Expert Authority Research Articles

Expert Authority in Crisis: Making Authority Real Through Struggle

There is an emerging consensus both within the social scientific research community and more widely in the public domain that expert authority is “in trouble.” However, there is much greater disagreement over the scope and scale of this trouble and what it might mean for the nature, status, and significance of expert authority in the 21st century. This paper identifies and assesses three different narratives concerning the crisis in expert authority. These constitute the delegitimation narrative, the demystification narrative, and the decomposition narrative. They can be seen as responses to the breakdown in the implicit social contract between experts, publics, and states under the extreme and continuous pressures exerted on expert authority by disjunctive change. We evaluate these various interpretations of the crisis in expert authority, particularly in terms of what they suggest about the future potency and stability of the concept of expert authority. In this process of evaluation, we also highlight the emergence of reflexive expert authority and its implications for organizational governance as potential outcomes of this ongoing crisis in the legitimacy and status of expert workers. Consequently, the paper provides a general analytical framework for understanding the emergent narratives around expert authority in democracies and highlights how all three narratives point to serious problems in sustaining this authority in the face of destabilizing change. Furthermore, in developing the notion of reflexive expert authority, we contend that theorization of expert authority needs to privilege the deeper dynamics of trust and control at the core of its analytical focus within organization theory.

Seduction, caution, fight: Media framing of research-based expertise in Norwegian print media coverage of low energy buildings (2005-2012).

In a little more than 10 years, Norway went from being a laggard in low energy construction to mandatory Passive House energy consumption levels for all new buildings. This is a remarkable story of expert-led sustainable change, in which considerable resistance had to be overcome. Based on a distant and a close reading of Norwegian print media coverage of low energy buildings between 2005 and 2012, we analyse one aspect of this success story: representations of research-based expert authority. Our empirical study is motivated by a concern for expert authority in conflicts that arise when sustainability policies are implemented. We found three distinct, but complementary groups of representations, cautious dissemination of research findings, open engagement in public controversies, and seductive 'home stories'. In a division of labour, we argue, they were able to assert research-based authority that persisted despite heated public controversies.

Framing the pandemic: from information to outformation in the COVID-19 era

ABSTRACT The COVID-19 pandemic has been the most mediatised health crisis in human history, involving a rapid circulation of knowledge in global networks and a continuous flow of spectacular images and narratives that have rendered the pandemic graspable in cultural, political, and moral terms. This article proposes that the intertwined nature of two opposite trends of knowledge production – scientific reasoning and affective storytelling – can be analytically approached through the concept of ‘outformation’ that provides explanatory power and conceptual clarity to make sense of the disorderly flows of knowledge in the pandemic-era. Using frame analysis, the article examines how one key term of the pandemic era, herd immunity, is taken from its scientific context and mobilised across different epistemic arenas from journalistic media to parliamentary debates as a vehicle for mistrust towards political and expert authorities in Finland that is a country characterised by high levels of trust towards authorities. The Finnish case is not only a national case about the framing of a specific term in times of epistemic instability but also provides a valuable lens to knowledge production during the pandemic era.

Quality indicators for the care of older adults with disabilities in long-term care facilities based on Maslow’s hierarchy of needs

PurposeThis study aimed to develop quality indicators for the care of older adults with disabilities in long-term care facilities (LTCFs) based on Maslow’s hierarchy of needs. MethodsThe draft of the quality indicators was drawn up based on a literature review and research group discussion. The quality indicators were finalized by two rounds of expert consultation (involving 15 experts) using the Delphi method. The Analytic Hierarchy Process was applied to calculate the indicators’ weight. ResultsThe response rates of the two rounds of consultation were 100% and 93%, and the expert authority coefficients were 0.86 and 0.87. After two rounds of consultation, the expert opinion coordination coefficients of the first-, second- and third-level indicators were 0.42, 0.25, and 0.96, respectively (P < 0.05), and the variation coefficient was ≤0.25. The final quality indicators for the care of older adults with disabilities in LTCFs included 7 first-level, 19 second-level, and 107 third-level indicators. ConclusionThe quality indicators for the care of older adults with disabilities in LTCFs are reliable, scientific, comprehensive, and practical and specify the content of person-centered care needs. This can provide a reference for evaluating and improving care quality in LTCFs.

