Higher USA State Resident Neuroticism Is Associated With Lower State Volunteering Rates

Higher USA State Resident Neuroticism Is Associated With Lower State Volunteering Rates. Stewart McCann. Personality and Social Psychology Bulletin, https://doi.org/10.1177/0146167217724802

Abstract: Highly neurotic persons have dispositional characteristics that tend to precipitate social anxiety that discourages formal volunteering. With the 50 American states as analytical units, Study 1 found that state resident neuroticism correlated highly (r = -.55) with state volunteering rates and accounted for another 26.8% of the volunteering rate variance with selected state demographics controlled. Study 2 replicated Study 1 during another period and extended the association to college student, senior, secular, and religious volunteering rates. Study 3 showed state resident percentages engaged in other social behaviors involving more familiarity and fewer demands than formal volunteering related to state volunteering rates but not to neuroticism. In Study 4, state resident neuroticism largely accounted statistically for relations between state volunteering rates and state population density, collectivism, social capital, Republican preference, and well-being. This research is the first to show that state resident neuroticism is a potent predictor of state volunteering rates.

Outrage-inducing content appears to be more prevalent and potent online than offline

Moral outrage in the digital age. M. J. Crockett. Nature Human Behaviour (2017). doi:10.1038/s41562-017-0213-3

Moral outrage is a powerful  emotion that motivates people to shame and punish wrongdoers. Moralistic punishment can be a force for good, increasing cooperation by holding bad actors accountable. But punishment also has a dark side — it can exacerbate social conflict by dehumanizing others  and escalating into destructive feuds.

Moral outrage is at least as old as civilization itself, but civilization is rapidly changing in the face of new technologies. Worldwide, more than a billion people now spend at least an hour a day on social media, and moral outrage is all the rage online. In recent years, viral online shaming has cost
companies millions, candidates elections, and individuals their careers overnight.

As digital media infiltrates our social lives, it is crucial that we understand how this technology might transform the expression of moral outrage and its social consequences. Here, I describe a simple psychological framework for tackling this question (Fig. 1). Moral outrage is triggered by stimuli that call attention to moral norm violations. These stimuli evoke a range of emotional and behavioural responses that vary in their costs and constraints. Finally, expressing outrage leads to a variety of personal and social outcomes. This framework reveals that digital media may exacerbate the expression of moral outrage by inflating its triggering stimuli, reducing some of its costs and amplifying many of its personal benefits.

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If moral outrage is a fire, is the internet like gasoline? Technology companies have argued that their products provide neutral platforms for social behaviours but do not change those behaviours. This is an empirical question that behavioural scientists should address, because its answer has ethical and regulatory implications.

The framework proposed here offers a set of testable hypotheses about the impact of digital media on the expression of moral outrage and its social consequences. Digital media may promote the expression of moral outrage by magnifying its triggers, reducing its personal costs and amplifying its personal benefits. At the same time, online social networks may diminish the social benefits of outrage by reducing the likelihood that norm-enforcing messages reach their targets, and could even impose new social costs by increasing polarization.

Preliminary data support the framework’s predictions, showing that outrage-inducing content appears to be more prevalent and potent online than offline. Future studies should investigate the extent to which digital media platforms intensify moral emotions, promote habit formation, suppress productive social discourse, and change the nature of moral outrage itself. There are vast troves of data that are directly pertinent to these questions, but not all of it is publicly available. These data can and should be used to understand how new technologies might transform ancient social emotions from a force for collective good into a tool for collective self-destruction.

Cognitive Resources in the Service of Identity Expression

An Expressive Utility Account of Partisan Cue Receptivity: Cognitive Resources in the Service of Identity Expression. Yphtach Lelkes, Ariel Malka, and Bert N. Bakker. https://www.dropbox.com/s/gbw56kdk8d0aoa1/expressivecues.pdf

Abstract: What motivates citizens to rely on partisan cues when forming political judgments? Extant literature offers two perspectives on this matter: an optimistic view that reliance on cues serves to enable adequate decision making when cognitive resources are low, and a pessimistic view that reliance on cues serves to channel cognitive resources to the goal of expressing valued political identities. In the present research we seek to further understanding of the relative importance of these two motives. We find that individuals low in cognitive resources are not more likely to follow partisan cues than are individuals high in cognitive resources. Furthermore, we find the highest level of cue receptivity is observed for those individuals who have both a strong social identification with their party and high cognitive resources. This suggests that partisan cue receptivity more often involves a harnessing of cognitive resources for the goal of identity expression.

