Reasoning about climate change

Why is disbelief in anthropogenic climate change common despite broad scientific consensus to the contrary? A widely held explanation involves politically motivated (system 2) reasoning: Rather than helping uncover the truth, people use their reasoning abilities to protect their partisan identities and reject beliefs that threaten those identities. Despite the popularity of this account, the evidence supporting it (i) does not account for the fact that partisanship is confounded with prior beliefs about the world and (ii) is entirely correlational with respect to the effect of reasoning. Here, we address these shortcomings by (i) measuring prior beliefs and (ii) experimentally manipulating participants' extent of reasoning using cognitive load and time pressure while they evaluate arguments for or against anthropogenic global warming. The results provide no support for the politically motivated system 2 reasoning account over other accounts: Engaging in more reasoning led people to have greater coherence between judgments and their prior beliefs about climate change-a process that can be consistent with rational (unbiased) Bayesian reasoning-and did not exacerbate the impact of partisanship once prior beliefs are accounted for.

Science beliefs, political ideology, and cognitive sophistication

Some theoretical models assume that a primary source of contention surrounding science belief is political and that partisan disagreement drives beliefs; other models focus on basic science knowledge and cognitive sophistication, arguing that they facilitate proscientific beliefs. To test these competing models, we identified a range of controversial issues subject to potential ideological disagreement and examined the roles of political ideology, science knowledge, and cognitive sophistication on science beliefs. Our results indicate that there was surprisingly little partisan disagreement on a wide range of contentious scientific issues. We also found weak evidence for identity-protective cognition (where cognitive sophistication exacerbates partisan disagreement); instead, cognitive sophistication (i.e., reasoning ability) was generally associated with proscience beliefs. In two studies focusing on anthropogenic climate change, we found that increased political motivations did not increase polarization among individuals who are higher in cognitive sophistication, which indicates that increased political motivations might not have as straightforward an impact on science beliefs as has been assumed in the literature. Finally, our findings indicate that basic science knowledge is the most consistent predictor of people's beliefs about science across a wide range of issues. These results suggest that educators and policymakers should focus on increasing basic science literacy and critical thinking rather than on the ideologies that purportedly divide people. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Emotion may predict susceptibility to fake news but emotion regulation does not seem to help

Misinformation is a serious concern for societies across the globe. To design effective interventions to combat the belief in and spread of misinformation, we must understand which psychological processes influence susceptibility to misinformation. This paper tests the widely assumed - but largely untested - claim that emotionally provocative headlines are associated with worse ability to identify true versus false headlines. Consistent with this proposal, we found correlational evidence that overall emotional response at the headline level is associated with diminished truth discernment, except for experienced anger which was associated with increased truth discernment. The second set of studies tested a popular emotion regulation intervention where people were asked to apply either emotional suppression or emotion reappraisal techniques when considering the veracity of several headlines. In contrast to the correlation results, we found no evidence that emotion regulation helped people distinguish false from true news headlines.

Polarized Citizen Preferences for the Ethical Allocation of Scarce Medical Resources in 20 Countries

Objective. When medical resources are scarce, clinicians must make difficult triage decisions. When these decisions affect public trust and morale, as was the case during the COVID-19 pandemic, experts will benefit from knowing which triage metrics have citizen support. Design. We conducted an online survey in 20 countries, comparing support for 5 common metrics (prognosis, age, quality of life, past and future contribution as a health care worker) to a benchmark consisting of support for 2 no-triage mechanisms (first-come-first-served and random allocation). Results. We surveyed nationally representative samples of 1000 citizens in each of Brazil, France, Japan, and the United States and also self-selected samples from 20 countries (total N = 7599) obtained through a citizen science website (the Moral Machine). We computed the support for each metric by comparing its usability to the usability of the 2 no-triage mechanisms. We further analyzed the polarizing nature of each metric by considering its usability among participants who had a preference for no triage. In all countries, preferences were polarized, with the 2 largest groups preferring either no triage or extensive triage using all metrics. Prognosis was the least controversial metric. There was little support for giving priority to healthcare workers. Conclusions. It will be difficult to define triage guidelines that elicit public trust and approval. Given the importance of prognosis in triage protocols, it is reassuring that it is the least controversial metric. Experts will need to prepare strong arguments for other metrics if they wish to preserve public trust and morale during health crises.