Construction on teaching quality evaluation indicator system of multi-disciplinary team (MDT) clinical nursing practice in China: A Delphi study

AimTo construct an evaluation indicator system for nursing multi-disciplinary team (MDT) clinical practice in China and to provide quantifiable indicators for MDT clinical teaching courses. MethodsBased on relevant literature retrieval and analysis, a evaluation indicator system of nursing MDT clinical teaching quality was preliminarily constructed using the Donabedian. Structure-Process-Outcome model as theoretical guidance. Then, a final indicators content was formed after two rounds of expert consultation and Analytic Hierarchy Process (AHP) was used to determine the weight of indicators at all levels. ResultsThe effective response rate of the questionnaires in two rounds were 95.23% (20/21) and 100% (20/20) respectively, the expert authority coefficient (Cr) were 0.838 and 0.853 respectively and the Kendall's coefficient of concordance (Kendall's W) of indicators at all levels were 0.137–0.612 (P < 0.05). The final evaluation index system consisted of three one-class indicators, 8 s-class indicators and 28 third-class indicators. ConclusionThe study constructed a comprehensive set of evaluation indicator system of nursing MDT clinical practice, which was scientific and reliable and provides reference for the clinical teaching quality evaluation of MDT nursing.

Using the Delphi method to establish pediatric emergency triage criteria in a grade A tertiary women’s and children’s hospital in China

BackgroundWe aimed to establish simplified and quantifiable triage criteria in pediatric emergency care, improving the efficiency of pediatric emergency triage and ensuring patient safety.MethodsWe preliminarily determined the pediatric emergency triage criteria with references to pediatric emergency department characteristics and internationally recognized triage tools after literature review and discussion. The final determination of the triage criteria was reached after two rounds of Delphi surveys completed by18 experts from 3 hospitals in China.ResultsBoth round 1 and round 2 surveys had a 100% response rate. The overall expert authority coefficient in the two rounds of surveys was 0.872. The experts had 100% enthusiasm for participating in the surveys. Kendall’s coefficients of concordance for conditions/symptoms in patients triaged to level 1, 2, 3, and 4 were 0.149, 0.193, 0.102, and 0.266, respectively. All p-values were less than 0.05. The coefficients of variation in conditions/symptoms, vital signs, and the Pediatric Early Warning Score (PEWS) ranged between 0.00 and 0.205, meeting the inclusion criteria. The pediatric emergency triage criteria containing conditions/symptoms, vital signs, PEWS scores, and other 4 level 1 indicators, 51 level 2 indicators and 23 level 3 indicators were built. The maximum waiting time to treatment for the patients triaged to level 1, 2, 3, and 4 was immediate, within 10 min, within 30 min, and within 240 min, respectively.ConclusionThe pediatric emergency triage criteria established in this study was scientific and reliable. It can be used to quickly identify the patients requiring urgent and immediate care, thereby ensuring the priorities for the care of critically ill patients.

Developing a third-degree burn model of rats using the Delphi method

Animal experiments play an essential role in advances in the research and treatment of burns. Currently, researchers often rely on personal experience or the literature to complete the construction of animal disease models, which may lead to a lack of scientific rigor and a wide range of animal disease models with reference value. The purposes of this study were to establish a third-degree burn model of rats using the Delphi method to provide a reference. Two rounds of a Delphi expert consultation survey were conducted on experts (n = 13) in this study, and then the boundary value method was used to screen, modify and supplement the indicators. Next, the indicator weight was determined by dividing the boundary value, and finally, the index system of the rat model of third-degree burns was established. The statistical analysis results show that the positive coefficients of the two rounds of expert consultation are 100% and 88.67% respectively. The expert authority coefficient values were 0.73 and 0.67, respectively, and the expert coordination coefficient test was P < 0.001. According to the experts' suggestion, the third-degree burn model of rats with 8 first-degree indexes, 14 second-degree indexes and 46 third-degree indexes was finally established. According to the characteristics and quality requirements of animal models, this study constructs a rat model of third degree burns, which is expected to expressively improve the overall proficiency of burn research quality.

