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Open Access Publications from the University of California


The International Journal of Comparative Psychology is sponsored by the International Society for Comparative Psychology. It is a peer-reviewed open-access digital journal that publishes studies on the evolution and development of behavior in all animal species. It accepts research articles and reviews, letters and audiovisual submissions.

Volume 27, Issue 1, 2014

Issue cover

Special Issue Introduction

Future Directions in Comparative Psychology: An Introduction to the Special Issue

The purpose of this special issue is to highlight the publication trends regarding research in today’s field of comparative psychology.  A survey was conducted to determine the research priorities of institutions and researchers currently pursuing research with animals.  Over 200 responses were received from 28 different countries representing scientists from many different backgrounds and institutions.  Top priorities for research interests were clearly divided by the setting in which scientists conducted their research with animals. Experts from the fields identified as the most important future research topics on comparative psychology were invited to review their respective fields for publication trends over the last 20 years.  The results of their significant efforts and the importance of continuing research in comparative psychology are presented and addressed in this special issue.  We hope that this information will not only guide research within these fields but also identify potential overlap between zoos/aquariums and academic institutions to further collaboration within the field.

Special Issue

Comparative Cognition: Past, Present, and Future

Comparative cognition is the field of inquiry concerned with understanding the cognitive abilities and mechanisms that are evident in nonhuman species.  Assessments of animal cognition have a long history, but in recent years there has been an explosion of new research topics, and a general broadening of the phylogenetic map of animal cognition. To review the past of comparative cognition, we describe the historical trends.  In regards to the present state, we examine current “hot topics” in comparative cognition.  Finally, we offer our unique and combined thoughts on the future of the field.

The Comparative Study of Learning from 1994-2013

The study of learning has long held a central position in the field of comparative psychology. Here we present a survey of the past 20 years of comparative learning research, covering publications from 1994 to 2013. We selected seven journals with a strong focus on comparative learning, and identified five major topics of study represented by the publications in those journals: non-associative learning, associative learning, perceptual/object learning, social learning, and neural correlates of learning. Of these topics, associative learning was by far the most popular, comprising about 85% of the research in comparative learning. We therefore subdivided this topic into seven subcategories of research questions, which included causal reasoning, compound cue interactions, extinction, stimulus control, outcome learning and motivation, spatial learning, and temporal integration or timing. The number of publications addressing each topic or research question, as well as the number of citations received by these publications, was examined for the combined seven journals across the 20 year period of review. The subject of spatial learning has grown rapidly over the past 20 years, and has attracted robust interest by researchers both in and outside of the field of comparative psychology.  Although much less popular in terms of publication number, recent growth was also identified for studies of causal reasoning, social learning, and perceptual or object learning.

Sex, Love, or War? A representation of 20 years of research on the social interactions of animals

To navigate through a social world, animals may form temporary or long-term associations with others, recognize kin and discriminate between familiar and unfamiliar conspecifics, protect themselves and their resources, fight and compete for the best mates, and produce offspring that require various forms of care.  The purpose of the current paper was to summarize the publication trends of research investigating animal social interactions over the last 20 years. We selected 8 journals for their diverse representation of animal taxa and examined the number of published articles representing research on affiliative, agonistic, and sexual social interactions.  Out of 18,993 published articles, social interactions (N = 4,273) were studied 5.5% to 30.8% of the published articles per journal between 1993-2013.  Agonistic social interactions (43%) were the most frequently published topic with affiliative social interactions representing less than a third (30%) of the articles and sexual social interactions accounting for the remaining articles (27%).  Mammalian social interactions were investigated the most (38.5%) with invertebrate (22%) and avian (21%) social interactions following closely behind.  Observational research and experimental research designs were divided almost equally across different social interactions except for affiliative interactions.  Social interactions were studied most often in laboratory settings (45%), then semi-natural field settings (32.5%), and less often in natural habitats (19%).  Interestingly, the rates of the different types of social interactions, certain taxa, type of research study, and research setting remained relatively consistent across the 20 year period.  Some fluctuations occurred in the frequency of specific topics and taxa within various years; however, research on mate choice, parental care, environmental influences, and group composition was consistently conducted across the years.  While many aspects of social interactions in a broad range of taxa have been studied, there are many areas that are still sparse and in need of additional research.

Trends in the field of mammalian social behavior and health over the last 20 years

In any scientific field there are thematic changes over time as new technologies and methods of investigation are developed and accumulated knowledge drives new research directions.  The current study examines how themes in the investigation of social behavior and health have changed over the last 20 years.  Literature searches were performed to identify articles published between 1993-2012 that investigate the intersection between social behavior and health in mammals.  Results identify the top journals that publish articles in this field and describe trends in how sub-divisions in social behavior (e.g. aggression or dominance) and health (e.g. immunity or brain chemicals) have changed over the last 20 years.  Our results suggest a dramatic increase in publications on the intersection between social behavior and health over this time span.  Major categories of study include relationships between general social behavior or social stress and health outcomes relating to stress responses, endocrinology, and the brain.

