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Visual and haptic integration in the estimation of softness of deformable objects.

Cellini C, Kaim L, Drewing K - Iperception (2013)

Bottom Line: However, through everyday experiences we learn correspondences between felt softness and the visual effects of exploratory movements that are executed to feel softness.Bisensory judgments were less reliable than predicted from optimal integration.We conclude that the visuo-haptic integration of softness information is biased toward vision, rather than being optimal, and might even be guided by a fixed weighting scheme.

View Article: PubMed Central - PubMed

Affiliation: Department of General Psychology, Justus-Liebig-University of Giessen, Otto-Behaghel-Strasse 10F, 35394 Giessen, Germany; e-mail: Cristiano.Cellini@psychol.uni-giessen.de.

ABSTRACT
Softness perception intrinsically relies on haptic information. However, through everyday experiences we learn correspondences between felt softness and the visual effects of exploratory movements that are executed to feel softness. Here, we studied how visual and haptic information is integrated to assess the softness of deformable objects. Participants discriminated between the softness of two softer or two harder objects using only-visual, only-haptic or both visual and haptic information. We assessed the reliabilities of the softness judgments using the method of constant stimuli. In visuo-haptic trials, discrepancies between the two senses' information allowed us to measure the contribution of the individual senses to the judgments. Visual information (finger movement and object deformation) was simulated using computer graphics; input in visual trials was taken from previous visuo-haptic trials. Participants were able to infer softness from vision alone, and vision considerably contributed to bisensory judgments (∼35%). The visual contribution was higher than predicted from models of optimal integration (senses are weighted according to their reliabilities). Bisensory judgments were less reliable than predicted from optimal integration. We conclude that the visuo-haptic integration of softness information is biased toward vision, rather than being optimal, and might even be guided by a fixed weighting scheme.

No MeSH data available.


Related in: MedlinePlus

Average JND reported as percentage of the standards' compliance values (average Weber fraction) for each modality and compliance set condition. Error bars represent standard errors of the mean (SEM). The y axis, as well the dotted gray line, is cutted in order to give a better rendering of the data.
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Figure 4: Average JND reported as percentage of the standards' compliance values (average Weber fraction) for each modality and compliance set condition. Error bars represent standard errors of the mean (SEM). The y axis, as well the dotted gray line, is cutted in order to give a better rendering of the data.

Mentions: The individual Weber fractions (Figure 4) were entered into an analysis of variance (ANOVA) with the two within-participants factors modality (only-visual, only-haptics, visuo-haptics) and compliance set (hard vs. soft). Both main effects were significant (modality: F(2,14) = 11.99, p = 0.001, compliance set: F(1,7) = 11.31, p = 0.012) as well as the interaction: F(2,14) = 8.55, p = 0.004. t-tests showed, as expected, Weber fractions for the hard stimuli were higher than those for the soft stimuli when participants used only-visual information, t(7) = 3.07, p = 0.009 (one-tailed) or both visual and haptic information, t(7) = 2.67, p = 0.016 (one-tailed). There was no significant difference between hard and soft conditions when exploring only haptically, t(7) = 1.00, p = 0.34 (two-tailed). Within the hard condition only, Weber fractions were, as anticipated, larger when using only-visual information as compared to when using only-haptic or when using visuo-haptic information, t(7) = 3.27, p = 0.006, and t(7) = 3.16, p = 0.007, respectively (one-tailed). Surprisingly, only-haptic Weber fractions tended to be lower, instead of being higher as predicted, than visuo-haptic Weber fractions, t(7) = 2.3, p = 0.061 (two-tailed). Within the soft condition, observed trends were in the expected directions: Weber fractions in the only-visual conditions were higher than in the visuo-haptic and the only-haptic conditions (t(7) = 4.66, p = 0.001 and t(7) = 4.16, p = 0.002, respectively). Only-haptic Weber fractions tended to be higher than visuo-haptic ones, t(7) = 1.58, p = 0.078 (all tests one-tailed).