Beliefs About COVID-19 in Canada, the United Kingdom, and the United States: A Novel Test of Political Polarization and Motivated Reasoning

What are the psychological consequences of the increasingly politicized nature of the COVID-19 pandemic in the United States relative to similar Western countries? In a two-wave study completed early (March) and later (December) in the pandemic, we found that polarization was greater in the United States (N = 1,339) than in Canada (N = 644) and the United Kingdom. (N = 1,283). Political conservatism in the United States was strongly associated with engaging in weaker mitigation behaviors, lower COVID-19 risk perceptions, greater misperceptions, and stronger vaccination hesitancy. Although there was some evidence that cognitive sophistication was associated with increased polarization in the United States in December (but not March), cognitive sophistication was nonetheless consistently negatively correlated with misperceptions and vaccination hesitancy across time, countries, and party lines. Furthermore, COVID-19 skepticism in the United States was strongly correlated with distrust in liberal-leaning mainstream news outlets and trust in conservative-leaning news outlets, suggesting that polarization may be driven by differences in information environments.

Beliefs About COVID-19 in Canada, the United Kingdom, and the United States: A Novel Test of Political Polarization and Motivated Reasoning

What are the psychological consequences of the increasingly politicized nature of the COVID-19 pandemic in the United States relative to similar Western countries? In a two-wave study completed early (March) and later (December) in the pandemic, we found that polarization was greater in the United States (N = 1,339) than in Canada (N = 644) and the United Kingdom. (N = 1,283). Political conservatism in the United States was strongly associated with engaging in weaker mitigation behaviors, lower COVID-19 risk perceptions, greater misperceptions, and stronger vaccination hesitancy. Although there was some evidence that cognitive sophistication was associated with increased polarization in the United States in December (but not March), cognitive sophistication was nonetheless consistently negatively correlated with misperceptions and vaccination hesitancy across time, countries, and party lines. Furthermore, COVID-19 skepticism in the United States was strongly correlated with distrust in liberal-leaning mainstream news outlets and trust in conservative-leaning news outlets, suggesting that polarization may be driven by differences in information environments.

Beliefs About COVID-19 in Canada, the United Kingdom, and the United States: A Novel Test of Political Polarization and Motivated Reasoning

What are the psychological consequences of the increasingly politicized nature of the COVID-19 pandemic in the United States relative to similar Western countries? In a two-wave study completed early (March) and later (December) in the pandemic, we found that polarization was greater in the United States (N = 1,339) than in Canada (N = 644) and the United Kingdom. (N = 1,283). Political conservatism in the United States was strongly associated with engaging in weaker mitigation behaviors, lower COVID-19 risk perceptions, greater misperceptions, and stronger vaccination hesitancy. Although there was some evidence that cognitive sophistication was associated with increased polarization in the United States in December (but not March), cognitive sophistication was nonetheless consistently negatively correlated with misperceptions and vaccination hesitancy across time, countries, and party lines. Furthermore, COVID-19 skepticism in the United States was strongly correlated with distrust in liberal-leaning mainstream news outlets and trust in conservative-leaning news outlets, suggesting that polarization may be driven by differences in information environments.

Intuition rather than deliberation determines selfish and prosocial choices

Human interactions often involve a choice between acting selfishly (in ones' own interest) and acting prosocially (in the interest of others). Fast and slow models of prosociality posit that people intuitively favor 1 of these choices (the selfish choice in some models, the prosocial choice in other models) and need to correct this intuition through deliberation to make the other choice. We present 7 studies that force us to reconsider this longstanding corrective dual-process view. Participants played various economic games in which they had to choose between a prosocial and a selfish option. We used a 2-response paradigm in which participants had to give their first, initial response under time pressure and cognitive load. Next, participants could take all the time they wanted to reflect on the problem and give a final response. This allowed us to identify the intuitively generated response that preceded the final response given after deliberation. Results consistently showed that both prosocial and selfish responses were predominantly made intuitively rather than after deliberate correction. Pace the deliberate correction view, the findings indicate that making prosocial and selfish choices does typically not rely on different types of reasoning modes (intuition vs. deliberation) but rather on different types of intuitions. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Fake news, fast and slow: Deliberation reduces belief in false (but not true) news headlines

