Why Primates? The Importance of Nonhuman Primates for Understanding Human Infancy

We introduce the thematic collection by noting some striking similarities in the cognitive abilities of human infants and nonhuman primates. What are the implications of these similarities for our comprehension of human infant cognition? After providing a brief historical and conceptual background on comparative behavioral research, we discuss how work with nonhuman primates has impacted theories of core knowledge, domain specificity, and language. We conclude by previewing the articles comprising this special issue of Infancy.     

Mechanisms Underlying Language Acquisition: Benefits From a Comparative Approach

One of the longstanding issues in language research has been the extent to which the mechanisms underlying language acquisition are uniquely human. The primary goal of this article is to introduce the reader to some of the recent developments in comparative language research that have shed new light on this issue. To appreciate the significance of the new developments, we begin with a brief historical overview of language studies that have adopted a comparative approach, and then discuss a subset of the relevant theoretical accounts that seek to explain why humans are the only species capable of acquiring language. We next focus on findings from behavioral studies comparing the performance of human infants and adults with nonhuman primates on tests that tap the perceptual and learning mechanisms that are fundamental to language acquisition. We argue that in cases where the behavioral data appear similar across populations, there is a need to investigate the underlying computational abilities and units of analysis to correctly specify the degree to which the mechanisms are truly shared or are uniquely specified.     

Using yeast to discover the fountain of youth

The budding yeast Saccharomyces cerevisiae has long served as a model organism for the study of basic cellular processes. Its short generation time, well-established molecular genetics, and fully sequenced genome have made this organism a favorite of researchers in diverse fields. Much of the information obtained has been shown to apply to higher eukaryotes, including humans. Recently, researchers have begun using yeast to tackle one of the outstanding questions in science: How and why do organisms age? The identification of individual genes in yeast that can affect the aging process itself has elevated this single-celled fungus to full contender status in the aging field. In this Perspective, we present two fundamentally different measures of aging in yeast: replicative life-span and stationary phase survival (chronological life-span). We describe the benefits and limitations of each and present models that attempt to explain these "aging" phenomena. Finally, we present compelling evidence that the use of yeast as a model system will ultimately prove beneficial to the study of human aging.     

Generalization of Relational Matching to Sample in Children: A Direct Replication

The ability of preschool age children to perform generalized relational matching to sample tasks with and without an overt mediating stimulus was examined. This experiment was a direct replication of a study by Lowenkron (1984) and examined a behavioral model relevant to complex human behavior that he later came to call joint control. Children were trained to code two-dimensional stimuli with the help of a handheld mediating stimulus. They were later tested for generalization of relational matching to sample with and without the mediating stimulus. Results indicated high levels of generalized matching to sample with the mediating stimulus and lower levels without. Findings also indicated that generalization was somewhat stronger with symmetrical shapes than with asymmetrical. Results are discussed in terms of a radical behavioral interpretation of complex human behavior.     

Considering Alternate Sources of Role Identity: Childless Parents and Their Animal “Kids”

Identity theory posits that role identity is negotiated between human social actors and is based in broader cultural expectations about how particular statuses should be performed. I argue that the formation of role identity in actors can also occur in relationship to nonhuman actors, if they are perceived as minded. Depending on context and human perception, identity can be formed as a result of interaction and developing “theory of mind” with nonhuman animals, directly implicating the animal. Using in‐depth interviews of childless and childfree companion animal owners, I demonstrate the existence of a parent identity in childless participants that would not otherwise be present were it not for interaction with the animal “child.” This identity is confirmed in participant narratives describing substantial behavioral output aligned with the U.S. cultural ideal of “parent.” Likewise, I find that significant others provide external support for the enactment of this role identity, allowing participants to verify self‐in‐situation. Overall, my analysis emphasizes the importance of considering nonhuman sources as occupying counterstatus positions in the formation of role identity while highlighting how these relationships affect interaction in the childfree and childless home, thus expanding scholarly understanding about both identity formation and emerging family types.     

Oxidative mutagenesis, mismatch repair, and aging

A PubMed search for the term "oxidative stress" yields over 29,000 articles published on the subject over the past 10 years; more than 2000 of these articles also include the term "aging" in their title or abstract. Many theories of aging predict causal roles for oxidative stress in the myriad of pathological changes that occur as a function of age, including an increasing propensity to develop cancer. A possible link between aging and cancer is the induction and accumulation of somatic mutations caused by oxidative stress. This Review focuses on small mutational events that are induced by oxidative stress and the role of mismatch repair (MMR) in preventing their formation. It also discusses a possible inhibitory effect of oxidative stress on MMR. We speculate that a synergistic interaction between oxidative damage to DNA and reduced MMR levels will, in part, account for an accumulation of small mutational events, and hence cancer, with aging.     

