Safety investigation jargon buster

A guide to the terms commonly used in safety investigations and their definitions.



Whether the design of the interface, layout, and storage facilities consider the range of end user capabilities e.g. physical, neurodiversity, in design for the reliability, ease and efficiency of use AND the time and place where it is needed.


Modifications of a task, which are considered necessary in a given context to achieve work goals e.g. safety, efficiency, wellbeing in the time, environment and presenting circumstances.


Where the appropriate use or operation of an item is conveyed in its design e.g. a handle on a door that implies it should be pulled not pushed.


'As low as reasonably practicable'/'so far as is reasonably practicable' (terms used interchangeably). The level to which we expect to see workplace risks controlled by weighing a risk against the trouble, time and money needed to control it (see more on the Health and Safety Executive website).


A measurement of physical characteristics among a population (e.g. elbow to fingertip length) recorded in either a fixed position, or whilst in motion. There are many such dimensions and, in knowing their range, these inform the physical design of objects and workspaces.


The focus of our cognitive process in the direction of a specific item or activity to consider information or our environment.


The ability to intuitively know what to do and to quickly recognise critical aspects of a situation (Juliusson et al, 2005), which requires less mental effort.



Features of individuals that influence what they can achieve. They encompass physical, psychological and social characteristics, which may be influenced by conditions that enhance or limit performance.

Closed question

A question asked in such a way as to expect response in a limited way – such as the provision of specific detail, or a response that is either positive or negative.

Cognitive bias

Cognitive bias can only be judged in hindsight and may not be a helpful term for healthcare investigations. Consideration to why performance may have made sense at the time and organisational influences would reflect a systems approach to considering any identified bias.

Cognitive interviewing

The use of techniques that aim to improve the reliability of interviewee recall, the quality of the information provided and to fully explore the decisions and actions taken in the context of the event.

Cognitive tasks

Activities that require mental activity from a person, such as concentration, vigilance, memory recall, detection of signs or of feedback, processing information, decision-making, judgements and problem solving.


Collaboration refers to the process of working together with others, typically towards a common goal or objective.

Commission (slip)

See ‘slip’.


The sharing of information, a response, thoughts, and feelings through any medium e.g. spoken, written, electronic.


Recognised level of performance, and use of knowledge and skills to do something successfully and efficiently.

Complex system

A complex system refers to systems that evolve rather than being designed by an organisation. A complex system will have many interacting parts that exists in a context of uncertainty and may lead to emergent outcomes that may not be predictable.

Complexity of task

A task that may require specialised knowledge, skills and experience to undertake a particular activity or a task that has multiple parts, which require precision and a high level of attention.

Configural maps

A visualisation of the interaction of the system elements relevant to a specific healthcare process. This can assist in presenting and understanding the emergent properties of the interactions.


Factors that influence or define a design to assist in correct use or application e.g. regulations and standards, physical controls, context or resources available.

Contextual factors

The factors within the environment or organisation relevant to the background of the work and events reported by staff.

Contributory factors

Factors influential to an event or outcomes. They may be separated in space and time from the actual event itself, and even from outside the organisation involved.


How individuals may vary in managing their reaction e.g. stress to a situation. There are different styles of coping:

  • problem (task) focused coping
  • emotion focused coping (avoidance or selective attention)
  • avoidance coping (actively avoid / distraction).

Counterfactual reasoning

Counterfactual thinking is a concept that involves the human tendency to create possible alternatives to life events that have already occurred; something that is contrary to what actually happened. Counterfactual thinking is, as it states: "counter to the facts" and incident reports that fall into this trap include words like ‘they could or should have done…’.


A reflection of the way that things are done or managed in any particular workspace or across an organisation.

Currency (of skills/training)

Having up to date skills, experience and knowledge of practices in the workplace.



The interpretation of information sources available to choose an action plan within the time required.


Activities that have the goal of developing a product, environment or process that is compatible, safe and desirable for those intended to use, work or experience the design.

Design (of a task)

What a person has to do. That it is undertaken in a logical way; that it aligns with a person’s capabilities (and limitations); and that it fits well with the demands of other activities associated with a person’s role (e.g. to provide safe and efficient care).

