## Errors 

Errors are a natural part of human performance. Beginners, as well as the most highly skilled experts, are vulnerable to error, and this is perhaps the most important thing to understand about error. To believe people can eliminate errors from their performance is to commit the biggest error of all. Instructors and learners alike should be prepared for occasional errors by learning about common kinds of errors, how errors can be minimized, how to learn from errors, and how to recover from errors when they are made. 

## Kinds of Errors 

There are two kinds of errors: slips and mistakes. 

## Slip 

A slip occurs when a person plans to do one thing, but then inadvertently does something else. Slips are errors of action. Slips can take on a variety of different forms. One of the most common forms of slips is to simply neglect to do something. Other forms of slips occur when people confuse two things that are similar. Accidentally using a manual that is similar to the one really needed is an example of this type of slip. 

Other forms of slips happen when someone is asked to perform a routine procedure in a slightly different way. For example, Beverly has been assigned runway 30 for many days in a row. This morning she approaches to land and ATC assigns runway 12 instead. As she approaches the traffic pattern, she turns to enter the pattern for runway 30 out of habit. 

Time pressure is another common source of slips. Studies of people performing a variety of tasks demonstrated a phenomenon called the speed-accuracy tradeoff. The more hurried one’s work becomes the more slips one is likely to make.$_{ }$ 

## Mistake 

A mistake occurs when a person plans to do the wrong thing and is successful. Mistakes are errors of thought. Mistakes are sometimes the result of gaps or misconceptions in the learner’s understanding. One type of mistake happens when a learner$_{ }$ formulates an understanding of a phenomenon and then later encounters a situation that shows how this understanding was incorrect or incomplete. For example, overly simplistic understanding of weather frequently leads inexperienced learners into situations that are unexpected. 

Experts are not immune to making mistakes, which sometimes arise from the way an expert draws upon knowledge of familiar problems and responds to them using familiar solutions. [Figure 3-21] Mistakes can occur when the expert categorizes a particular case incorrectly. For example, an experienced pilot may become accustomed to ignoring nuisance alerts issued by his traffic alerting system when approaching his home airport, as many aircraft on the ground turn on their transponders prior to takeoff. One night, he ignores an alert that was generated not by an aircraft on the ground, but rather by another aircraft that has turned in front of him on final approach. 

## Reducing Error 

Although it is impossible to eliminate errors entirely, there are ways to reduce them, as described in the following paragraphs. 

## Learning and Practicing 

The first line of defense against errors is learning and practice. Higher levels of knowledge and skill are associated with a lower frequency and magnitude of error. 

## Taking Time 

Errors can often be reduced by working deliberately at a comfortable pace. Hurrying does not achieve the same results as faster performance that is gained by increasing one’s skill through continued practice.$_{ }$ 

## Checking for Errors 

Another way to help avoid errors is to look actively for evidence of them. Many tasks in aviation offer a means of checking work. Learners should be encouraged to look for new ways of checking their work. 