Keywords: Partisan Cues, Social Identity, Cognitive Reflection, Motivated Reasoning

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This work complements and extends two recent projects on the role of reflection on political reasoning. First, Arceneaux and Vander Wielen (2017) argue that those who are the least likely to be affectively attached to issues or parties and the most likely to be reflective exhibit behavior most akin to democratic ideals. In particular, these low affect/high reflection citizens are less likely to conform to elite cues than those who are high in affect and low in reflection. This is because these citizens combine relative weak emotional attachments to party-consistent issue positions with a relatively strong tendency to engage in effortful reasoning that could override emotional intuitions. As our strength of party identity measures affective attachment to a party (Huddy et al., 2015), the present work investigates the effect of high affect/high reflection on political reasoning, and our results are in line with Arceneaux and Vander Wielen (2017) untested predictions which they suggest for future research. Specifically, strong cognitive resources combined with an emotional attachment to partisanship seems to lead to toeing the party line. Second, Groenendyk (2013) argues that cognitive resources are required to defend one’s partisan identity–one reason partisan identities may remain stable among those high in cognitive resources is because they are able to rationalize changing attitude structures. The present findings reinforce that perspective as well.

How the Presence of Others Affects Desirability Judgments in Heterosexual and Homosexual Participants

Scofield, John E, Bogdan Kostic, and Erin M Buchanan. 2017. “How the Presence of Others Affects Desirability Judgments in Heterosexual and Homosexual Participants”. Open Science Framework. September 17. www.osf.io/ej5kh.

Abstract: Mate-choice copying is a mating strategy wherein females rely on contextual information to assist in securing accurate assessments of potential mates. Mate-choice copying has been extensively studied in non-human species and has begun to be examined in humans as well. Hill and Buss (2008) found evidence of opposing effects for men and women in desirability judgments based on the presence of other opposite-sex people. The current project successfully replicated Hill and Buss (2008), Experiment 1, finding support for the desirability enhancement effect and the desirability diminution effect. The current project also extended Hill and Buss, Experiment 1, to include homosexual participants. Homosexual men showed similar patterns as heterosexual women, and homosexual women showed similar patterns as heterosexual men, revealing differences across sexual orientation in human mate-choice copying.

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The purpose of the current project was to replicate Hill and Buss (2008), Experiment 1 and to extend their findings to include homosexual populations. Hill and Buss found opposing sex differences while investigating the presence of others on judgments of desirability. Hill and Buss found evidence for the desirability enhancement effect, in which females rated male targets surrounded by females as more desirable compared to those same males surrounded by other males. Desirability judgments had the opposite effect on male participants, known as the desirability diminution effect. Male participants rated target females as less desirable when surrounded by males, compared to when those same females were surrounded by other females.

Females were suggested to employ mate-choice copying mating tactics, such as social information provided in stimulus photographs when making mate assessments. In evolutionary theory, females may take into consideration the presence of other females, providing cues to the mate quality of males. Specifically, with females surrounding males, the mate quality of the male is assumed to be higher. Men were shown not to use typical mate-choice copying mating tactics. Males rated female targets surrounded by males as less desirable than when surrounded by other females or when alone. Males were suggested to assess potential mates with a probabilistic orientation, suggesting that the presence of other males in the scene hint at a decreased probability of gaining access to that mate, negatively influencing desirability judgments of that target female.

[...]

Results showed that homosexual male participants rated target males surrounded by females as more desirable compared to male targets surrounded by other males. Homosexual female participants, however, showed the opposite effect in that they rated target females less desirable when surrounded by males compared to when surrounded by females. This result is contrary to our predictions that heterosexual and homosexual judgments would both follow similar patterns, dictated per biological sex (regardless of sexual orientation). That is, homosexual and heterosexual men would both exhibit the desirability diminution effect, and both homosexual and heterosexual women would exhibit the desirability enhancement effect.

