The brain creates illusions not just for us: sharks (Chiloscyllium griseum) can ‘see the magic’ as well.
Bamboo sharks (Chiloscyllium griseum) were tested for their ability to perceive subjective and illusionary contours as well as line length illusions. Individuals were first trained to differentiate between squares, triangles and rhomboids in a series of two alternative forced-choice experiments. Tra...
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doaj-c78bd442ed7e479eaef14e6f37198c002020-11-24T21:04:46ZengFrontiers Media S.A.Frontiers in Neural Circuits1662-51102014-03-01810.3389/fncir.2014.0002482187The brain creates illusions not just for us: sharks (Chiloscyllium griseum) can ‘see the magic’ as well.Theodora eFuss0Horst eBleckmann1Vera eSchluessel2Rheinische Friedrich-Wilhelms-University BonnRheinische Friedrich-Wilhelms-University BonnRheinische Friedrich-Wilhelms-University BonnBamboo sharks (Chiloscyllium griseum) were tested for their ability to perceive subjective and illusionary contours as well as line length illusions. Individuals were first trained to differentiate between squares, triangles and rhomboids in a series of two alternative forced-choice experiments. Transfer tests then elucidated whether Kanizsa squares and triangles, grating gaps and phase shifted abutting gratings were also perceived and distinguished. The visual systems of most vertebrates and even invertebrates perceive illusionary contours despite the absence of physical luminance, colour or textural differences. Sharks are no exception to the rule; all tasks were successfully mastered within 3 to 24 training sessions, with sharks discriminating between various sets of Kanizsa figures and alternative stimuli, as well as between subjective contours in >75% of all tests. However, in contrast to Kanizsa figures and subjective contours, sharks were not deceived by Müller-Lyer (ML) illusions. Here, two centre lines of equal length are comparatively set between two arrowheads or –tails, in which case the line featuring the two arrow tails appears to be longer to most humans, primates and birds. In preparation for this experiment, lines of varying length, and lines of unequal length randomly featuring either two arrowheads or -tails on their ends, were presented first. Both sets of lines were successfully distinguished by most sharks. However, during presentation of the ML illusions sharks failed to succeed and succumbed either to side preferences or chose according to chance.http://journal.frontiersin.org/Journal/10.3389/fncir.2014.00024/fullelasmobranchKanizsaOptical illusionsubjective contourMüller-Lyer deceptionChiloscyllium griseum |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Theodora eFuss Horst eBleckmann Vera eSchluessel |
spellingShingle |
Theodora eFuss Horst eBleckmann Vera eSchluessel The brain creates illusions not just for us: sharks (Chiloscyllium griseum) can ‘see the magic’ as well. Frontiers in Neural Circuits elasmobranch Kanizsa Optical illusion subjective contour Müller-Lyer deception Chiloscyllium griseum |
author_facet |
Theodora eFuss Horst eBleckmann Vera eSchluessel |
author_sort |
Theodora eFuss |
title |
The brain creates illusions not just for us: sharks (Chiloscyllium griseum) can ‘see the magic’ as well. |
title_short |
The brain creates illusions not just for us: sharks (Chiloscyllium griseum) can ‘see the magic’ as well. |
title_full |
The brain creates illusions not just for us: sharks (Chiloscyllium griseum) can ‘see the magic’ as well. |
title_fullStr |
The brain creates illusions not just for us: sharks (Chiloscyllium griseum) can ‘see the magic’ as well. |
title_full_unstemmed |
The brain creates illusions not just for us: sharks (Chiloscyllium griseum) can ‘see the magic’ as well. |
title_sort |
brain creates illusions not just for us: sharks (chiloscyllium griseum) can ‘see the magic’ as well. |
publisher |
Frontiers Media S.A. |
series |
Frontiers in Neural Circuits |
issn |
1662-5110 |
publishDate |
2014-03-01 |
description |
Bamboo sharks (Chiloscyllium griseum) were tested for their ability to perceive subjective and illusionary contours as well as line length illusions. Individuals were first trained to differentiate between squares, triangles and rhomboids in a series of two alternative forced-choice experiments. Transfer tests then elucidated whether Kanizsa squares and triangles, grating gaps and phase shifted abutting gratings were also perceived and distinguished. The visual systems of most vertebrates and even invertebrates perceive illusionary contours despite the absence of physical luminance, colour or textural differences. Sharks are no exception to the rule; all tasks were successfully mastered within 3 to 24 training sessions, with sharks discriminating between various sets of Kanizsa figures and alternative stimuli, as well as between subjective contours in >75% of all tests. However, in contrast to Kanizsa figures and subjective contours, sharks were not deceived by Müller-Lyer (ML) illusions. Here, two centre lines of equal length are comparatively set between two arrowheads or –tails, in which case the line featuring the two arrow tails appears to be longer to most humans, primates and birds. In preparation for this experiment, lines of varying length, and lines of unequal length randomly featuring either two arrowheads or -tails on their ends, were presented first. Both sets of lines were successfully distinguished by most sharks. However, during presentation of the ML illusions sharks failed to succeed and succumbed either to side preferences or chose according to chance. |
topic |
elasmobranch Kanizsa Optical illusion subjective contour Müller-Lyer deception Chiloscyllium griseum |
url |
http://journal.frontiersin.org/Journal/10.3389/fncir.2014.00024/full |
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