In an interview with the Daily Mail's Weekend magazine, the Take That star revealed that he was surprised at how arrogant some of the hopefuls became.
"One of the biggest shocks for me last year was how quickly people become lazy once they get into this competition," he said.
"I found myself thinking, 'Hold on, this is just the start. You haven't made it yet. Even if you win it is just the start.'"
The 'Patience' singer mentored the boys category last year, which included controversial contestant Frankie Cocozza. The then 18-year-old - who was eventually disqualified from the competition - was frequently criticised for his weak performances and off-stage attitude.
"It is weird," Barlow said. "You take people off the street and put them in this bubble and they start to act like they have arrived.
"You can see them thinking, 'I was born to do this, I don't have to work at it'."
The singer told The Sun that the quality of the auditions has improved since the last series.
"The standard has definitely gone up a few notches. I think the audience is going to love it," he said.
Barlow was also quick to praise new judge Nicole Scherzinger, saying: "We're really pleased to have Nicole on the panel with us. She's amazing. She really feels like a Hollywood star.
"She got the job because she clicked... With all her experience in the industry and as a judge on the US X Factor, she has definitely earned her place.
"I think she'll be quite good with the contestants. She's quite emotional, maternal almost. To be honest, I think you could have the same four judges every year [as] I think it's more about the contestants. If they're no good, no-one will watch."
Barlow is said to be performing at this evening's Olympics closing ceremony, despite announcing the tragic loss of his daughter Poppy last week. The new series of The X Factor will begin on August 18.