Distal outcome

An outcome that is not immediately obvious and identifiable close to the event, but takes effect in the longer term and/or in circumstances that are not directly features of the actual incident event or conditions.

Distributed cognition

Where information is not only within a person’s mind but incorporates input from the technology and environment (the system) in which thought processes occur and enables multiple people to share knowledge and a common mental model of a situation.

Donabedian model

A foundation approach to evaluation of quality of care. There are three areas of focus – the structure (factors such as facilities, technology and people), the processes (adopted to deliver patient care), and outcomes (as reflected in patient health and quality of life).

Duty of Candour

A regulatory requirement for care providers to be open and transparent with service users and includes situations where things have gone wrong with care or treatment. The requirements span communication, support, truthfulness and an apology (see Guidance: Duty of Candour, 2020 on the GOV.UK website).



Outcomes that result from the interactions between elements in the system that cannot be fully explained or always predicted by examining the elements separately (Hollnagel et al. 2006). Emergent outcomes may sometimes seem disproportionate to the interactions, or the characteristic of the elements involved.


The components of the system, such as the people, the equipment, documentation etc., but also less tangible things such organisational culture and external social, political or legal influences.


A method where researchers observe and/or interact with a study's participants to record the context and real-life environment.

External factors

The external environment influences patient safety and quality of care by shaping the context in which care is provided. In modern healthcare systems these external forces are stronger and change more frequently than ever before.


Family engagement

The prompt, effective liaison between a family and an investigation team to ensure the family is integral to the investigation and is treated professionally, respectfully and according to their individual needs.


A physiological state of reduced mental or physical performance resulting from sleep loss, extended wakefulness, time of day and/or workload (mental and/or physical activity) that can impair a person’s alertness and ability to perform safety related operational duties’ (modified from International Civil Aviation Organization, 2015, page xiii).


The extent to which a user is aware of their interaction (both successful and unsuccessful) with technology.


Functional Resonance Analysis Method. Supports the analysis and creation of a model depicting how work processes interact and where variability may exist in the context of everyday work.


Gap analysis

The steps taken to support the development of knowledge and understanding of an area of enquiry by identifying evidential gaps to be addressed, to ensure a comprehensive set of evidence informs the analysis and conclusions made within an investigation.


Health inequalities

Health inequalities are unfair and avoidable differences in health across the population, and between different groups within society.

Healthcare human factors/ergonomics

A scientific discipline that seeks to understand the interactions between humans and the elements of systems in which they provide or receive care/service. This knowledge is used to optimise system design for human well-being and overall performance.

Health Services Safety Investigations Body (HSSIB)

HSSIB investigates patient safety concerns across the NHS in England and in independent healthcare settings where safety learning could also help to improve NHS care.

We started our work in 2017 as the Healthcare Safety Investigation Branch (HSIB). Between April 2022 and October 2023 HSIB went through a period of transformation to become HSSIB. Read more about HSIB legacy.


Mental shortcuts we use in everyday decision making, in situations that are familiar to experienced people.

Hierarchical task analysis (HTA)

A technique that isolates the steps, actions and pre-conditions needed for the successful completion of a task. It is commonly presented as a diagram which depicts the sequence of actions as a hierarchy.

Hierarchy of control

A strategy for risk control that promotes an intervention approach through sequentially considering those that are potentially more effective and protective. The hierarchy moves from those considered to have most impact (such as removal or substitution of a hazard) through to controls that isolate people from hazards, or introduce administrative controls that change work practices (see: The National Institute for Occupational Safety and Health, 2020 on the Centers for Disease Control and Prevention website).

Hierarchy of intervention effectiveness

A strategy for risk control that compares both efficacy and difficulties of intervention choices. Those most effective, albeit harder to implement, typically concern design changes. Those with medium efficacy have greater demands for ‘updating or reinforcement’, whereas those with lesser efficacy, albeit easier to implement, are reliant on behaviour change.

Human error

A hindsight judgement that attributes blame to individuals involved in an incident. It is a symptom of underlying systems issues within which error was able to occur.

