Lydia Hopper

Lydia Hopper
Johns Hopkins Medicine | JHUSOM

BSc, PhD

About

124
Publications
27,352
Reads
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2,922
Citations
Citations since 2016
77 Research Items
2168 Citations
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20162017201820192020202120220100200300400
20162017201820192020202120220100200300400
20162017201820192020202120220100200300400
Additional affiliations
January 2010 - August 2012
Georgia State University
Position
  • PostDoc Position
January 2008 - December 2009
Durham University
Position
  • PostDoc Position
September 2004 - December 2007
University of St Andrews
Position
  • PhD Student

Publications

Publications (124)
Article
Many zoos are committed to conservation efforts and answering applied questions about veterinary care and welfare. It is less common, however, for basic science to be conducted in zoos. Comparative cognitive research run in zoos is gaining momentum, with more zoos becoming involved and a greater diversity of species being studied. The majority of c...
Article
Nonhuman primates are more likely to learn from the actions of a social model than a non-social " ghost display " , however the mechanism underlying this effect is still unknown. One possibility is that live models are more engaging, drawing increased attention to social stimuli. However, recent research with humans has suggested that live models f...
Article
In this study, we evaluated the potential for a behavioral research study, designed to evaluate chimpanzee decision-making behavior, to also encourage increased activity in a group of zoo-housed chimpanzees. For the behavioral study, the chimpanzees had to carry tokens to different locations such that they always had to travel farther to obtain a m...
Article
Full-text available
Evolutionary theory predicts that natural selection will fashion cognitive biases to guide when, and from whom, individuals acquire social information but the precise nature of these biases, especially in ecologically valid group contexts, remains unknown. We exposed four captive groups of chimpanzees (Pan troglodytes) to a novel extractive foragin...
Article
Full-text available
Short-term memory is implicated in a range of cognitive abilities and is critical for understanding primate cognitive evolution. To investigate the effects of phylogeny, ecology and sociality on short-term memory, we tested the largest and most diverse primate sample to date (421 non-human primates across 41 species) in an experimental delayed-resp...
Chapter
Researchers have studied non-human primate cognition along different paths, including social cognition, planning and causal knowledge, spatial cognition and memory, and gestural communication, as well as comparative studies with humans. This volume describes how primate cognition is studied in labs, zoos, sanctuaries, and in the field, bringing tog...
Article
Full-text available
In zoos, primates experience markedly different interactions with familiar humans, such as the zookeepers who care for them, compared with those with unfamiliar humans, such as the large volume of zoo visitors to whom they are regularly exposed. While the behaviour of zoo-housed primates in the presence of unfamiliar, and to a lesser extent familia...
Article
Across captive settings, nonhuman primates may develop an array of abnormal behaviors including stereotypic and self-injurious behavior. Abnormal behavior can indicate a state of poor welfare, since it is often associated with a suboptimal environment. However, this may not always be the case as some behaviors can develop independently of any psych...
Article
Primatological research in zoos is increasing globally. Such research allows scientists to study primate biology, behavior, and cognition while helping to advance the welfare of captive primates. Moreover, zoos welcome millions of visitors annually, which creates unique opportunities for public engagement with this research. Reflecting the importan...
Article
With age, primates’ activity levels and ease of movement may decline and changes in locomotory behaviour may reflect changes in health. Thus, developing quick and reliable measures of movement has important applications for measuring recovery from disease, injury, or any age-related mobility declines. While behavioural observations can offer a rich...
Article
Full-text available
Gorillas (Gorilla gorilla gorilla) are polygynous so zoos are challenged to provide lifelong socialisation for males not living in mixed-sex or breeding troops. One approach is to establish and manage all-male "bachelor" groups; however, there is little published information on the behavioural and physiological impacts that group formation may have...
Article
The gaze-signaling hypothesis and the related cooperative-eye hypothesis posit that humans have evolved special external eye morphology, including exposed white sclera (the white of the eye), to enhance the visibility of eye-gaze direction and thereby facilitate conspecific communication through joint-attentional interaction and ostensive communica...
Presentation
As touchscreen computers have become more practical and affordable, they are increasingly used in zoos to study animal cognition and welfare. At Lincoln Park Zoo, we have conducted voluntary touchscreen research with chimpanzees (Pan troglodytes), gorillas (Gorilla gorilla gorilla), and Japanese macaques (Macaca fuscata) in a group setting and on p...
Preprint
The gaze-signaling hypothesis and the related cooperative-eye hypothesis posit that humans have evolved special external eye morphology, including exposed white sclera (the white of the eye), to enhance the visibility of eye-gaze direction and thereby facilitate conspecific communication through joint-attentional interaction and ostensive communica...