How to evaluate surgical tourism service organizations in China: indicators system development and a pilot application

BackgroundSurgical tourism is an emerging economic sector, with the most growth potential demonstrated in China's health industry before the COVID-19 pandemic. Surgical tourism accounts for a large part of medical tourism services in China, with high requirements in terms of quality and safety. By contrast, China suffers from insufficient measurement tools and theoretical research. The aim of this study was to develop a set of reliable and feasible indicators by augmenting the Donabedian model to evaluate the quality of surgical tourism services.MethodsA literature review and focus group interview were used to generate indicators for the quality of surgical tourism services. The basic framework of the evaluation system was based on the structure–process–outcome Donabedian model. The screening and weight setting were conducted through an analytical hierarchy process (AHP) and a two-round Delphi consultation with 13 panelists. The validity and reliability of experts were tested by the experts' positive coefficient, authority coefficient, and coordination coefficient. The reliability of the questionnaire was assessed by a pre-test distributed within an International Medical Department of a public hospital in China.ResultsBased on the Donabedian quality theory, a novel evaluation system of surgical tourism service institutions was constructed with three dimensions, nine first-level items and 39 second-level items. The three dimensions consisted of the structure (0.315), process (0.287), and outcome (0.398), with several indicators for each dimension and each indicator was given a weight. Of the two rounds of Delphi consultation, the response rates were 86.67% and 100%. The coordination coefficient of expert opinions in the two rounds of consultation were 0.49 and 0.65 (p < 0.05). For the empirical study, the self-evaluation score of a public hospital was 86, which could rate as a two-star institution.ConclusionsOur evaluation system identified three suitable quality dimensions of surgical tourism services to improve the safety and quality of practical healthcare. It reflects the access criterion of surgical tourism institutions, provides references for the best choice of surgical services for tourists, and can be applied by healthcare managers and policy makers to allocate resources more efficiently and promote more surgical tourism services with international standards.

Judging Expert Trustworthiness: The Difference Between Believing and Following the Science

ABSTRACT Expert-informed public policy often depends on a degree of public trust in the relevant expert authorities. But if lay citizens are not themselves authorities on the relevant area of expertise, how can they make good judgements about the trustworthiness of those who claim such authority? I argue that the answer to this question depends on the kind of trust under consideration. Specifically, I maintain that a distinction between epistemic trust and recommendation trust has consequences for novices judging the trustworthiness of experts. I argue for this by identifying the unique difficulties that emerge when a novice is asked not just to believe expert testimony, but to follow expert recommendations. I outline criteria for novice judgements of expert trustworthiness that have been proposed by Elizabeth Anderson and show that novel problems emerge for her criteria when we shift focus from epistemic trust to recommendation trust. More is needed when we are asked not just to believe the experts but to act as they recommend, because novices looking for trustworthy expert recommendations need to establish whether the recommended course of action supports what is important to them and accords with their values.

Development of humanistic nursing practice guidelines for stroke patients.

PurposeTo construct humanistic nursing practice guidelines suitable for stroke patients.DesignThis study was a development and validation study of guidelines using multiple methods, including literature review, qualitative research, questionnaire survey, thematic discussion, and Delphi expert consultation.MethodsTwenty-five experts from seven provinces and municipalities in China were interviewed over two rounds from December 2020 to February 2021. The first-level index was scored for importance and rationality, while the second-level index was scored for importance and feasibility using a five-point Likert scale. Delphi data was collected via a paper version of the questionnaire. The coefficients of variation and coordination were used to represent the degree of dispersion of expert opinions.FindingsIn the two rounds of letter consultation, the questionnaire's recovery and effective rates were both 100%, while the opinion submission rates of the two rounds were 84 and 52%, respectively. Moreover, the expert authority coefficient was 0.91, and the coordination coefficients of expert opinions in the first round were as follows: importance of 0.03 and rationality of 0.07 for the first-level index; importance of 0.09 and feasibility of 0.11 for the secondary index. In round two, the coordination coefficients of expert opinions were as follows: importance of 0.04 and rationality of 0.05 for the first-level indicators; importance of 0.12 and feasibility of 0.10 for the secondary index. The results for the secondary index were P < 0.001 for the two rounds. The humanistic nursing practice guidelines for stroke patients that were ultimately formed included five first-level indicators (physiological care, safety care, emotional care, dignity care, and rehabilitation needs) and 46 s-level indicators.ConclusionOur results show that the “Practice Guidelines for Humanistic Nursing for Stroke” established by experts adopts Maslow's hierarchy of needs as its structural framework. It meets people's basic needs and can provide a reference for the construction of a humanistic nursing specialty practice for stroke patients.Clinical relevanceHumanistic nursing guidelines for stroke could provide a reference for the construction of humanistic nursing practice in the stroke specialty.Clinical resourcesCopeptin and long-term risk of recurrent vascular events after transient ischemic attack and ischemic stroke: population-based study https://pubmed.ncbi.nlm.nih.gov/26451023/. Effectiveness and usage of a decision support system to improve stroke prevention in general practice: a cluster randomized controlled trial https://pubmed.ncbi.nlm.nih.gov/28245247/. Guidelines for adult stroke rehabilitation and recovery: a guideline for healthcare professionals from the American Heart Association/American Stroke Association https://pubmed.ncbi.nlm.nih.gov/27145936/.