Visual and haptic integration in the estimation of softness of deformable objects.

Cellini C, Kaim L, Drewing K - Iperception (2013)

Average JND reported as percentage of the standards' compliance values (average Weber fraction) for each modality and compliance set condition. Error bars represent standard errors of the mean (SEM). The y axis, as well the dotted gray line, is cutted in order to give a better rendering of the data.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4129386&req=5

Figure 4: Average JND reported as percentage of the standards' compliance values (average Weber fraction) for each modality and compliance set condition. Error bars represent standard errors of the mean (SEM). The y axis, as well the dotted gray line, is cutted in order to give a better rendering of the data.
Mentions: The individual Weber fractions (Figure 4) were entered into an analysis of variance (ANOVA) with the two within-participants factors modality (only-visual, only-haptics, visuo-haptics) and compliance set (hard vs. soft). Both main effects were significant (modality: F(2,14) = 11.99, p = 0.001, compliance set: F(1,7) = 11.31, p = 0.012) as well as the interaction: F(2,14) = 8.55, p = 0.004. t-tests showed, as expected, Weber fractions for the hard stimuli were higher than those for the soft stimuli when participants used only-visual information, t(7) = 3.07, p = 0.009 (one-tailed) or both visual and haptic information, t(7) = 2.67, p = 0.016 (one-tailed). There was no significant difference between hard and soft conditions when exploring only haptically, t(7) = 1.00, p = 0.34 (two-tailed). Within the hard condition only, Weber fractions were, as anticipated, larger when using only-visual information as compared to when using only-haptic or when using visuo-haptic information, t(7) = 3.27, p = 0.006, and t(7) = 3.16, p = 0.007, respectively (one-tailed). Surprisingly, only-haptic Weber fractions tended to be lower, instead of being higher as predicted, than visuo-haptic Weber fractions, t(7) = 2.3, p = 0.061 (two-tailed). Within the soft condition, observed trends were in the expected directions: Weber fractions in the only-visual conditions were higher than in the visuo-haptic and the only-haptic conditions (t(7) = 4.66, p = 0.001 and t(7) = 4.16, p = 0.002, respectively). Only-haptic Weber fractions tended to be higher than visuo-haptic ones, t(7) = 1.58, p = 0.078 (all tests one-tailed).

Bottom Line: However, through everyday experiences we learn correspondences between felt softness and the visual effects of exploratory movements that are executed to feel softness.Bisensory judgments were less reliable than predicted from optimal integration.We conclude that the visuo-haptic integration of softness information is biased toward vision, rather than being optimal, and might even be guided by a fixed weighting scheme.

View Article: PubMed Central - PubMed

Affiliation: Department of General Psychology, Justus-Liebig-University of Giessen, Otto-Behaghel-Strasse 10F, 35394 Giessen, Germany; e-mail: Cristiano.Cellini@psychol.uni-giessen.de.

ABSTRACT
Softness perception intrinsically relies on haptic information. However, through everyday experiences we learn correspondences between felt softness and the visual effects of exploratory movements that are executed to feel softness. Here, we studied how visual and haptic information is integrated to assess the softness of deformable objects. Participants discriminated between the softness of two softer or two harder objects using only-visual, only-haptic or both visual and haptic information. We assessed the reliabilities of the softness judgments using the method of constant stimuli. In visuo-haptic trials, discrepancies between the two senses' information allowed us to measure the contribution of the individual senses to the judgments. Visual information (finger movement and object deformation) was simulated using computer graphics; input in visual trials was taken from previous visuo-haptic trials. Participants were able to infer softness from vision alone, and vision considerably contributed to bisensory judgments (∼35%). The visual contribution was higher than predicted from models of optimal integration (senses are weighted according to their reliabilities). Bisensory judgments were less reliable than predicted from optimal integration. We conclude that the visuo-haptic integration of softness information is biased toward vision, rather than being optimal, and might even be guided by a fixed weighting scheme.

No MeSH data available.


Related in: MedlinePlus