Human Reliability Analysis (HRA)

A family of approaches (over 75 methods) that looks at the different ways in which people can fail, such as predicting human error likelihood and assess their impact on the task. Also known as ‘Human Failure Analysis’ it should be based on ‘work as done’ (albeit can inform ‘work as imagined’).



Impactful describes something that has a significant effect or influence, typically producing important or noticeable results.


Impolite or unsociable communication or behaviour that contravenes the norms of respectful interaction. It can appear in varied forms, such as bullying, passive aggression or verbal abuse, and may have an impact upon safety.


Active steps taken to avoid discrimination or alienation of any particular stakeholder (e.g. giving equal access irrespective of race, gender, social diversity, disability, medical or other needs).


Ensures the involvement, participation, and representation of all individuals, regardless of their background, identity, or differences.

Inclusive design

Where an item is designed to be accessible and usable by as many intended end-users as possible without the need for further adaptations.

Inclusive report

A means of presenting an investigation report that is accessible to all stakeholders and enables learning in a way that is usable and meaningful to the intended audience.

Information processing

How knowledge is acquired, updated and modified (abridged, Christie and Gardiner, 1990).


Describes something that introduces new ideas, methods, or technologies, often resulting in significant improvements or advancements.


Where features of one or more entities combine to produce an outcome or impact performance. In an investigation we seek ‘clusters’ and themes of prominent interactions that can explain and ‘tell the story’ around how system factors contributed to the outcome or incident.


The screen, control system or physical features of a product or tool which influences how easily a user can understand and interact with it.

Investigative interviewing

A purposeful and meaningful conversation that aims to maximise the amount and quality of information that will enhance understanding of the how and why something occurred or didn’t occur.


Just culture

"A just culture considers wider systemic issues where things go wrong, enabling professionals and those operating the system to learn without fear of retribution", Professor Sir Norman Williams Review on the GOV.UK website.



Failure to do something, such as missing a step in a procedure (an omission).

Leading questions

A question that is asked in such a way as to prompt or encourage the respondent to answer in a specific or particular manner based on the way the question is framed.

Learning culture

Refers to an organisation that values and promotes continuous learning, growth, and development in all that it does.

A visual representation to enable analysis of a work environment, social network or lines of communication. It charts the lines of travel taken from one system entity to another and informs layout design, interactions within a team or across a workplace. Typically used in observation of a series of activities within a workspace (e.g. walk through talk through (WTTT)) to understand the frequency, sequence, and importance of specific interactions and can identify variability or potential for redesign.

Local rationality

Seeking to understand why practices and processes made sense at the time of an event, through exploring the nature of the work, the personal and team goals and prevailing systems conditions.

Long-term memory

Information in the mind that is stored and that can be retrieved following a few hours, days or years.


Mental model

The representations we create in our minds of external events. These are individual but when team working is necessary a shared mental model is how effective teamwork and communication can be supported.

Mental workload

The demands placed on a person’s cognitive capabilities (resources) by a task or activities. Successful performance is influenced both by overload and underload


A failure of decision-making - doing the wrong thing but believing that it is correct. Can arise when following incorrect rules for a particular event.


Paying attention to and undertaking of two or more tasks in a similar timeframe.


Never events

Patient safety incidents that can cause harm (or have the potential to do so) and are “wholly preventable because guidance or safety recommendations that provide strong systemic protective barriers are available at a national level and have been implemented by healthcare providers”, NHS Improvement (2018).

No blame

Investigations which attribute no blame or liability and focus on the system factors which contributed to an incident without seeking to blame an individual.



The residual free room in a workspace, that is not taken up by furniture, storage, fittings and equipment, for people to move around and freely use a work area.


See 'lapse'.

Open prompt questions

Posing sentences that include key words, such as ‘tell me’, ‘explain’, ‘describe’ and ‘show me’, that help elicit perspective and allow for more conversational exchange.

Open question

A question worded in such a way as to enable an interviewee to provide a descriptive answer, using their own choice of words.

Operational sustainability

Refers to the way in which we run our organisation to be socially, economically and environmentally responsible.

Organisational culture

The unconscious norm within an organisation concerning values, practices and assumptions.

