Current theories propose that our sense of curiosity is determined by the learning progress or information gain that our cognitive system expects to make. However, few studies have explicitly tried to quantify subjective information gain and link it to measures of curiosity. Here, we asked people to report their curiosity about the intrinsically engaging perceptual ‘puzzles’ known as Mooney images, and to report on the strength of their aha experience upon revealing the solution image (curiosity relief). We also asked our (...) participants (279) to make a guess concerning the solution of the image, and used the distribution of these guesses to compute the crowdsourced semantic entropy (or ambiguity) of the images, as a measure of the potential for information gain. Our results confirm that curiosity and, even more so, aha experience is substantially associated with this semantic information gain measure. These findings support the expected information gain theory of curiosity and suggest that the aha experience or intrinsic reward is driven by the actual information gain. In an unannounced memory part, we also established that the often reported influence of curiosity on memory is fully mediated by the aha experience or curiosity relief. We discuss the implications of our results for the burgeoning fields of curiosity and psychoaesthetics. (shrink)

How to account for the power that art holds over us? Why do artworks touch us deeply, consoling, transforming or invigorating us in the process? In this paper, we argue that an answer to this question might emerge from a fecund framework in cognitive science known as predictive processing (a.k.a. active inference). We unpack how this approach connects sense-making and aesthetic experiences through the idea of an ‘epistemic arc’, consisting of three parts (curiosity, epistemic action and aha experiences), which we (...) cast as aspects of active inference. We then show how epistemic arcs are built and sustained by artworks to provide us with those satisfying experiences that we tend to call ‘aesthetic’. Next, we defuse two key objections to this approach; namely, that it places undue emphasis on the cognitive component of our aesthetic encounters—at the expense of affective aspects—and on closure and uncertainty minimization (order)—at the expense of openness and lingering uncertainty (change). We show that the approach offers crucial resources to account for the open-ended, free and playful behaviour inherent in aesthetic experiences. The upshot is a promising but deflationary approach, both philosophically informed and psychologically sound, that opens new empirical avenues for understanding our aesthetic encounters. -/- This article is part of the theme issue ‘Art, aesthetics and predictive processing: theoretical and empirical perspectives’. (shrink)

A recently proposed model of sensory processing suggests that perceptual experience is updated in discrete steps. We show that the data advanced to support discrete perception are in fact compatible with a continuous account of perception. Physiological and psychophysical constraints, moreover, as well as our awake-primate imaging data, imply that human neuronal networks cannot support discrete updates of perceptual content at the maximal update rates consistent with phenomenology. A more comprehensive approach to understanding the physiology of perception (and experience at (...) large) is therefore called for, and we briefly outline our take on the problem. (shrink)

We show that TTOM has a lot to offer for the study of the evolution of cultures, but that this also brings to the fore the dark implications of TTOM, unexposed in Veissière et al. Those implications lead us to move beyond meme-centered or an organism-centered concept of fitness based on free-energy minimization, toward a social system-centered view.

Autism Spectrum Condition presents a challenge to social and relational accounts of the self, precisely because it is broadly seen as a disorder impacting social relationships. Many influential theories argue that social deficits and impairments of the self are the core problems in ASC. Predictive processing approaches address these based on general purpose neurocognitive mechanisms that are expressed atypically. Here we use the High, Inflexible Precision of Prediction Errors in Autism approach in the context of cultural niche construction to explain (...) atypicalities of the relational self, specifically its minimal, extended, and intersubjective aspects. We contend that the social self in ASC should not be seen as impaired, but rather as an outcome of atypical niche construction. We unpack the scientific, ethical, and practical consequences of this view, and discuss implications for how the challenges that autistic persons face should be approached. (shrink)

