Limits...
Individuation and holistic processing of faces in rhesus monkeys.

Dahl CD, Logothetis NK, Hoffman KL - Proc. Biol. Sci. (2007)

Bottom Line: Two characteristics of face processing observed in humans are a subordinate-level entry point, here, the default recognition of faces at the subordinate, rather than basic, level of categorization, and holistic effects, i.e. perception of facial displays as an integrated whole.In experiments 1 and 2, macaques showed greater rebound from adaptation to conspecific faces than to other animals at the individual or subordinate level.Scan path analysis supported this assertion: during rebound, fixation to the unchanged eye region was renewed, but only for aligned stimuli.

View Article: PubMed Central - PubMed

Affiliation: Max Planck Institute for Biological Cybernetics, Tübingen 72012, Germany.

ABSTRACT
Despite considerable evidence that neural activity in monkeys reflects various aspects of face perception, relatively little is known about monkeys' face processing abilities. Two characteristics of face processing observed in humans are a subordinate-level entry point, here, the default recognition of faces at the subordinate, rather than basic, level of categorization, and holistic effects, i.e. perception of facial displays as an integrated whole. The present study used an adaptation paradigm to test whether untrained rhesus macaques (Macaca mulatta) display these hallmarks of face processing. In experiments 1 and 2, macaques showed greater rebound from adaptation to conspecific faces than to other animals at the individual or subordinate level. In experiment 3, exchanging only the bottom half of a monkey face produced greater rebound in aligned than in misaligned composites, indicating that for normal, aligned faces, the new bottom half may have influenced the perception of the whole face. Scan path analysis supported this assertion: during rebound, fixation to the unchanged eye region was renewed, but only for aligned stimuli. These experiments show that macaques naturally display the distinguishing characteristics of face processing seen in humans and provide the first clear demonstration that holistic information guides scan paths for conspecific faces.

Show MeSH

Related in: MedlinePlus

(a) Total fixation densities for each of the six trial types in experiment 2. The outline demarcates the eye region used for analysis. For reference, fixation densities are superimposed on greyscale versions of one set of face composites. (b) The proportion of fixation time within the eye region to total fixation time on the image, occurring within each 8 s rebound window. Whereas in the aligned condition, the novel trials do not differ significantly from the adaptation trials, the eye fixations in the misaligned novel trials are significantly decreased. Asterisk indicates a significance level of p<0.05 (corrected for multiple comparisons).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC1919404&req=5

fig4: (a) Total fixation densities for each of the six trial types in experiment 2. The outline demarcates the eye region used for analysis. For reference, fixation densities are superimposed on greyscale versions of one set of face composites. (b) The proportion of fixation time within the eye region to total fixation time on the image, occurring within each 8 s rebound window. Whereas in the aligned condition, the novel trials do not differ significantly from the adaptation trials, the eye fixations in the misaligned novel trials are significantly decreased. Asterisk indicates a significance level of p<0.05 (corrected for multiple comparisons).

Mentions: The fixation durations for the background region in the top half were calculated as the proportion of time spent looking at the upper half of the background to the total time looking at the picture. Data were pooled across sessions and trials (adaptation and novel) and statistically compared between aligned and misaligned. For display purposes only, densities were calculated at a resolution of 0.125° of visual angle and spatially smoothed by a Gaussian kernel with a standard deviation of 0.3125° of visual angle (figure 4).


Individuation and holistic processing of faces in rhesus monkeys.

Dahl CD, Logothetis NK, Hoffman KL - Proc. Biol. Sci. (2007)

(a) Total fixation densities for each of the six trial types in experiment 2. The outline demarcates the eye region used for analysis. For reference, fixation densities are superimposed on greyscale versions of one set of face composites. (b) The proportion of fixation time within the eye region to total fixation time on the image, occurring within each 8 s rebound window. Whereas in the aligned condition, the novel trials do not differ significantly from the adaptation trials, the eye fixations in the misaligned novel trials are significantly decreased. Asterisk indicates a significance level of p<0.05 (corrected for multiple comparisons).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1919404&req=5

fig4: (a) Total fixation densities for each of the six trial types in experiment 2. The outline demarcates the eye region used for analysis. For reference, fixation densities are superimposed on greyscale versions of one set of face composites. (b) The proportion of fixation time within the eye region to total fixation time on the image, occurring within each 8 s rebound window. Whereas in the aligned condition, the novel trials do not differ significantly from the adaptation trials, the eye fixations in the misaligned novel trials are significantly decreased. Asterisk indicates a significance level of p<0.05 (corrected for multiple comparisons).
Mentions: The fixation durations for the background region in the top half were calculated as the proportion of time spent looking at the upper half of the background to the total time looking at the picture. Data were pooled across sessions and trials (adaptation and novel) and statistically compared between aligned and misaligned. For display purposes only, densities were calculated at a resolution of 0.125° of visual angle and spatially smoothed by a Gaussian kernel with a standard deviation of 0.3125° of visual angle (figure 4).

Bottom Line: Two characteristics of face processing observed in humans are a subordinate-level entry point, here, the default recognition of faces at the subordinate, rather than basic, level of categorization, and holistic effects, i.e. perception of facial displays as an integrated whole.In experiments 1 and 2, macaques showed greater rebound from adaptation to conspecific faces than to other animals at the individual or subordinate level.Scan path analysis supported this assertion: during rebound, fixation to the unchanged eye region was renewed, but only for aligned stimuli.

View Article: PubMed Central - PubMed

Affiliation: Max Planck Institute for Biological Cybernetics, Tübingen 72012, Germany.

ABSTRACT
Despite considerable evidence that neural activity in monkeys reflects various aspects of face perception, relatively little is known about monkeys' face processing abilities. Two characteristics of face processing observed in humans are a subordinate-level entry point, here, the default recognition of faces at the subordinate, rather than basic, level of categorization, and holistic effects, i.e. perception of facial displays as an integrated whole. The present study used an adaptation paradigm to test whether untrained rhesus macaques (Macaca mulatta) display these hallmarks of face processing. In experiments 1 and 2, macaques showed greater rebound from adaptation to conspecific faces than to other animals at the individual or subordinate level. In experiment 3, exchanging only the bottom half of a monkey face produced greater rebound in aligned than in misaligned composites, indicating that for normal, aligned faces, the new bottom half may have influenced the perception of the whole face. Scan path analysis supported this assertion: during rebound, fixation to the unchanged eye region was renewed, but only for aligned stimuli. These experiments show that macaques naturally display the distinguishing characteristics of face processing seen in humans and provide the first clear demonstration that holistic information guides scan paths for conspecific faces.

Show MeSH
Related in: MedlinePlus