Liberals and Conservatives Are Similarly Motivated to Deny Attitude-Inconsistent Science

Science Denial Across the Political Divide -- Liberals and Conservatives Are Similarly Motivated to Deny Attitude-Inconsistent Science. Anthony N. Washburn, Linda J. Skitka. Social Psychological and Personality Science, 10.1177/1948550617731500

Abstract: We tested whether conservatives and liberals are similarly or differentially likely to deny scientific claims that conflict with their preferred conclusions. Participants were randomly assigned to read about a study with correct results that were either consistent or inconsistent with their attitude about one of several issues (e.g., carbon emissions). Participants were asked to interpret numerical results and decide what the study concluded. After being informed of the correct interpretation, participants rated how much they agreed with, found knowledgeable, and trusted the researchers’ correct interpretation. Both liberals and conservatives engaged in motivated interpretation of study results and denied the correct interpretation of those results when that interpretation conflicted with their attitudes. Our study suggests that the same motivational processes underlie differences in the political priorities of those on the left and the right.

Check also: Kahan, Dan M. and Peters, Ellen, Rumors of the 'Nonreplication' of the 'Motivated Numeracy Effect' are Greatly Exaggerated (August 26, 2017). Available at SSRN: https://ssrn.com/abstract=3026941

And: Biased Policy Professionals. Sheheryar Banuri, Stefan Dercon, and Varun Gauri. World Bank Policy Research Working Paper 8113. https://t.co/Jga1EUEkbF.

And: Dispelling the Myth: Training in Education or Neuroscience Decreases but Does Not Eliminate Beliefs in Neuromyths. Kelly Macdonald et al. Frontiers in Psychology, Aug 10 2017. https://doi.org/10.3389/fpsyg.2017.01314

And: Wisdom and how to cultivate it: Review of emerging evidence for a constructivist model of wise thinking. Igor Grossmann. European Psychologist, in press. Pre-print: https://osf.io/preprints/psyarxiv/qkm6v/

Liberals Possess More National Consensus on Political Attitudes in the US

Liberals Possess More National Consensus on Political Attitudes in the United States -- An Examination Across 40 Years. Peter Ondish, Chadly Stern. Social Psychological and Personality Science, https://doi.org/10.1177/1948550617729410

Abstract: Do liberals or conservatives have more agreement in their political attitudes? Recent research indicates that conservatives may have more like-minded social groups than do liberals, but whether conservatives have more consensus on a broad, national level remains an open question. Using two nationally representative data sets (the General Social Survey and the American National Election Studies), we examined the attitudes of over 80,000 people on more than 400 political issues (e.g., attitudes toward welfare, gun control, same-sex marriage) across approximately 40 years. In both data sets, we found that liberals possessed a larger degree of agreement in their political attitudes than did conservatives. Additionally, both liberals and conservatives possessed more consensus than did political moderates. These results indicate that social–cognitive motivations for building similarity and consensus within one’s self-created social groups may also yield less consensus on a broad, national level. We discuss implications for effective political mobilization and social change.

“All my life I have been told that capitalism, particularly the American type, was bad,” Mr. Gujanicic, 63, said

As China Moves In, Serbia Reaps Benefits, With Strings Attached. By BARBARA SURK. The New York Times, Sep 09, 2017, https://www.nytimes.com/2017/09/09/world/europe/china-serbia-european-union.html

"
Mileta Gujanicic, a steelworker and union leader, is one of those who hope China fulfills its vision for the Smederevo mill: He has worked there for 40 years and says he got used to the ways of the Americans, whom he called “the aristocracy of the industrial world.”

“All my life I have been told that capitalism, particularly the American type, was bad,” Mr. Gujanicic, 63, said. “But we workers have been valued, well paid and respected when the Americans ran this place.”

The Chinese approach to running the mill, he said, is sharply different. So far, the new owners have maintained their pledge to retain jobs. But none of the promises Mr. Xi made during his visit have been kept.

Workers’ contracts are veiled in secrecy, safety standards have fallen, maintenance is at the bare minimum, and contact between the owners and the employees does not exist, he said. The erosion of workers’ rights and the employers’ disregard of labor laws are troubling, he said.
"

My comment: Mr Gujanicic, 63, was a Communist some time, but changed his opinion. What do you think, that he is being (more or less) objective, or that he has idealized his American bosses?

