A 2026 research study found that individual earwigs showed consistent personality differences in how much they explored their environment, but these personalities were not clearly shaped by their childhood diet quality or how crowded they were during development. According to Gram Research analysis, this suggests that personality traits may be more determined by individual differences than by early-life conditions, at least in this insect species.
Scientists studied whether the food baby earwigs eat and how crowded they are affects their behavior as adults. They raised young earwigs on good food or poor food, and in groups of different sizes. When the earwigs grew up, researchers tested how active and bold they were. They found that individual earwigs had consistent personalities—some were always more active than others. However, the early-life conditions didn’t seem to change these personalities much. According to Gram Research analysis, this suggests that personality traits in earwigs may be more determined by who they are as individuals rather than their childhood experiences.
Key Statistics
A 2026 research article on European earwigs found that while individual females showed repeatable differences in exploration behavior across multiple tests, developmental diet quality and social density during childhood did not consistently explain these personality differences.
In a split-brood experiment with European earwigs, survival rates were significantly lower for nymphs raised on nutrient-diluted diets and for those raised in larger groups, confirming biological stress from treatments despite limited effects on adult personality.
Research on earwig behavior showed that distance traveled and center use were strongly negatively correlated, suggesting earwigs express a single underlying exploration axis rather than independent behavioral traits.
The Quick Take
- What they studied: Whether the quality of food and crowding levels during childhood affect how active and bold earwigs are as adults
- Who participated: Female European earwigs raised from nymphs (babies) under different conditions: some got good food and others got poor food, and some were raised alone while others were raised in groups of four or eight
- Key finding: Earwigs showed consistent individual personalities—some were always more active explorers while others were less active. However, their childhood diet and crowding didn’t strongly change these personality traits in adults
- What it means for you: This research suggests that personality and behavior traits may be more ‘hardwired’ into individuals than shaped by early experiences, at least in earwigs. While the study is about insects, it adds to our understanding of how personality develops across different species
The Research Details
Scientists used a ‘split-brood’ experiment, which means they took baby earwigs from the same families and raised them in different conditions. Some nymphs received a normal, nutrient-rich diet while others received a diet with fewer nutrients. They also varied how many earwigs lived together—some were alone, some in groups of four, and some in groups of eight. After the earwigs became adults, researchers tested their behavior six times over about three weeks by placing them in an open arena and measuring how much they moved around and where they spent time.
This experimental design is powerful because it controls for genetics—since all the earwigs came from the same families, differences in behavior couldn’t be blamed on different genes. Any behavioral differences would have to come from their different childhood experiences.
The researchers used advanced statistical methods called Bayesian mixed-effects models to analyze whether the treatments (diet and crowding) actually changed behavior, personality consistency, or how much individual earwigs varied from test to test.
Understanding how early experiences shape adult behavior is important for biology because it helps explain why individuals are different. If childhood conditions strongly affected behavior, we’d expect to see clear patterns. Finding that they don’t suggests personality may be more stable and individual than previously thought. This approach also matters because it shows how scientists can test whether environmental factors really matter versus just assuming they do.
The study’s strength is its controlled experimental design—researchers carefully manipulated specific conditions and measured outcomes systematically. However, the sample size wasn’t specified in the abstract, which makes it harder to assess statistical power. The researchers also noted an important limitation: survival rates differed between treatment groups, meaning some earwigs died before testing. This ‘selective survival’ could have hidden the true effects of the treatments by removing certain personality types from the analysis. The study was published in a peer-reviewed journal, which means other scientists reviewed it before publication.
What the Results Show
The most striking finding was that individual earwigs showed repeatable personality differences—particularly in how far they traveled in the open arena. Some earwigs consistently explored more while others consistently explored less, and this pattern held true across multiple tests over several weeks.
However, when researchers looked at whether diet quality or crowding during development changed these personalities, they found limited evidence that it did. The developmental treatments didn’t clearly affect how active earwigs were on average, how consistent their personalities were, or how much they varied from test to test.
Interestingly, earwigs that traveled more distance tended to spend less time in the center of the arena, and vice versa. Researchers interpreted this as earwigs having different ’exploration styles’ rather than separate personality traits.
