Differences In Behavioral Traits Research Articles

Genetic variants that modify neuroendocrine gene expression and foraging behavior of C. elegans.

The molecular mechanisms underlying diversity in animal behavior are not well understood. A major experimental challenge is determining the contribution of genetic variants that affect neuronal gene expression to differences in behavioral traits. In Caenorhabditis elegans, the neuroendocrine transforming growth factor-β ligand, DAF-7, regulates diverse behavioral responses to bacterial food and pathogens. The dynamic neuron-specific expression of daf-7 is modulated by environmental and endogenous bacteria-derived cues. Here, we investigated natural variation in the expression of daf-7 from the ASJ pair of chemosensory neurons. We identified common genetic variants in gap-2, encoding a Ras guanosine triphosphatase (GTPase)-activating protein homologous to mammalian synaptic Ras GTPase-activating protein, which modify daf-7 expression cell nonautonomously and promote exploratory foraging behavior in a partially DAF-7-dependent manner. Our data connect natural variation in neuron-specific gene expression to differences in behavior and suggest that genetic variation in neuroendocrine signaling pathways mediating host-microbe interactions may give rise to diversity in animal behavior.

Water-borne testosterone levels predict exploratory tendency in male poison frogs

Hormones play a fundamental role in mediating social behaviors of animals. However, it is less well understood to what extent behavioral variation between individuals can be attributed to variation in underlying hormonal profiles. The goal of the present study was to infer if individual androgen levels, and/or the modulation thereof, can explain among-individual variation in aggressiveness, boldness and exploration. We used as a model the dart-poison frog Allobates femoralis and took repeated non-invasive water-borne hormonal samples of individual males before (baseline) and after (experimental) a series of behavioral tests for assessing aggression, boldness, and exploratory tendency. Our results show that androgen levels in A. femoralis are quite stable across the reproductive season. Repeatability in wbT baseline levels was high, while time of day, age of the frog, and trial order did not show any significant impact on measured wbT levels. In general, experimental wbT levels after behavioral tests were lower compared to the respective baseline levels. However, we identified two different patterns with regard to androgen modulation in response to behavioral testing: individuals with low baseline wbT tended to have increased wbT levels after the behavioral testing, while individuals with comparatively high baseline wbT levels rather showed a decrease in hormonal levels after testing. Our results also suggest that baseline wbT levels are linked to the personality trait exploration, and that androgen modulation is linked to boldness in A. femoralis males. These results show that differences in hormonal profiles and/or hormonal modulation in response to social challenges can indeed explain among-individual differences in behavioral traits.

A single-nucleus transcriptomic atlas of the dog hippocampus reveals the potential relationship between specific cell types and domestication.

The process of domestication has led to dramatic differences in behavioral traits between domestic dogs and gray wolves. Whole-genome research found that a class of putative positively selected genes were related to various aspects of learning and memory, such as long-term potentiation and long-term depression. In this study, we constructed a single-nucleus transcriptomic atlas of the dog hippocampus to illustrate its cell types, cell lineage and molecular features. Using the transcriptomes of 105 057 nuclei from the hippocampus of a Beagle dog, we identified 26 cell clusters and a putative trajectory of oligodendrocyte development. Comparative analysis revealed a significant convergence between dog differentially expressed genes (DEGs) and putative positively selected genes (PSGs). Forty putative PSGs were DEGs in glutamatergic neurons, especially in Cluster 14, which is related to the regulation of nervous system development. In summary, this study provides a blueprint to understand the cellular mechanism of dog domestication.

Depression and financial planning horizon

Major depression is associated with biased information processing and decision making. Previous research suggests that people dealing with depression view the future negatively and exhibit a higher discounting rate than healthy people do. This study tests the hypothesis that depression is associated with financial planning horizon–the time horizon by which individuals and households formulate their saving and spending schedules. Analyses conducted using data drawn from multiple waves of the Health and Retirement Study showed an inverse association between major depressive episodes and financial planning horizon, indicating that depressed people plan their finances over a shorter horizon. We also found that major depression is associated with various health and financial outcomes representing evidence of myopic decision making. The link between depression and financial planning horizon is partially explained by depression-oriented differences in behavioral traits, such as optimism/pessimism, perceived control, perceived mastery, and self-assessed survival probability. Overall, our findings point to a significant economic cost of depression, which compounds through myopic financial planning.

Inter-annual fluctuations of sociability in the common shrew (Sorex araneus L.) as determined by a preference test: A case of balancing selection?

