It's fascinating to hear Truffaut picking Hitchcock's brain for filmmaking techniques. And to realize how much things stay the same: Hitchcock admits he made a mistake falling for the childish victory of landing actress-du-jour Ingrid Bergman for Under Capricorn, which lacked thrills. Hitchcock keeps beating himself up about things he should have done differently--and talks about how to play it safe when you are on insecure footing. He seems quite invested in how his films fared with critics and at the box office. He seems to enjoy sparring with a worthy adversary whom he respects; he's not looking to have his ego stoked.
He also seems competitive with Jean Renoir--he calls his direction "vague." Then Truffaut diplomatically explains how their filmmaking approaches couldn't be more antithetical.