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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.


Related in: MedlinePlus

Just noticeable differences (JNDs) and Point of subjective equalities (PSEs) in both real and VR setups, GLMM estimates. (A) JND; the higher JND means a noisier response. (B) PSE, internal control, the response is expected to be accurate by the experimental design. Error bars are 95% confidence interval.
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Figure 5: Just noticeable differences (JNDs) and Point of subjective equalities (PSEs) in both real and VR setups, GLMM estimates. (A) JND; the higher JND means a noisier response. (B) PSE, internal control, the response is expected to be accurate by the experimental design. Error bars are 95% confidence interval.

Mentions: In the real environment accommodation and convergence provided a cue to depth, whereas in the virtual environment the two cues were in conflict since observers accommodated at the screen level. We compared the JNDs in real and virtual environments in order to evaluate the contribution of accommodation and convergence cues in action space. The predicted JND was about twice as large in VR condition compared to the real environment (Figure 5A). Crucially, 95% confidence intervals of the two JNDs were not overlapping, which means that the difference was statistically significant (p < 0.05). This finding suggests that the accommodation and convergence cues convey important information about depth in the tested stimulus range. Rolland et al. (1995) found similar results in peripersonal space. Our results extended their findings into action space. As expected for the PSE, we did not record any bias in both environments (Figure 5B), as the change in physical depth was the only relevant difference between the comparison and the reference stimulus.


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)

Just noticeable differences (JNDs) and Point of subjective equalities (PSEs) in both real and VR setups, GLMM estimates. (A) JND; the higher JND means a noisier response. (B) PSE, internal control, the response is expected to be accurate by the experimental design. Error bars are 95% confidence interval.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 5: Just noticeable differences (JNDs) and Point of subjective equalities (PSEs) in both real and VR setups, GLMM estimates. (A) JND; the higher JND means a noisier response. (B) PSE, internal control, the response is expected to be accurate by the experimental design. Error bars are 95% confidence interval.
Mentions: In the real environment accommodation and convergence provided a cue to depth, whereas in the virtual environment the two cues were in conflict since observers accommodated at the screen level. We compared the JNDs in real and virtual environments in order to evaluate the contribution of accommodation and convergence cues in action space. The predicted JND was about twice as large in VR condition compared to the real environment (Figure 5A). Crucially, 95% confidence intervals of the two JNDs were not overlapping, which means that the difference was statistically significant (p < 0.05). This finding suggests that the accommodation and convergence cues convey important information about depth in the tested stimulus range. Rolland et al. (1995) found similar results in peripersonal space. Our results extended their findings into action space. As expected for the PSE, we did not record any bias in both environments (Figure 5B), as the change in physical depth was the only relevant difference between the comparison and the reference stimulus.

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.


Related in: MedlinePlus