Developing a professional-practice-model-based nursing organizational informatics competency model

BackgroundThe development of nursing informatics started late in China. There is an urgent need to develop a clinical practice model that can guide nursing managers in constructing an organizational nursing informatics competency. ObjectiveThe objective of this study was to develop a nursing organizational informatics competency model based on the Professional Practice Model (PPM) and to provide a reference for training in clinical nursing informatics in hospitals. MethodsA multidisciplinary team in the hospital was first formed as the working group, consisting of nurses trained with the TIGER (Technology Informatics Guiding Education Reform) Taiwan model and had practical experience in system development. We used an exploration map to help build the prototype of the hospital nursing informatics competency model. Then, a final model was constructed by experienced out-of-hospital experts using the Delphi method. The final model was determined according to the validity analysis. ResultsTen hospital stakeholders were invited to form the multidisciplinary working team to develop the prototype organizational PPM model. Two rounds of Delphi were conducted to twelve experienced nurses' informatics experts outside the hospital by e-mail. The results showed that the questionnaire return rate was 100 %, the expert authority coefficient was 0.84, the general validity of the two rounds of content was 92.46 % and 100 %, respectively, and the coefficient of variation of all items was < 0.3. The final model included five categories, including management strategy and leadership, organizational structure and operation, improvement of the environment for nursing information practice, cultivation of core competence in nursing information, and project management of the nursing information system, with 61 elements in total. ConclusionsWe propose this model to help hospital nursing managers to establish a plan of action to build up organizational clinical informatics competency.

Construction of Nursing Quality Index System in Assisted Reproduction Hospitals Based on the Model of "Three-Dimensional Quality Structure"

Objective To construct a nursing quality index system for the assisted reproduction hospitals integrating outpatient department,wards,and operating rooms and provide a reference for the application of the system in the quality control of clinical reproductive care. Method On the basis of Donabedian's health care quality model of structure-process-outcome,we established a nursing quality index system for assisted reproduction hospitals via literature retrieval,semi-structured interviews,Delphi method,and analytic hierarchy process. Results The two rounds of expert's questionnaire survey demonstrated the response rates of 100% and 92%,the expert authority coefficients of 0.911 and 0.919,and the Kendall coefficients of concordance of 0.228 and 0.253,respectively (all P<0.001).The nursing quality index system for assisted reproduction hospitals was established,which consisted of 3 first-level indicators,13 second-level indicators,and 39 third-level indicators. Conclusion The nursing quality index system of assisted reproduction hospitals is comprehensive,systematic and reasonable,which can be used as quality management standard and provide a reference for clinical application.

Development and initial validation of a clinical measure to assess symptoms of post-stroke depression in stroke patients at the rehabilitation stage

BackgroundThe high incidence of post-stroke depression (PSD) during rehabilitation exerts a negative effect on the treatment and functional recovery of patients with stroke and increases the risk of mortality. It is necessary to screen PSD in the rehabilitation stage and thus provide effective intervention strategies. However, existing measurements used to assess PSD in the rehabilitation stage in patients with stroke lack specificity. This study aimed to develop a clinical measure to assess symptoms of PSD in the rehabilitation stage.MethodsThe research team created the initial items through a literature review and semi-structured interviews of patients with stroke. Then, the symptom-related items were estimated by three panels: healthcare professionals (N = 41), Delphi experts (N = 15), and patients with stroke in the rehabilitation stage (N = 30).ResultsThe literature review and semi-structured interview produced 51 symptom-related items including six domains, and the items were reduced to 47 by the healthcare professionals. The symptom-related items were further reduced to 33 items by a two-round Delphi consultation. The initiative coefficients of the two Delphi rounds were 71.4 and 100%, the expert authority coefficients were both 0.85, Kendall’s W were 0.152 and 0.408 (p < 0.01), and the coefficient of variation (CV) were 0.05–0.32 and 0.00–0.18, respectively. The item-level content validity index (I-CVI) was 0.53–1.00, the scale-level CVI/universal agreement (S-CVI/UA) was 0.26, and the S-CVI/average (S -CVI/Ave) was 0.85 for the first found Delphi consultation; the I-CVI was 0.67–1.00, the S-CVI/UA was 0.61, and the S-CVI/Ave was 0.97 for the second round Delphi consultation. All content validity indicators have been significantly improved compared with the first round. Using mean ≥ 4 and full score ≥ 0.5, combined with CV ≤ 0.16 as the item criteria, a clinical measure of PSD with 33 items and 6 dimensions (cognition, sleep, behavior, emotion, body, and guilt) was finally formed after two rounds. The patients with stroke made no further revisions after evaluation.ConclusionThe research team developed a specific tool with good content validity to assess the symptoms of PSD in the rehabilitation stage.