Article
It is important to those managing Japanese macaques (Macaca fuscata) in captive settings to understand predictors of wounding. While studies have demonstrated that season (breeding or nonbreeding) and sex predict rates of wounding received by zoo-housed Japanese macaques, we investigated whether individual differences in personality ratings also mi...
Presentation
As touchscreen computers have become more practical and affordable, they have been increasingly used in zoos to study animal cognition and welfare. At Lincoln Park Zoo, we have conducted voluntary touchscreen research with chimpanzees and gorillas, in a group setting and on public display, for over 15 years. Beyond the basic and applied research th...
Article
Among the growing list of novel tools with which to assess animal welfare is the use of thermal (infrared) imaging. The technology has already been utilized to identify emotional arousal in several nonhuman primate species, though most of these approaches have necessitated the use of relatively controlled settings. Here, we were interested to deter...
Article
The influence of visitors on zoo-housed primate behavior and welfare is relatively well-studied but less is known about the possible impact of zoo visitor presence on primates’ cognition. The Japanese macaques (Macaca fuscata) at Lincoln Park Zoo, USA, participate in voluntary cognitive research sessions in two touchscreen testing booths adjacent t...
Article
While previous research has focused on the impact of visitors on zoo-housed animals’ behavior, here, we evaluated the impact of visitors on the performance of four zoo-housed Japanese macaques (Macaca fuscata) in a cognitive task. The macaques completed a touchscreen-based match-to-sample task in glass-sided booths at the perimeter of their enclosu...
Article
Full-text available
The Stroop effect describes interference in cognitive processing due to competing cogni-tive demands. Presenting emotionally laden stimuli creates similar Stroop-like effects that result from participants' attention being drawn to distractor stimuli. Here, we adapted the methods of a pictorial Stroop study for use with chimpanzees (N = 6), gorillas...
Article
Full-text available
Primates' food preferences are typically assessed under conditions of certainty. To increase ecological validity, and to explore primates' decision making from a comparative perspective, we tested three primate species (Pan troglodytes, Gorilla gorilla gorilla, Macaca fuscata) (N = 18) in two food-preference tests that created different conditions...
Article
Full-text available
The past several decades have seen significant progress in zoo exhibit design, with naturalistic spaces replacing many of the traditional concrete enclosures. Furthermore, research studying the impact of such exhibit design in terms of animal welfare and zoo visitor experience has increased. While this has been especially true for studies of zoo-ho...
Book
The study of the chimpanzee, one of the human species’ closest relatives, has led scientists to exciting discoveries about evolution, behavior, and cognition over the past half century. In this book, rising and veteran scholars take a fascinating comparative approach to the culture, behavior, and cognition of both wild and captive chimpanzees. By s...
Article
Full-text available
Scientists study fairness in humans, apes, and monkeys to understand the evolutionary origins of our own behavior and to better understand the behavior of other primates. Scientists studying monkeys have found that, sometimes, monkeys will share food equally with others, but their choices often depend on their species and the specific circumstances...
Article
Full-text available
Cognitive flexibility allows individuals to adapt to novel situations. However, this ability appears to develop slowly over the first few years of life, mediated by task complexity and opacity. We used a physically simple novel task, previously tested with nonhuman primates, to explore the development of flexible problem solving in 2-, 3-, and 4-ye...
Article
Full-text available
The zone of latent solutions (ZLS) hypothesis provides an alternative approach to explaining cultural patterns in primates and many other animals. According to the ZLS hypothesis, non-human great ape (henceforth: ape) cultures consist largely or solely of latent solutions. The current competing (and predominant) hypothesis for ape culture argues in...
Article
Over the past 50 years there has been a strong interest in applying eye-tracking techniques to study a myriad of questions related to human and nonhuman primate psychological processes. Eye movements and fixations can provide qualitative and quantitative insights into cognitive processes of nonverbal populations such as nonhuman primates, clarifyin...
Article
Although humans tend to be risk averse, gambling, an inherently risky behavior, remains exceedingly popular and is an increasingly legal activity. The advent of electronic and online gambling games has further exacerbated the risk of gambling addiction. Given the frequently disadvantageous results of gambling, it is important to explore its evoluti...
Article
Full-text available
Tool use is documented in both wild and captive chimpanzees, but the creation of tool sets (e.g., two, or more, tools used in a sequence to solve a task), seems to be less common. This has raised the question of whether tool sets are a culture-dependent trait (CDT), or can be re-innovated independently, and thus fall within chimpanzees’ Zone of Lat...
