Perhaps the most familiar examples of Hitchcock's public disturbances are those bourgeois social occasions which are suddenly disrupted by an ‘improper’ event, e.g. Bruno almost strangling Mrs Cunningham during Senator Morton's party in STRANGERS ON A TRAIN, or Roger making a nuisance of himself in the auction room in NORTH BY NORTHWEST. There seems little doubt that Hitchcock enjoys the confusion and embarrassment such disruptions provoke – we could indeed see them as illustrating Hitchcock the practical joker, amusing himself at the expense of bourgeois stuffiness. However, if we take a public disturbance to include any disruption which causes a group of onlookers to react en masse, then there are a number of different categories to consider. The bourgeois disturbances, for instance, may be contrasted with their lower-class equivalents, in which a group of working-class men suddenly begin brawling. This occurs at the beginning of THE 39 STEPS, when a commissionaire tries to eject one of the noisy crowd at the music hall bar, and in YOUNG AND INNOCENT, when Erica's questions in a transport café cause the patrons to fall out over how much information to give her. In other words, there is a class distinction in Hitchcock's disturbances: inherently unruly, working-class crowds are readily prone to outbreaks of violence; inherently constrained by social propriety, bourgeois groups require a more or less outrageous triggering event to upset them.

Another distinction may be drawn between an event which prompts a crowd to gather out of alarm or curiosity (e.g. Mary Hearn's hysterics in THE FARMER's WIFE, when Sam is rude to her after she rejects his proposal), and one which provokes panic, with people fleeing to escape (e.g. when, moments later in THE 39 STEPS, a gun is fired by someone in the audience). We could call these centripetal and centrifugal public disturbances: in each case, there is an event which provokes a crowd reaction, but in opposite directions. Specific examples of this second pair may overlap with the first: Mary Hearn's attack occurs during a pretentious tea party, so a bourgeois occasion is also being disrupted; in THE 39 STEPS, it's as if the panic of the audience fleeing the music hall has arisen directly out of the violence which began at the bar.