The gastrointestinal tract is an asymmetrically patterned organ system. The signals which initiate left‐right asymmetry in the developing embryo have been extensively studied, but the downstream steps required to confer asymmetric morphogenesis on the gut organ primordia are less well understood. In this paper we outline key findings on the tissue mechanics underlying gut asymmetry, across a range of species, and use these to synthesise a conserved model for asymmetric gut morphogenesis. We also discuss the importance of correct establishment of (...) left‐right asymmetry for gut development and the consequences of perturbations in this process. (shrink)

We present behavioral lateralizations of spiders and ants and their probable survival value. They clearly conform to the vertebrate lateralizations reviewed by Vallortigara & Rogers and to earlier arthropod studies. We suggest two complementary reviews: differences in lesion susceptibility and muscle strength between left and right body side, and perceptual biases and predator inspection in invertebrates.

The field of left–right (LR) patterning—the study of molecular mechanisms that yield directed morphological asymmetries in otherwise symmetrical organisms—is in disarray. On one hand is the undeniably elegant hypothesis that rotary beating of inclined cilia is the primary symmetry‐breaking step: they create an asymmetric extracellular flow across the embryonic midline. On the other hand lurk many early symmetry‐breaking steps that, even in some vertebrates, precede the onset of ciliary flow. We highlight an intracellular model of LR patterning where gene (...) expression is initiated by physiological asymmetries that arise from subcellular asymmetries (e.g. motor‐protein function along oriented cytoskeletal tracks). A survey of symmetry breaking in eukaryotes ranging from protists to vertebrates suggests that intracellular cytoskeletal elements are ancient and primary LR cues. Evolutionarily, quirky effectors like ciliary motion were likely added later in vertebrates. In some species (like mice), developmentally earlier cues may have been abandoned entirely. Late‐developing asymmetries pose a challenge to the intracellular model, but early mid‐plane determination in many groups increases its plausibility. Multiple experimental tests are possible. BioEssays 29: 271–287, 2007. © 2007 Wiley Periodicals, Inc. (shrink)

A mechanism for the generation of the morphological left‐right asymmetry in higher organisms is proposed, based on the idea that chirality at the molecular level is the primordial source for macroscopic asymmetry. This mechanism accounts for a variety of experimental results on artificial production of situs inversus and fits well with mutations in mice causing visceral transposition.

Embryonic development results in animals whose body plans exhibit a variety of symmetry types. While significant progress has been made in understanding the molecular events underlying the early specification of the antero‐posterior and dorso‐ventral axes, little information has been available regarding the basis for left‐right (LR) differences in animal morphogenesis. Recently however, important advances have been made in uncovering the molecular mechanisms responsible for LR patterning. A number of genes (including well‐known signaling molecules such as Sonic hedgehog and activin) are (...) asymmetrically expressed in early chick embryos, well before the appearance of morphological asymmetries. One of these, nodal, is asymmetrically expressed in frogs and mice as well, and its expression is altered in mouse mutants exhibiting defects in laterality. In the chick, these genes regulate each other in a sequential cascade, which independently determines the situs of the heart and other organs. (shrink)

The prevailing theory states that either Japanese voters have stopped ideologically distinguishing parties or that the main political parties in Japan have become more centrist in recent years. These arguments are based on survey questions asking citizens to locate parties on an ideological scale. However, these questions may suffer from noise caused by respondents who misinterpret the question wording or answer the questions inappropriately to mask their misunderstanding of the terms and . To address this problem by extracting only the (...) views of those who know the meaning of leftright terminology largely perceived parties’ ideologies in the same way as experts. Additionally, I find that even these voters face difficulties in placing ambiguous or new parties on the political spectrum. This study has implications not only for understanding trends in Japanese political ideology, but also for survey design and analysis of heterogeneous survey responses. (shrink)

The internal organs of all vertebrates are asymmetrically organised across the left–right axis. The development of this asymmetry is controlled by a molecular pathway that includes the signalling molecule Nodal and the transcription factor Pitx2, proteins encoded by genes that are predominantly expressed on the left side of all vertebrate embryos studied to date. Vertebrates share Phylum Chordata with two other groups of animals, amphioxus and the urochordates (including ascidians). Both these taxa develop left–right asymmetries, and recent studies (...) have begun to address the degree of conservation of nodal and Pitx2 in this process. Pitx2 is a member of the Pitx homeobox gene family, and in both amphioxus and ascidians Pitx gene expression is predominantly left sided. These studies suggest that left–right asymmetry in all chordates is regulated by a conserved developmental pathway, and that this pathway evolved before the separation of the lineages leading to living chordates. BioEssays 24:1004–1011, 2002. © 2002 Wiley‐Periodicals, Inc. (shrink)