Article
At zoos, and some sanctuaries, members of the public can observe the resident animals. Examining the characteristics and consequences of this type of human–animal encounter is important to understand public education and engagement as well as animal behavior and welfare. Zoos typically have a large and consistent visitor presence, and researchers r...
Article
Full-text available
Wild chimpanzees frequently make arboreal nests, while wild lowland gorillas typically nest on the ground. We aimed to understand whether zoo-housed apes’ use of elevated spaces for retiring similarly differed between species and across exhibits. Using a pre-planned exhibit switch at Lincoln Park Zoo (Chicago, USA), we compared where (elevated or t...
Article
Full-text available
Understanding captive animals’ preferences is important for their care and management. However, pairwise testing for preference can be time consuming, open to bias, and typically restricted to stimuli that can be presented manually. We tested the efficacy of using touchscreens to test zoo-housed primates’ food preferences and evaluated the primates...
Article
Despite careful attention to animal nutrition and wellbeing, gastrointestinal distress remains relatively common in captive non-human primates (NHPs), particularly dietary specialists such as folivores. These patterns may be a result of marked dietary differences between captive and wild settings and associated impacts on the gut microbiome. Howeve...
Article
Full-text available
Inferring the evolutionary history of cognitive abilities requires large and diverse samples. However, such samples are often beyond the reach of individual researchers or institutions, and studies are often limited to small numbers of species. Consequently, methodological and site-specific-differences across studies can limit comparisons between s...
Article
Full-text available
Using methods comparable to those used previously to test closely related taxa (Pan troglodytes and Macaca mulatta), our aim was to better understand how gorillas (Gorilla gorilla gorilla) and Japanese macaques (M. fuscata) learn sequences. Using a disappearing-type simultaneous chain, we trained 5 gorillas and 8 macaques on a 2-item list of color...
Article
Much work has been dedicated to defining and describing animal innovation. Despite this, efforts to compare human and animal innovation have been hindered by perceived fundamental differences between how, and why, humans and animals innovate. Furthermore, there is not a useful framework for comparisons across different taxa. Here, we provide an ove...
Poster
Full-text available
Despite most humans being risk averse, we sometimes act against our own economic interests, such as when gambling. To explore the evolutionary origins of this, we are testing 12 zoo-housed primates (chimpanzees, gorillas, Japanese macaques) on the Primate Gambling Task (PGT), which tests subjects in three payout distributions. We adapted the manual...
Poster
Wild chimpanzees frequently make arboreal nests, while gorillas mostly nest on the ground. We aimed to understand whether zoo-housed apes’ use of elevated spaces for retiring differed between species and across exhibits. Using a pre-planned exhibit switch at Lincoln Park Zoo (Chicago, IL), we compared where (elevated or on-ground) two groups of ape...
Article
Full-text available
The weekend effect hypothesis proposes that captive primates are more likely to give birth during times of low disturbance and reduced staff activity. The hypothesis specifically predicts that laboratory-housed primates will be more likely to give birth during the weekend than weekdays when staff activity is reduced. To date, support for the weeken...
Article
Full-text available
Animal ambassador programs are increasingly prevalent in zoos, yet few studies have investigated their impact on animal welfare. We assessed the effects of an ambassador program on the behavior of a colony (N = 15) of zoo-housed African penguins (Spheniscus demersus) and evaluated whether individual characteristics were predictive of participation....
Preprint
Inferring the evolutionary history of cognitive abilities requires large and diverse samples. However, such samples are often beyond the reach of individual researchers or institutions, and studies are often limited to small numbers of species. Consequently, methodological and site-specific-differences across studies can limit comparisons between s...
Article
Full-text available
Typically, animals’ food preferences are tested manually, which can be both time-consuming and vulnerable to experimenter biases. Given the utility of ascertaining animals’ food preferences for research and husbandry protocols, developing a quick, reliable, and flexible paradigm would be valuable for expediting many research protocols. Therefore, w...
Article
This study was designed to investigate the foraging behavior of zoo-housed western lowland gorillas (Gorilla gorilla gorilla) and compare it with that of zoo-housed chimpanzees (Pan trogloydytes) tested previously in a similar paradigm. Specifically, we aimed to document how a group of zoo-housed gorillas foraged within a familiar environment to di...
Article
Full-text available
In contrast to reports of wild primates, studies of captive primates' flexibility often reveal conservatism: individuals are unable to switch to new and more efficient strategies when task demands change. We propose that such conservatism might be a result of task design and hypothesize that conservatism might be linked to primates' lack of causal...