What role does deliberation play in susceptibility to political misinformation and "fake news"? The Motivated System 2 Reasoning (MS2R) account posits that deliberation causes people to fall for fake news, because reasoning facilitates identity-protective cognition and is therefore used to rationalize content that is consistent with one's political ideology. The classical account of reasoning instead posits that people ineffectively discern between true and false news headlines when they fail to deliberate (and instead rely on intuition). To distinguish between these competing accounts, we investigated the causal effect of reasoning on media truth discernment using a 2-response paradigm. Participants (N = 1,635 Mechanical Turkers) were presented with a series of headlines. For each, they were first asked to give an initial, intuitive response under time pressure and concurrent working memory load. They were then given an opportunity to rethink their response with no constraints, thereby permitting more deliberation. We also compared these responses to a (deliberative) 1-response baseline condition where participants made a single choice with no constraints. Consistent with the classical account, we found that deliberation corrected intuitive mistakes: Participants believed false headlines (but not true headlines) more in initial responses than in either final responses or the unconstrained 1-response baseline. In contrast-and inconsistent with the Motivated System 2 Reasoning account-we found that political polarization was equivalent across responses. Our data suggest that, in the context of fake news, deliberation facilitates accurate belief formation and not partisan bias. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Fake news, fast and slow: Deliberation reduces belief in false (but not true) news headlines

What role does deliberation play in susceptibility to political misinformation and "fake news"? The Motivated System 2 Reasoning (MS2R) account posits that deliberation causes people to fall for fake news, because reasoning facilitates identity-protective cognition and is therefore used to rationalize content that is consistent with one's political ideology. The classical account of reasoning instead posits that people ineffectively discern between true and false news headlines when they fail to deliberate (and instead rely on intuition). To distinguish between these competing accounts, we investigated the causal effect of reasoning on media truth discernment using a 2-response paradigm. Participants (N = 1,635 Mechanical Turkers) were presented with a series of headlines. For each, they were first asked to give an initial, intuitive response under time pressure and concurrent working memory load. They were then given an opportunity to rethink their response with no constraints, thereby permitting more deliberation. We also compared these responses to a (deliberative) 1-response baseline condition where participants made a single choice with no constraints. Consistent with the classical account, we found that deliberation corrected intuitive mistakes: Participants believed false headlines (but not true headlines) more in initial responses than in either final responses or the unconstrained 1-response baseline. In contrast-and inconsistent with the Motivated System 2 Reasoning account-we found that political polarization was equivalent across responses. Our data suggest that, in the context of fake news, deliberation facilitates accurate belief formation and not partisan bias. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Second-guess: Testing the specificity of error detection in the bat-and-ball problem

In the last decade conflict detection studies in the reasoning and decision-making field have suggested that biased reasoners who give an intuitive response that conflicts with logico-mathematical principles can often detect that their answer is questionable. In the present studies we introduced a second guess paradigm to test the nature and specificity of this error or conflict signal. Participants solved the bat-and-ball problem and were allowed to make a second guess after they had entered their answer. Three studies in which we used a range of second guess elicitation methods show that biased reasoners predominantly give second guesses that are smaller than the intuitively cued heuristic response ("10 cents"). Findings indicate that although biased reasoners do not know the exact correct answer ("5 cents") they do correctly grasp that the right answer must be smaller than the intuitively cued "10 cents" answer. This suggests that reasoners might be savvier about their errors than traditionally assumed. Implications for the conflict detection and dual process literature are discussed.

Exploring the determinants of confidence in the bat-and-ball problem

People often fail to solve deceptively simple mathematical problems, a tendency popularly demonstrated by the bat-and-ball problem. The most prominent explanation of this finding is that, to spare cognitive effort, people substitute the difficult task with an easier one, without being aware of the substitution. Despite this latter assumption, recent studies have found decreased levels of post-decision confidence ratings when people gave the answer of an easier calculation, suggesting that people are sensitive to their errors. In the current study, we investigated a mechanism that might be responsible for such a decrease in people's confidence ratings when they make errors: their attempts to make certain that their answer is correct (verification) and the perceived level of task difficulty (verifiability). We found that these two factors predicted people's confidence, suggesting that people's self-assessment of the perceived task difficulty and of their attempt to verify their response might determine their confidence. Implication for current models of post-decision confidence on reasoning problems is discussed.

Measuring Individual Differences in Decision Biases: Methodological Considerations

Individual differences in people's susceptibility to heuristics and biases (HB) are often measured by multiple-bias questionnaires consisting of one or a few items for each bias. This research approach relies on the assumptions that (1) different versions of a decision bias task measure are interchangeable as they measure the same cognitive failure; and (2) that some combination of these tasks measures the same underlying construct. Based on these assumptions, in Study 1 we developed two versions of a new decision bias survey for which we modified 13 HB tasks to increase their comparability, construct validity, and the participants' motivation. The analysis of the responses (N = 1279) showed weak internal consistency within the surveys and a great level of discrepancy between the extracted patterns of the underlying factors. To explore these inconsistencies, in Study 2 we used three original examples of HB tasks for each of seven biases. We created three decision bias surveys by allocating one version of each HB task to each survey. The participants' responses (N = 527) showed a similar pattern as in Study 1, questioning the assumption that the different examples of the HB tasks are interchangeable and that they measure the same underlying construct. These results emphasize the need to understand the domain-specificity of cognitive biases as well as the effect of the wording of the cover story and the response mode on bias susceptibility before employing them in multiple-bias questionnaires.

