The investigator described to ABC News what she says is taking place in one of the scenes shot on video: "This is a baby who is completely alert, completely awake, completely aware of his surroundings, and he's getting a substance forced down his throat. He is screaming, and he was very terrified throughout this and you can hear the screams of the other babies and mothers in the background because the mothers were in there too."
The Humane Society of the Unites States video appears to support claims made by another former New Iberia Research Center employee.
Narriman Fakier, who was the coordinator for 100 chimpanzees at the center from the fall of 2002 until February 2004, said she was told to quit or be fired after repeatedly complaining about what she said were illegal and abusive practices at the lab. She has since filed a lawsuit against New Iberia as a whistle-blower.
"I am for the responsible use of animals in research," Fakier said.
Fakier has worked in several prestigious labs, and she said she's never seen anything like the practices at the New Iberia Research Center.
"Nothing like this," Fakier said. "I have to tell you, I've seen rats and mice treated better than this."
The New Iberia Research Center said that Fakier chose to quit, filed her lawsuit seeking "monetary gain," and that her allegations of abuse were false and not made until after she left the lab. An oversight board rejected her claims of abuse.
Fakier and the Humane Society of the United States investigator have never met one another. They worked at the facility at different times between 2002 and 2008.
"Nightline" conducted the interview with Narriman Fakier without telling her that the Humane Society investigation had taken place or that the undercover video existed. When she saw the footage for the first time, she said much of what was on the tape was what was happening at the facility when she was there five years earlier.
"They're still at it; nothing has changed," Fakier said. "It's about the money. There's big bucks in this research, especially chimp research. We're talking millions. Millions of dollars."
Dr. Martin Stephens works for the U.S. Humane Society and reviewed the undercover footage from the New Iberia Research Center.
"They [chimpanzees] have very complex emotions," he said. "Their social life is very rich. They live for years and years, they remember things from the past. Sadly, there is a downside to all that, and that kind of emotional sophistication and cognitive sophistication can lead to a vulnerability."
The video shows scenes of animals in what the Humane Society says is emotional distress and showcasing what is called "stereotypic behavior," pathologically repeated acts signifying mental breakdown.
"The spinning around in the cages, the biting of open wounds, self-mutilation, those are indicators of frustration, neurosis and even psychosis," Stephens said.
Fakier said she witnessed distress scenes similar to the video and that animals are anesthetized without proper care at the New Iberia Research Center.
Stephens said, "You saw a monkey slide off a table because he was unattended and crashed to the floor. That's outrageous."
Fakier and the Humane Society investigator also allege violations of safe and appropriate housing for the primates.