Organisational learning

A continuous cycle of action and reflection, which takes place at different levels, including the individual, the team or department, the organisation and the NHS as a whole (see: ‘Achieving sustainable change’ on the Chartered Institute of Ergonomics & Human Factors website).


An emergent property, wanted or unwanted, affecting human or system performance.


A ‘helicopter view’ of what is going on. A term that describes the practice of situational awareness.


Patient work

Activities required of patients in the complex system, such as complying with conditions needed to receive treatment and in providing feedback to clinicians.

PEACE model

An investigative interviewing model detailing stages from preparation and practice to closure and evaluation. Used alongside a systems based investigative model (such as SEIPS) in healthcare.

Performance influencing factors

Aspects of the work system that can have both immediate and latent (background) effect on individual or organisational performance (the effectiveness of things) and may also contribute to unwanted outcomes. Also known as performance shaping factors.

Performance variability

Variation in the way that work is completed and the degree to which goals are adjusted, in accordance with individual capabilities, organisational capacity/resources and the needs of everyday work. There may be resulting trade-off in efficiency and thoroughness by individuals or a team (depending on work condition and demands), and outcomes may or may not be as intended.

Personal characteristics

The various individual traits that impact performance and capability, including:

  • personality
  • attitudes
  • aptitude
  • confidence
  • morale
  • physical and/or mental health status

Physical tasks

Both static and dynamic activities of the body that place demands on a person’s energy expenditure. The personal experience and task performance are impacted by:

  • individual capabilities and the nature of opportunities to recover
  • duration and frequency of exposure
  • suitability of tools/technology and workspace for those undertaking the task
  • compatibility with other work requirements.


The purchase of products and services to fulfil staff and patient work requirements.


Means to make something conform to the standards or qualities associated with a professional or a profession.


The mock up and testing of early design ideas to enable progressive development of a design while preparing to create a final product. Incorporating user testing, evaluation and iterative development in order to fine tune and optimise performance.


The varied investigative techniques (e.g. observation, interview, analysis of existing records data or guidance) that contribute to the understanding of how ‘work is done’ in an investigation. In isolation each provides only a partial representation (such as in ‘work as imagined’ or ‘work as disclosed’). It is in their collation (or ‘triangulation’) that a depth of understanding of ‘work as done’, and the system in which work occurs, can be built.

Proximal outcome

An outcome that is ‘of the moment’ and occurs and identified within the context of the incident.

Psychological safety

A shared understanding within a team that you can speak up with ideas, questions or concerns, without fear of embarrassment or humiliation.

Psychosocial safety

Providing opportunities for people to control possible sources of stress through managing their workload, work scheduling and ways of working.



A statement to indicate the system improvement required. Recommendations from an investigation will result from analysis of themes identified in an investigation and may be achieved using a variety of possible ways.

Reliability (validity)

The likelihood of consistent achievement of an intended performance e.g. a task, use of equipment, delivery of a service or care.

Requirements generation

Preparation of baseline criteria to develop a design. Design requirements consider what is functionally and technically required, the intended end users and known constraints.

Risk perception

The recognition and judgement made on potential hazards and the likelihood that harm (or failure) may occur.

Root cause analysis

A predecessor linear investigation approach that was used to isolate deep underlying causes of an event in simpler or engineered systems.


Safety case

A compilation of claims and evidence that gives assurance that a system, within a specified context, can be operated safely.

Safety climate

The local workforce attitudes and perceptions at a given point in time.

Safety culture

Combination of values, perceptions, beliefs, and leadership styles which lie below the surface and define the landscape. They are not easily visible without ‘diving’ below the surface.

Safety I

Safety-I approach presumes that things go wrong because of identified failures or malfunctions of specific components: technology, procedures, the human workers and the organisations in which they are embedded. Investigation in Safety-I is to identify the causes and contributory factors of adverse outcomes and failures. The safety management principle is to respond when something happens or is categorised as an unacceptable risk, usually by trying to eliminate causes or improve barriers, or both (see: From Safety-I to Safety-II: A White Paper by Professor Erik Hollnagel on the NHS England website).