Is it time for studying real-life debiasing? Evaluation of the effectiveness of an analogical intervention technique

The aim of this study was to initiate the exploration of debiasing methods applicable in real-life settings for achieving lasting improvement in decision making competence regarding multiple decision biases. Here, we tested the potentials of the analogical encoding method for decision debiasing. The advantage of this method is that it can foster the transfer from learning abstract principles to improving behavioral performance. For the purpose of the study, we devised an analogical debiasing technique for 10 biases (covariation detection, insensitivity to sample size, base rate neglect, regression to the mean, outcome bias, sunk cost fallacy, framing effect, anchoring bias, overconfidence bias, planning fallacy) and assessed the susceptibility of the participants (N = 154) to these biases before and 4 weeks after the training. We also compared the effect of the analogical training to the effect of ‘awareness training’ and a ‘no-training’ control group. Results suggested improved performance of the analogical training group only on tasks where the violations of statistical principles are measured. The interpretation of these findings require further investigation, yet it is possible that analogical training may be the most effective in the case of learning abstract concepts, such as statistical principles, which are otherwise difficult to master. The study encourages a systematic research of debiasing trainings and the development of intervention assessment methods to measure the endurance of behavior change in decision debiasing.

An empirical analysis of the methodology of automatic imitation research in a strategic context

Since the discovery of the mirror neuron system, it has been proposed that the automatic tendency to copy observed actions exists in humans and that this mechanism might be responsible for a range of social behavior. A strong argument for automatic behavior can be made when actions are executed against motivation to do otherwise. Strategic games in which imitation is disadvantageous serve as ideal designs for studying the automatic nature of participants' behavior. Most recently, Belot, Crawford, and Heyes (2013) conducted an explorative study using a modified version of the Rock-Paper-Scissors game, and suggested that in the case of asynchrony in the execution of the gestures, automatic imitation can be observed early on after the opponent's presentation. In our study, we video recorded the games, which allowed us to examine the effect of delay on imitative behavior as well as the sensitivity of the previously employed analyses. The examination of the recorded images revealed that more than 80% of the data were irrelevant to the study of automatic behavior. Additional bias in the paradigm became apparent, as previously presented gestures were found to affect the behavior of the players. After noise filtering, we found no evidence of automatic imitation in either the whole filtered data set or in selected time windows based on delay length. Besides questioning the strength of the results of previous analyses, we propose several experimental and statistical modifications for further research on automatic imitation.

Is there evidence for automatic imitation in a strategic context?

Over the past decade, a compelling number of studies reported that observing an action makes the imitation of that action more likely. The automatic character of human imitative behaviour was often claimed, but rarely tested. The demonstration of the absence of conscious control has been attempted in a recent report claiming that imitation can occur in the rock-paper-scissors (RPS) game, where strategic players should avoid imitating their opponents. This surprising result could serve as strong evidence that humans imitate each other unconsciously. We find, however, that this conclusion is problematic. In addition to reviewing the original methods, in this work, we also replicated the experiment with double the sample size. Thorough examination of the original analyses and the results of the present replication do not support the original conclusion. In our view, testing the theory of automatic imitation in RPS games is a potentially promising avenue of exploration, yet the interpretation of the data requires further understanding of the subsidiary effects controlling the behaviour of the players.

The glyoxylate cycle in an arbuscular mycorrhizal fungus. Carbon flux and gene expression