The clearest effect of the treatments was on survival: earwigs raised on poor nutrition had lower survival rates, and earwigs raised in larger groups had lower survival rates than those raised alone. This suggests the treatments did create real biological stress, but this stress didn’t obviously change the personalities of the survivors.
The study found that distance traveled and center use were strongly negatively correlated—meaning these two behaviors were linked to each other rather than being independent traits. This suggests earwigs may have a single underlying ‘boldness’ or ’exploration’ axis rather than multiple separate personality dimensions. The consistency of individual differences across repeated tests (called ‘repeatability’) was substantial, indicating that personality measurement was reliable.
Previous research has shown that developmental environments can shape adult behavior in many species. This study adds nuance by showing that while individual differences in behavior are real and consistent, the specific early-life factors tested here didn’t strongly explain those differences. This fits with some recent research suggesting that personality traits may be more stable and less environmentally plastic than once thought, though other studies in different species have found stronger environmental effects.
The main limitation is that survival rates differed between groups, which means the earwigs tested as adults weren’t a random sample—they were the survivors. This ‘selective survival’ could have masked treatment effects if certain personality types were more likely to die under poor conditions. The study didn’t report the total sample size, making it difficult to assess statistical power. Additionally, the research was conducted on one species of insect, so findings may not apply to other animals or to humans. The study only tested females, so results may not apply to males.
The Bottom Line
Based on this research, there is limited evidence that early diet quality or social crowding strongly determines adult personality in earwigs. If you’re interested in animal behavior or personality development, this study suggests looking beyond simple environmental factors—individual differences may be more fundamental than previously assumed. Confidence level: Moderate, as this is one study on one species.
Biologists and animal behavior researchers should care about this finding because it challenges assumptions about environmental plasticity. People interested in personality development in general may find it interesting, though the findings are specific to earwigs and may not apply to humans or other species. Farmers or pest managers might care about understanding earwig behavior, though this study doesn’t directly address pest control.
This is a basic research study, not a practical intervention, so there’s no ’timeline to benefits.’ The findings are relevant to understanding animal behavior in general and may influence future research directions.
Frequently Asked Questions
Does what you eat as a kid affect your personality as an adult?
In earwigs, research shows limited evidence that childhood diet affects adult personality, despite diet clearly affecting survival. This suggests personality may be more stable and individual than shaped by early nutrition, though findings in other species may differ.
Can growing up in a crowded environment change how bold or shy you are?
This earwig study found that crowding during development didn’t clearly change adult boldness or exploration behavior, even though crowded conditions reduced survival rates. Individual personality differences remained consistent regardless of childhood crowding.
Why do some animals explore more than others?
This research suggests individual differences in exploration may be more fundamental to personality than shaped by early experiences. Earwigs showed consistent exploration styles across repeated tests, indicating stable individual traits rather than environmentally determined behaviors.
How do scientists test animal personality?
Researchers placed earwigs in open arenas multiple times and measured how far they traveled and where they spent time. Repeating tests over weeks showed which earwigs consistently explored more, revealing stable individual personality differences.
What is selective survival and why does it matter in behavior studies?
Selective survival occurs when certain individuals die under harsh conditions, leaving only survivors to test. This matters because it can hide treatment effects—if bold earwigs survived poor conditions better, testing only survivors might miss how conditions actually affect behavior.
Want to Apply This Research?
- Track your own personality consistency over time by rating your activity level and boldness daily on a 1-10 scale for 3-4 weeks. This mirrors the study’s approach of measuring the same trait repeatedly to see if it’s stable.
- Observe your own behavioral patterns in new situations (like open spaces or social gatherings). Notice whether you consistently explore more or less than others, similar to how the earwigs showed consistent individual differences in exploration.
- Use the app to log your activity levels and social preferences weekly over several months. Compare your patterns to see if early-life experiences (diet, social environment) correlate with your current behavior, testing the study’s findings on yourself.
This research is conducted on European earwigs and may not apply to humans or other species. The findings are from a single study and should not be used to make medical or behavioral decisions for people. If you have concerns about child development or personality, consult with qualified healthcare professionals or psychologists. This article is for educational purposes and does not constitute medical or psychological advice.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.