Article
Perhaps surprisingly then, little overt collaboration between zoos and sanctuaries that house captive primates has occurred within the United States. Though zoo and sanctuary communities’ core raison d’etre is the housing and care of captive (primarily exotic) species, the divergence in philosophy in other areas, including captive breeding and publ...
Article
The question of what has shaped primates’ (and other species’) cognitive capacities, whether technical or social demands, remains a hot topic of inquiry. Indeed, a key area of study within the field of comparative psychology in the last few decades has been the focus on social life as a driving force behind the evolution of cognition, studied from...
Article
When trying to understand the behavior and cognition of nonhuman primates, primatologists have to interpret the decision making of nonverbal species and quantify (indirect) behavioral responses as metrics for cognitive processes. To develop a full picture most likely requires input from both wild and captive settings, and combining such data with r...
Chapter
Consideration of social cognition—how an individual’s decision-making is influenced by her/his social environment—is key to understanding the behaviour of socially living nonhuman primates. In this chapter we discuss primate social cognition by focusing on primates’ behavioural responses to the presence and actions of others, how they adjust their...
Article
There are two commonly‐used methods for calculating primates’ personality dimensions, behavioral assessments and surveys, which can be used separately or in conjunction. However, these methods have limitations. Behavioral assessments, such as the novel object test or human intruder test, often require subjects to be separated and demand highly‐cont...
Article
Full-text available
Studies of transmission biases in social learning have greatly informed our understanding of how behaviour patterns may diffuse through animal populations, yet within-species inter-individual variation in social information use has received little attention and remains poorly understood. We have addressed this question by examining individual perfo...
Article
Full-text available
Video cameras are increasingly being used to monitor captive animals in zoo, laboratory, and agricultural settings. This technology may also be useful in sanctuaries with large and/or complex enclosures. However, the cost of camera equipment and a lack of formal evaluations regarding the use of cameras in sanctuary settings make it challenging for...
Article
Full-text available
In the zoo environment, anthropogenic noise is common as sound levels fluctuate due to visitors, construction, habitat design, and special events. In this study, changes in the mood of three species of zoo-housed primates in response to a loud annual event were evaluated with the response-slowing paradigm. In this paradigm, animals experiencing anx...
Article
Full-text available
Various non-human animal species have been shown to exhibit behavioural traditions. Importantly, this research has been guided by what we know of human culture, and the question of whether animal cultures may be homologous or analogous to our own culture. In this paper, we assess whether models of human cultural transmission are relevant to underst...
Article
Full-text available
Background Studying animal cognition in a social setting is associated with practical and statistical challenges. However, conducting cognitive research without disturbing species-typical social groups can increase ecological validity, minimize distress, and improve animal welfare. Here, we review the existing literature on cognitive research run w...
Data
Published experiments of primate cognition in a social setting (2000-2015) The publications that reported tests of primate cognition in a social setting published between 2000 and 2015 (inclusive), sorted by species, with one entry per unique combination of environment type and species per publication.
Conference Paper
Full-text available
DO SANCTUARY CHIMPANZEES (PAN TROGLODYTES) BEHAVE DIFFERENTLY WHEN UNFAMILIAR PEOPLE ARE PRESENT? B. K. Hansen1,2, S. R. Ross1, L. M. Hopper1 and A. L. Fultz2 1Lester E. Fisher Center for the Study and Conservation of Apes, Lincoln Park Zoo, 2001 N Clark St, Chicago, IL 60614, USA, 2Chimp Haven, Keithville, LA Sanctuaries are typically closed to...
Conference Paper
Full-text available
Opportunities and challenges of conducting observational research at a chimpanzee sanctuary Bethany K. Hansen1, 2, Stephen R. Ross1, Lydia Hopper1, Amy Fultz2 1. Lester E. Fisher Center for the Study and Conservation of Apes, Lincoln Park Zoo, 2001 N Clark St, Chicago, IL, 60614 2. Chimp Haven, Keithville, LA, 71047 Sanctuaries care for a variety o...
Chapter
When trying to understand the behavior and cognition of nonhuman primates, researchers have to interpret the decision making of nonverbal species and quantify (indirect) behavioral responses as metrics for cognitive processes. The methods used to achieve this are as diverse as the topics primatologists study. Research with primates varies both in t...
Article
Full-text available
Zoo-housed animals are provided with many temporary elements in their exhibit, such as environmental enrichment devices (EEDs), which may not match the aesthetic of their exhibit. Some zoos object to the use of artificial EEDs in naturalistic exhibits, but there has been little research into whether the appearance of these temporary elements influe...
Chapter
Full-text available