It is generally assumed that human beings have personalities, while animals do not. This assumption is not only derived from common sense, but also a basic principle of western philosophy and social theory (Mead, 1934). Still, dog owners will not stop mumbling about their cute puppy's unique personality. And they find support from unexpected source: Biologists argue that humans are nothing more, nothing less than animals. So they, too, begin to take into consideration that animals – including humans – might have a personality. What seems like a solely philosophical question at first glance, has important practical impacts, because the existence of animal personality contradicts the assumption that animals used in biological experiments can be standardized, and have uniform properties. If despite all efforts of standardization a residual variation cannot be eliminated, pharmaceutical and medical experiments might lose part of their validity.
Therefore the hypothesis that laboratory mice possess a personality was tested in an empirical study. In this study a set of standard behavior tests was performed with 40 female mice of the strain C57BL/6N. The data was then analyzed for correlations over time and across contexts, since this is a requirement for animal personality.
Table of Contents
1. Introduction
1.1 Definition
1.2 State of the Art
1.3 Standardization
1.4 Hypotheses
2. Animals, Material, and Methods
2.1 Animals, housing, and experimental conditions
2.2 Behavioral tests
2.3 Experimental Design
2.3.1 The Elevated Plus Maze (EPM)
2.3.2 The Open Field Test (OF)
2.3.3 The Object Exploration Test (OBX)
2.3.4 The Social Investigation Test (SI)
2.3.5 The Dark/Light Test (DL)
2.3.6 The Free Exploration Task (FET)
2.4 Videos and computer software
2.4.1 VirtualDub
2.4.2 Optimas
2.4.3 Tracking Analysis
2.4.4 Statistical analysis
3. Results
3.1 Correlations over time
3.1.1 The Elevated Plus Maze (EPM)
3.1.2 The Open Field Test (OF)
3.1.3 The Object Exploration Test (OBX)
3.1.4 The Social Investigation Test (SI)
3.1.5 The Dark/Light Test (DL)
3.1.6 The Free Exploration Task (FET)
3.2 Correlation across contexts
3.2.1 The Elevated Plus Maze (EPM)
3.2.2 The Open Field Test (OF)
3.2.3 The Object Exploration Test (OBX)
3.2.4 The Social Investigation Test (SI)
3.2.5 The Dark/Light Test (DL)
3.2.6 The Free Exploration Task (FET)
3.3 Differences between individuals
4. Discussion
4.1 Correlation over time
4.2 Correlation across contexts
4.3 Differences between individuals
4.4 Implications
5. Conclusion
Objectives & Research Themes
This study aims to investigate whether laboratory inbred mice exhibit personality traits by testing the hypotheses that individual behavior is correlated over time, correlated across contexts, and that individuals differ in their behavioral responses under standardized conditions.
- Intra-individual consistency in behavior (inter-temporal and across-context).
- Evaluation of standardized behavior tests in mice.
- Assessment of animal personality as a potential source of experimental variability.
- Analysis of correlations between different behavioral parameters (e.g., anxiety-like and exploratory behavior).
Excerpt from the Book
1.1 Definition
As a starting point, it is essential to define the concept of animal personality. As for most scientific concepts, a univocally shared understanding of animal personality does not exist. Definitions range from concepts, which stress the plasticity of personality, to the other extreme, which focuses on its invariability and static nature. As Dingemanse and Réale (2010) put it: „The first, prevalent in behavioural ecology, considers behaviours as highly plastic traits with individuals being capable of rapidly changing the expression of behaviour in response to changes in the surrounding environmental conditions […] Alternatively, each individual might be limited in its expression of a behavioural trait relative to the overall expression of that trait in the population”. One argument for the second, relatively stable understanding of personality is also the mutual reinforcement of different personality traits. Dingemanse and Réale (2010) put this as follows: „Selection often also acts on the correlation between seemingly unrelated traits, such that focusing on a single trait might result in a mismatch with the predictions of adaptive models“.
The first, rather fluid concept grasps personality as a phenomenon which can change at any time in any situation, and which is only shaped and influenced by environmental conditions. The theoretical value of the concept of personality consists in the fact that the action or reaction of an individual is not completely determined by environmental conditions. Hence, the explanatory value of a concept that focuses on the plasticity of personality is rather limited for the discussion at hand.
Summary of Chapters
1. Introduction: Discusses the theoretical background of animal personality, the challenges of standardization in laboratory settings, and formulates the study's core hypotheses regarding behavioral consistency.
2. Animals, Material, and Methods: Details the subject animals (C57BL/6N mice), housing conditions, and the specific behavioral tests utilized to measure anxiety, exploration, and social curiosity.
3. Results: Presents the statistical data regarding correlations of behavioral parameters over time and across different experimental contexts.
4. Discussion: Interprets the experimental findings, addresses potential limitations such as test-design-related floor effects, and reflects on the broader implications for animal experimentation.
5. Conclusion: Summarizes the confirmation of the study's hypotheses and provides suggestions for future research concerning individual behavioral differences.
Keywords
Animal personality, behavioral consistency, laboratory mice, C57BL/6N, standardization, behavioral syndromes, anxiety-like behavior, exploratory behavior, social investigation, inter-individual variation, inter-temporal consistency, across-context consistency, biomedical research, behavioral tests, reproducibility.
Frequently Asked Questions
What is the primary focus of this research?
The research investigates whether laboratory inbred mice possess personality traits, characterized by consistent behavioral patterns over time and across different situations.
What are the main thematic areas?
The study centers on animal personality, standardized behavioral testing, the impact of non-random behavioral variability on biomedical results, and individual differences in mice.
What is the central research question?
The primary goal is to determine if individual laboratory mice display stable personality traits that can be detected via standard behavioral assays despite attempts at strict standardization.
Which scientific methods were employed?
The study used a series of six standard behavioral tests (e.g., Elevated Plus Maze, Open Field Test) conducted on 40 female mice, analyzed with statistical software to determine correlations over time and context.
What is covered in the main body of the work?
It covers the definitions of animal personality, the detailed methodology of the behavioral test battery, results from correlation analyses, and a critical discussion of the observed data.
Which keywords characterize this work?
Key terms include animal personality, behavioral consistency, standardization, laboratory mice, anxiety, and inter-individual variation.
Why did the Free Exploration Task (FET) fail to yield results?
The researcher identified a probable floor effect where the test environment was either too aversive or the specific test design failed to encourage the mice to leave their home cage, resulting in no activity data.
How do the results impact medical or pharmaceutical testing?
The existence of animal personality suggests that residual behavioral variation may influence experiment outcomes, potentially reducing the validity of standardized medical tests that assume uniformity among subjects.
Is there a significant difference in how mice react to male versus female conspecifics?
Yes, the study observed that mice differentiated between sexes, as evidenced by shorter latency to enter the social compartment for male contact mice, suggesting potential mating-related motivation.
- Arbeit zitieren
- Mieke Heidenreich (Autor:in), 2011, Variation despite Standardization: Evidence for Animal Personality in Laboratory Mice?, München, GRIN Verlag, https://www.grin.com/document/201322