The arbuscular mycorrhizal (AM) symbiosis is responsible for huge fluxes of photosynthetically fixed carbon from plants to the soil. Lipid, which is the dominant form of stored carbon in the fungal partner and which fuels spore germination, is made by the fungus within the root and is exported to the extraradical mycelium. We tested the hypothesis that the glyoxylate cycle is central to the flow of carbon in the AM symbiosis. The results of (13)C labeling of germinating spores and extraradical mycelium with (13)C(2)-acetate and (13)C(2)-glycerol and analysis by nuclear magnetic resonance spectroscopy indicate that there are very substantial fluxes through the glyoxylate cycle in the fungal partner. Full-length sequences obtained by polymerase chain reaction from a cDNA library from germinating spores of the AM fungus Glomus intraradices showed strong homology to gene sequences for isocitrate lyase and malate synthase from plants and other fungal species. Quantitative real-time polymerase chain reaction measurements show that these genes are expressed at significant levels during the symbiosis. Glyoxysome-like bodies were observed by electron microscopy in fungal structures where the glyoxylate cycle is expected to be active, which is consistent with the presence in both enzyme sequences of motifs associated with glyoxysomal targeting. We also identified among several hundred expressed sequence tags several enzymes of primary metabolism whose expression during spore germination is consistent with previous labeling studies and with fluxes into and out of the glyoxylate cycle.

The glyoxylate cycle in an arbuscular mycorrhizal fungus. Carbon flux and gene expression

The arbuscular mycorrhizal (AM) symbiosis is responsible for huge fluxes of photosynthetically fixed carbon from plants to the soil. Lipid, which is the dominant form of stored carbon in the fungal partner and which fuels spore germination, is made by the fungus within the root and is exported to the extraradical mycelium. We tested the hypothesis that the glyoxylate cycle is central to the flow of carbon in the AM symbiosis. The results of (13)C labeling of germinating spores and extraradical mycelium with (13)C(2)-acetate and (13)C(2)-glycerol and analysis by nuclear magnetic resonance spectroscopy indicate that there are very substantial fluxes through the glyoxylate cycle in the fungal partner. Full-length sequences obtained by polymerase chain reaction from a cDNA library from germinating spores of the AM fungus Glomus intraradices showed strong homology to gene sequences for isocitrate lyase and malate synthase from plants and other fungal species. Quantitative real-time polymerase chain reaction measurements show that these genes are expressed at significant levels during the symbiosis. Glyoxysome-like bodies were observed by electron microscopy in fungal structures where the glyoxylate cycle is expected to be active, which is consistent with the presence in both enzyme sequences of motifs associated with glyoxysomal targeting. We also identified among several hundred expressed sequence tags several enzymes of primary metabolism whose expression during spore germination is consistent with previous labeling studies and with fluxes into and out of the glyoxylate cycle.

Carbon metabolism in spores of the arbuscular mycorrhizal fungus Glomus intraradices as revealed by nuclear magnetic resonance spectroscopy

Arbuscular mycorrhizal (AM) fungi are obligate symbionts that colonize the roots of over 80% of plants in all terrestrial environments. Understanding why AM fungi do not complete their life cycle under free-living conditions has significant implications for the management of one of the world's most important symbioses. We used (13)C-labeled substrates and nuclear magnetic resonance spectroscopy to study carbon fluxes during spore germination and the metabolic pathways by which these fluxes occur in the AM fungus Glomus intraradices. Our results indicate that during asymbiotic growth: (a) sugars are made from stored lipids; (b) trehalose (but not lipid) is synthesized as well as degraded; (c) glucose and fructose, but not mannitol, can be taken up and utilized; (d) dark fixation of CO(2) is substantial; and (e) arginine and other amino acids are synthesized. The labeling patterns are consistent with significant carbon fluxes through gluconeogenesis, the glyoxylate cycle, the tricarboxylic acid cycle, glycolysis, non-photosynthetic one-carbon metabolism, the pentose phosphate pathway, and most or all of the urea cycle. We also report the presence of an unidentified betaine-like compound. Carbon metabolism during asymbiotic growth has features in between those presented by intraradical and extraradical hyphae in the symbiotic state.

Nuclei of symbiotic arbuscular mycorrhizal fungi as revealed by in vivo two-photon microscopy

The present work reports the results obtained from in vivo studies on the distribution and behavior of nuclei of two arbuscular mycorrhizal (AM) fungi growing in symbiosis with tomato root organ cultures (AM monoxenic cultures). Upon staining with 4',6-diamidino-2-phenylindole and two-photon microscopy (2PM) observations, symbiotic thick runner hyphae appeared mostly opaque to 2PM and did not reveal nuclei within them; thin runner hyphae showed dimly stained nuclei along them, whereas nuclei were clearly visible within the branches of the so-called branched absorbing structures. When visible, nuclei appeared anchored laterally at regular intervals along the symbiotic AM extraradical hyphae. Other nuclei migrate through the hyphal central core; this migration occurs in pulses. Simultaneous observations on different areas of extraradical AM mycelium revealed the existence of lysed compartments along the fungal hyphae, containing nuclei remnants and/or chromatin masses. All these results give new insights in (i) the differential permeability of AM hyphae in the symbiotic versus the asymbiotic state; (ii) the behavior and distribution of nuclei along the symbiotic extraradical mycelium; (iii) the occurrence of ageing events within the AM fungal colony; and (iv) the existence of "healing" mechanisms aiming to restrict the damage induced by such ageing or lytic events. An AM fungal strategy for hyphal survival under adverse conditions is also suggested.

