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Kandel and his colleagues showed that after habituation from siphon touching ( gill withdrawal response weakened ) , applying a paired noxious electrical stimulus to the tail and a touch to the siphon , gill withdrawal was once again noted .
 Kandel
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Kandel