Colonel Mike Bumgarner said Mr Hicks saw himself as different from others at the US military prison on Cuba.
Mr Hicks' American military lawyer Major Michael Mori, who recently visited his client, complained Mr Hicks continued to be held in solitary confinement and was forced to wear the same clothes for three weeks.
Col. Bumgarner said this was because Hicks refused to hand in his laundry.
"He was upset that he had not been issued a second towel, one beyond that which the other detainees had been issued. And so he refused to turn in his laundry," he told ABC Radio.
"Even if he refuses to turn in his laundry with the other detainees, he still would have the possibility to clean his clothes in his cell which many detainees do, as there is a sink and running water and soap available to them.
Col. Bumgarner said this was not a deliberate act by authorities. "Every seven to 10 days there is cycle by which we collect their laundry for them. They are issued new sets of linen and clothes," he said.
"Mr Hicks always sees himself as quite different than any other detainees here. He is always asking for special privileges and extra items beyond that which the other detainees get.
"It's just in his nature. He is constantly doing that. He likes to have a special menu. He sees himself different than the other detainees for some reason."
Col. Bumgarner rejected Maj. Mori's claim Hicks was distressed. "I don't see him as distressed at all," he said.
"The times that I have gone by and visited with him and watched him, he is normally buried in his books. But I don't certainly see him as despondent. He is just normally in a very ill mood."
Adelaide-born Mr Hicks, 30, has been held by US authorities at Guantanamo Bay since he was captured with Taliban forces in Afghanistan in late 2001.
He has pleaded not guilty to charges of conspiracy to commit war crimes, attempted murder and aiding and abetting the enemy.
Mr Hicks has sought British citizenship because the UK government, unlike Australia, has successfully fought for the release of its nationals from Guantanamo Bay.