Animal Welfare Science: Recent Publication Trends and Future Research Priorities

Animal welfare science is a young and thriving field. Over the last two decades, the output of scientific publications on welfare has increased by c. 10-15% annually (tripling as a proportion of all science papers logged by ISI’s Web of Science), with just under half the c. 8500 total being published in the last 4 years. These papers span an incredible 500+ journals, but around three quarters have been in 80 animal science, veterinary, ethology, conservation and specialized welfare publications, and nearly 25% are published in just two: Animal Welfare and Applied Animal Behaviour Science. Farmed animals – especially mammals – have attracted by far the most research. This broadly reflects the vastness of their populations and the degree of public concern they elicit; poultry, however, are under-studied, and farmed fish ever more so: fish have only recently attracted welfare research, and are by far the least studied of all agricultural species, perhaps because of ongoing doubts about their sentience. We predict this farm animal focus will continue in the future, but embracing more farmed fish, reptiles and invertebrates, and placing its findings within broader international contexts such as environmental and food security concerns. Laboratory animals have been consistently well studied, with a shift in recent years away from primates and towards rodents. Pets, the second largest animal sector after farmed animals, have in contrast been little studied considering their huge populations (cats being especially overlooked): we anticipate research on them increasing in the future. Captive wild animals, especially mammals, have attracted a consistent level of welfare research over the last two decades. Given the many thousands of diverse species kept by zoos, this must, and we predict will, increase. Future challenges and opportunities including refining the use of preference tests, stereotypic behaviour, corticosteroid outputs and putative indicators of positive affect, to enable more valid conclusions about welfare; investigating the evolution and functions of affective states; and last but not least, identifying which taxonomic groups and stages of development are actually sentient and so worthy of welfare concern.

Where has all our research gone? A 20-year assessment of the peer-reviewed wildlife conservation literature

We conducted a review of the wildlife conservation literature to identify broad trends in the publishing record and focal areas of research over the past 20 years. A total of 5,853 papers were reviewed with an emphasis on decadal changes between 1993, 2002, and 2012. For each paper we identified the journal and common keywords, and also determined the research scope, conservation issues and applications, and geographic focus. We found that both the numer of journals publishing in the field, as well as the number of published articles, has increased significantly over time. The proportional contribution of the most prominent journals in the field has decreased over time, but not the importance of the articles within those journals. Previously reported biases in the literature towards mammlas and birds persisted in our study, leaving large proportions of globally threatened taxa (e.g. amphibians) underrepresented. There was als a disparity in the number of publications from particular geographic regions, however the proportional contribution of under-represented geographic regions (e.g. Central & South America) increased over time. Finally, using the prevalence of keywords, we identified wildlife/adaptive management, hunting/bushmeat, and human wildlife conflict as contemporary (1998-2012) research priorities. The persistence of biases towards charismatic taxa can hinder conservation efforts, and we suggest that researchers refocus their efforts towards vulnerable regions and taxa in order to better address conservation priorities.

Human-animal interactions, relationships and bonds: a review and analysis of the literature

The study of human-animal interactions (HAI), and the resulting human-animal relationships (HARs) and bonds (HABs) which are set up as a consequence, is currently a topical issue in comparative psychology. Here we review the HAI/HAR/HAB literature to detect the main publication trends, and to identify the predominant research themes in this area. Research in HAI/HAR/HAB only really started in the 1980s, but since then there has been a growth in studies which is still continuing. Most of these studies have been in the contexts of companion animal or agricultural animal research, but there is now a growing literature on laboratory, zoo and wild animals too. In the companion animal HAI/HAB literature the greatest emphasis has been on Animal-assisted Interventions (AAI), and the benefits to people of pet ownership and interaction with pets. Agricultural HAI/HAR research, on the contrary, has been more concerned with the welfare consequences of HAI/HARs to the animals. This disjunction is reflected in the preference of companion animal researchers to use the term ‘bond’, but agricultural researchers to use ‘relationship’. Other themes prominent in the literature include methodological issues, the characteristics of caretakers, the role of veterinarians, sociological approaches, and theoretical aspects. It is concluded that currently HAI/HAR/HAB research does not constitute a unified field, and there is a need to: i) agree and define a standard terminology; ii) undertake more research on the effects of HAI on companion animals; iii) undertake more research on the form and frequency of interactions; and iv) increase research on HAI/HAR/HABs in laboratory, zoo and wild-living animals. This research is important to understand whether HAI has positive, neutral or negative consequences, both for humans and for animals.