Effects of aging on Type II muscle fibers: a systematic review of the literature

The authors conducted a systematic review of the literature for scientific articles in selected databases to determine the effects of aging on Type II muscle fibers in human skeletal muscles. They found that aging of Type II muscle fibers is primarily associated with a loss of fibers and a decrease in fiber size. Morphological changes with increasing age particularly included Type II fiber grouping. There is conflicting evidence regarding the change of proportion of Type II fibers. Type II muscle fibers seem to play an important role in the aging process of human skeletal muscles. According to this literature review, loss of fibers, decrease in size, and fiber-type grouping represent major quantitative changes. Because the process of aging involves various complex phenomena such as fiber-type coexpression, however, it seems difficult to assign those changes solely to a specific fiber type.     

Caring for an aging society: cohort values and eldercare services

Understanding the impact of cohort values is important in trying to project future aging service needs. The cultural characteristics of cohorts yet to reach the age of 65 are compared with those already "old," with specific focus on the Baby Boomers. Aging policies (and available services) reflect the cultural notions of age and aging held as normative during the historical era in which they are enacted. Previous research into lifestyle preferences, consumer practices, and key characteristics is drawn upon to investigate the values of Baby Boomers in light of their projected needs for eldercare services. Cohort research and generational marketing practices offer a promising foundation for exploring how best to develop, target, and deliver aging services that most effectively utilize our social resources.     

Competency Requirements for Policy Gerontologists

"Policy gerontologists" are professionals knowledgeable about both public policy and aging. Through a survey of potential employers about the education of these specialists, the authors examined what is desired in terms of knowledge base, skill proficiencies, and behavioral characteristics. Although a solid knowledge of aging policies and the policymaking process are considered essential for policy gerontologists, respondents suggested that communication and political skills as well as the ability to take initiative and to follow through were also essential.     

Competency requirements for policy gerontologists: what are the essentials?

"Policy gerontologists" are professionals knowledgeable about both public policy and aging. Through a survey of potential employers about the education of these specialists, the authors examined what is desired in terms of knowledge base, skill proficiencies, and behavioral characteristics. Although a solid knowledge of aging policies and the policymaking process are considered essential for policy gerontologists, respondents suggested that communication and political skills as well as the ability to take initiative and to follow through were also essential.     

Successful Aging in the Middle-Aged Gay Man

Abstract

Successful aging into middle age is impeded by internalized ageism in the gay man. Developmental theory inadequately details the tasks at this stage. Lesbian and gay human developmental theory is now being conceptualized to encompass the entire lifespan. This article identifies and elaborates specific developmental tasks for the middle-aged gay man based on psychotherapy clients who successfully aged into midlife. Focusing on the elimination of internalized ageism and the development of a positive attitude towards aging, the author provides a human developmental model for successful aging at midlife.     

ASSET MANAGEMENT,ALLOCATION OF TIME,AND RETURNS TO SAVING*

The paper entertains the proposition that individuals' time performs a productive role in generating nonwage income through the management of nonhuman capital assets. The asset management hypothesis is used to develop a life cycle model of consumptive and productive decisions. The model allows for variations in gross rates of return both across persons at a point in time and for any one person over his life cycle. The behavioral implications developed show that differences across consumption units in their time allocations and in their borrowing, saving, and asset holding decisions may be the result of differences in opportunities rather than “tastes.”     

Telomeres and human aging: facts and fibs

Can telomere dynamics, defined by telomere length and attrition rate, provide information about the biology of human aging above and beyond that provided by chronological age? Accruing data suggest that it can. White blood cells (WBCs) have been used as the primary model in attempts to decipher links between aging, aging-related disorders, and telomere dynamics in humans. The WBC model may be appropriate in clinical settings, provided that we fully appreciate its drawbacks and limitations. On the basis of WBC telomere data, it is evident that age-adjusted telomere length is highly variable, highly heritable, longer in women than men, and shorter in people who harbor a host of age-related disorders, whose common denominators may prove to be increased oxidative stress and inflammation. It appears that shorter age-adjusted WBC telomere length augurs a greater risk of morbidity and premature mortality in the elderly. However, it is unsettled whether human telomere dynamics is only a proxy for fundamental mechanisms that govern the course of aging or a key determinant in its progression.     

Caloric restriction in trans

Caloric (or dietary) restriction (CR) is the most potent, robust, and reproducible known means of extending longevity and decreasing morbidity in laboratory mammals. Two of the major questions faced by researchers in this field are the applicability to humans and the biochemical mechanism(s) involved in the actions of CR. Studies in nonhuman primates are beginning to address the former; studies in phylogenetically lower organisms such as yeast and Drosophila are beginning to address the latter. de Cabo and colleagues now provide evidence that some aspects of CR can be reproduced in mammalian tissue culture cells exposed to sera from rats and monkeys subjected to CR. This work presents the initial development of a new model with which to approach mechanistic studies of CR and provides a new form of direct evidence that CR exerts at least some of its effects in trans.     

