Attention Failures are execution errors that occur because the person's cognitive "radar screen" or attention is directed elsewhere, leading them to fail to perform an attention check or to make errors in the attention check, such as glossing over key items.

　

When it is suspected that a person had an attention failure, the analysis should be checked by verifying that the person remembered what attention checks they were to make, and when they were to be made. An attention failure involves failing to make these checks or mistiming them despite a clear memory of the need to do so. If the person momentarily forgot what they were doing, this is a memory failure, not an attention failure.

　

Memory Failures are execution errors that occur because the person's memory is faulty, leading them to forget to perform an attention check, or to make errors in the attention check, such as forgetting what one is looking for.

　

When it is suspected that a person had a memory failure, the analysis should be checked by identifying the key piece of information that the person forgot. Examples of key pieces of information include the need to check the progress of an action, or specific signs that the task is not accomplishing its purpose. People often view memory failures as more unprofessional than an attention failure, and claim they remembered all the key items, but simply didn't pay that much attention to a key item, when in fact, more often people have forgotten entirely to look at that item.

　

An attention failure or memory failure can cause execution errors. In practice, however, these attention and memory failures manifest themselves in two distinct types of errors: inattention and mistiming errors. Note that this is a further distinction or classification of errors. A given unsafe act should be classified, for example, as an execution error--> attention failure --> mistiming error--> omission.

　

Mistiming errors are execution errors where a memory failure or an attention failure leads a person to perform their attention checks at the wrong time in the preprogrammed sequence. While there is no exhaustive list of execution errors of the mistiming type, the following paragraphs describe several of the most common. As stated in the Overview, the classifications below the level of mistiming errors are required only for formal investigations.

　

VI.C.1.a Omission (required only for Formal investigations)

Definition: "Many tasks are of the action-test-wait-test-action-exit variety; making tea, for example. During these action sequences, people can "lose their place" through checking ("test") at the wrong time (recall that not paying attention or forgetting is an inattention slip or lapse). In omission errors, the person pays attention to the progress of an action sequence at the wrong time, and concludes that the process is further along than it actually is. As a consequence, the person omits some necessary step in the sequence, not realizing it hasn't already been done." [Reason 73-74]

Example: While bunkering a vessel, the chief engineer is continuously sounding tanks and notes that the first tank is nearly full. He immediately closes the valve to the tank and forgets to radio instructions to the bunker barge to reduce the rate of transfer.

Summary: The defining characteristics of an omission error are: i) there is an inappropriately timed check of an action sequence; ii) the assessment is that the action sequence is futher along than it really is and iii) a segment of the action sequence is omitted.

　

VI.C.1.b. Repetition (required only for Formal investigations)

Definition: "Paying attention to the progress of an action sequence at the wrong time can also result in a conclusion that the process is not yet at the point where in fact it actually is. As a result, the person repeats an action that has already been done." [Reason: 73-74]

Example: During an approach into a busy port, a watch officer continuously adds targets to an ARPA. Seeing a close call situation developing, the watch officer orders starboard rudder. After adding new targets, the officer sees the same target, and again order starboard rudder, taking the vessel significantly off track and almost out of the channel.

Summary: The defining characteristics of a repetition error are: i) there is an inappropriately timed check of an action sequence; and ii) the assessment is that the action sequence is not as far along as it really is; and iii) a segment of the action sequence is repeated.

　

VI.C.1.c. Reversal (required only for Formal investigations)

Definition: "In some rare situations, mistiming checks can cause can cause an action sequence to double back on itself for a step or two, "undoing" the normal action sequence." [Reason 73-74].

Example: During an approach into a busy port, a watch officer is monitoring ARPA targets, adding new ones as needed. As the vessel comes into port, the watch officer switches the radar range to 1-mile, but is interrupted by a vessel with "constant bearing - decreasing range" (CBDR). After the CBDR encounter, the watch officer accidentally switches to the 1/2-mile range, forgetting that she already reduced her range as intended.

