The first group was handled daily from 3 to 14 weeks of age, the second from 7 to 14 weeks of age and the third received no handling from birth to 14 weeks. Different experimenters handled each kitten on different days. "Handling" was defined as an experimenter holding a kitten on his/her lap while petting it for 15 minutes. Friendliness was measured by how long each kitten stayed with the experimenter when not restrained, and by how long it took each kitten to reach the experimenter. Karsh found that the kittens handled from 3 to 14 weeks stayed longer with the experimenter and ran more quickly to the experimenter than kittens handled from 7 to 14 weeks. Also, kittens handled from 7 to 14 weeks were more "friendly" than kittens who received no handling at all. Karsh concluded that kittens should be handled as early as possible to ensure life-long friendliness towards humans.
What are the possible confounds in Karsh’s experimental design: The possible confounds in Karsh’s experimental design are the way experimenters handled each kitten on different days. Each experimenter will hold a kitten on his/her lap while petting it differently for 15 minutes. The petting a kitten will be different for each experimenter and each kitten will feel it differently. This have affect on both handling and friendliness in cats.
An investigator believed that sensory deprivation inhibits the intellectual development of animals. He ran an experiment to examine this thesis in the following way. He used two rats, each of which had just given birth to eight pups. One rat and her litter were placed in a large cage. This cage had ample space and lots of objects to explore. The baby rats in this cage breastfed off their mother. The second rat’s pups were separated from the mother, and each was placed in a separate cage. These cages were quite small, and the only objects they could see or hear were the four walls and the food and water