At that moment there had happened to him what happens to most people when unexpectedly caught in some shameful act: he had not had time to assume an expression suitable to the position in which he stood toward his wife now that his guilt was discovered. Instead of taking offence, denying, making excuses, asking forgiveness, or even remaining indifferent (anything would have been better than what he did), he involuntarily ('reflex action of the brain,' thought Oblonsky, who was fond of physiology) smiled his usual kindly and therefore silly smile.
Le había sucedido lo que a toda persona sorprendida en una situación demasiado vergonzosa: no supo adaptar su aspecto a la situación en que se encontraba. Así, en vez de ofenderse, negar, disculparse, pedir perdón o incluso permanecer indiferente ––cualquiera de aquellas actitudes habría sido preferible–, hizo una cosa ajena a su voluntad («reflejos cerebrales» , juzgó Esteban Arkadievich, que se interesaba mucho por la fisiología): sonreír, sonreír con su sonrisa habitual, benévola y en aquel caso necia.