Autism Spectrum Condition presents a challenge to social and relational accounts of the self, precisely because it is broadly seen as a disorder impacting social relationships. Many influential theories argue that social deficits and impairments of the self are the core problems in ASC. Predictive processing approaches address these based on general purpose neurocognitive mechanisms that are expressed atypically. Here we use the High, Inflexible Precision of Prediction Errors in Autism approach in the context of cultural niche construction to explain (...) atypicalities of the relational self, specifically its minimal, extended, and intersubjective aspects. We contend that the social self in ASC should not be seen as impaired, but rather as an outcome of atypical niche construction. We unpack the scientific, ethical, and practical consequences of this view, and discuss implications for how the challenges that autistic persons face should be approached. (shrink)

In the last few years, a remarkable convergence of interests and results has emerged between scholars interested in the arts and aesthetics from a variety of perspectives and cognitive scientists studying the mind and brain within the predictive processing (PP) framework. This convergence has so far proven fruitful for both sides: while PP is increasingly adopted as a framework for understanding aesthetic phenomena, the arts and aesthetics, examined under the lens of PP, are starting to be seen as important windows (...) into our mental functioning. The result is a vast and fast-growing research programme that promises to deliver important insights into our aesthetic encounters as well as a wide range of psychological phenomena of general interest. Here, we present this developing research programme, describing its grounds and highlighting its prospects. We start by clarifying how the study of the arts and aesthetics encounters the PP picture of mental functioning (§1). We then go on to outline the prospects of this encounter for the fields involved: philosophy and history of art (§2), psychology of aesthetics and neuroaesthetics (§3) and psychology and neuroscience more generally (§4). The upshot is an ambitious but well-defined framework within which aesthetics and cognitive science can partner up to illuminate crucial aspects of the human mind. -/- This article is part of the theme issue ‘Art, aesthetics and predictive processing: theoretical and empirical perspectives’. -/- . (shrink)

Happiness is an increasingly prominent topic of interest across academia. However, relatively little attention has been paid to how it is created, especially not in a multidimensional sense. By ‘created’ we do not mean its influencing factors, for which there is extensive research, but how it actually forms in the person. The work that has been done in this arena tends to focus on physiological dynamics, which are certainly part of the puzzle. But they are not the whole picture, with (...) psychological, phenomenological, and socio cultural processes also playing their part. As a result, this paper offers a multidimensional overview of scholarship on the ‘architecture’ of happiness, providing a stimulus for further work into this important topic. (shrink)

ABSTRACTThe aim of this observational study is to explore how history teachers promote historical contextualisation in their lessons. Historical contextualisation is the ability to situate phenomen...

This exploratory study presents an example of how a historical contextualization framework can be used to develop and implement a lesson unit on Cold War events. The effects of the lesson unit on students’ ability to perform historical contextualization are explored in a quasi-experimental pre-test–post-test design with an experimental (n = 96) and a control (n = 73) condition. The students’ answers on a historical contextualization test were analysed. The results indicate that students in the experimental condition increased their ability (...) to perform historical contextualization and displayed less present-oriented perspectives in their answers compared to students in the control condition. (shrink)

Historische en systematische artikelen van Nederlandstalige filosofen over diverse aspecten van scepticisme, toen en nu, in filosofie, religie en wetenschap.

Coaching is a systematic and goal-oriented one-on-one intervention by a coach aimed to guide clients in their professional and personal development. Previous research on coaching has demonstrated effects on a number of positive outcomes, including well-being and performance, yet little is known about the processes that underlie these outcomes, such as the type of questions coaches use. Here, we focus on three different types of coaching questions, and aim to uncover their immediate and sustained effects for affect, self-efficacy, and goal-directed (...) outcomes, using a between-subjects experiment. One hundred and eighty-three medical residents and PhD students from various medical centers and healthcare organizations in the Netherlands were recruited to participate in a self-coaching writing exercise, where they followed written instructions rather than interacting with a real coach. All participants were randomly allocated to one of three conditions: either one of two solution-focused coaching conditions or a problem-focused coaching condition. Self-report questionnaires were used to measure key outcomes of coaching, that is positive and negative affect, self-efficacy, goal orientation, action planning and goal attainment. Two follow-up measurements assessed if the effects of the self-coaching exercise led to problem-solving actions within an initial follow-up period of 14 days and a subsequent follow-up period of 10 days. Findings showed that participants experienced more positive affect, less negative affect, and higher approach goal orientation after the solution-focused coaching exercise compared to the problem-focused coaching exercise. In all conditions, goal attainment increased as a consequence of the self-coaching intervention. We discuss the implications of our findings for the science and practice of contemporary coaching. (shrink)

