Field Marshall Kitchener was arguably the face of British recruitment for World War I.Everything about this poster compels you to join the fight. Firstly, he is in a position of authority, relatively high in the military hierarchy during a time of war and conflict. This makes it almost a direct command, or order, from someone in a position of authority, and carries all the influence that comes with that. However, if you look at the war as a global emergency, and the fact that the British population is so big, this poster addresses the issue of the diffusion of responsibility that could arguably be occurring among people during the wartime. by pointing directly at the viewer, and telling them exactly how they can help and what they can be doing to help, it personalizes the problem, making the audience feel more personally responsible for the emergency, as there is something they can be doing, but aren't (yet, of course)
The bystander effect has been demonstrated very effectively by Darley and Latane, who placed participants in a room, alone, supposedly connected to other rooms via microphones and speakers, under the pretense that they would be taking part in a discussion. All conditions contained at least one other confederate who was to pretend to have a seizure, with the other two conditions containing one or four other confederates to act as other bystanders, all of which did not act to help the confederate in distress. It was found that as more bystanders were added, participants became significantly less likely to act to aid the confederate in need.
Applying this to the wartime effort, the size of the populace would act as a very big group of "bystanders", and a diffusion effect would occur.
Darley, J. M., & Latane, B. (1968). Bystander intervention in emergencies: Diffusion of responsibility. Journal of Personality and Social Psychology, 4, 377-383.)