Research: The readability of scientific texts is decreasing over time

Research: The readability of scientific texts is decreasing over time. Pontus Plavén-Sigray et al. eLife 2017;6:e27725. https://elifesciences.org/articles/27725

Abstract: Clarity and accuracy of reporting are fundamental to the scientific process. Readability formulas can estimate how difficult a text is to read. Here, in a corpus consisting of 709,577 abstracts published between 1881 and 2015 from 123 scientific journals, we show that the readability of science is steadily decreasing. Our analyses show that this trend is indicative of a growing use of general scientific jargon. These results are concerning for scientists and for the wider public, as they impact both the reproducibility and accessibility of research findings.

My comment: Why is this so? Is there a part of snob behavior? A way to separate oneself from the great unwashed?

Local mating markets in humans and non-human animals

Local mating markets in humans and non-human animals. Ronald Noë. Behavioral Ecology and Sociobiology, October 2017, 71:148. https://doi.org/10.1007/s00265-017-2376-3

Abstract: In biology, the term ‘mating market’ has been fashionable for a few decades only, but sexual selection theory was implicitly based on economic principles from the start. I regard mating individuals explicitly as traders on markets and distinguish ‘global mating markets’, consisting of all reproducing members of a population, from ‘local mating markets’ (LMMs) that are disconnected in space and/or time. I focus on ways in which individuals make the best of variation among LMMs by adapting their mating strategy to each local market they enter. The ‘operational sex ratio’ (OSR; Emlen ST, Oring LW (1977) Science 197:215–223) gives a first approximation of the balance of power between the two trader classes: males and females ready to reproduce. The parameter I use is the local OSR (LOSR), the OSR of a single LMM. The balance of power is dependent not only on the LOSR, however, but also on the production costs and exchange values of ‘crucial commodities’, which often vary locally and over time. Distinguishing LMMs is most useful for species with strong variation in the LOSR. Human mating markets distorted by war, selective abortion and sex-biased migration are among the best-documented local markets with aberrant OSRs. Traders on LMMs may strategically adjust to supply and demand ratios and changes in their own market value but also attempt to change local market conditions or transfer to another local market with better conditions. Fine-tuning can result not only from conditional strategies, evolved under natural and sexual selection, but also from learning processes as far as species-specific cognitive constraints allow.

Significance statement: Biological market theory (BMT), which deals with cooperation among unrelated agents in general, is combined with sexual selection theory (SST), which deals with reproductive cooperation, to focus on an aspect that received little attention in the vast SST literature: adaptations that improve mating success when the market value of an individual varies considerably from one local mating market (LMM) to the next. An individual’s market value on an LMM is determined not only by the local operational sex ratio (LOSR) but also by the value of the goods and services that both sexes invest in their mates and/or the communal offspring. Case studies of both humans and non-human animals are used to illustrate the difference between global and local markets and to evaluate predictions based on the LMM-hypothesis.

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Prediction 2: sensitivity to one’s own market value and adjustment to changes in market value of self and others

...Broadly speaking, individual changes inmarket value can be due to changes relative to local competitors, changes in the LOSR, or changes in the production costs of commodities. As the consequences of the latter are hard to predict, I will concentrate on the other two factors, the first of which is notably well documented in humans. ***A universal, frequently reported human pattern is that men are attracted by youth in women and women are attracted by men that can offer resources***... During their exceptionally long mating career, men can gradually gain in value with age by slowly accumulating wealth or a steady rise in salary. Their market value can also increase abruptly, for example by high gains in the lottery, or a sudden ascent to a powerful position. ***After reaching maximal fertility in their early twenties (Hawkes and Smith 2010), women tend to gradually lose market value, as far as this is contingent on their age. Men are sensitive to cues informing about age, which is ultimately linked to reproductive potential***. Humans of either sex tend to adjust their demands and expectations to changes in their market value. For example, following earlier papers... in both methods and ideas, Pawłowski and Dunbar... showed that ***with increasing age, women become less demanding, quantified as the number of preferred characteristics listed in ‘Lonely Hearts’ advertisements. This sensitivity to market value of self in humans has since been confirmed in numerous other studies...  Climbing down a peg when one is not doing very well on the mating market, often is a ‘best-of-a-bad-job’ strategy***... Inferior competitors in several species use strategies radically different from those of their high-quality rivals. ***For example, big bullfrogs croak loudly in order to attract females, but small males of the same species remain silent and ambush the females that are on their way to the big bullies, a strategy known as ‘sneaking’...  Strategies that differ radically from the main stream exist among humanmales too, of course, e.g. rape and brothel visits.***

