Monoscopic Condition Research Articles

Does stereopsis improve face identification? A study using a virtual reality display with integrated eye-tracking and pupillometry

Stereopsis is a powerful depth cue for humans, which may also contribute to object recognition. In particular, we surmise that face identification would benefit from the availability of stereoscopic depth cues, since facial perception may be based on three-dimensional (3D) representations. In this study, a virtual reality (VR) headset with integrated eye-tracking was used to present stereoscopic images of faces. As a monoscopic contrast condition, identical images of faces were displayed to the two eyes. We monitored the participants' gaze behavior and pupil diameters while they performed a sample-to-match face identification task. We found that accuracy was superior in the stereoscopic condition compared to the monoscopic condition for frontal and intermediate views, but not profiles. Moreover, pupillary diameters were smaller when identifying stereoscopically seen faces than when viewing them without stereometric cues, which we interpret as lower processing load for the former than the latter conditions. The analysis of gaze showed that participants tended to focus on regions of the face rich in volumetric information, more so in the stereoscopic condition than the monoscopic condition. Together, these findings suggest that a 3D representation of faces may be the natural format used by the visual system when assessing face identity. Stereoscopic information, by providing depth information, assists the construction of robust facial representations in memory.

Perception of stereoscopic direct gaze: The effects of interaxial distance and emotional facial expressions.

Gaze perception has received considerable research attention due to its importance in social interaction. The majority of recent studies have utilized monoscopic pictorial gaze stimuli. However, a monoscopic direct gaze differs from a live or stereoscopic gaze. In the monoscopic condition, both eyes of the observer receive a direct gaze, whereas in live and stereoscopic conditions, only one eye receives a direct gaze. In the present study, we examined the implications of the difference between monoscopic and stereoscopic direct gaze. Moreover, because research has shown that stereoscopy affects the emotions elicited by facial expressions, and facial expressions affect the range of directions where an observer perceives mutual gaze-the cone of gaze-we studied the interaction effect of stereoscopy and facial expressions on gaze perception. Forty observers viewed stereoscopic images wherein one eye of the observer received a direct gaze while the other eye received a horizontally averted gaze at five different angles corresponding to five interaxial distances between the cameras in stimulus acquisition. In addition to monoscopic and stereoscopic conditions, the stimuli included neutral, angry, and happy facial expressions. The observers judged the gaze direction and mutual gaze of four lookers. Our results show that the mean of the directions received by the left and right eyes approximated the perceived gaze direction in the stereoscopic semidirect gaze condition. The probability of perceiving mutual gaze in the stereoscopic condition was substantially lower compared with monoscopic direct gaze. Furthermore, stereoscopic semidirect gaze significantly widened the cone of gaze for happy facial expressions.

Evaluation of monoscopic and stereoscopic displays for visual–spatial tasks in medical contexts

In the medical field, digital images are present in diagnosis, pre-operative planning, minimally invasive surgery, instruction, and training. The use of medical digital imaging has afforded new ways to interact with a patient, such as seeing fine details inside a body. This increased usage also raises many basic research questions on human perception and performance when utilizing these images. The work presented here attempts to answer the question: How would adding the stereopsis depth cue affect relative position tasks in a medical context compared to a monoscopic view? By designing and conducting a study to isolate the benefits between monoscopic 3D and stereoscopic 3D displays in a relative position task, the following hypothesis was tested: stereoscopic 3D displays are beneficial over monoscopic 3D displays for relative position judgment tasks in a medical visualization setting. 44 medical students completed a series of relative position judgments tasks. The results show that stereoscopic condition yielded a higher score than the monoscopic condition with regard to the hypothesis.

Temporal dynamics in the relation between presence and fear in virtual reality

Virtual reality (VR) is increasingly investigated as a new medium for exposure therapy, but process variables are not well understood. In particular, presence and fear during VR exposure correlate strongly, but the causal relationship between them remains unclear. We assigned 22 female spider-fearful participants randomly to either a stereoscopic (high presence) or a monoscopic (low presence) condition and exposed them repeatedly to a large virtual spider presented on a Powerwall. Presence and fear were assessed on subjective, physiological, and behavioral levels. Fear reactions were stronger and presence ratings were higher in the stereoscopic than the monoscopic condition. Presence in the first exposure trial correlated significantly with fear in the second exposure trial, while fear in the first exposure trial did not correlate significantly with presence in the second exposure trial. For the following exposure trials, correlations between presence and fear were significant in both directions. Limitations of our study include the small sample and the fact that we did not check diagnostic criteria of specific phobia. This is the first study to show temporal dynamics of the relationship between presence and fear. Initially, presence in VR seems to directly influence fear, while over time, presence and fear appear mutually dependent.

Age-Related Differences in Navigational Performance within an Immersive Virtual Environment

This paper presents an empirical investigation of the effects of aging on spatial performance in an immersive virtual environment. Adults (20 to 75 years of age) were taught a route through a six-room virtual house, while wearing a helmet mounted display (HMD) and using a joystick to navigate the virtual environment. Participants viewed the environment under monoscopic conditions with a display resolution of 640 pixels by 480 pixels, a field-of-view (FOV) of 30° H × 22° V, and a scene update rate of 15 Hz. Participants performed tasks designed to assess their spatial knowledge in terms of landmark knowledge, route knowledge, and configuration knowledge metrics. Locomotion efficiency and landmark knowledge did not significantly change with age. As age increased, route and configuration knowledge significantly decreased while the time needed to complete virtual environment spatial tasks increased (p < 0.05). The occurrence of side effects was also recorded; however, no significant differences with respect to age were found. The results are discussed in terms of designing virtual environments for adults.

Effects of Age and Field-of-Viewon Spatial Learning in an Immersive Virtual Environment

Adults and middle elementary schoolchildren (7-9 years old) were taught a route through a six room virtual house, while wearing a helmet mounted display (HMD) and using a joystick to navigate the virtual environment (VE). Participants viewed the environment under monoscopic conditions with field-of-view (FOV) set at either 30° H × 22° V or 48° H × 36° V. Participants performed tasks designed to assess their spatial knowledge in terms of landmark knowledge, route knowledge, and three configuration knowledge metrics. Landmark knowledge did not significantly change with age or FOV (p > .05). As both age and FOV increased, route and configuration knowledge significantly increased (p < .05). The results are discussed in terms of designing VEs for children.

Expert Agreement in Evaluating the Optic Disc for Glaucoma

The authors studied intraobserver and interobserver agreement, under monoscopic and stereoscopic conditions, in estimating vertical cup-to-disc ratios and in assessing whether a disc had glaucomatous damage. Six glaucoma experts evaluated 75 optic disc photographs under both viewing conditions. The experts also re-evaluated 25 photographs. Intraobserver agreement in estimating vertical cup-to disc ratios was high (median weighted kappa, 0.79). Interobserver agreement in estimating vertical cup-to-disc ratios was moderate (stereoscopic median weighted kappa, 0.67); individual experts differed by as much as 0.2 disc diameters (DD) monoscopically and 0.16 DD stereoscopically. The observers estimated larger vertical cup-to-disc ratios when evaluating the same discs under stereoscopic conditions than under monoscopic conditions. Intraobserver agreement in assessing glaucomatous disc damage was substantial (median kappa, 0.76). Interobserver agreement in assessing glaucomatous damage was moderate (stereoscopic median kappa, 0.50). This study confirms the ability of experts to reliably evaluate the optic disc within themselves and emphasizes the need for developing standardized methods for interobserver evaluation of the optic disc in glaucoma.