An attention span is the amount of time a person will pay attention to a message before getting distracted. Most people's attention span will accommodate only messages that are short and relatively simple and do not put heavy demands on their ability to concentrate.
Watching television can shorten people's attention spans if they engage in channel surfing -- frequently changing channels to find something different to watch. The short length of commercials also has accustomed people to hearing short messages.
People also have the tendency to fake attention, so that a speaker does not realize that audience members are not actively listening to the message. This is a habit that many people learn as young schoolchildren, making it easier for their minds to wander during a message because it looks as though they're paying attention.
When a listener does not like something about a speaker -- such as the speaker's voice, clothes, political stance, race or gender -- this bias may create a barrier to listening to that speaker's message. To overcome this, people should pay attention to the message and ignore the characteristics of the speaker.
Sometimes, based on past experience, people assume that they know what someone is going to say, and this conclusion causes them to tune out from a message. This often happens when people talk about politics, because listeners assume that when someone belongs to a political party, he will always stick to the party line. Listeners then may jump to conclusions about what a speaker will say, and these assumptions are not necessarily the case.
Noise is a barrier that prevents people from listening to messages. External noise includes anything that makes it difficult to hear and pay attention to a speaker, such as sirens blaring outside of a window, other people talking and dogs barking. Listeners may also get distracted by internal noise, which is anything they may be thinking about that prevents them from listening. Relationship problems, a death in the family or worrying about money may create an inner dialogue that makes it impossible to concentrate on what someone else is saying.