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It was shown yet again in a 1978 experiment by Dr. Barrie J. Frost , in which pigeons were placed on treadmills ; it was observed that they did not bob their heads , as their surroundings were constant .
 Barrie J. Frost
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Barrie J. Frost