Josef Fritzl, 73, appears to have been driven by pronounced narcissism and a need to exercise power over others - and that may help explain how he got away with the abuse for so long - said Austrian psychiatrist Reinhard Haller.
"This man must have been insane and must have felt he was far superior to others," Haller said.
Court psychiatrist Sigrun Rossmanith said Fritzl essentially had two personalities: "the underground one, and the one that existed above."
"He was obviously a ruler. If the cellar was taboo for his wife and (other) children, and they heard that over and over, then they didn't dare to check on anything," she said. "If someone has power and forces it on someone else, then his word is like the word of God."
Police said Fritzl confessed Monday to holding captive his daughter - now 42 - sexually abusing her, fathering her children and tossing into a furnace the body of one child who died in infancy. He was to appear in court Tuesday.
Investigators say they believe his wife, with whom he had seven other children, was unaware that the daughter she believed ran away to join a religious cult in 1984 was living below her in the basement cell that Fritzl built beneath their apartment in Amstetten, 75 miles west of Vienna.
Authorities said the daughter, the children and Fritzl's wife were all getting counseling at an undisclosed location.
"He is really hit by this. He is very serious, but he is emotionally broken," Fritzl's lawyer, Rudolf Mayer, told The Associated Press on Tuesday.
Mayer said Fritzl also was under psychiatric care. Asked whether he showed any remorse, Mayer said only: "I cannot say at this point."
Austria is still scandalized by a 2006 case involving a girl who was kidnapped and imprisoned in a basement outside Vienna for more than eight years, and residents of this working-class town west of the capital were puzzled as to how the latest instance could go undetected.
Questions were being raised as to how Fritzl deceived neighbors, social workers and police for so long.
"How is it possible that no one knew anything for 24 years?" asked Anita Fabian, a teacher in Amstetten. "This was not possible without accomplices."
Reintraud Weissenberger, who runs a pharmacy down the street from the Fritzl home, said Tuesday that Josef and his wife, Rosemarie, were clients.
But she said there was nothing strange in their purchasing patterns. She would not discuss any medication they might have bought.
Officials said Fritzl faces up to 15 years in prison if charged, tried and convicted on rape charges, the most grave of his alleged offenses under Austrian law.
Police released Fritzl's full name and photograph at a news conference Monday, after his identity was widely reported by media in Austria and elsewhere in Europe.
Fritzl was born in 1935 and was a young child when the Nazis annexed Austria before World War II.
His daughter Elisabeth was 18 when she was imprisoned in the cell constructed deep beneath the family's apartment in the building, said Franz Polzer, head of the Lower Austrian Bureau of Criminal Affairs.
"He admitted that he locked his daughter ... in the cellar, that he repeatedly had sex with her, and that he is the father of her seven children," Polzer told the AP.
According to police, Elisabeth said she gave birth to twins in 1996 but one died several days later.
Police said the surviving children are three boys and three girls, the youngest of whom is 5. The oldest child is 19. DNA tests were expected to determine whether Fritzl is the father of the children, as he claims.
Investigators said they were trying to determine how the victims could have been hidden away for so long from other families in the building and everyone else in the town of 23,000 people.
Fritzl "managed to deceive everyone," including his wife, who apparently was unaware of the existence of the children in the cellar, Polzer said.
Officials said three of the secret children - aged 19, 18 and 5 - "never saw sunlight" until they were freed a few days ago.
Polzer told reporters that Fritzl was an authoritarian who took care never to allow anyone near the cellar. Hans-Heinz Lenze, a senior local official, said experts were trying to figure out if anything could have been heard beyond the cell's padded, reinforced concrete walls.
Polzer said investigators believe Fritzl acted alone, but appealed to the public to come forward with information.
Elisabeth had been missing since 1984, and authorities said her father had concocted a cover story that she had joined a cult and disappeared. Police in Amstetten found her on Saturday evening after receiving a tip.
Police released several photos showing parts of the cramped basement cell, with a gaily decorated small bathroom and a narrow passageway leading to a tiny bedroom. Investigators said the keyless-entry system apparently kept the daughter from escaping.
Three of the children lived with the grandparents. Fritzl and his wife registered those children with authorities, saying that they had found them outside their home in 1993, 1994 and 1997, at least one with a note from Elisabeth saying she could not care for the child.
Authorities said the victims and Fritzl's wife were under psychiatric care in an undisclosed location.
Lenze said the 5-year-old, a boy, appeared "cheerful."
"Of course, they are very pale," he added.
Kampusch was 10 when she was kidnapped in Vienna on her way to school in 1998. Her abductor, Wolfgang Priklopil, threw himself in front of a train hours after her escape.
Kampusch, now 20, issued a statement Monday saying she wanted to contact Elisabeth to offer emotional and financial help.
The Amstetten case unfolded after the eldest of the secret children, a 19-year-old, was found unconscious and gravely ill on April 19 in the building and was taken to a hospital. Authorities publicly appealed for her mother to come forward to help diagnose her condition.
After receiving a tip, police picked up Elisabeth and her father on Saturday near the hospital. Fritzl freed the captive children that same day, Polzer said.
Police said Elisabeth appeared "greatly disturbed" during questioning. She agreed to talk only after authorities assured her she would no longer have to have contact with her father and that her children would be cared for.
Investigators said the area where she and three of the children were held included rooms whose height did not exceed 5 feet, 6 inches. The area had a TV and small hot plates for cooking.
Authorities said Elisabeth told them her father began sexually abusing her when she was 11. She told police that in 1984, he sedated her, handcuffed her and locked her in the cellar.
Police said a letter written by Elisabeth had apparently surfaced a month after her disappearance, asking her parents not to search for her.
Lenze said that because the couple had custody of the children, social workers made a "considerable" number of visits to the family. "Interestingly, the father was seldom present during such visits," he said.
The social workers found nothing out of the ordinary, reporting that Fritzl's wife was attentive, the three children were doing well in school and clubs, and that all of them played musical instruments.