The State of Research on Human–Animal Relations: Implications for Human Health

ABSTRACT

Since the late 1970s, scientific evidence has accumulated showing that pet ownership can have positive effects on people’s physical and mental wellbeing. This paper reviews the current state of affairs regarding the relationship between companion animals and human health, focusing on both the physical and psychological health outcomes related to human–animal interactions. Although designed to set the general scene on the link between animals and human wellbeing, research specific to older adults is highlighted where relevant. A particular emphasis is placed on disorders prevalent in modern-day society, notably cardiovascular disease and depression. The possible mechanisms by which companion animals might be able to enhance human wellbeing and quality of life are discussed, focusing on routes including, amongst others, the provision of companionship, social lubrication, and improvements to physical fitness. The role of the social bonding hormone, oxytocin, in facilitating attachment to our pets and the implications for human health is also discussed. Inconsistencies in the literature and methodological limitations are highlighted throughout. It is concluded that future human–animal interaction experiments should aim to account for the confounding variables that are inherent in studies of this nature.     

Can Economic Analysis Contribute to Disease Elimination and Eradication? A Systematic Review

Background

Infectious diseases elimination and eradication have become important areas of focus for global health and countries. Due to the substantial up-front investments required to eliminate and eradicate, and the overall shortage of resources for health, economic analysis can inform decision making on whether elimination/eradication makes economic sense and on the costs and benefits of alternative strategies. In order to draw lessons for current and future initiatives, we review the economic literature that has addressed questions related to the elimination and eradication of infectious diseases focusing on: why, how and for whom?

Methods

A systematic review was performed by searching economic literature (cost-benefit, cost-effectiveness and economic impact analyses) on elimination/eradication of infectious diseases published from 1980 to 2013 from three large bibliographic databases: one general (SCOPUS), one bio-medical (MEDLINE/PUBMED) and one economic (IDEAS/REPEC).

Results

A total of 690 non-duplicate papers were identified from which only 43 met the inclusion criteria. In addition, only one paper focusing on equity issues, the “for whom?” question, was found. The literature relating to “why?” is the largest, much of it focusing on how much it would cost. A more limited literature estimates the benefits in terms of impact on economic growth with mixed results. The question of how to eradicate or eliminate was informed by an economic literature highlighting that there will be opportunities for individuals and countries to free-ride and that forms of incentives and/or disincentives will be needed. This requires government involvement at country level and global coordination. While there is little doubt that eliminating infectious diseases will eventually improve equity, it will only happen if active steps to promote equity are followed on the path to elimination and eradication.

Conclusion

The largest part of the literature has focused on costs and economic benefits of elimination/eradication. To a lesser extent, challenges associated with achieving elimination/eradication and ensuring equity have also been explored. Although elimination and eradication are, for some diseases, good investments compared with control, countries’ incentives to eliminate do not always align with the global good and the most efficient elimination strategies may not prioritize the poorest populations. For any infectious disease, policy-makers will need to consider realigning contrasting incentives between the individual countries and the global community and to assure that the process towards elimination/eradication considers equity.     

How to Explore Morphological Integration in Human Evolution and Development?

Most studies in evolutionary developmental biology focus on large-scale evolutionary processes using experimental or molecular approaches, whereas evolutionary quantitative genetics provides mathematical models of the influence of heritable phenotypic variation on the short-term response to natural selection. Studies of morphological integration typically are situated in-between these two styles of explanation. They are based on the consilience of observed phenotypic covariances with qualitative developmental, functional, or evolutionary models. Here we review different forms of integration along with multiple other sources of phenotypic covariances, such as geometric and spatial dependencies among measurements. We discuss one multivariate method [partial least squares analysis (PLS)] to model phenotypic covariances and demonstrate how it can be applied to study developmental integration using two empirical examples. In the first example we use PLS to study integration between the cranial base and the face in human postnatal development. Because the data are longitudinal, we can model both cross-sectional integration and integration of growth itself, i.e., how cross-sectional variance and covariance is actually generated in the course of ontogeny. We find one factor of developmental integration (connecting facial size and the length of the anterior cranial base) that is highly canalized during postnatal development, leading to decreasing cross-sectional variance and covariance. A second factor (overall cranial length to height ratio) is less canalized and leads to increasing (co)variance. In a second example, we examine the evolutionary significance of these patterns by comparing cranial integration in humans to that in chimpanzees.     

What Is the Good of It—Ethical Controls of Human Subject Health Research?

The term “ethics” covers a multitude of virtues and possibly some sins where ethical perspectives differ. Given the diversity of ethical philosophies there is a question about what common ground can, or should, inform health research ethics. At a minimum it must be consistent with the law. Beyond that, ethics embraces a variety of possible approaches. This raises the question—what criteria are applied in determining the appropriate approach and what standards by way of quality control are applied to its decisional application by ethics committees or other authorities exercising responsibility in this difficult area. The particular issue of ethical perspectives on the use of “big data” in medical research also raises complex issues for consideration.     

From “Us vs. Them” to “Shared Risk”: Can Animals Help Link Environmental Factors to Human Health?

Linking human health risk to environmental factors can be a challenge for clinicians, public health departments, and environmental health researchers. While it is possible that nonhuman animal species could help identify and mitigate such linkages, the fields of animal and human health remain far apart, and the prevailing human health attitude toward disease events in animals is an “us vs. them” paradigm that considers the degree of threat that animals themselves pose to humans. An alternative would be the development of the concepts of animals as models for environmentally induced disease, as well as potential “sentinels” providing early warning of both noninfectious and infectious hazards in the environment. For such concepts to truly develop, critical knowledge gaps need to be addressed using a “shared risk” paradigm based on the comparative biology of environment–host interactions in different species.     

Adaptive and Genomic Explanations of Human Behaviour: Might Evolutionary Psychology Contribute to Behavioural Genomics?

Evolutionary psychology and behavioural genomics are both approaches to explain human behaviour from a genetic point of view. Nonetheless, thus far the development of these disciplines is anything but interdependent. This paper examines the question whether evolutionary psychology can contribute to behavioural genomics. Firstly, a possible inconsistency between the two approaches is reviewed, viz. that evolutionary psychology focuses on the universal human nature and disregards the genetic variation studied by behavioural genomics. Secondly, we will discuss the structure of biological explanations. Some philosophers rightly acknowledge that explanations do not involve laws which are exceptionless and universal. Instead, generalisations that are invariant suffice for successful explanation as long as two other stipulations are recognised: the domain within which the generalisation has no exceptions as well as the distribution of the mechanism described by the generalisation should both be specified. It is argued that evolutionary psychology can contribute to behavioural genomic explanations by accounting for these two specifications.     

How Much Do Metamemory Beliefs Contribute to the Font-Size Effect in Judgments of Learning?

Evidence shows that the font size of study items significantly influences judgments of learning (JOLs) and that people’s JOLs are generally higher for larger words than for smaller words. Previous studies have suggested that font size influences JOLs in a belief-based way. However, few studies have directly examined how much people’s beliefs contribute to the font-size effect in JOLs. This study investigated the degree to which font size influenced JOLs in a belief-based way. In Experiment 1, one group of participants (learners) studied words with different font sizes and made JOLs, whereas another group of participants (observers) viewed the learners'' study phase and made JOLs for the learners. In Experiment 2, participants made both JOLs and belief-based recall predictions for large and small words. Our results suggest that metamemory beliefs play an important role in the font-size effect in JOLs.