This book brings together for the first time an updated, revised collection of influential essays and articles that capture some of the most exciting scientific and scholarly contributions to the topic of political ideology. John Jost tackles fundamental questions about how psychology, neuroscience, and societal factors impact political attitudes and group divisions. In what sense, if any, are ordinary citizens "ideological"? Is it useful to locate political attitudes on a single dimension of representation? Are there meaningful differences in the beliefs, (...) opinions, and values of leftists and rights-or liberals and conservatives? How are personality traits related to ideological preferences? What situational or contextual factors contribute to liberal and conservative shifts in the general population? What are the implications of ideological polarization for the future of democracy? Drawing on Max Weber's concept of elective affinities, one of the world's leading political psychologists discusses the myriad ways in people choose ideas and ideas choose people. (shrink)

Disruption of Nodal in the lateral plate mesoderm (LPM) usually leads to left‐right (LR) patterning defects in multiple organs. However, whether the LR patterning of organs is always regulated in a coupled way has largely not yet been elucidated. In addition, whether other crucial regulators exist in the LPM that coordinate with Nodal in regulating organ LR patterning is also undetermined. In this paper, after briefly summarizing the common process of LR patterning, the most puzzling question regarding the initiation of (...) asymmetry is considered and the divergent mechanisms underlying the uncoupled LR patterning in different organs are discussed. On the basis of cases in which different organ LR patterning is determined in an uncoupled way via an independent mechanism or at a different time, we propose that there are other critical factors in the LPM that coordinate with Nodal to regulate heart LR asymmetry patterning during early LR patterning.Also watch the Video Abstract. (shrink)

A fundamental aspect of biological systems is their spatial organization. In development, regeneration and repair, directional signals are necessary for the proper placement of the components of the organism. Likewise, pathogens that invade other organisms rely on directional signals to target vulnerable areas. It is widely understood that chemical gradients are important directional signals in living systems. Less well recognized are electrical fields, which can also provide directional information. Small, steady electrical fields can directly guide cell movement and growth and (...) can generate chemical gradients of charged macromolecules against the leveling action of diffusion. At the site of a lesion in an ion‐transporting epithelium, for example, a substantial electrical field is instantly generated and may extend over many cell diameters. There are numerous other situations in which relatively long‐range electrical fields have been shown to exist naturally. Recently, there has been substantial progress in identifying specific processes that are controlled, to some extent, by these endogenous electrical fields. This review highlights these recent data and discusses possible mechanisms by which the fields might affect biological processes. BioEssays 25:759–766, 2003. © 2003 Wiley Periodicals, Inc. (shrink)

The imagery of Left and Right has been a common way to conceive democratic politics in modern Europe, and commentators have suggested it be extended to the European Union. This article examines the normative implications and plausibility of European politics being cast in these terms. It focuses on the challenges of rendering political division recognizable and acceptable at a transnational level, of evoking its continuities of structure, and of symbolizing the ties of political community. The article probes the Left–Right (...) dichotomy’s potential in these regards, together with the conjunctural factors likely to raise or diminish its appeal. (shrink)

According to Silvan Tomkins polarity theory, ideological thought is universally structured by a clash between two opposing worldviews. On the left, a humanistic worldview seeks to uphold the intrinsic value of the person; on the right, a normative worldview holds that human worth is contingent upon conformity to rules. In this article, we situate humanism and normativism within the context of contemporary models of political ideology as a function of motivated social cognition, beliefs about the social world, and personality traits. (...) In four studies conducted in the U.S. and Sweden, normativism was robustly associated with rightist self-placement; conservative issue preferences; resistance to change and acceptance of inequality; right-wing authoritarianism and social dominance orientation; system justification and its underlying epistemic and existential motives to reduce uncertainty and threat; and a lack of openness, emotionality, and honesty-humility. Humanism exhibited the opposite relations to most of these constructs, but it was largely unrelated to epistemic and existential needs. Humanism was strongly associated with preferences for equality, openness to change, and low levels of authoritarianism, social dominance, and general and economic system justification. We conclude that polarity theory possesses considerable potential to explain how conflicts between worldviews shape contemporary politics. (shrink)

The present study examined the relationship between left–right discrimination (LRD) performance and handedness, sex and cognitive abilities. In total, 31 men and 35 women – with a balanced ratio of left-and right-handers – completed the Bergen Left–Right Discrimination Test. We found an advantage of left-handers in both identifying left hands and in verifying “left” propositions. A sex effect was also found, as women had an overall higher error rate than men, and increasing difficulty impacted their reaction time more (...) than it did for men. Moreover, sex interacted with handedness and manual preference strength. A negative correlation of LRD reaction time with visuo-spatial and verbal long-term memory was found independently of sex, providing new insights into the relationship between cognitive skills and performance on LRD. (shrink)

The situation-dependent lateralization of sympathetic electrodermal arousal during real-life stress (Picard, Fedor, & Ayzenberg, 2016) may challenge a unitary notion of arousal, and call into question the practice of unilateral electrodermal recording, but there are broader implications. Here we consider a potential relationship between stress-induced lateralized shifts in electrodermal activity, and a theory concerning lateralized emotion-induced cardiac arrhythmia.