Flavonoids and arbuscular-mycorrhizal fungi

Arbuscular mycorrhizal fungi (AMF) are ancient Zygomycetes forming the most widespread plant-fungus symbiosis. The regulation of this association is still poorly understood in terms of the communication between the two partners. Compounds inside the root and released by the root, such as flavonoids, are hypothesized to play a role in this plant-fungus communication, as already demonstrated in other symbiotic associations (e.g. Rhizobium-leguminoseae). Here we give a general overview of the research concerning this question.

Nitrate depletion and pH changes induced by the extraradical mycelium of the arbuscular mycorrhizal fungus Glomus intraradices grown in monoxenic culture

The effect of the extraradical mycelium of the arbuscular mycorrhizal (AM) fungus Glomus intraradices Smith & Schenck on nitrate uptake and on the pH of the medium was studied in a monoxenic culture with tomato (Lycopersicon esculentum Mill. var. Vendor) roots obtained from root organ culture. The symbiosis was established in compartmented Petri dishes containing agar media amended with the pH indicator bromocresol purple. A pattern of pH changes was revealed as the symbiosis progressed in the media of the Petri dish compartments containing the dual, arbuscular-mycorrhizal fungi/root, culture as well as in the media of the hyphae, root-free compartments, in which the extraradical hyphae developed extensively, coming from the compartment containing the symbiosis. The colour changes in the media were measured spectrophotometrically, whilst maintaining the monoxenic conditions. The extraradical hyphae of G. intraradices strongly increased the pH of nutrient-free medium when supplied with nitrate, whereas the pH decreased m the absence of this N source. The hyphae developing from germinated spores and growing in axenic, nitrate-amended media did not induce any increase in pH. Nitrogen analysis revealed that a depletion of nitrate in the media accompanied increased pH. These results point towards an active uptake of nitrate by the extraradical mycelium of G. intraradices, probably coupled to a H⁺ -symport mechanism. The pH changes induced by AM fungal hyphae and the possible influence of the establishment of a functional symbiosis on these pH changes are discussed.

Nitrate depletion and pH changes induced by the extraradical mycelium of the arbuscular mycorrhizal fungus Glomus intraradices grown in monoxenic culture

The effect of the extraradical mycelium of the arbuscular mycorrhizal (AM) fungus Glomus intraradices Smith & Schenck on nitrate uptake and on the pH of the medium was studied in a monoxenic culture with tomato (Lycopersicon esculentum Mill. var. Vendor) roots obtained from root organ culture. The symbiosis was established in compartmented Petri dishes containing agar media amended with the pH indicator bromocresol purple. A pattern of pH changes was revealed as the symbiosis progressed in the media of the Petri dish compartments containing the dual, arbuscular-mycorrhizal fungi/root, culture as well as in the media of the hyphae, root-free compartments, in which the extraradical hyphae developed extensively, coming from the compartment containing the symbiosis. The colour changes in the media were measured spectrophotometrically, whilst maintaining the monoxenic conditions. The extraradical hyphae of G. intraradices strongly increased the pH of nutrient-free medium when supplied with nitrate, whereas the pH decreased m the absence of this N source. The hyphae developing from germinated spores and growing in axenic, nitrate-amended media did not induce any increase in pH. Nitrogen analysis revealed that a depletion of nitrate in the media accompanied increased pH. These results point towards an active uptake of nitrate by the extraradical mycelium of G. intraradices, probably coupled to a H⁺ -symport mechanism. The pH changes induced by AM fungal hyphae and the possible influence of the establishment of a functional symbiosis on these pH changes are discussed.

Intelligent medical instruments

The authors introduce system design methods that can contribute to the resolution of the rather complex requirements in the field of medical instrumentation, drawing on their own experiences in the development of intelligence EEG recorders and analyzers. They focus on the integration of the knowledge base with the numerical database and the algorithms within the unified real-time control structure of the measuring system. Possible alternatives are presented for the implementation of both conventional data processing and knowledge-based data processing. The authors discuss the problem-oriented user interface and conclude with a short presentation of an intelligent EEG recorder development.