Erasmus's Annotations on 1. Tim. to Apocalypse have been edited in a critical edition with commentary. Thus, the Latin texts are made accessible to readers interested in philological, theological and historical issues. Erasmus' Anmerkungen zu 1. Tim. bis einschliesslich der Apokalypse sind kritisch herausgegeben und mit Kommentar versehen. In dieser Weise ist der betreffende lateinische Text für philologisch, theologisch und historisch interessierte Leser zugänglich.

AimsThis preliminary study aimed to investigate therapy-induced electrophysiological changes in persons with primary progressive aphasia. The investigated event-related potential components associated with language processing were the mismatch negativity, P300, N400, and P600.MethodsA linguistic ERP test battery and standardized language assessment were administered in four patients with PPA of which two received speech-language therapy and two did not receive therapy. The battery was administered twice with approximately 6 months in between in each patient. The results of the follow-up assessments were compared (...) to the results of the initial assessments.ResultsAlthough the results of the behavioral language assessment remained relatively stable between the initial and follow-up assessments, changes in the mean amplitudes, onset latencies, and duration of the ERP components were found in the four patients. In the two patients that did not receive SLT, an increased delay in 50% and a decreased mean amplitude in 25% of the measured ERP components were found. The electrophysiological changes found in the patients that received SLT were variable. Interestingly, the mismatch negativity and the N400 effect elicited by the categorical priming paradigm were less delayed and had an increased mean amplitude at the follow-up assessment in the patient with the non-fluent variant who received SLT. In this patient, the P600 component was absent at the initial assessment but present at the follow-up assessment.ConclusionAlthough no clear patterns in electrophysiological changes between patients who received SLT and patients who did not receive SLT were found by our preliminary study, it seems like the SLT induced improvements or compensation mechanisms in some specific language comprehension processes in the patient with the NFV. The results of this study are still preliminary because only four heterogeneous patients were included. Future studies should include larger patient groups of the three clinical variants because the therapy-induced electrophysiological changes might differ depending on the clinical variant and the underlying pathology. (shrink)

Deze tekst vertrekt vanuit een van de meest invloedrijke denkers in de metafysica, namelijk Aristoteles. We lezen hem via de interpretatie van Giorgio Agamben in het artikel On potentiality. 4 Agamben werpt in die tekst een nieuw licht op het onderscheid tussen potentialiteit en act. De Westerse metafysica heeft vaak de act geprivilegieerd boven de potentialiteit. Enkel actuele entiteiten zouden bestaan, terwijl mogelijkheden behoren tot het domein van de verbeelding. Aristoteles ondermijnt deze stelling volgens Agamben. De mens als redelijk dier (...) is een potentieel wezen. De verwerkelijking van zijn essentie is het cultiveren van de rede als potentialiteit. In de mens zijn act en potentialiteit één. Daarom moeten wij begrijpen in welke zin potentialiteiten bestaan en hoe zij zich verhouden tot de act. Het antwoord vinden wij in de verwerkelijking van impotentialiteit, of het vermogen om dingen niet te doen. De mens kan niet enkel x doen, maar ook actief x niet-doen. Bijvoorbeeld in de vasten kan men van niet-eten een project maken. Agambens studie van impotentialiteit verduidelijkt daarmee wat de termen ‘act’ en ‘potentialiteit’ precies betekenen. Agamben stelt voor om elke actualisering te begrijpen als de opschorting van een impotentialiteit. De vaster die begint te eten, schort zijn project tot niet-eten op. Los van deze of gene actualisering is de wereld eerst de verzamelnaam voor alle mogelijke actualiseringen en die mogelijkheden zijn nooit uitgeput in eender welke actualisering van de wereld. De mens is dan het wezen dat, dankzij zijn impotentialiteit, inziet dat de wereld steeds meer is dan enkel wat het geval is. (shrink)