The invariant left–right asymmetry of animal body plans raises fascinating questions in cell, developmental, evolutionary, and neuro‐biology. While intermediate mechanisms (e.g., asymmetric gene expression) have been well‐characterized, very early steps remain elusive. Recent studies suggested a candidate for the origins of asymmetry: rotary movement of extracellular morphogens by cilia during gastrulation. This model is intellectually satisfying, because it bootstraps asymmetry from the intrinsic biochemical chirality of cilia. However, conceptual and practical problems remain with this hypothesis, and the genetic data (...) is consistent with a different mechanism. Based on wide‐ranging data on ion fluxes and motor protein action in a number of species, a model is proposed whereby laterality is generated much earlier, by asymmetric transport of ions, which results in pH/voltage gradients across the midline. These asymmetries are in turn generated by a new candidate for “step 1”: asymmetric localization of electrogenic proteins by cytoplasmic motors. BioEssays 25:1002–1010, 2003. © 2003 Wiley Periodicals, Inc. (shrink)

In the last few years, an understanding has emerged of the developmental mechanism for the consistent internal left–right structure, termed situs, that characterises vertebrate anatomy. This involves largely vertebrate‐conserved (i.e. ‘phylotypic’) gene expression cascades that encode ‘leftness’ and ‘rightness’ in appropriate tissues either side of the embryo's midline soon after gastrulation. Recent evidence indicates that the initial, directional symmetry breaking that initiates these cascades utilises mechanisms that are conserved or at least closely related in different vertebrate types. I describe (...) a scenario whereby the capacity for directional modification of an otherwise bilateral body plan can be viewed as an adaptive innovation rather closely connected with vertebrate origins, enabling optimal ‘design’ for very active lifestyles. But an alternative scenario, while retaining the view that situs and indeed other vertebrate functional lateralisations are deeply adaptive, proposes that they originated in the co‐optation of left–right developmental information inherited from a very early stage in metazoan diversification. It is proposed that a remote chordate ancestor lost its original or ‘ur‐bilaterian’ symmetry to pass through an altogether non‐symmetrical stage, and that the vertebrate dorsoventral midline plane is not descended from that original one. I review the considerable evidence in favour of this scenario, and discuss its wider implications for directional asymmetries across the Metazoa. BioEssays 26:413–421, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

We examine schoolchildren’s reasoning with spatial relations, such as ‘is to the left of’. Our aims are to obtain a more precise account of the effect of working memory on reasoning, a more detaile...

