"It is so presumptuous for us to think that we know all there is to know about how another creature suffers," she said. "I don't think it's for us to say whether certain species suffer or not."
Sweetland points out that in the past, scientists have proposed many theories that have since been proven wrong.
"Science is not an exact science," Sweetland said. "Theories are proved wrong over time."
The controversy may hinge on the human tendency to empathize with other beings, and our tendency to assume that animals think and feel the way we do.
"I think that individuals, based on their heritage and their genetic makeup, do project their emotions onto animals," said Richard Cawthorn, director of the Lobster Science Center at the University of Prince Edward Island in Canada, who supports the research finding that lobsters do not feel pain.
"When people do anthropomorphize animals -- even cartoon animals -- it reflects our needs and our desires," said Stevens. "It's more of a political agenda than any kind of scientific or social discussion of the issue.
"If you're going to look for the possibility of pain in any animal, it has to be based on comparative neurology -- comparing the brain structures and the neurology of the animal," Stevens said.
Regardless of any new scientific research, the debate over animals and pain is unlikely to be resolved anytime soon. The issue strikes at the heart of conflicting cultural values, and emotions tend to run high on all sides.
"What are we going to use as a system of truth?" Stevens asked. "Is it going to be an emotional or religious system of belief? Or is it going to be based on logic and science?"