Authority in tobacco control in Pacific Small Island Developing States: a qualitative study of multisectoral tobacco governance in Fiji and Vanuatu

ObjectiveSmall Island Developing States (SIDS) struggle with implementing multisectoral tobacco control measures, and health sector actors often lack capacity to forge multisectoral commitment. This study aims to explore the sources...

Evidence in Norwegian child protection interventions – Analysing cases of familial violence

AbstractHow is expert evidence used in care order proceedings when children are considered for foster care placement because of familial violence? What are important factors and how do the decision‐makers use and evaluate evidence from specialists and experts? In this in‐depth analysis of 104 published care order decisions from the Norwegian County Boards, I investigate how decision‐makers use and evaluate evidence from expert witnesses to determine whether a care order may be granted. The analysis shows that the evidence largely revolves around social functioning, care context and topics about how parents and children relate to each other. Led by the law, the decision‐makers use this evidence to determine whether the child's situation is harmful, whether support services are viable and whether a care order is in the child's best interests. I find that decision‐makers draw unevenly on evidence with regards to these legal requirements, and that the use predominantly defers to expert authority. However, there is also evidence of independent reasoning, where deferral to the epistemic authority of the experts is weakened. This is shown through evaluative and critical assessments and scrutiny of the disciplinary evidence.

Comprehensive evaluation of land reclamation schemes in mining areas based on linguistic intuitionistic fuzzy group decision-making.

Schemes to protect the geological environment and reclaim land are core requirements for an application for mining rights and complying with mining regulations. Mining enterprises must be supervised to ensure they fulfill their obligations. To guide oversight of such schemes and to provide references for their compilation and review, this study evaluates land reclamation schemes in mining areas using a multi-attribute group decision-making method. First, linguistic intuitionistic fuzzy numbers are used to describe the evaluation information. Considering the authority and preferences of experts, methods for determining expert weights in four cases are established. Max-min deviation then determines the attribute weights, and a method for linguistic intuitionistic fuzzy group decision-making is proposed. Finally, the practicability of this method is verified through a comparative analysis of land reclamation schemes for four mining areas in Sichuan Province, China. The results show the proposed method to give simple and effective evaluation, making it reasonably applicable to the compilation and review of land reclamation schemes.

Construction of Internet +home Care Quality Supervision Indicators in China Based on the Delphi Method.

BackgroundWith the aging of China’s population, the incidence rate of chronic diseases is rising. At the same time, residents’ health awareness is also increasing. Implementing Internet +home care is an inevitable trend in adapting social development. Currently, Internet +home care is in the pilot stage in China, relevant institutional measures are neither standardized nor perfect, and there is no set of quality supervision indicators (QSIs).PurposeThe construction of Internet +home care QSIs in China will provide a theoretical basis for Internet +home care quality supervision.Materials and MethodsThe Service-Quality model was used as the theoretical framework, and a literature review, semi-structured interviews, focus group discussions, and Delphi consultations determined the contents of the QSIs and the weight of each indicator.ResultsInternet +home care QSIs were constructed and included 5 first-level indicators, 17 secondary indicators, and 69 tertiary indicators. The effective recovery rates of the two rounds of Delphi expert consultation were 100% and 85%, the expert authority coefficients were 0.810 and 0.833, and the Kendall harmony coefficients were 0.189 and 0.125 (P<0.01). The final set of Internet +home care QSIs was as follows: tangibility (4 secondary and 16 tertiary indicators), reliability (4 secondary and 19 tertiary indicators), guarantee (5 secondary and 20 tertiary indicators), responsiveness (2 secondary and 8 tertiary indicators), and empathy (2 secondary and 6 tertiary indicators).ConclusionThe construction of Internet +home care QSIs based on the SERVQUAL model is scientifically valid, and the indicators are reliable. They provide guidance and reference values for the continuous improvement and promotion of Internet +home care. This work also provides a theoretical basis for researching and developing an Internet +home care quality supervision platform.