Erasmus's Annotations on 1. Tim. to Apocalypse have been edited in a critical edition with commentary. Thus, the Latin texts are made accessible to readers interested in philological, theological and historical issues. Erasmus' Anmerkungen zu 1. Tim. bis einschliesslich der Apokalypse sind kritisch herausgegeben und mit Kommentar versehen. In dieser Weise ist der betreffende lateinische Text für philologisch, theologisch und historisch interessierte Leser zugänglich.

Wij presenteren Berardi’s herwerking van de ideologiekritiek in drie stappen. Eerst schetsen wij de context waarin Berardi de ideologiekritiek herdenkt. Hij bouwt verder op de ontdekking van Deleuze en Guattari dat de taal van het kapitalisme niet de code, maar de axiomatiek is. De economische wetenschap biedt, volgens hen, mensen geen identiteit aan, maar bestaat uit een reeks commando’s die stromen van geld, arbeid, elektriciteit, enzovoort reguleert. Daaraan koppelt Berardi de observatie dat het hedendaagse kapitalisme vooral tekens verhandelt in plaats (...) van producten waarnaar zulke tekens zouden verwijzen. In een tweede stap brengen wij tegen deze opvatting in dat Berardi nog steeds vasthoudt aan de representatieve waarde van de economische wetenschap. Deze laatste zou enkel een afbeelding bieden van de realiteit en die vervalsen in het voordeel van het status quo. Sociologen uit de traditie van de actor-netwerktheorie (ANT) hebben dat echter betwist. Zij beweren dat de economische wetenschap de economische realiteit niet zozeer afbeeldt, maar actief vormgeeft. De economische wetenschap heeft de mens geschapen naar zijn evenbeeld: als homo oeconomicus. Het is dan ook een vergissing om de economische wetenschap te bekritiseren voor haar valse representaties. Zij maakt die immers waar. In een derde en laatste stap leggen wij in Berardi’s teksten een nieuw criterium bloot voor ideologiekritiek. In plaats van de economische wetenschap te bekritiseren voor haar valse uitspraken over de realiteit, moeten wij nagaan of de economische wetenschap een manier van leven promoot die mensen in staat zijn te onderhouden. De economische wetenschap is dan ideologisch als en slechts als zij een onhoudbare vorm van leven propageert. Volgens Berardi kan de hedendaagse economische wetenschap hiervan terecht beschuldigd worden. In zijn psychopathologie van het kapitalisme wijst hij immers op de negatieve psychische gevolgen van het hedendaagse kapitalisme, namelijk de instandhouding van een cyclus tussen paniek en depressie, een verlies aan betekenisvol menselijk contact en een neiging tot neurotisch vasthouden aan oude economische recepten die hun failliet reeds meermaals bewezen hebben. Niet de waarheid zal ons verlossen, maar in de verlossing ligt het ware leven. (shrink)

