Domain-specific Mechanisms Research Articles

Child abuse and the balance of power in parental relationships: an evolved domain-independent mental mechanism that accounts for behavioral variation.

Previous studies use zero-order analyses to show a link between child abuse and exposure to "stepfathers." These studies rest on a proposed evolved, domain-specific cognitive mechanism that induces adult males to abuse or kill offspring not their own and, so, contribute directly to reproductive success. However, child abuse may reflect an evolved neurological mechanism that creates behavioral plasticity and adaptability by assigning emotional weights (which in consciousness appear rationalized as costs and benefits) to choice alternatives in all behavioral domains. This mechanism should act as a selective mechanism to create enhanced ability to avoid predation (social exploitation) and to obtain access to resources, given the properties of specific ecosystems, and should control behavioral responses to variation in the balance of power in social relationships. Power equalities should elicit good treatment for both parties; power inequalities, by contrast, should elicit exploitative and coercive behavior on the part of those who hold the balance of power. This paper reports a test of both hypotheses simultaneously, controlling for a standard social science risk factor (growing up in poverty). Once we control for the balance of power in parental relationships, exposure to a stepfather and growing up in poverty show no effect on the intensity of child abuse. Powerful women negotiated affectionate behavior from their partners for both themselves and their children; powerless women's negotiations with partners usually left both themselves and their children open to violence.

THE ROBUSTNESS OF CRITICAL PERIOD EFFECTS IN SECOND LANGUAGE ACQUISITION

This study was designed to test the Fundamental Difference Hypothesis (Bley-Vroman, 1988), which states that, whereas children are known to learn language almost completely through (implicit) domain-specific mechanisms, adults have largely lost the ability to learn a language without reflecting on its structure and have to use alternative mechanisms, drawing especially on their problem-solving capacities, to learn a second language. The hypothesis implies that only adults with a high level of verbal analytical ability will reach near-native competence in their second language, but that this ability will not be a significant predictor of success for childhood second language acquisition. A study with 57 adult Hungarian-speaking immigrants confirmed the hypothesis in the sense that very few adult immigrants scored within the range of child arrivals on a grammaticality judgment test, and that the few who did had high levels of verbal analytical ability; this ability was not a significant predictor for childhood arrivals. This study replicates the findings of Johnson and Newport (1989) and provides an explanation for the apparent exceptions in their study. These findings lead to a reconceptualization of the Critical Period Hypothesis: If the scope of this hypothesis is limited to implicit learning mechanisms, then it appears that there may be no exceptions to the age effects that the hypothesis seeks to explain.

Still More Complexity in Mammalian Basement Membranes

At the epithelial/mesenchymal interface of most tissues lies the basement membrane (BM). These thin sheets of highly specialized extracellular matrix vary in composition in a tissue-specific manner, and during development and repair. For about two decades it has been apparent that all BMs contain laminins, entactin-1/nidogen-1, Type IV collagen, and proteoglycans. However, within the past few years this complexity has increased as new components are described. The entactin/nidogen (E/N) family has expanded with the recent description of a new isoform, E/N-2/osteonidogen. Agrin and Type XVIII collagen have been reclassified as heparan sulfate proteoglycans (HSPGs), expanding the repertoire of HSPGs in the BM. The laminin family has become more diverse as new alpha-chains have been characterized, increasing the number of laminin isoforms. Interactions between BM components are now appreciated to be regulated through multiple, mostly domain-specific mechanisms. Understanding the functions of individual BM components and their assembly into macromolecular complexes is a considerable challenge that may increase as further BM and cell surface ligands are discovered for these proteins.

Coordination Approaches and Systems - Part I: A Strategic Perspective

This is the first part of a two-part paper presenting a fundamental review and summary of research of design coordination and cooperation technologies. The theme of this review is aimed at the research conducted within the decision management aspect of design coordination. The focus is therefore on the strategies involved in making decisions and how these strategies are used to satisfy design requirements. The paper reviews research within collaborative and coordinated design, project and workflow management, and, task and organization models. The research reviewed has attempted to identify fundamental coordination mechanisms from different domains, however it is concluded that domain independent mechanisms need to be augmented with domain specific mechanisms to facilitate coordination. Part II is a review of design coordination from an operational perspective.

