Evaluation of the Tobii EyeX Eye tracking controller and Matlab toolkit for research

The Tobii Eyex Controller is a new low-cost binocular eye tracker marketed for integration in gaming and consumer applications. The manufacturers claim that the system was conceived for natural eye gaze interaction, does not require continuous recalibration, and allows moderate head movements. The Controller is provided with a SDK to foster the development of new eye tracking applications. We review the characteristics of the device for its possible use in scientific research. We develop and evaluate an open source Matlab Toolkit that can be employed to interface with the EyeX device for gaze recording in behavioral experiments. The Toolkit provides calibration procedures tailored to both binocular and monocular experiments, as well as procedures to evaluate other eye tracking devices. The observed performance of the EyeX (i.e. accuracy < 0.6°, precision < 0.25°, latency < 50 ms and sampling frequency ≈55 Hz), is sufficient for some classes of research application. The device can be successfully employed to measure fixation parameters, saccadic, smooth pursuit and vergence eye movements. However, the relatively low sampling rate and moderate precision limit the suitability of the EyeX for monitoring micro-saccadic eye movements or for real-time gaze-contingent stimulus control. For these applications, research grade, high-cost eye tracking technology may still be necessary. Therefore, despite its limitations with respect to high-end devices, the EyeX has the potential to further the dissemination of eye tracking technology to a broad audience, and could be a valuable asset in consumer and gaming applications as well as a subset of basic and clinical research settings.     

Hardware debugging for on-line psychologists

As computers become more prevalent as laboratory equipment, psychologists and graduate assistants will be more likely to be involved with interfacing the experiment to the computer. This paper presents some general ideas about the design and construction of digital computer interfaces and ways to facilitate their check-out and integration into the computer system. The suggestions center around the identification of functional modules within the interface or device from the beginning of the design process. These modules are preserved in the design and construction and are tested separately where possible. Specification of the interface signals between these functional units speeds debugging of a new device and facilitates maintenance of the device at a later date if adequately documented. It is important to ensure that these signals are readily available through test points and/or indicators. The paper suggests minimal equipment necessary to construct and debug an interface. It is suggested that an interactive construction procedure may be the most successful. The device is constructed in stages, with each part being verified as it is built, A simple interface is suggested for the beginner which gives him practice and a useful debugging aid as well.     

A computerized system for analyzing linear locomotion

An accurate and reliable, yet simple and inexpensive electronic tracking device delivers voltages that denote changing positions of moving objects. In combination with an analog-to-digital converter, a microcomputer, and specific software, this device enables the depiction and analysia of linear or linearly represented locomotion. The system is particularly useful for laboratory analysis of animal movements. An application in preference-avoidance testing is described.     

A hardware and software interface for sensing changes in rotary position with an Apple II microcomputer

A design for an Apple II interface that senses relative rotary position and/or motion via a digital potentiometer is presented. A thorough discussion of the circuit’s theory of operation and a fully commented BASIC software listing are included. Suggested applications include an infinite-turn rotary device for psychophysical methods of adjustment, the sensing of rotary translations of a steering wheel in a driving simulator, and a digital tachometer/odometer for tracking performance on stationary exercise bicycles and treadmills.     

Development of a fully automated system for delivering odors in an MRI environment

We describe the development and evaluation of a computer-controlled system for delivering odors in a magnetic resonance imaging (MRI) environment. The system allows a timely presentation of different odors in synchrony with MRI sequences and participant’s inspiration phase. The rise/fall time of odor deliverance has been optimized to generate prompt and strong stimulations. Equipped with a user-friendly programming interface, the system can be used reliably in a wide range of experimental paradigms. We have paid particular attention to developing a portable system that is relatively easy, rapid, and inexpensive to replicate. The equipment has been tested in a 3-Tesla MRI in a boxcar paradigm, in which stimulation conditions alternated with rest periods (no stimulation). The experiment demonstrated the good functioning of the device and its efficiency in producing the expected activation in the olfactory cortex; it also revealed some methodological and technical aspects to be improved.     

Eye tracking research and technology: Towards objective measurement of data quality

Two methods for objectively measuring eye tracking data quality are explored. The first method works by tricking the eye tracker to detect an abrupt change in the gaze position of an artificial eye that in actuality does not move. Such a device, referred to as an artificial saccade generator, is shown to be extremely useful for measuring the temporal accuracy and precision of eye tracking systems and for validating the latency to display change in gaze contingent display paradigms. The second method involves an artificial pupil that is mounted on a computer controlled moving platform. This device is designed to be able to provide the eye tracker with motion sequences that closely resemble biological eye movements. The main advantage of using artificial motion for testing eye tracking data quality is the fact that the spatiotemporal signal is fully specified in a manner independent of the eye tracker that is being evaluated and that nearly identical motion sequence can be reproduced multiple times with great precision. The results of the present study demonstrate that the equipment described has the potential to become an important tool in the comprehensive evaluation of data quality.     