Alexander Maconochie, the originator of the “Mark System”, is a major figure in the history of penal discipline and is best known for his attempt to implement it at the Norfolk Island penal station from 1840 to 1844. Among Maconochie’s many works is the eight-page “Comparison Between Mr. Bentham’s Views on Punishment, and Those Advocated in Connexion with the Mark System”, in which Maconochie rejected Bentham’s critique of transportation, as well as fundamental elements of his theory of punishment. Maconochie concluded (...) that mainstream thinking on penal discipline was dominated by “mistakes” that either “in great measure originat[ed] with Mr. Bentham”, or had been “at least sanctioned by his high authority”.This paper questions whether Maconochie’s rejection of Bentham’s views is entirely convincing, since his penal practices, as well as an earlier and lesser-cited work, indicate that Maconochie was, at times, considerably closer to Bentham’s position on punishment than “Comparison” suggests. Section I will provide some brief biographical background. Section II will explore Maconochie’s attempt to implement his reformative system at Norfolk Island, at the heart of which was surveillance and extensive record-keeping to monitor individual behaviour and progress, and in which there are echoes of Bentham’s panopticon scheme. Section III will examine Maconochie’s changing views on criminal transportation, from his adherence to the Benthamite anti-transportation line in 1818, to his qualified support for transportation from 1838 onwards. Finally, Section IV will examine the Mark System and Maconochie’s criticism of Bentham in more detail. (shrink)

The aim of this paper is to study Williams's relativism of distance and to examine the conception of the history of ethics that follows from it. Relativism of distance, applied to the history of ethics, can be understood as saying that the language of appraisal is inappropriate in confrontations with ethical outlooks of the past; no real judgments are made. The author argues that this view does not follow from Williams's general meta-ethical position. Moreover, he tries to show that it (...) rests on an implicit but implausible view of the hermeneutics of history. More in particular, it rests on the premise that we should set aside our ethical convictions while studying the past. In the concluding section, an alternative view is explored with regard to the attitude that we should adopt towards the historical processes that have shaped our own ethical outlook. This analysis, purged of Williams's implausible view of the hermeneutics of history as it is, is actually more in line with his meta-ethics than his own relativism of distance. (shrink)

Amsterdam University Press is a leading publisher of academic books, journals and textbooks in the Humanities and Social Sciences. Our aim is to make current research available to scholars, students, innovators, and the general public. AUP stands for scholarly excellence, global presence, and engagement with the international academic community.

Hoe politieke macht veroveren en behouden? Het antwoord op deze vraag staat te lezen in een van de beruchtste boeken uit de geschiedenis van het politieke denken: Il Principe van Niccolo Machiavelli . Zijn antwoord is zonneklaar: voor élke heerser – of hij nu de troon heeft geërfd als telg van een oude dynastie of hem met geweld heeft veroverd – 'is het noodzakelijk het volk te vriend te houden'.

Organizations such as the EU High-Level Expert Group on AI and the IEEE have recently formulated ethical principles and (moral) values that should be adhered to in the design and deployment of artificial intelligence (AI). These include respect for autonomy, non-maleficence, fairness, transparency, explainability, and accountability. But how can we ensure and verify that an AI system actually respects these values? To help answer this question, I propose an account for determining when an AI system can be said to embody (...) certain values. This account understands embodied values as the result of design activities intended to embed those values in such systems. AI systems are here understood as a special kind of sociotechnical system that, like traditional sociotechnical systems, are composed of technical artifacts, human agents, and institutions but—in addition—contain artificial agents and certain technical norms that regulate interactions between artificial agents and other elements of the system. The specific challenges and opportunities of embedding values in AI systems are discussed, and some lessons for better embedding values in AI systems are drawn. (shrink)

How are we to appraise new technological developments that may bring revolutionary social changes? Currently this is often done by trying to predict or anticipate social consequences and to use these as a basis for moral and regulatory appraisal. Such an approach can, however, not deal with the uncertainties and unknowns that are inherent in social changes induced by technological development. An alternative approach is proposed that conceives of the introduction of new technologies into society as a social experiment. An (...) ethical framework for the acceptability of such experiments is developed based on the bioethical principles for experiments with human subjects: non-maleficence, beneficence, respect for autonomy, and justice. This provides a handle for the moral and regulatory assessment of new technologies and their impact on society. (shrink)

