in chimpanzees and have been shown to be important social signals. In platyrrhine and strepsirrhine primates, it has been doubted that facial expressions are differentiated enough, or the species socially capable enough, for facial expressions to be part of their communication system. However, in a series of experiments presenting olfactory, auditory and visual stimuli, we found that common marmosets (Callithrix jacchus) displayed an unexpected variety of facial expressions. Especially, olfactory and auditory stimuli elicited obvious facial displays (such as disgust), some of which are reported here for the first time. We asked whether specific facial responses to food and predator-related stimuli might act as social signals to conspecifics. We recorded two contrasting facial expressions (fear and pleasure) as separate sets of video clips and then presented these to cage mates of those marmosets shown in the images, while tempting the subject with food. Results show that the expression of a fearful face on screen significantly reduced time spent near the food bowl compared to the duration when a face showing pleasure was screened. This responsiveness to a cage mate’s facial expressions suggests that the evolution of facial signals may have occurred much earlier in primate evolution than had been thought.     

Regulatory Fit and Resisting Temptation during Goal Pursuit

Because avoiding obstacles to goal attainment is a favored means of prevention-focused self-regulation, the authors proposed that resisting tempting diversions from task completion would better fit a prevention focus than a promotion focus, thus affecting task enjoyment and performance. Whether deciphering encrypted messages (Study 1) or solving math problems (Study 2), when exposed to attractive distracting video clips, participants in a prevention focus reported greater task enjoyment than did participants in a promotion focus, whereas the reverse was true when the distracting clips were not presented. Indeed, prevention-focused participants enjoyed the tasks more when they had to resist temptation than when they did not. In Study 2, prevention-focused participants outperformed promotion-focused participants under distracting (but not nondistracting) conditions, and regression analyses suggested that task enjoyment mediated this effect. Different regulatory states thus appear to differentially equip people to deal with tempting diversions from goal attainment.     

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.     

Modality differences in timing and temporal memory throughout the lifespan

The perception of time is heavily influenced by attention and memory, both of which change over the lifespan. In the current study, children (8 yrs), young adults (18–25 yrs), and older adults (60–75 yrs) were tested on a duration bisection procedure using 3 and 6-s auditory and visual signals as anchor durations. During test, participants were exposed to a range of intermediate durations, and the task was to indicate whether test durations were closer to the “short” or “long” anchor. All groups reproduced the classic finding that “sounds are judged longer than lights”. This effect was greater for older adults and children than for young adults, but for different reasons. Replicating previous results, older adults made similar auditory judgments as young adults, but underestimated the duration of visual test stimuli. Children showed the opposite pattern, with similar visual judgments as young adults but overestimation of auditory stimuli. Psychometric functions were analyzed using the Sample Known Exactly-Mixed Memory quantitative model of the Scalar Timing Theory of interval timing. Results indicate that children show an auditory-specific deficit in reference memory for the anchors, rather than a general bias to overestimate time and that aged adults show an exaggerated tendency to judge visual stimuli as “short” due to a reduction in the availability of controlled attention.     

PET Flasher: A machine language subroutine for timing visual displays and response latencies

PET Flasher presents a one-line stimulus display at any location on a PET/CBM (Commodore Business Machines) screen and measures reaction time from display onset. Display duration is accurately controlled in 16.7-msec steps, and reaction time measurement is accurate within ±1 msec. PET Flasher is easily incorporated within any PET/CBM BASIC program, since as a subroutine, it is called only when precise timing operations are required.