A new device to present textured stimuli to touch with simultaneous EEG recording

The study of touch has recently grown, due mainly to the extensive use of several types of actuators that stimulate several subsystems of touch. There is a widespread interest in applying these mechanisms to the study of the neurophysiological correlates of tactual perception. In this article, we present a new device (the tactile spinning wheel [TSW]) for delivering textured surfaces to the finger pad. The TSW allows one to control several parameters of the stimulation (angular speed, texture, etc.) and, connected to an EEG recording system, makes it possible to study neural electrophysiological events. The device consists of a rotating platform on which the tactile stimuli are fixed, a system that synchronizes stimuli onset with the EEG system, and an electronic interface that controls the platform. We present the technical details of the TSW, its calibration, and some experimental results we have obtained with this device.     

Reaching within video-capture virtual reality: using virtual reality as a motor control paradigm.

We have developed a virtual reality (VR) system that integrates a three-dimensional tracking device with a video-capture VR platform to record upper limb movements. The influence of target velocity on planning and execution of reaching movements was studied in five healthy subjects. Our initial results suggest that a target's velocity is considered when planning an interceptive action and that a hand reaching toward a moving virtual target is controlled in a similar way to how it is in the real visual environment.     

A microcomputer system for temperature biotelemetry

A microcomputer (Apple II) system for recording body temperature measured by a commercially made, implantable biotelemetry device (Mini-Mitter) is described. The system includes an inexpensive radio receiver interface circuit and software written in BASIC and 6502 assembly language. The utility of the system is illustrated in a study that shows that various handling procedures (including that normally involved in rectal temperature measurement) elevate body temperature in rats.     

Can computer mice be used as low-cost devices for the acquisition of planar human movement velocity signals?

The main goal of this work is to determine whether a computer mouse can be used as a low-cost device for the acquisition of two-dimensional human movement velocity signals in the context of psychophysical studies and biomedical applications. A comprehensive overview of the related literature is presented, and the problem of characterizing mouse movement acquisition is analyzed and discussed. Then, the quality of velocity signals acquired with this kind of device is measured on horizontal oscillatory movements by comparing the mouse data to the signals acquired simultaneously by a video motion tracking system and a digitizing tablet. A synthesis of the information gathered in this work indicates that the computer mouse can be used for the reliable acquisition of biosignals in the context of human movement studies, particularly for many applications dealing with the velocity of the end effector of the upper limb. This paper concludes by discussing the possibilities and limitations of such use.     

Teaching directional skills to preschool and kindergarten children

Studied a new device and training procedure for teaching the directional orientation and sentence tracking skills used in reading and writing western languages. Twelve preschool and 14 kindergarten children were randomly assigned to E and C groups. Between pre- and posttests, Es practiced for a total of 20 min. over a two-week period with an electronic device which flashed a correct signal only when S scribed left-to-right through successive sentences from top to bottom of the display. Any error in sequence extinguished the signal. Cs received only pre- and posttests. On test sentences prior to practice neither Es nor Cs were able to show where the sentences began or how they went from beginning to end. After using the device, Es tripled their orientation and tracking scores, while Cs not given access to the device did not improve (p < .002). Left-right and up-down directional confusion, often the subject of many hours of remedial training, were shown to be rapidly corrected in normal children by the use of a simple electronic device providing clear feedback distinguishing correct from incorrect responses. Implications for prereading instruction are discussed.     

Instrumentation for an electrocutaneous communication device

The device described is a prototype that uses spatiotemporal resolution for electrocutaneous stimulation. Signals initiated through a keyboard activate a matrix of four electrodes that may be applied to the fingers, forearm, abdomen, back, or other parts of the integument. The instrumentation described includes a pulse generator, the active time and delay time controls, the control of the total length of a pulse train, and the constant-current generators whose output is fed into the electrodes. This device may be used as an interface with an alphanumeric device (e.g., a calculator or computer) and as a basic instrument in research investigating the spatial and temporal resolving capacities of the skin senses.     

Using high frame rate CMOS sensors for three-dimensional eye tracking

A novel three-dimensional eye tracker is described and its performance evaluated. In contrast to previous devices based on conventional video standards, the present eye tracker is based on programmable CMOS image sensors, interfaced directly to digital processing circuitry to permit real-time image acquisition and processing. This architecture provides a number of important advantages, including image sampling rates of up to 400/sec measurement, direct pixel addressing for preprocessing and acquisition, and hard-disk storage of relevant image data. The reconfigurable digital processing circuitry also facilitatesin-line optimization of the front-end, time-critical processes. The primary acquisition algorithm for tracking the pupil and other eye features is designed around the generalized Hough transform. The tracker permits comprehensive measurement of eye movement (three degrees of freedom) and head movement (six degrees of freedom), and thus provides the basis for many types of vestibulo-oculomotor and visual research. The device has been qualified by the German Space Agency (DLR) and NASA for deployment on the International Space Station. It is foreseen that the device will be used together with appropriate stimulus generators as a general purpose facility for visual and vestibular experiments. Initial verification studies with an artificial eye demonstrate a measurement resolution of better than 0.1° in all three components (i.e., system noise for each of the components measured as 0.006° H, 0.005° V, and 0.016° T. Over a range of ±20° eye rotation, linearity was found to be <0.5% (H), <0.5% (V), and <2.0% (T). A comparison with the scierai search coil technique yieldednear equivalent values for the systemnoise and the thickness of Listing’s plane.     

