Implicit bias is the way people show a preference for or aversion to certain groups of people without a conscious acknowledgement of such biases. Because we live in a world that asks that we make many quick decisions in a day, our biases have the potential to affect decision-making without our even being aware of it.
Implicit bias spans countries of origin, gender, and race. Our implicit biases are often a better predictor of how we will react in any situation than our conscious values. Studies have found that whites with high levels of bias against dark-skinned people are more likely to categorize non-weapons (such as phones or brushes) as weapons (such as guns or knives).
People who have been exposed to certain cultural influences may consider women weak, see them as unable to achieve positions of power, and believe that all women should be at home raising children. Other people may look at Asians as "foreign" and be surprised when people of a certain color can speak fluent English—or be an American citizen. Or perhaps a successful woman in her seventies is met with scorn when she voices a desire to continue working in her field, as some with innate biases prefer youth over experience.
Since thoughts often precipitate actions, these implicit biases can shape the way we interact with others. Even people who make a genuine and honest effort to eliminate prejudices have some forms of implicit bias within their belief systems.
Implicit bias can affect outcomes in the justice system, the healthcare a patient receives, and the way a child is educated. There is current research being done to determine how much humans are capable of shedding their implicit biases through intentional efforts.