Summary: The defining characteristics of a Reversal error are: i) there is an inappropriately timed check of a bi-directional action sequence (note: the "bi- directional action sequence" refers to the opportunity for the action to take one of two alternate paths); and ii) the action sequence is reversed.

　

Inattention errors are execution errors where a memory failure or an attention failure leads a person to fail to perform their attention checks or fail to pay sufficient attention when performing their checks in the preprogrammed sequence. While there is no exhaustive list of execution errors of the inattention type, the following paragraphs describe several of the most common. As stated in the Overview, the classifications below the level of inattention errors are required only for formal investigations.

　

VI.C.2.a. Capture Error (required only for Formal investigations)

Definition: "This error happens when a person's attention is claimed either by some internal preoccupation or by some external distracter at a time when they need to pay attention momentarily to choose their intended sequence. People may forget their intended choice, but more often remember the intended choice on the fringes of their consciousness, but their attention is not directed to it. Because they are not paying attention at the right time (or at all), and because the sequence they're performing is similar to a more familiar sequence, the familiar (and therefore stronger) sequence "captures" control of the action. The person ends up doing something they usually do, but which they did not intend to do in this specific case." [Reason: 68-71]

Example: After crossing the equator and while logging the vessel's position, the 3^rd mate consistently writes North latitude despite being south of the equator. The mate has been captured by the more familiar routine of writing north latitude despite the intention to write south latitude.

Summary: The defining characteristic of a capture error is that people don't pay attention at a "node" or crossroad in their action plan, and a strong sequence replaces the weaker intended sequence, such that the person ends up doing something familiar but not what they intended.

　

VI.C.2.b. Description Error (required only for Format Investigations)

Definition: This slip is extremely similar to perceptual confusion, and also usually results in performing the correct action on the wrong object. With highly routine tasks, people "save cognitive energy" by degrading or making rougher their matching or selection criteria. In these highly routine action sequences, our internal description of the intended action may not be sufficiently precise. The more the wrong and right objects have in common (especially approximate physical location), the more likely the error is to occur. Also, being distracted, bored, preoccupied, under stress, and not inclined to pay full attention to the task can lead to description errors." [Reason: 72]

Example: The watch officer turns the radar off accidentally because he is talking to the second mate (who is working on charts) and fails to pay sufficient attention to which knob he had switched. He unintentionally turned the power knob and not the range knob (which looks exactly the same and is located just above the power knob).

Summary: The defining characteristic of a description error is that ambiguity and/or distractions interfere with performance of the intended action. Usually the correct action is performed on the wrong object.

　

VI.C.2.c. Perceptual Confusion (required only for Formal investigations)

Definition: "In some situations, people doing highly routine tasks encounter objects that look like one another, are in the expected position of another, or does a similar job as another. When the person does not pay sufficient attention to the task of matching their expectations to the object they actually encounter, they accept one object as a match for the intended object. As a result, they perform the intended action sequence on the wrong object." [Reason: 72] The problem here is not that the description is faulty (see above paragraph), but that the objects are so similar that they both meet the description.

Example: While bringing a vessel into port, a mariner plots their position on a chart that had not been updated. New charts were delivered the day before and were placed on the chart table shelves underneath the old versions.

Summary: The defining characteristics of perceptual confusion slips are i) the task is highly routine; ii) a rough approximation is accepted for the real object; iii) the rough approximation looks like, is in the expected location, and/or does a similar job as the real object.

　

VI.C.2.d. Reduced Intentionally (required only for Formal investigations)

Definition "There is frequently a delay between when a person formulates the intention to do something and the time when it should be done. Unless the person's intention is periodically refreshed by attention checks during the delay, the intention can be pushed to the background of consciousness by other more immediate demands. As a result the person may experience a slip, such as forgetting entirely what they were intending to do, or a lapse. In reduced intentionally lapses, the intended action may get "detached" from its proper object (closing the wrong door, etc.), may be delayed or changed because the person was " captured" by their environment (going into the engine control room overlays and melds the intention with other engineering concerns), or might include multiple "sidesteps" (such as wandering from room to room until grasping exactly what was intended and what object the sequence involves)." [Reason: 71-72]

Example: An engineer notes at the start of the watch that a normally automated system is placed in manual control mode, and plans to monitor the system periodically to control it properly. Half way through the watch, however, an alarm goes off on another system, requiring immediate attention. The engineer fails to re-assign monitoring of the manual system to another person or to monitor it himself. The system exceeds normal operating parameters and fails.