이 글은 유가에서 좌선하는 천도를 통해 예제에서의 좌우 방위를 천체운행 관념으로 밝히고, 조선 예학에서 논의된 천도와의 관련성을 성호와 경호의 변설을 중심으로 고찰하였다. 좌선과 우행은 천체가 운행하는 방향으로 묘사된 것인데 예학에서 발견되는 방위서술 가운데 周旋하는 의절의 원리로서 검토된다. 고대의 예제가 천인관계에서 천문 역상을 본떠 인문제도에 적용한 모형으로 선행연구에서 밝힌 바에 따라 주선하는 행례와 좌우의 상위 개념이 좌선하는 천도와의 관련성에서 볼 때 천체운행의 관념을 지닌 것으로 파악하였다. 이를 위해 소옹의 易圖說에서 그려낸 차서도와 주희의 방위도를 천도 좌선과 일월 우행의 구체적인 형상과 그 방향을밝히는 (...) 근거로서 제시하였다.BR 이러한 배경에서 예서에서의 좌우 구분과 방위로 서술된 의절은 고대 동아시아의 천체운행론의 관점으로 검토된다. 역은 태극이요, 우주론으로 논의되어온 역학이 천문 역상을 본떠 제작된 예제의 원리를 밝히는 방법론으로 매우 유용할 것이다. 이 과정에서 유가에서 말해지는 좌선하는 천도가 천도론에서 깊이 고찰된다. 고대 우주론에서 천체구조론은 한대 이후 남송대 주희에 이르기까지 천문역법을 구하는 과정에서 역가와 유가가 공유해온 천문현상이다. 이러한 천좌선과 일월우행은 개천설과 혼천설에서도 공유되지만 이를 주희는 좌선설로서 논란을 주도하였다. 최근까지도 어떤 이유에서인지 밝혀지지 않은 주희의 헷갈리는 주장은 본고가 제출한 소강절의 역도설에서 그 형상과 의미를 밝힐 수 있었다. 이는 주희가 주장한 좌선설과 배치되는 천좌선하고 일월우행하는 우선설인데 이를 주희 스스로 易學에서 실증한 셈이 된 것이다. 이러한 결과는 尙左가 역학에서 順天하는 陽의 방향으로 천도와의 관련성을 입증한 것이고 尙右는 천도와 어긋나는 逆天으로 陰의 방향 즉 神道와의 관련성에서 對比된다.BR 조선 예학에서는 천도론의 관점에서 예제를 논의한 경우는 없었을까? 조선의 예학자 가운데 성호의 ‘導柩右旋’과 경호의 尙左･尙右에 관한 변설을 중심 사례로서 검토하였다. 조선의 유자들이 예학을 천도 좌선과의 관련성에서 좌우 방위를 어떻게 적용하였고 또 인식하였는지를 살피기 위해서였다. 성호는 상례에서 널의 머리 쪽이 우선한 것을 좌선하는 천도에 대응되는 地道로서 右旋이라 하였다. 그의 제자 이병휴에 따르면 좌선은 왼쪽에서 부터 오른쪽으로 향하고, 우선은 오른쪽에서부터 왼쪽으로 향하는 형상으로 인식하였다. 그의 이 같은 견해는 역도설에서 밝힌 천도론과 천체운행론의 관점으로 본 좌우 방위 관념과 일치하는 형상이다.BR 경호는 『가례증해』에서 상좌와 상우를 모두 천도 좌선에 처한다고 인식하여 팔괘에서 그 좌선하는 천도 방향을 밝히고 일월의 출입이 동에서 시작되는 것으로서 동쪽과 왼쪽을 천도에 따른 것이라 하였다. 이러한 경호의 해석은 공영달과 이하 曆家의 천도 좌선하고 일월의 우행이기 보다는 天道와 地道로서 대응한 천도론적 관점이었다.BR 그의 천도에 따른 상좌의 당위성은 역학에서 천도를 본뜬 좌선하는 형상을 높여 상좌라고 하였고 땅에서의 형세에 따라 상우로 하였다. 따라서 예학에서의 人道는 천도를 따라 尙左를 생인의 상위로 삼고, 제례에서 신위를 모실 때에는 尙右로서 하였다. 결과적으로 조선 예학에서의 검토되는 사례는 행례에서 천도 좌선의 관점을 견지하고 천체운행론의 관념을 함의한 것으로 드러날 것이다. (shrink)

Imagine a child′s toy arrow, sticking by its rubber sucker to a mirror′s reflective surface. We can call the direction in which such an arrow would point the finwards direction ; and we can call the opposite direction boutwards . When we look at things in a mirror, their images are apparently just as far finwards of the mirror as the things themselves are boutwards of it. For example, if we look at the tail of our arrow and cast our (...) glance finwards, we see first the tail, then the head, then the mirror, then the reflection of the head, and finally the reflection of the tail. We can therefore say that a mirror reverses things in the finwards/boutwards dimension. Moreover, the straight line connecting each thing to its image passes perpendicularly through the plane of the mirror. Hence there is no plane, apart from that of the mirror itself, such that the apparent location of each thing′s image is just as far to the one side of that plane as the original is to the other. This means that the reversal in the finwards/ boutwards dimension is the only reversal of its kind to take place. In particular, there is no such reversal in any dimension at right angles to finwards/boutwards. (shrink)

In this study, we explored the time and space relationship according to two different spatial codings, namely, the left/right extension and the reachability of stimulus along a near/far dimension. Four experiments were carried out in which healthy participants performed the time and spatial bisection tasks in near/far space, before and after short or long tool-use training. Stimuli were prebisected horizontal lines of different temporal durations in which the midpoint was manipulated according to the Muller-Lyer illusion. The perceptual illusory effects emerged (...) in spatial but not temporal judgments. We revealed that temporal and spatial representations dynamically change according to the action potentialities of an individual: temporal duration was perceived as shorter and the perceived line’s midpoint was shifted to the left in far than in near space. Crucially, this dissociation disappeared following a long but not short tool-use training. Finally, we observed age-related differences in spatial attention which may be crucial in building the memory temporal standard to categorize durations. (shrink)

A critique of ‘beyond left and right’ ideologies, from red Toryism to techno-libertarianism.

The only contemporary moral problems text to focus directly on the ethics of current, divisive political issues, Ethics, Left and Right features newly commissioned essays on twenty contentious debates, written expressly with undergraduate students in mind. It offers two position pieces on each issue--one left-leaning, one right--followed by a reply from each author, giving you and your students the opportunity to engage in in-depth discussions of serious issues. The essays cover compelling topics including whether we should have an "America First" (...) approach to policy, whether it's okay to have religious tests for immigration, the merits of political correctness, the ethics of voting, whether progressive taxation is legitimate, and what to make of accusations of privilege. Case studies at the end of every main contribution encourage students to examine related problems and/or delve deeper into the current issue. (shrink)