Members of several other species are also able to calibrate their mate preferences according to their own market value.  Spotted bowerbird males decorate their bowers with Solanum berries, the number of which shows considerable variation among males with higher numbers correlating with higher mating success. After experimental changes of the number of berries that decorated their bower, males added or removed berries to such an extent that the natural number was more or less restored. Males with berry-numbers considerably larger than what they had contributed themselves, suffered an increased risk of having their bowers disrupted by neighbouring males. - (Griggio and Hoi 2010). The latter authors also found indications of sensitivity to the own attractivity in bearded reedlings... Another house sparrow study (Schwagmeyer 2014) showed similar market effects, not only during pair formation at the start of the reproductive season but also in the form of partner switches during the season. ***The latter reminds of humans again: people report more satisfaction with their present partner when their prospects of switching to a higher quality mate are dim...***

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Check also: Behavioral display of lumbar curvature in response to the opposite sex. Zeynep Şenveli Bilkent University, Graduate Program in Neuroscience - Master's degree thesis. http://repository.bilkent.edu.tr/handle/11693/33362

And: The Reversed Gender Gap in Education and Assortative Mating in Europe. De Hauw, Yolien, Grow, Andre, and Van Bavel, Jan. European Journal of Population, https://link.springer.com/article/10.1007/s10680-016-9407-z

And: Marzoli, D., Havlícek, J. and Roberts, S. C. (2017), Human mating strategies: from past causes to present consequences. WIREs Cognitive Science, e1456. doi:10.1002/wcs.1456

And: The Causes and Consequences of Women’s Competitive Beautification. Danielle J. DelPriore, Marjorie L. Prokosch, and Sarah E. Hill. The Oxford Handbook of Women and Competition, edited by Maryanne L. Fisher. http://www.oxfordhandbooks.com/view/10.1093/oxfordhb/9780199376377.001.0001/oxfordhb-9780199376377-e-34

Understanding what makes terrorist groups’ propaganda effective: an integrative complexity analysis of ISIL and al Qaeda

Understanding what makes terrorist groups’ propaganda effective: an integrative complexity analysis of ISIL and Al Qaeda. Shannon C. Houck, Meredith A. Repke & Lucian Gideon Conway III. Journal of Policing, Intelligence and Counter Terrorism, Vol. 12, issue 2, Pages 105-118.
http://dx.doi.org/10.1080/18335330.2017.1351032

ABSTRACT: The Islamic State of Iraq and the Levant (ISIL) became an increasingly powerful terrorist organisation in a relatively short period of time, drawing more recruits than its former affiliate, Al Qaeda. Many have attributed ISIL’s successful expansion in part to its extensive propaganda platform. But what causes terrorist groups to be effective in their communication to the public? To investigate, we examined one aspect of terrorists’ rhetoric: Integrative complexity. In particular, this historical examination provides a broad integrative complexity analysis of public statements released by key members of ISIL and Al Qaeda over a 10-year period when ISIL was rapidly growing as a terrorist entity (2004–2014). Findings revealed that (a) ISIL demonstrated less complexity overall than Al Qaeda (p < .001) and (b) ISIL became increasingly less complex over this focal time period (p < .001), while Al Qaeda’s complexity remained comparatively stable (p = .69). Taken together, these data suggest that as ISIL grew in size and strength between 2004 and 2014 – surpassing Al Qaeda on multiple domains such as recruitment, monetary resources, territorial control, and arms power – it simultaneously became less complex in its communication to the public.

KEYWORDS: Terrorism, propaganda, integrative complexity, ISIL, Al Qaeda

Myths and truths about the cellular composition of the human brain: A review of influential concepts

Myths and truths about the cellular composition of the human brain: A review of influential concepts. Christopher S.Bvon Bartheld. Journal of Chemical Neuroanatomy, https://doi.org/10.1016/j.jchemneu.2017.08.004

Highlights
•    The myth of a 10:1 glia-neuron ratio in human brains has been debunked.
•    The myth of one trillion glial cells in human brains has been debunked.
•    The number of cortical neurons does not decline significantly in normal aging.
•    All counting methods benefit from calibration and validation.
•    Proof is needed for altered cell numbers in neurological and psychiatric disorders.

