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Depth discrimination of constant angular size stimuli in action space: role of accommodation and convergence cues.

Naceri A, Moscatelli A, Chellali R - Front Hum Neurosci (2015)

Bottom Line: We replicated the task in virtual and real environments and we found that the performance was significantly different between the two environments.Whereas, in virtual reality (VR) the responses were significantly less precise, although, still above chance level in 16 of the 20 observers.The values of Weber fractions estimated in our study were compared to those reported in previous studies in peripersonal and action space.

View Article: PubMed Central - PubMed

Affiliation: Department of Cognitive Neuroscience, Cognitive Interaction Technology Center of Excellence (CITEC), Bielefeld University Bielefeld, Germany.

ABSTRACT
In our daily life experience, the angular size of an object correlates with its distance from the observer, provided that the physical size of the object remains constant. In this work, we investigated depth perception in action space (i.e., beyond the arm reach), while keeping the angular size of the target object constant. This was achieved by increasing the physical size of the target object as its distance to the observer increased. To the best of our knowledge, this is the first time that a similar protocol has been tested in action space, for distances to the observer ranging from 1.4-2.4 m. We replicated the task in virtual and real environments and we found that the performance was significantly different between the two environments. In the real environment, all participants perceived the depth of the target object precisely. Whereas, in virtual reality (VR) the responses were significantly less precise, although, still above chance level in 16 of the 20 observers. The difference in the discriminability of the stimuli was likely due to different contributions of the convergence and the accommodation cues in the two environments. The values of Weber fractions estimated in our study were compared to those reported in previous studies in peripersonal and action space.

No MeSH data available.


Generalized linear mixed model (GLMM) fit and count data (N = 20) in the VR experiment. One participant responded at chance-level, irrespectively of the change in the stimulus (in blue in the plot). Three participants produced a paradox response, i.e., they reported as farther in space the closer stimuli and vice versa (in red in the plot).
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Figure 3: Generalized linear mixed model (GLMM) fit and count data (N = 20) in the VR experiment. One participant responded at chance-level, irrespectively of the change in the stimulus (in blue in the plot). Three participants produced a paradox response, i.e., they reported as farther in space the closer stimuli and vice versa (in red in the plot).

Mentions: The AIC was smaller in modelVR2 (AIC2 = 1335.1) than in modelVR1 (AIC1 = 3003.9) revealing large differences between the observers in the discriminability of the stimuli (Figure 3). The LR test confirmed that modelVR2 provided a better fit to the data than modelVR1 and modelVR3 (p < 0.001). On the other hand, the values of the AIC were similar between modelVR2 and modelVR3 (AIC2 = 1335.1, AIC3 = 1335.7) and the difference between the two models was not significant at the LR test (p = 0.07). The non-significant improvement in model fit between modelVR3 and modelVR2 indicates that the azimuth and elevation angles (stimulus lines) do not affect observers’ performance. Based on these results, we selected the model modelVR2 for further analysis.


Depth discrimination of constant angular size stimuli in action space: role of accommodation and convergence cues.

Naceri A, Moscatelli A, Chellali R - Front Hum Neurosci (2015)

Generalized linear mixed model (GLMM) fit and count data (N = 20) in the VR experiment. One participant responded at chance-level, irrespectively of the change in the stimulus (in blue in the plot). Three participants produced a paradox response, i.e., they reported as farther in space the closer stimuli and vice versa (in red in the plot).
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4584972&req=5

Figure 3: Generalized linear mixed model (GLMM) fit and count data (N = 20) in the VR experiment. One participant responded at chance-level, irrespectively of the change in the stimulus (in blue in the plot). Three participants produced a paradox response, i.e., they reported as farther in space the closer stimuli and vice versa (in red in the plot).
Mentions: The AIC was smaller in modelVR2 (AIC2 = 1335.1) than in modelVR1 (AIC1 = 3003.9) revealing large differences between the observers in the discriminability of the stimuli (Figure 3). The LR test confirmed that modelVR2 provided a better fit to the data than modelVR1 and modelVR3 (p < 0.001). On the other hand, the values of the AIC were similar between modelVR2 and modelVR3 (AIC2 = 1335.1, AIC3 = 1335.7) and the difference between the two models was not significant at the LR test (p = 0.07). The non-significant improvement in model fit between modelVR3 and modelVR2 indicates that the azimuth and elevation angles (stimulus lines) do not affect observers’ performance. Based on these results, we selected the model modelVR2 for further analysis.

Bottom Line: We replicated the task in virtual and real environments and we found that the performance was significantly different between the two environments.Whereas, in virtual reality (VR) the responses were significantly less precise, although, still above chance level in 16 of the 20 observers.The values of Weber fractions estimated in our study were compared to those reported in previous studies in peripersonal and action space.

View Article: PubMed Central - PubMed

Affiliation: Department of Cognitive Neuroscience, Cognitive Interaction Technology Center of Excellence (CITEC), Bielefeld University Bielefeld, Germany.

ABSTRACT
In our daily life experience, the angular size of an object correlates with its distance from the observer, provided that the physical size of the object remains constant. In this work, we investigated depth perception in action space (i.e., beyond the arm reach), while keeping the angular size of the target object constant. This was achieved by increasing the physical size of the target object as its distance to the observer increased. To the best of our knowledge, this is the first time that a similar protocol has been tested in action space, for distances to the observer ranging from 1.4-2.4 m. We replicated the task in virtual and real environments and we found that the performance was significantly different between the two environments. In the real environment, all participants perceived the depth of the target object precisely. Whereas, in virtual reality (VR) the responses were significantly less precise, although, still above chance level in 16 of the 20 observers. The difference in the discriminability of the stimuli was likely due to different contributions of the convergence and the accommodation cues in the two environments. The values of Weber fractions estimated in our study were compared to those reported in previous studies in peripersonal and action space.

No MeSH data available.