Safety II

Safety-II approach assumes that everyday performance variability provides the adaptations that are needed to respond to varying conditions, and hence is the reason why things go right. Humans are consequently seen as a resource necessary for system flexibility and resilience. In Safety-II investigations seek to understand how things usually go right, since that is the basis for explaining how things occasionally go wrong. Risk assessment tries to understand the conditions where performance variability can become difficult or impossible to monitor and control (see: From Safety-I to Safety-II: A White Paper by Professor Erik Hollnagel on the NHS England website).

Safety science

A multidisciplinary research driven approach to understanding how hazards and their risk of harm to people and their wellbeing can be reduced or prevented.


'Systems Engineering Initiative for Patient Safety' is a framework that can be used in understanding inter-relationships across the structures, processes and outcomes in healthcare (see resources in Canvas, the online learning management system for those enrolled on an HSIB course).

Sensory input

Information received by any of the senses, such as:

  • sight
  • smell
  • touch
  • sound
  • taste.


Systematic Human-Error Reduction and Prediction Approach (Embrey, 1986). A technique that builds upon a hierarchical task analysis (HTA) to support understanding of performance influencing factors and identification of potential errors that may occur at each stage of a task. It also promotes consideration of error reduction recommendations that might be directed at procedures, training and equipment design.


Through use of a sign or other form of indicator identifying how an action should be performed.

Situational awareness

A concept that refers to the ability to have real time knowledge and anticipation of what is and is about to happen. Consideration to how well information, equipment and processes can support an awareness of a situation needs to be considered in a systems-based investigation.

Situational factors

The range of factual details (e.g. quality and reliability of available information, communications, acuity, workforce) specific to the time and place in which the event occurred.

Skill based error

An error made when undertaking a familiar activity that doesn’t require much attention.

Skills, rule knowledge classification

A form of classifying human performance and behaviour (derived by Rasmussen, 1983) according to demands, or requirements, expected of an individual. ‘Skill’ behaviour is familiar and can be undertaken with little concentration. ‘Rule’ behaviour is more complex but requires the pursuit of familiar instructions. 'Knowledge’ behaviour is a novel scenario that requires planning and decision making.

Slip (commission)

A form of skill-based error where there has been failure in carrying out part of an activity (such as missing out a step, an incorrect sequence, or incorrect use of equipment).

Sociotechnical system (STS)

Recognition both of the social needs of people (staff, patients and those supporting them) and of their work and organisational situation (e.g. technology and the work environment). Optimising design/fit across both entities promotes mutually beneficial performance, wellbeing and safety outcomes.


Individuals or key groups representing patients, staff and those providing services to enable care. Able to support the development of the terms of references for an investigation, provide pertinent evidence and contribute to the application of learning in decision-making.


Deliberate uniformity across the features of tools and technology (i.e. in their presentation and operation) to be easily identified to assist reliable and ease of use.


The sharing of details that describe a sequence of events in an investigation in a meaningful way. Combined, the reader might develop insight and an ability to visualise both the unfolding of a scenario and how contributory factors influenced the outcome.


Stress is a consequence of the relationship between the person and their environment, an interaction, rather than a property of an individual. How much an individual believes they are in control influences the stress they will experience and hence how they will cope.


A ‘system’ describes a set of activities or parts that interact and have a shared purpose; where the effectiveness of the whole system is greater than the sum of the parts (abridged: Wilson, 2014).

Systemic barriers

The strongest type of safety control is referred to as a barrier. The term barrier has a distinct description within safety industries as "A risk control that seeks to prevent unintended events from occurring, or prevent escalation of events into incidents with harmful consequences" (International Association of Oil and Gas Producers, 2016).

Systems approach/thinking

A mindset of ensuring that an investigation explores the multiple interacting contributory factors across the care system. That these are explored in seeking to understand the differing entities and activities that may (over time) contribute to an outcome or an incident.

Systems frameworks

A diagram or model that serves as a guide, and that depicts core areas of enquiry for an investigation to explore significant interrelationships of system factors represented within the framework.



A specific action undertaken under specific conditions, with a particular goal, which takes place within wider work processes or activities.

Team work

The working co-operatively together among a group of people towards a common goal, through distributed roles, authorities, responsibilities, skills and capabilities.