Culture and the evolution of social learning

Applications of modern evolutionary theory to human culture have generated several different theoretical approaches that challenge traditional anthropological perspectives. “Cultural selection” and “mind parasite” theories model culture as an independent evolutionary system because transmission of cultural traits via social learning is distinct from transmission of genes via DNA replication. “Dual-inheritance” and “co-evolution” theories model culture as an intermediary evolutionary process that involves information from two inheritance systems: genetics and social learning. “Evolutionary psychology” theories emphasize that the evolutionary history of natural selection on mental processes links culture and biological adaptation; hence, cultural information is viewed as part of the organic phenotype and not an independent evolutionary system. Cross-cultural universals and scenarios of the “environment of evolutionary adaptedness” are used to identify characteristics of the “evolved mind” (human nature). “Behavioral ecology” theories examine relations between behavior and environmental context. Behavioral/cultural variations are viewed as products of flexible decision-making processes (evolved mind) that may respond adaptively to micro-environmental differences. It is difficult to devise empirical tests that distinguish among these theories, because they share many basic premises and make similar predictions about human behavior. Indeed, some of the apparent differences may be more semantic than substantive. Social learning is the key process underlying these evolutionary paradigms. Here I argue that human learning mechanisms are products of natural selection, and hence process information in ways that reflect evolutionary design. I review common objections to this hypothesis, including (1) learning processes are uncoupled from genetics and biological adaptation; (2) culture (or its effects) is partly extrasomatic; (3) culture, by most definitions, involves mental phenomena, including conscious thought; (4) culture involves the use of arbitrary symbols to communicate information; (5) culture appears to have emergent properties at the group level, such as shared values and beliefs resulting in political and religious institutions; (6) culture involves historical processes; and (7) complex culture is uniquely human—we need an explanation for why the human species alone evolved such extensive social learning aptitudes. I suggest that these controversies can be resolved, although empirical tests are difficult. I posit that social competition was a primary selective pressure on human mental abilities (Alexander 1989) and that this favored domain-general, constructivist learning capabilities (e.g., Quartz and Sejnowski, in press) that can manage context-dependent analysis and integrate information from domain-specific mechanisms (Hirschfeld and Gelman 1994; MacDonald 1991; Sperber 1996). Humans are unique in the extraordinary levels of novelty that are generated by the processing of socially learned information. Human culture is cumulative; human cognition produces new ideas built upon the old. To a degree that far surpasses that of any other species, human mental processes must contend with a constantly changing information environment of their own creation. Cultural information may be especially dynamic because it is a fundamental aspect of human social competition. Apparently arbitrary changes in cultural traits, such as clothing styles, music, art, food, dialects, and so forth, may reflect information arms races among social competitors. The remarkable developmental plasticity and cross-domain integration of some cognitive mechanisms may be products of selection for special sensitivity to variable social context. Human “culture” is not just a pool or source of informational; it is an arena and theater of social manipulation and competition. Studies of human behavior—including language, kinship, mating relationships, subsistence, economics, and politics—generally are consistent with an evolutionary basis for social learning, but often they fail to add specific new knowledge about the mechanisms. Analyses of cognitive aptitudes underlying language, kinship, and so forth, often are inconclusive because cultural information (and consequent behavior) involves complex interaction among history, environmental variation, ontogenetic pathways of mental processes, and specific context. I suggest that empirical tests of evolutionary culture theory must build upon identification of apparent universals and examine individual variability by incorporating developmental psychology, environmental conditions, and social and historical context. This synthesis would benefit from enhanced cooperation between cognitive psychologist and cultural anthropologist.