Rape in nonhuman animal species: Definitions,evidence, and implications

This paper examines the controversial issue of rape in nonhuman animal species. Many existing studies on nonhuman rape appear to suffer from inappropriate definitions and questionable interpretations. Many existing critiques of these studies are limited by their own misunderstandings of evolutionary theory. An attempt is made to reduce the resulting controversy by defining rape in a way that can be applied to nonhuman animals, without provoking unwarranted implications about human rape. Applying this definition to existing studies indicates that behavior meeting the definition of rape does exist in several nonhuman species. However, comparisons of these species do not provide clear implications for either proximate or ultimate explanations of human rape.     

Alternate roles for the elderly: an example from a Midwestern retirement community

Increasing numbers of individuals are surviving to retirement age in relatively good health. With the loss of the work role and other roles typically associated with middle age, they are faced with the dilemma of the "roleless role," an absence of well-articulated, age-appropriate expectations and standards of behavior by which to structure everyday life. Recent anthropological, sociological, and psychological studies indicate the possibility of the development of alternate roles and age-appropriate normative systems in age-homogeneous environments. An example of one such alternate behavioral system is provided from data collected on a small retirement community in the Midwest. A normative system seems to have developed in which personal qualities such as trust, friendliness, and concern for others are more highly valued than former achievements or occupational status. Residents most frequently cited as having made a good adjustment to aging were not necessarily those who were most active, but rather those individuals who showed a determination to "keep going," lacked self-pity, kept mentally alert and aware, were willing to help others, and showed a sense of responsibility to the community. Various roles were developed and were expected to be assumed by incoming residents: alternate "work roles," represented by committee memberships and volunteer activity; "family roles," represented by the supportive or helping relations adopted toward other residents; and leisure-type roles. These behavioral standards and expectations helped to structure the relationships and everyday life of residents within the community.     

Lipofuscin and aging: a matter of toxic waste

Lipofuscin is membrane-bound cellular waste that can be neither degraded nor ejected from the cell but can only be diluted through cell division and subsequent growth. The fate of postmitotic cells is to accumulate lipofuscin, which as an "aging pigment" has been considered a reliable biomarker for the age of cells such as neurons and, by extension, their hosts. In the aging human brain, deposits of lipofuscin are not uniformly distributed but are concentrated in specific regions of functional interest. The prevailing thought is that the major source of lipofuscin is incomplete lysosomal degradation of damaged mitochondria. Accumulating evidence suggests that lipofuscin is not benign but can impair the functioning of seemingly unrelated cellular systems, including the ubiquitin/proteasome pathway. A damaging feedback loop of lysosomal and proteasomal inhibition may occur as lipofuscin accumulates, leading to what has been appropriately named a "garbage catastrophe." Reversing this catastrophe presents a formidable challenge.     

Gonadal steroids and visuo-spatial abilities in adult males: Implications for generalized age-related cognitive decline

The relationship between the gonadal steroids, testosterone and estrogen, and individual and group differences in performance on some cognitive tasks remains unclear but sex differences favoring males on some tests of visuo-spatial ability are large and robust. This aim of this review is to assess evidence for both organizational and activational effects of gonadal steroids as the principle cause of sex difference in visuo-spatial ability. Additionally, the implications of this relationship are discussed in the context of decreasing levels of gonadal steroids in aging males and psychological theories of generalized age-related cognitive decline. Based upon human and non-human research gonadal steroids have organizational effects on visuo-spatial ability in adulthood. Activational effects of gonadal steroids on visuo-spatial ability appear most dominant in older men and are necessary for maintaining optimal visuo-spatial ability; randomized clinical trials show that testosterone supplementation improves performance. Additionally, decreasing gonadal steroid levels in aging males may contribute to generalized age-related cognitive decline. Future supplementation studies in men should attempt to control for constituent abilities related to visuo-spatial task performance, and investigate interactions between dosage levels and baseline gonadal status. Further future animal research is required to investigate changes in gonadal steroid levels and their relationship to neurotransmitter systems, neural plasticity, and behavioral correlates.     

Aging in the Biosocial Order: Repairing Time and Cosmetic Rejuvenation in a Medical Spa Clinic

This article examines the relationship between biosocial meanings of aging and anti‐aging culture, whereby new standards of measuring age derive from nonchronological models of plasticity. The first part explores recent models of functional age, sexual performance, and cognitive health, while the second part outlines the cosmetic rejuvenation practices, discourses, and technologies of medi‐spa clinics that promise to repair the effects of time on the bodies of aging women. Both parts illustrate the sociological significance of the aging body in posttraditional society as the object of increasing public anxieties about the health of aging populations and ethical concerns for extending life.     

Nursing home medicine--a gloomy profession?

By controlling life-style and environmental hazards and seeking appropriate medical care, many people can enjoy a healthy, independent old age; various psychological schema provide models for such "successful" aging. But we must turn to the humanities for a vision of aging that sees meaning in lives characterized by incontinence, immobility, and confusion.