Terms of reference

The scope of an investigation that defines the boundary of the system and healthcare processes to be considered within an investigation, combined with a rationale for what isn’t considered. The development of terms of references requires the different perspectives of stakeholders and should include representatives that include patients, family/carers and staff.

Thematic analysis

The process of examining and assigning codes to text (e.g. incident narratives), in order to identify and group information into common themes. This assists in the interpretation across a range of inter-related data and can support learning across multiple investigations.


Technique for Human Error Prediction Rate (Swain and Guttmann, 1983). A comprehensive methodology used to assess human reliability. It incorporates the way that task errors are identified, visually represented and quantified.


A chronology of events, incorporating details from a range of possible resources, that provides a temporal sequence of what happened as reported or recorded within the period of time around an incident.


Facilitating the development of a behaviour or skills, encompassing aspects influencing access to training; quality of content, style and delivery for user needs; and skill consolidation and retention.

Training issues

Aspects that affect access to training (such as recognition of training needs and resourcing), provision of training (appropriacy of delivery style, duration and content; trainer skills) and measures for skills consolidation and maintenance.


Universal design

Design intended to accommodate as many people as possible: a ’one size fits all’ concept.

Up and out v.s down and in

Balancing the investigation focus across the details of an incident. Increasing the effort to not just understand the ‘who’, ‘what’ and ‘when’ details to also understanding the ‘how’ and ‘why’ which can inform on the influence of the decision making and wider system factors (e.g. regulations, policy, targets, training, procurement), that influence practice and processes on a day-to-day basis.


An outcome that determines how successfully a product or process supports the interaction between a person and a product, in its context of use, to create an effective, efficient, and satisfying outcome.

User-centred design

An approach to the design of activities or equipment which engages the user early on to ensure the intended use and environment is considered to enhance ease of use and reduce errors.


Walk through talk through (WTTT)

A data collection method that supports observation, discussion and understanding of particular practices, tasks, or scenarios as they are ‘in practice’. Undertaken on location, it incorporates as much of the typical working conditions (environment, staff, equipment) as is safe and feasible, and supports development of Work as Done (WAD) knowledge.

Work As Done/Work As Imagined

Understanding how day to day work is actually undertaken (Work as Done) compared with a belief of how work is undertaken (Work as Imagined), for example in procedures and guidelines. The comparison can reveal gaps between insights of frontline staff and those more removed from everyday work practices e.g. managers, governance leads.

Working memory

Information that is stored for a brief period and accessible for retrieval where its use supports comprehension for achievement of a particular goal.

Working scheduling

Features concerning the management of working time, with particular reference to the nature of work demands, including aspects such as shift systems, the pacing of work, and work-rest patterns (e.g. duration or work relative to opportunity for rest and recovery, and work pacing).


Workload describes the demands experienced by an individual from physical and cognitive activities (work) and the perceived effort required to complete them. Performance can be affected both by activity overload and underload.


Chartered Institute of Ergonomics and Human Factors (2020) Achieving sustainable change: Capturing lessons from COVID-19, version 1, CIEHF.

Christie, B. and Gardiner, M (1990) ‘Evaluation of the human-computer interface’, in Wilson, J.R. and Corlett, E.N. (eds) Evaluation of human work: A practical ergonomics methodology, London: Taylor and Francis, pp 271-321.

Embrey, D. SHERPA: a systematic human error reduction and prediction approach. Proceedings of the international topical meeting on advances in human factors in nuclear power systems. American Nuclear Society; 1986; p.184-93.

Hollnagel, E, Wear, R.L and Braithwaite,J (2015) From Safety-I to Safety-II: A White Paper.

Hollnagel, E., Woods, D.D and Leveson, N (2006) Resilience Engineering: Concepts and precepts. Ashgate, Farnham.

International Association of Oil and Gas Producers, (2016) Standardization of barrier definitions Report 544 - Supplement to Report 415, IOGP, London.

International Civil Aviation Organization (2015) Fatigue Management Guide for Airline Operators, 2nd Edition.

Juliusson EA, Karlsson N, Gärling T (2005) Weighing the past and the future in decision making. European Journal of Cognitive Psychology 17: 561-575.