How policy actors assert authority in the governance of food marketing policies

The regulation of unhealthy food marketing is a highly contested space that involves a diverse range of actors and institutions. There is a paucity of research on the strategies used by the different actors to influence these policies. This study examined the use of authority by different regulatory actors to influence food marketing policies. We conducted semi-structured interviews with (N = 24) government, industry, civil society and technical experts involved in the regulation of food and beverage marketing in Australia. We identified five types of authority: institutional, delegated, expert, principled and capacity-based authority. Actors from the advertising, food and media industries claim more authority than technical experts, civil society, and government actors, suggesting that industry actors have multiple pathways to influence policy. The industry's claims of delegated and institutional authority are highly contested by civil society, technical experts, and state/territory government actors and recognised by federal government actors. Claims of circumscribed institutional authority are common among federal government actors such as the National Department of Health, Australian Media and Communications Authority and Food Standards Australia New Zealand. The assertions of authority observed in this study highlight the fragmented manner of the Australian food marketing regulatory system and have implications for which actors should be held accountable for the current challenges in the governance of food marketing policies.

Design and evaluation of maternal early warning system to reduce preventable maternal mortality in pregnancy and puerperium for high-risk women in China

BackgroundThe maternal early warning system is an effective tool to reduce maternal mortality and morbidity. However, there has been limited research on developing a maternal early warning system especially suitable for Chinese high-risk pregnant women. ObjectiveThe purpose is to develop a maternal early warning system to reduce preventable maternal mortality in pregnancy and puerperium in high-risk women in China. DesignA cross-sectional survey design. SettingThe study was conducted in a first-level hospital in China. ParticipantsA total of 306 pregnant women were selected as the objects who were admitted to give birth from April to June 2021 in xxx. MethodsA convenience sampling method was used to select 42 experts from 20 hospitals in more than 10 cities in east and west China, which represents the developed and undeveloped cities. The maternal early warning indicators of high-risk pregnancy during pregnancy and after birth were determined via literature research, research group discussion, and the Delphi expert consultation. Measurements and findingsThe final maternal early warning system for high-risk women in pregnancy and puerperium included 8 first-level indicators and 30 second-level indicators. The expert authority coefficients of the two rounds of consultation were 0.92 and 0.94, respectively. The Kendall harmony coefficients were 0.252 and 0.386, respectively (P<0.001). The area under the ROC curve predicted by the early warning system for high-risk pregnancy during childbirth was higher than 0.86, and the best cut-off point was 9.97. It was statistically significant (P<0.001). Key conclusionsThe constructed maternal early warning system for high-risk pregnancy in pregnancy and puerperium has comprehensive contents and high reliability, which will help midwives to identify high-risk pregnancies during childbirth. Implications for practiceThe results of this study can help to detect deterioration of the patient, predict morbidity in high-risk women and enable timely intervene to prevent possible severe illness.

The Nature of Illusions: A New Synthesis Based on Verifiability.

This overview discusses the nature of perceptual illusions with particular reference to the theory that illusions represent the operation of a sensory code for which there is no meaningful ground truth against which the illusory percepts can be compared, and therefore there are no illusions as such. This view corresponds to the Bayesian theory that “illusions” reflect unusual aspects of the core strategies of adapting to the natural world, again implying that illusions are simply an information processing characteristic. Instead, it is argued that a more meaningful approach to the field that we call illusions is the Ebbinghaus approach of comparing the illusory percept with a ground truth that is directly verifiable as aberrant by the observer in the domain of the illusory phenomenology (as opposed to relying on the authority of other experts). This concept of direct verifiability not only provides an operational definition of “illusion”; it also makes their interactive observation more effective and informative as to the perceptual processes underlying the illusory appearance. An expanded version of Gregory’s categorization of types of illusion is developed, and a range of classic and more recent illusions that illustrate the differences between these philosophical viewpoints is considered in detail. Such cases make it clear that the discrepancies from the measurable image structure cannot be simply regarded as idiosyncrasies of sensory coding, but are categorical exemplars of perceptual illusions. The widespread existence of such illusory percepts is indicative of the evolutionary limits of adaptive sensory coding.