This paper examines why fundamental freedoms are so unevenly distributed across the earth. Climato-economic theorizing proposes that humans adapt needs, stresses, and choices of goals, means, and outcomes to the livability of their habitat. The evolutionary process at work is one of collectively meeting climatic demands of cold winters or hot summers by using monetary resources. Freedom is expected to be lowest in poor populations threatened by demanding thermal climates, intermediate in populations comforted by undemanding temperate climates irrespective of income (...) per head, and highest in rich populations challenged by demanding thermal climates. This core hypothesis is supported with new survey data across 85 countries and 15 Chinese provinces and with a reinterpretative review of results of prior studies comprising 174 countries and the 50 states in the United States. Empirical support covers freedom from want, freedom from fear, freedom of expression and participation, freedom from discrimination, and freedom to develop and realize one's human potential. Applying the theory to projections of temperature and income for 104 countries by 2112 forecasts that (a) poor populations in Asia, perhaps except Afghans and Pakistanis, will move up the international ladder of freedom, (b) poor populations in Africa will lose, rather than gain, relative levels of freedom unless climate protection and poverty reduction prevent this from happening, and (c) several rich populations will be challenged to defend current levels of freedom against worsening climato-economic livability. (shrink)

This work provides proof-search algorithms and automated counter-model extraction for a class of STIT logics. With this, we answer an open problem concerning syntactic decision procedures and cut-free calculi for STIT logics. A new class of cut-free complete labelled sequent calculi G3LdmL^m_n, for multi-agent STIT with at most n-many choices, is introduced. We refine the calculi G3LdmL^m_n through the use of propagation rules and demonstrate the admissibility of their structural rules, resulting in auxiliary calculi Ldm^m_nL. In the single-agent case, we (...) show that the refined calculi Ldm^m_nL derive theorems within a restricted class of (forestlike) sequents, allowing us to provide proof-search algorithms that decide single-agent STIT logics. We prove that the proof-search algorithms are correct and terminate. (shrink)

Forty-nine commentators have reviewed the theory that needs-based stresses and freedoms are shaped differently in threatening, comforting, and challenging climato-economic habitats. Their commentaries cover the white domain, where the theory does apply (e.g., happiness, collectivism, and democracy), the gray domain, where it may or may not apply (e.g., personality traits and creativity), and the black domain, where it does not apply (e.g., human intelligence and gendered culture). This response article provides clarifications, recommendations, and expectations.

Samenvatting van de grote wijsgerige systemen van Plato tot en met Hegel, gevolgd door een kritische analyse van de metafysica als uitingsvorm van westers intellectualisme.

We present cut-free labelled sequent calculi for a central formalism in logics of agency: STIT logics with temporal operators. These include sequent systems for Ldm , Tstit and Xstit. All calculi presented possess essential structural properties such as contraction- and cut-admissibility. The labelled calculi G3Ldm and G3Tstit are shown sound and complete relative to irreflexive temporal frames. Additionally, we extend current results by showing that also Xstit can be characterized through relational frames, omitting the use of BT+AC frames.

Value Sensitive Design (VSD) is an established method for integrating values into technical design. It has been applied to different technologies and, more recently, to artificial intelligence (AI). We argue that AI poses a number of challenges specific to VSD that require a somewhat modified VSD approach. Machine learning (ML), in particular, poses two challenges. First, humans may not understand how an AI system learns certain things. This requires paying attention to values such as transparency, explicability, and accountability. Second, ML (...) may lead to AI systems adapting in ways that ‘disembody’ the values embedded in them. To address this, we propose a threefold modified VSD approach: 1) integrating a known set of VSD principles (AI4SG) as design norms from which more specific design requirements can be derived; 2) distinguishing between values that are promoted and respected by the design to ensure outcomes that not only do no harm but also contribute to good; and 3) extending the VSD process to encompass the whole life cycle of an AI technology in order to monitor unintended value consequences and redesign as needed. We illustrate our VSD for AI approach with an example use case of a SARS-CoV-2 contact tracing app. (shrink)

