woman in a tv projection

Hypodermic Needle Theory


Proponents of the hypodermic needle theory argue the media can have a tremendous influence on the audience’s opinions and actions because we accept the text’s intended meaning. Comparing the communication of a message to a patient being injected with serum, the model suggests the public are easily brainwashed by the media.

hypodermic needle theory of communication infographic

Importantly, the hypodermic needle theory assumes the audience is passive. This means we do not critically assess the programmes we watch on television, the posts on our social media feeds, or the stories we read in newspapers and magazines. We simply believe what we are told.


After World War One, research began to focus on how governments managed to sway public opinion and convince so many young men to enlist in the army. The political scientist, Harold Lasswell, thought propaganda was worthy of study because he felt that people were “puzzled, uneasy, or vexed at the unknown cunning which seems to have duped or degraded them”.1 His criticism of the “cunning” politicians and their propaganda certainly still resonates with modern audiences and our world of Twitter and Fake News.

In 1927, Lasswell argued the “civilian mind is standardized by news” and believed audiences were especially vulnerable if the message was “cooked and garnished by adroit and skilful chefs”.2 Put simply, a good media text will convince the audience to believe in its message.

World War One Recruitment Poster Propaganda
World War One Recruitment Poster

The Theory

Although some textbooks suggest Lasswell coined the phrase “hypodermic needle theory”, no one actually knows for certain who came up with the term. He did describe propaganda as a “subtle poison” which was injected into the “veins” of the public.3

The model’s definition is also problematic. It could refer to the direct and powerful effects the media has on the audience, or the uniformity of the public’s reaction to a message. Perhaps it merely describes the immediacy of a text’s impact. Importantly, each of these ideas assume the audience is a passive and helpless recipient of the message.

War of the Worlds

The widespread panic caused by the 1938 “War of the Worlds” radio broadcast is often cited as proof of the hypodermic needle theory’s validity. According to newspaper reports, many listeners became incredibly frightened by storytellers’ depiction of the alien invasion of New York and ran out into the streets to see the spaceships and their weapons of mass destruction. Apparently, people believed the Martians had reached the city and “rushed out of their houses” to escape the “gas raid”.4 Look at this emotive headline from “The Boston Daily Globe”.

newspaper front page

The idea that a radio play was able terrify a nation was seen as clear evidence that the passive audience could be injected with a message – no matter how ridiculous. Were listeners really brainwashed into thinking Martians had landed in New Jersey and were attacking people with their ray guns?

Of course, the traditional print media were eager to highlight the dangers of radio broadcasts because it was a new platform which threatened their market share and advertising revenue. In fact, they probably exaggerated the panic in order to promote their own agenda.

For a more detailed exploration of this historically important media text, you should read our guide to the “War of the Worlds” radio broadcast.

Modern Examples

Linear flow of communication models describes a very simple relationship between institutions and the consumer, suggesting the media encodes ideas and feelings which are then received by the audience. The hypodermic needle theory goes one step further and argues the propaganda can be so powerful it is able to manipulate the audience into believing they should join the war effort or that that Martians are invading planet earth.

This model could explain why so many people believe the QAnon conspiracy theories or refuse to ignore the fake news stories widely circulated on various social media channels. These examples are quite extreme and so let’s look at some more straightforward messages to see if the media has the ability to influence the audience.

Puss in Boots

Voiced by Antonio Banderas, Puss in Boots first appeared in “Shrek 2” when he was hired by the wicked king to kill the lovable protagonist. Watch this clip from the film and pay particular attention to the representation of the character when he pleads to Shrek and Donkey to let him accompany them on their journey.

How did you react to the shot of the cat’s eyes? Did the tinkling piano help anchor your interpretation? One critic referred to Puss in Boots “working those big, green eyes for maximum manipulative effect” while another said his “cute-cat eyes” are “not easy resist”.

When “Shrek 2” was playing in cinemas around the world, the message was decoded according to the producers’ preferred reading and evoked an immediate and uniform response from the audience. The scene really did persuade the audience to sympathise with the poor cat and the impact must have been powerful because Puss in Boots got his own film.

Criticism of the Model

Many critics dismiss this linear flow of communication because it reduces the audience to passive consumers of the media who are incapable of having their own interpretations and reactions to the message. For instance, Paul Lazarsfeld (1944) and his colleagues researched the decision-making process of voters during the 1940’s American presidential election campaigns. Their analysis suggested newspapers and radio campaigns did not have a profound impact on the individual voter. Instead, they argued mass media influenced important opinion leaders who then persuaded other voters with less political knowledge.This became known as the two-step theory of communication.

In 1971, Wilbur Schramm called the linear model the Bullet Theory of communication, but he dismissed the idea that audiences could be “changed and converted” by the “mighty power of the mass media”.6 You might find some text books use Schramm’s title to describe this relationship between the audience and the media, but it is the exact same as the hypodermic needle theory.

George Gerbner (1983) also warned that “no responsible communications researcher ever advanced a theory of helpless receivers falling under a hail of media bullets”.7 However, he recognised that heavy users of the media would be influenced by what they saw on television. You can read more about his research in our article on the cultivation theory.

Despite all of the criticism, the hypodermic needle theory remains an interesting framework for evaluating the media and its attempts to persuade the audience. Perhaps there are some media texts which are fantastically persuasive and do have an immediate and direct impact on the audience. There might be some products whose shock tactics will have a powerful effect. The social and cultural context is another factor to consider.

Exam Practice and Revision

The best way to develop your understanding of the hypodermic needle theory is to apply the model to a variety of media texts. You can find examples on our audience exam practice page, but you should begin by analysing the delicious cover of “Baking Heaven” or exploring the Dior campaign which tries to grab the audience’s attention through the use of celebrity endorsement.

Many advertising agencies use shock tactics to engage the audience and provoke an immediate reaction. This dramatic drink-driving campaign poster is a great example of a media text which tries to inject the viewer with a message. However, the main image is quite distressful.

1 Lasswell, Harold D. (1927): “Propaganda Technique In the World War”.
2 ditto
New York Times (1938)
Lazarsfeld, P. F., Berelson, B., & Gaudet, H. (1944): “The People’s Choice”.
6 Schramm, W. (1971): “The Nature of Communication between Humans”. In W. Schramm, & D. F. Roberts (Eds.), “The Process and Effects of Mass Communication”.
Gerbner, G. (1983): “Epilogue: The Importance of Being Critical in One’s Own Fashion”.

Further Reading

Thanks for reading!