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Temporal Structure of Human Gaze Dynamics Is Invariant During Free Viewing.

Marlow CA, Viskontas IV, Matlin A, Boydston C, Boxer A, Taylor RP - PLoS ONE (2015)

Bottom Line: We find H is robust regardless of the spatial complexity generated by the fractal images.The value we find for H of 0.57 shows that the gaze dynamics during free viewing of fractal images are consistent with a random walk process with persistent movements.Our research suggests the human visual system may have a common strategy that drives the dynamics of human gaze during exploration.

View Article: PubMed Central - PubMed

Affiliation: Keck Center for Integrative Neuroscience, University of California, San Francisco, California, 94143-044, United States of America; Physics Department, California Polytechnic State University, San Luis Obispo, California, 93407, United States of America.

ABSTRACT
We investigate the dynamic structure of human gaze and present an experimental study of the frequency components of the change in gaze position over time during free viewing of computer-generated fractal images. We show that changes in gaze position are scale-invariant in time with statistical properties that are characteristic of a random walk process. We quantify and track changes in the temporal structure using a well-defined scaling parameter called the Hurst exponent, H. We find H is robust regardless of the spatial complexity generated by the fractal images. In addition, we find the Hurst exponent is invariant across all participants, including those with distinct changes to higher order visual processes due to neural degeneration. The value we find for H of 0.57 shows that the gaze dynamics during free viewing of fractal images are consistent with a random walk process with persistent movements. Our research suggests the human visual system may have a common strategy that drives the dynamics of human gaze during exploration.

No MeSH data available.


Related in: MedlinePlus

Box plots showing comparison of the Hurst exponent, H, across (A) image spatial complexity with the number of images analyzed n = 19, 5, 7, 6, 7, 8, 8, 6, 7 and 7 respectively, (B) individuals within the participant group H with n = 83, 21, 72, 8, 19, 9, 10, 6, 10, 18 and 3 respectively and (C) participant groups with n = 259, 24, 14, and 43 respectively.
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pone.0139379.g004: Box plots showing comparison of the Hurst exponent, H, across (A) image spatial complexity with the number of images analyzed n = 19, 5, 7, 6, 7, 8, 8, 6, 7 and 7 respectively, (B) individuals within the participant group H with n = 83, 21, 72, 8, 19, 9, 10, 6, 10, 18 and 3 respectively and (C) participant groups with n = 259, 24, 14, and 43 respectively.

Mentions: To assess the effect that image complexity has on the gaze dynamics, we tracked the value of H for each of the participants across all the images they viewed. The resulting H values are shown for participant Y1 in Fig 4A. Box plots of H are grouped by image complexity. The accuracy of our analysis method was determined by generating several different artificial times series of known H and performing the variation method algorithm on them. The precision for determining H was found to be ± 0.03. To determine any significant differences between the image groups, a two-sample doubled sided t-test (α-level of 0.01) was performed with the Bonferroni correction for multiple comparisons. The Bonferroni correction adjusts the significance threshold to α/m where m is the number of groups being compared. In this case, the correction sets the significance threshold to 0.001. In all cases, there were no significant differences between H values across image complexity, with all instances giving p-values of at least 0.1 and the majority giving p-values larger than 0.5. The specific values for this participant (Y1) are listed in Table 1 as an example. Counter to our expectations, all participants showed no significant difference in the observed H value across image complexity indicating we see no change in the diffusive properties of gaze with image. These results suggest that the overall spatial complexity of an image does not affect the gaze dynamics during free viewing. Furthermore, scale invariance is seen in all cases of the Euclidean (non-fractal) images, even the simpler geometric images which have very low saliency. This suggests that scale invariant gaze dynamics prevail as long as participants are not actively fixating.


Temporal Structure of Human Gaze Dynamics Is Invariant During Free Viewing.

Marlow CA, Viskontas IV, Matlin A, Boydston C, Boxer A, Taylor RP - PLoS ONE (2015)

Box plots showing comparison of the Hurst exponent, H, across (A) image spatial complexity with the number of images analyzed n = 19, 5, 7, 6, 7, 8, 8, 6, 7 and 7 respectively, (B) individuals within the participant group H with n = 83, 21, 72, 8, 19, 9, 10, 6, 10, 18 and 3 respectively and (C) participant groups with n = 259, 24, 14, and 43 respectively.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4589360&req=5

pone.0139379.g004: Box plots showing comparison of the Hurst exponent, H, across (A) image spatial complexity with the number of images analyzed n = 19, 5, 7, 6, 7, 8, 8, 6, 7 and 7 respectively, (B) individuals within the participant group H with n = 83, 21, 72, 8, 19, 9, 10, 6, 10, 18 and 3 respectively and (C) participant groups with n = 259, 24, 14, and 43 respectively.
Mentions: To assess the effect that image complexity has on the gaze dynamics, we tracked the value of H for each of the participants across all the images they viewed. The resulting H values are shown for participant Y1 in Fig 4A. Box plots of H are grouped by image complexity. The accuracy of our analysis method was determined by generating several different artificial times series of known H and performing the variation method algorithm on them. The precision for determining H was found to be ± 0.03. To determine any significant differences between the image groups, a two-sample doubled sided t-test (α-level of 0.01) was performed with the Bonferroni correction for multiple comparisons. The Bonferroni correction adjusts the significance threshold to α/m where m is the number of groups being compared. In this case, the correction sets the significance threshold to 0.001. In all cases, there were no significant differences between H values across image complexity, with all instances giving p-values of at least 0.1 and the majority giving p-values larger than 0.5. The specific values for this participant (Y1) are listed in Table 1 as an example. Counter to our expectations, all participants showed no significant difference in the observed H value across image complexity indicating we see no change in the diffusive properties of gaze with image. These results suggest that the overall spatial complexity of an image does not affect the gaze dynamics during free viewing. Furthermore, scale invariance is seen in all cases of the Euclidean (non-fractal) images, even the simpler geometric images which have very low saliency. This suggests that scale invariant gaze dynamics prevail as long as participants are not actively fixating.

Bottom Line: We find H is robust regardless of the spatial complexity generated by the fractal images.The value we find for H of 0.57 shows that the gaze dynamics during free viewing of fractal images are consistent with a random walk process with persistent movements.Our research suggests the human visual system may have a common strategy that drives the dynamics of human gaze during exploration.

View Article: PubMed Central - PubMed

Affiliation: Keck Center for Integrative Neuroscience, University of California, San Francisco, California, 94143-044, United States of America; Physics Department, California Polytechnic State University, San Luis Obispo, California, 93407, United States of America.

ABSTRACT
We investigate the dynamic structure of human gaze and present an experimental study of the frequency components of the change in gaze position over time during free viewing of computer-generated fractal images. We show that changes in gaze position are scale-invariant in time with statistical properties that are characteristic of a random walk process. We quantify and track changes in the temporal structure using a well-defined scaling parameter called the Hurst exponent, H. We find H is robust regardless of the spatial complexity generated by the fractal images. In addition, we find the Hurst exponent is invariant across all participants, including those with distinct changes to higher order visual processes due to neural degeneration. The value we find for H of 0.57 shows that the gaze dynamics during free viewing of fractal images are consistent with a random walk process with persistent movements. Our research suggests the human visual system may have a common strategy that drives the dynamics of human gaze during exploration.

No MeSH data available.


Related in: MedlinePlus