Abstract: Over the last 50 years, quantitative methodology has made important contributions to our understanding of the cellular composition of the human brain. Not all of the concepts that emerged from quantitative studies have turned out to be true. Here, I examine the history and current status of some of the most influential notions. This includes claims of how many cells compose the human brain, and how different cell types contribute and in what ratios. Additional concepts entail whether we lose significant numbers of neurons with normal aging, whether chronic alcohol abuse contributes to cortical neuron loss, whether there are significant differences in the quantitative composition of cerebral cortex between male and female brains, whether superior intelligence in humans correlates with larger numbers of brain cells, and whether there are secular (generational) changes in neuron number. Do changes in cell number or changes in ratios of cell types accompany certain diseases, and should all counting methods, even the theoretically unbiased ones, be validated and calibrated? I here examine the origin and the current status of major influential concepts, and I review the evidence and arguments that have led to either confirmation or refutation of such concepts. I discuss the circumstances, assumptions and mindsets that perpetuated erroneous views, and the types of technological advances that have, in some cases, challenged longstanding ideas. I will acknowledge the roles of key proponents of influential concepts in the sometimes convoluted path towards recognition of the true cellular composition of the human brain.

Abbreviations: CNScentral nervous system
GNR glia-neuron ratio
IF isotropic fractionator

Individuals who follow and are followed by the people who correct them are significantly more likely to accept the correction than individuals confronted by strangers

Political Fact-Checking on Twitter: When Do Corrections Have an Effect? Drew Margolin, Aniko Hannak and Ingmar Weber. Political Communication, http://dx.doi.org/10.1080/10584609.2017.1334018

Abstract: Research suggests that fact checking corrections have only a limited impact on the spread of false rumors. However, research has not considered that fact-checking may be socially contingent, meaning there are social contexts in which truth may be more or less preferred. In particular, we argue that strong social connections between fact-checkers and rumor spreaders encourage the latter to prefer sharing accurate information, making them more likely to accept corrections. We test this argument on real corrections made on Twitter between January 2012 and April 2014. As hypothesized, we find that individuals who follow and are followed by the people who correct them are significantly more likely to accept the correction than individuals confronted by strangers. We then replicate our findings on new data drawn from November 2015 to February, 2016. These findings suggest that the underlying social structure is an important factor in the correction of misinformation.

Keywords: accountability, fact-checking, misinformation, rumor, social networks

Land plants have regulated their stomatal conductance to allow their intrinsic water use efficiency to increase in nearly constant proportion to the rise in atmospheric [CO2]

Atmospheric evidence for a global secular increase in carbon isotopic discrimination of land photosynthesis. Ralph F. Keeling et al. Proceedings of the National Academy of Sciences, http://m.pnas.org/content/early/2017/09/05/1619240114

Significance: Climate change and rising CO2 are altering the behavior of land plants in ways that influence how much biomass they produce relative to how much water they need for growth. This study shows that it is possible to detect changes occurring in plants using long-term measurements of the isotopic composition of atmospheric CO2. These measurements imply that plants have globally increased their water use efficiency at the leaf level in proportion to the rise in atmospheric CO2 over the past few decades. While the full implications remain to be explored, the results help to quantify the extent to which the biosphere has become less constrained by water stress globally.

Abstract: A decrease in the 13C/12C ratio of atmospheric CO2 has been documented by direct observations since 1978 and from ice core measurements since the industrial revolution. This decrease, known as the 13C-Suess effect, is driven primarily by the input of fossil fuel-derived CO2 but is also sensitive to land and ocean carbon cycling and uptake. Using updated records, we show that no plausible combination of sources and sinks of CO2 from fossil fuel, land, and oceans can explain the observed 13C-Suess effect unless an increase has occurred in the 13C/12C isotopic discrimination of land photosynthesis. A trend toward greater discrimination under higher CO2 levels is broadly consistent with tree ring studies over the past century, with field and chamber experiments, and with geological records of C3 plants at times of altered atmospheric CO2, but increasing discrimination has not previously been included in studies of long-term atmospheric 13C/12C measurements. We further show that the inferred discrimination increase of 0.014 ± 0.007‰ ppm−1 is largely explained by photorespiratory and mesophyll effects. This result implies that, at the global scale, land plants have regulated their stomatal conductance so as to allow the CO2 partial pressure within stomatal cavities and their intrinsic water use efficiency to increase in nearly constant proportion to the rise in atmospheric CO2 concentration.