A classification of human behavior is analyzed and given by the model skill-rule-knowledge (SRK) made by Dr. J. Rasmussen.

This model divides human behavior into three types which require an increasing level of complexity and so attention and cognitive engagement.

Skill-based behavior

It is the routine behavior based on learned skills for which the cognitive commitment is very low and reasoning is unconscious, automatic.

The person reacts to the stimulus almost instantaneously performing an action related to a procedure well interiorized.

Rule-based behavior

The behavior is guided by rules which the person has to perform known tasks.

The person recognizes the situation and applies the right procedure to perform the task, and then performs a series of actions by the use of procedures.

In this case, the cognitive engagement is higher and implies a certain reasoning.

Knowledge-based behavior

It is the behavior to use when you are in the presence of new or unforeseen situations, that is not known, for which you do not know the rules or procedures of reference.

The person must react creatively and independently, i.e. without the use of procedures or instinctive behaviors, based on the information available and the knowledge gained.

Based on the model proposed by Rasmussen there are three main types of human error:

1. Lapse error: memory lapse
   It is a run-time error caused by an oversight
   The action has a result different from the one expected due to the memory
   The error is not directly observable
   The action plan designed by the person is correct but one or more of the actions scheduled are skipped and have not been performed.
2. slip error: forgetfulness or involuntary mistake
   It is a runtime error that concerns the level of skill
   The actions are executed in a different way than planned, the person should know how to perform the task but it doesn’t and executes it incorrectly.
   The error is directly observable.
   In this case, the action plan designed by the person is correct but one or more of the actions envisaged were conducted incorrectly.
3. Mistake: you do the wrong things
   The error is not committed during the practical execution of the action plan, in fact the actions are carried out as planned, but there are other problems that lead to error.
   The actions have been carried out successfully, but all the plan prepared by the person is wrong.
   For this type of error we can have:
   rule-based mistakes: errors due to the choice of the wrong rule due to an erroneous perception of the situation, or omissions in the application of a rule;
   knowledge-based mistakes: mistakes due to lack of knowledge or incorrect application.

We can add a fourth type of error to these three types: the violation.

Errors occur because you want to speed up the process by taking the short cut; mistakes are made through inexperience or overconfidence in our own abilities.

It is very important to understand which kind of error we are committing because we puts us in the position to decide what to do to avoid repeating the same mistake in a similar situation.

To understand the difference between these three main types of error we propose the following exercise in which we summarize three different situations with the same object.
Each of them exemplifies one of the three main errors committed

First situation:
I’m going to make a gift to my wife and because it is always difficult for me to make gifts as I am not accustomed, after a lot of indecision, I found which is the best gift for her.
As soon as she opens it I can understand from the expression that she doesn’t like it and that she is disappointed, even if she tried to gloss over.

Second situation:
At Christmas my brother bought a gift for his wife and one for me.
As soon as I open my one, we understand that my brother exchanged the two gifts, so I’m left with a pretty dress and his wife with a shiny fountain pen.

Third situation:
My father comes home on the evening of the wedding anniversary without any gift and just he see my mother with a long face, he remembers that he forgot to buy  the red roses that he had promised to do in the early morning.
In fact, returning from work he drove up to the house automatically, as he does every night, completely forgetting to stop at the florist.

As can be seen, in all three situations were committed errors that have been more or less unpleasant consequences.
The three errors are significantly different and represent the three main types of error that a person  can commit.

In fact, the three situations can be projected to the human actions:

• social relationships with other people
• practice of profession
• use of a household appliance or PC
• use of a facility or industrial equipment

Do you understand which of the three types of error described at the beginning corresponds to each of the situations described?

• In the first situation, I have correctly followed all the actions defined in my plan, but my plan was wrong as I had chosen the wrong gift for my wife.
  I have therefore made a mistake.
• In the second situation, the plan of action of my brother was correct, but one of the actions carried out by him was wrong, having wrongly exchanged the two gifts.
  This is a typical slip error.
• In the third situation, the plan of my father was right, but he missed one of the measures included in the plan: he forgot to stop by the florist.
  The error committed by my father is lapse.

With this simple exercise we understand the difference between the three main types of error, now we have to analyze which mistakes we commit more frequently.

If we usually commit mistakes, it means that the action plans that we activate are not good, they are incorrect.
Probably we lack the right skills to perform well  the task and achieve the goal we have set ourselves, or the skills are not detailed and developed enough, or our knowledge is incorrect.

To reduce or eliminate mistakes we must strive to improve our knowledge, we have to study, to better prepare and train us.

If the errors we make are o lapse or slips, it means that we have the right and complete knowledge to carry out our task but we have to be more focused on what we do, we must reduce distractions and increase attention and rest.
In fact, the origin of slips and lapses are excessive distractions, fatigue, haste, excessive workload, lack of focus and stress.

We can conclude that it is not enough to divide and classify the mistakes we make to avoid them, but this is a first step to implement the best solutions to prevent them, such as the proper training, or the attention and the rest, etc..

If you want, you can do this exercise and test the solution, leaving your answers in the comments:

• First situation:
  in a biscuit factory at the time of packaging the operator realizes that all the chocolate cookies have a strange dark color.It happened that during the night shift, the implant operator forgot to adjust the temperature of the furnace and the biscuits were burned.
• Second situation:
  during the preparation of molding material for the production of tires, the supervisor realizes that instead of being black, the material that was presented to him looks pure white.The new warehouse worker turns out that instead picking up the box with the label “tires”, he had picked the one with the label “rubber”.
• Third situation:
  in the quality control department of a shoe factory, the operators are euphoric because opening the packs of “boots for man” ready for shipment, they find some pretty green shoes with stiletto heel.The operator in charge of packaging reversed the dispenser with adhesive labels.                                                                    

        Reproduced by Shaunak Basu