Summary: The defining characteristics of a reduced intentionally error are: i) there is a delay between planning and executing an action; ii) the appropriate attention checks are not made; and iii) actions stemming from other demands replace the intended action.

　

VI.C.2.e. Mode Error (required only for Formal investigations)

Definition "A mode error can occur when a situation is assessed incorrectly, giving the person an inaccurate picture of how things are, resulting in inappropriate actions. The misclassification is termed a mode error when equipment is designed to have more actions than it has controls or displays, so the controls are required to do more than one action. When the equipment does not make the mode in which it is operating visible (for example, on/off), the information provided to the operator is ambiguous and mode errors are likely."

Example: A tugboat operator is controlling the tow from the wheelhouse maneuvering station. While leaning over the console to check the chart, the operator's belt buckle brushes the station control knob, switching it to the starboard bridge wing station. The mariner continues to try to control the tow from the deckhouse stick, wondering why the tug does not seem to respond to commands, and nearly collides with another tow.

Summary: The defining characteristics of a mode error are: i) the equipment in-use provides ambiguous information regarding control functions; and, ii) the user is unsure of the mode status of the equipment and chooses inappropriate actions.

　

VI.C.2.f. Omission Following Interruption (required only for Formal investigations)

Definition: "In this kind of error, a required attention check is interrupted by some external event. In this case, people often "lose their place," with regard to original action sequence but continue with parts of it omitted. A single step may be left out, and a series of steps may be left out. In fact, the interruption may even get "counted into" the original sequence." [Reason: 71]

Example: The bow lookout intends to make reports every ten minutes while the vessel is in deep fog. At the mid-point between reports, however, a friend brings the lookout a cup of coffee, and they chat for a few minutes. The lookout doesn't end up making his intended report.

Summary: The defining characteristics of an omission following interruption error are: i) an interruption disrupts an attention check; and ii) an omission in the original action sequence results from the interruption.

　

VI.C.2.g. Blends and Spoonerisms (required only for Formal investigations)

Definition: "When people have two plans active, or when there are two action elements within a single plan active at the same time, the two plans can get tangled in a struggle to gain control. This results in incongruous blends of actions, or in bizarre transposition of sequences of actions or of actions on objects (spoonerisms)." [Reason 72]

Example: As person can make a blend error by not paying attention to keeping action sequences separate. A person is talking on the phone when visitors enter her office. She blends her activities of welcoming visitors with talking on the phone, saying, "Ms. Smith, how may I help you?" as she would to the person on the phone. People make spoonerism errors when action sequences transpose. People doing housework typically try to "multi-task" to be more efficient. While watering houseplants and starting a bath for themselves, a person might unintentionally bring a plant into the bathroom with them and leave a bathrobe in the living room. Similarly when coming home after a work, a person might get a glass of milk from the refrigerator while putting away his keys. A few moments later the person may find the milk on the counter and the keys in the refrigerator.

Summary: The defining characteristic of blend and spoonerism errors is that people are performing more than one routine action or action sequence at the same time. Usually actions are transposed or the action sequences are blended in some unusual and inappropriate way.

When an unsafe act or decision results from a failure in the person's plan (rather than their execution of the plan), the problem with the plan originates in one of two ways. In the usual case, the person intends a positive outcome (i.e., they want to solve the problem and choose a good plan). In some unusual cases, however, the person willfully breaks rules they know in order to attain a positive outcome or for malicious purposes. In analyzing planning errors, it must be determined whether the person's plan was faulty because they made a mistake while trying to solve the problem according to the rules or because they knowingly violated rules.