Silver Binding to Rabbit Liver Metallothionein: Circular dichroism and emission study of silver-thiolate cluster formation with apometallothionein and the α and β fragments

We report new spectroscopic properties for a range of silver-metallothionein species. The binding reactions that take place following addition of Ag+ to rabbit liver apoMT 2, and the apo alpha and -beta fragments have been studied using the techniques of circular dichroism (CD) and emission spectroscopy. Titrations carried out at 20 degrees C and 55 degrees C reveal for the first time the formation of a sequence of clusters (Ag6-MT, Ag12-MT and, finally, Ag18-MT) as Ag+ is added to rabbit apoMT 2. (The division of mammalian metallothioneins into two major subforms, MT 1 and MT 2, is based on differences in molecular charge, which results from differences in the sequence of amino acids that do not involve the cysteines.) It is proposed that the novel Ag18-MT complex forms with a structure that involves a well defined three-dimensional structure, in the same manner as that recently reported for the Hg18-MT complex (Cai, W. and Stillman, M. J., (1988) J. Am. Chem. Soc. 110, 7872-7873). Addition of silver in excess of 20 mol equivalents leads to the collapse of this structure. At the elevated temperatures, it is suggested that the protein can exert cooperativity so that completely filled domains are formed rather than mixtures of complexes. This contrasts with the kinetic product in which metals are bound across the peptide chain forming more random cross-linked regions in place of the cluster structure. CD spectra were recorded as Ag+ was added to the alpha and beta fragments formed from rabbit liver MT 1. The silver-containing fragments are less stable than the Ag-MT. The alpha and beta fragments exhibit CD spectral patterns indicative of stoichiometrically defined species. The presence of Ag3- alpha MT 1 and Ag6- alpha MT 1 is suggested by the spectral data obtained at 20 and 55 degrees C. Formation of Ag3- beta MT 1 is suggested by the spectral data recorded at 20 degrees C for the beta fragment. We also report that silver-containing metallothioneins are luminescent. Both the position of the band maximum in the 460-600 nm region and the emission intensity are strongly dependent on the stoichiometry of silver to protein. In the range of molar ratios for silver:MT of 1-12, bands at 465 and 520 nm intensify to a maximum for Ag10-MT 2. A band at 575 nm reaches a maximum for Ag16-MT 2. Analysis of the emission data suggests that Ag+ binds in a domain specific mechanism to apoMT 2.

Domain specificity in metal binding to metallothionein. A circular dichroism and magnetic circular dichroism study of cadmium and zinc binding at temperature extremes.

Rabbit liver Zn metallothionein-(MT) will bind cadmium readily between -26 degrees C and 70 degrees C. The binding reaction was monitored by recording the circular dichroism and magnetic circular dichroism spectra, in the region of the RS(-)----Cd2+ charge transfer transition at 250 nm, at intervals as aliquots of cadmium were added. For all temperatures, these data can be analyzed in terms of a distributed mechanism for cadmium binding when Zn-MT is used, and a domain-specific mechanism when apo-MT is used. The CD spectrum measured at -26 degrees C for Cd,Zn-MT, which was made by adding excess cadmium directly to Zn7-MT at -26 degrees C, is not the same as the CD spectrum of Cd-MT prepared at room temperature from the same Zn7-MT. Measurements of the stoichiometry of the cadmium and zinc bound to MT in the presence of excess cadmium at different temperatures indicates that below 5 degrees C at least one zinc atom remains bound to the protein. The mixed metal metallothionein, Cd/Zn-MT, that always forms below 5 degrees C, is characterized by a single maximum near 250 nm in the CD spectrum, rather than the derivative-shaped CD envelope that is diagnostic of the (Cd4-S11)alpha cluster, which indicates that the zinc occupies a site in the alpha domain. Rearrangement of the bound metals to the domain-specific distribution takes place if Cd,Zn-MT, prepared at subzero temperatures, is warmed above 30 degrees C.