There is a growing recognition that philosophy isn’t unique to the West, that it didn’t begin only with the classical Greeks, and that Greek philosophy was influenced by Near Eastern traditions. Yet even today there is a widespread assumption that what came before the Greeks was "before philosophy." In Philosophy before the Greeks, Marc Van De Mieroop, an acclaimed historian of the ancient Near East, presents a groundbreaking argument that, for three millennia before the Greeks, one Near Eastern people had (...) a rich and sophisticated tradition of philosophy fully worthy of the name. In the first century BC, the Greek historian Diodorus of Sicily praised the Babylonians for their devotion to philosophy. Showing the justice of Diodorus’s comment, this is the first book to argue that there were Babylonian philosophers and that they studied knowledge systematically using a coherent system of logic rooted in the practices of cuneiform script. Van De Mieroop uncovers Babylonian approaches to knowledge in three areas: the study of language, which in its analysis of the written word formed the basis of all logic; the art of divination, which interpreted communications between gods and humans; and the rules of law, which confirmed that royal justice was founded on truth. The result is an innovative intellectual history of the ancient Near Eastern world during the many centuries in which Babylonian philosophers inspired scholars throughout the region—until the first millennium BC, when the breakdown of this cosmopolitan system enabled others, including the Greeks, to develop alternative methods of philosophical reasoning. (shrink)

In "Off Track" art and philosophy are the inspiration to look differently at daily life and organizations. The book is a plea to approach the complexity of the current world with new metaphors. The author calls this "hinking around". She sees that in "square worlds" there is a need for tools to approach entrenched patterns and systems differently and to get thought processes moving. Sarai van de Boel challenges the reader to look at one's own systems from the inside with (...) a philosophical approach. In eight chapters there are eight "tracks" to follow, but it is also possible to go off the rails. More than fifty works of art by well-known and lesser-known artists and designers play a role in these traces. The author questions the essence of their works and asks philosophical questions about phenomena they evoke. With Marlene Dumas, Marinus Boezem, L.A. Raeven, Ed Atkins, Wong Ping, Kazumasa Nagai, Remy Jungerman, Otto Piene, Eiko Ishioka, Campana brothers, Ann Demeulemeester and Kara Walker. The book ends with the Art & Philosophy Strategy, a theoretical framework for the use of art and philosophy. (shrink)

— We prescnt here a comparative study on the decay of chlorophyll a fluorescence yield in thylakoid membranes and photosystem 11 ‐enriched samples, measured with multifrequency cross‐correlation phase fluorometry. These measurements confirm the general conclusions of Van Mieghem ef al., obtained with a flash method, on the effects of reduction of the primary quinone acceptor on ChI a fluorescence yield of PSI. Different states of the reaction centers of PSII were produced by: pretreatment with sodium dithionite and mcthyl viologen followed (...) by laser illumination: the doubly reduced QA centers: with laser illumination or pretreatment with diuron: QA‐ centers; and the addition of micromolar concentration of dichlorobenzoquinonc : oxidized QA centers. The data were analyzed with Lorentzian distribution as well as with multiexponential fluorescence decay functions. The analysis with Lorcntzian distribution function showed that upon formation of QA. the major lifetime distribution peak shifted to longer lifetimes: from 0.25 ns to 1.66 ns and from 0.24 ns to 1.31 ns. However, when QAHZ was formed, the lifetime distribution peaks shifted back to shorter lifetimes both in thylakoids and PSIl membranes. Multiexponential analysis showed three lifetime components: fast, middle and slow. When QA was formed in PS11 centers, the amplitude of the fast Component decreased, but both thc amplitude and the lifetime of the middle component increased severalfold. However, when QA was doubly reduccd, the amplitude of the fast component increased and the amplitude of the middle component decreased: in addition, the lifetime of the slow component increased. All of the above results are consistent with the conclusions that PS11 charge separation is decreased when QA is formed and increased when doubly reduced QA is formed. Copyright © 1993, Wiley Blackwell. All rights reserved. (shrink)