A computer-controlled matrix system for presentation to the skin of complex spatiotemporal patterns

A system for presenting complex spatiotemporal patterns to the skin is described. The computer-controlled device consists of a matrix of 64 piezoceramic benders mounted in a support system that can be fitted to steeply contoured skin surfaces such as the thigh. Vibrotactile patterns that include movement across the skin’s surface and/or intensitive variation within or across display epochs are programmed and presented in a frame-by-frame manner, similar to the production of motion pictures. Patterns can be predefined, or modified by observers’ responses to allow for an interactive haptographic display. Design considerations for the construction of the tactile matrix, computer interface, and software are discussed.     

A simple special-purpose interval-duration timer for acoustic research

A special-purpose interval-duration timer is described. The device is designed to interface with commercially available psychophysical packages, to be used in time interval calibration. The extremely low cost of materials justifies the construction of this essentially single-purpose device.     

身份交换对多身份追踪表现的影响

本研究探讨了身份交换对多身份追踪表现的影响。实验1和实验2分别考察了全部报告法和部分报告法下身份交换对多身份追踪表现的具体影响。结果均发现, 身份交换对身份−位置绑定干扰程度越大, 位置追踪和身份识别容量也均越低, 但位置容量始终高于身份容量, 并且这些特性在不同追踪负荷上相同。此外, 部分报告法比全部报告法更具有容量测量优势。实验3则进一步从听觉通道上控制了语音复述对当前任务的干扰, 所得结果仍支持实验1和实验2。这表明, 身份交换对多身份追踪的干扰机制是身份−位置绑定机制受到损害, 而非语音复述的作用。     

A solid-state device for eliminating electrical noise and biopotentials in electromyographic (EMG) recordings

A small, low-cost, integrated circuit device is described. This circuit reduces electrical noise, such as that produced from a poor electrode-skin interface and power-line interference (60 Hz). Advantages of this device, with regard to use in electrically noisy environments and with long cables, are discussed.     

Interpersonal coordination tendencies and perception of visual information for decision-making in futsal

This study investigated how futsal players visually perceived information on angular interpersonal coordination relations, between available sources such as nearest defender, goalkeeper position and ball, when deciding to shoot at goal. Experienced players (n = 180) participated in eighteen, video-recorded futsal matches, during which 32 participants wore an eye tracking device. Forty-five sequences of play were selected and edited from the moment a teammate passed the ball to the shooter, until the moment a shot was undertaken. Independent variables included the angle connecting the shooter to their closest defender and goalkeeper, and it’s rate of change (velocity and variability) during performance. Then eye tracking system (TOBII PRO) was used to examine gaze patterns of shooters during task performance. Findings revealed that: (i) futsal players adapted their gaze patterns differently between key information sources when shooting confirmed as: their closest defender, goalkeeper, ball, and court floor; and (ii), the ball was the information source which was most fixated on, regardless of the characteristics of interpersonal coordination tendencies that emerged when shooting. These findings can be interpreted as evidence of functional perceptual behaviours used to regulate actions needed to ensure precise contact with the ball when shooting at goal. Further, adaptations of fixation patterns, varied between marking defender, goalkeeper, and ball, may provide functional postural orientation to facilitate a successful shot at goal.     

Box for interaction with objects (BIO): A new device to synchronize the presentation of objects with electrophysiological recordings

Brain event-related potentials are a useful tool for investigating visual processing and action planning. This technique requires extremely accurate synchronization of stimulus delivery with recordings. The precision of the onset time of visual stimulus delivery is a major challenge when attempting to use real, three-dimensional objects as stimuli. Here, we present an innovative device, the “box for interaction with objects” (BIO), that is designed to synchronize the presentation of objects with electroencephalographic (EEG) recordings. To reach the required resolution of stimulus-onset timing, the BIO system features an interface with reflective glass and light-emitting diodes (LEDs). When the LEDs inside the BIO are turned on, the object inside becomes visible, and a synchronizing pulse is sent to the recording systems. The BIO was tested in a motivational study that focused on visual and motor event-related potentials. EEG signals were recorded during the presentation of an emotion-laden object that could be grasped and brought close to the participant’s chest. BIO successfully synchronized the appearance of a three-dimensional object with EEG recordings, which would allow for an analysis of visual and motor event-related potentials in the same experiment. The BIO device, through a high-quality psychophysiological approach, offers a new perspective for the study of the motivational factors that drive actions toward relevant stimuli.     

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.