The specific aim of our study was to test individual common shrews from a population monitored long-term. In a preference test, we revealed sex-related differences in behavioral traits of young common shrews and consistent individual differences in sociability, boldness and in an exploration pattern that have not been reported previously. More active animals were bolder and more superficial in the exploration of non-social objects as compared to shier shrews. Significant inter-annual differences in sociability, boldness and exploratory activity were observed. When we assessed correlations of sociability with population density, non-residents’ abundance, activity shared in space, survivorship and home range size, we found a positive association with shared spatial activity and home range size. Contrary to expectation, sociability did not correlate with the density of residents and survivorship. A significant negative association of sociability with non-residents’ abundance was documented. Survivorship was associated only with an exploration pattern. The thoroughness of exploration positively correlated with non-residents’ abundance. We regard the inter-annual changes in sociability that we observed in the test as a by-product of survival of shrews with various exploration patterns that are associated with dispersal. We can hypothesize that the personality differences registered in this study are maintained by balancing frequency-dependent selection of animals that is associated with differences in habitat quality throughout the population cycle.

The effects of owner and domestic cat (Felis catus) demographics on cat personality traits

Personality has been researched in many companion animals and is described as differences in behavioural traits of individuals that often remain consistent over time. In domestic cats many factors have been discovered to influence personality, including breed, coat colour, gender, rearing experience, number of cats within a household, owner age, owner gender and owner personality. However, research is limited for certain factors, including owner demographics, so the aim was to demonstrate that a simple survey could be used to infer personality traits and identify domestic cat and owner demographical factors that influence certain traits. An online personality survey with 34 traits was sent out to cat owners in the UK, Europe and North America, containing cat and owner demographical questions. Housing type, total number of cats in household and owner animal preference all had significant effects on many of the personality trait scores. Unexpectedly, cat breed, owner age, neutering status and country of residence showed distinct clusters in the multifactor analysis individual model but did not have any significant effects on any of the personality traits, along with coat colour, owner gender and cat gender which were initially considered of importance to the study, contradicting some of the previous research. This study highlights the importance of considering demographical factors that influence personality traits, to predict cat personality based on these factors to cater for specific husbandry practices and to improve the chances of successful adoption for those within shelters.

Sex differences in behavioral traits related with high sensitivity to the reinforcing effects of cocaine

Cocaine is the most prevalent illegal stimulant drug in Europe among the adult population. Its abuse is characterized by a faster substance abuse disorder (SUD) development than other drugs, with high vulnerability to relapse. However, there does not exist an effective treatment for cocaine dependence. Sex differences have been reported in psychological disorders including SUD. For this reason, it is essential to identify risk factors that predict susceptibility or resilience to cocaine addiction for the development of effective prevention strategies considering sex differences. In the present study, the main objective was to determine more sensitive phenotypes to the conditioned reinforcing effects of cocaine in both sexes. Anxiety-like behavior and the locomotor response to novelty were evaluated in the elevated plus maze, and despair in the tail suspension test, as well as vulnerability traits linked with a high sensitivity to the reinforcing effects of a subthreshold dose of cocaine (1 mg/kg) in the conditioned place preference (CPP) paradigm in male and female mice. Our results indicated that only female mice with high anxiety, low locomotor response to novelty or low despair levels acquired CPP induced by cocaine, while male mice with low anxiety, high locomotor response to novelty or high despair levels presented a higher susceptibility to the rewarding effects of cocaine than others. These sex differences in the results reveal an opposite pattern in males and females on the relationship between anxiety- and depressive-like behaviors and cocaine vulnerability, demonstrating the need to include female mice in preclinical studies.

Aggressiveness-related behavioural types in the pearly razorfish.

Behavioural types (i.e., personalities or temperament) are defined as among individual differences in behavioural traits that are consistent over time and ecological contexts. Behavioural types are widespread in nature and play a relevant role in many ecological and evolutionary processes. In this work, we studied for the first time the consistency of individual aggressiveness in the pearly razorfish, Xyrichtys novacula, using a mirror test: a classic method to define aggressive behavioural types. The experiments were carried out in semi-natural behavioural arenas and monitored through a novel Raspberry Pi-based recording system. The experimental set up allowed us to obtain repeated measures of individual aggressivity scores during four consecutive days. The decomposition of the phenotypic variance revealed a significant repeatability score (R) of 0.57 [0.44–0.60], suggesting high predictability of individual behavioural variation and the existence of different behavioural types. Aggressive behavioural types emerged irrespective of body size, sex and the internal condition of the individual. Razorfishes are a ubiquitous group of fish species that occupy sedimentary habitats in most shallow waters of temperate and tropical seas. These species are known for forming strong social structures and playing a relevant role in ecosystem functioning. Therefore, our work provides novel insight into an individual behavioural component that may play a role in poorly known ecological and evolutionary processes occurring in this species.

Individual behavioural traits not social context affects learning about novel objects in archerfish

Learning can enable rapid behavioural responses to changing conditions but can depend on the social context and behavioural phenotype of the individual. Learning rates have been linked to consistent individual differences in behavioural traits, especially in situations which require engaging with novelty, but the social environment can also play an important role. The presence of others can modulate the effects of individual behavioural traits and afford access to social information that can reduce the need for ‘risky’ asocial learning. Most studies of social effects on learning are focused on more social species; however, such factors can be important even for less-social animals, including non-grouping or facultatively social species which may still derive benefit from social conditions. Using archerfish, Toxotes chatareus, which exhibit high levels of intra-specific competition and do not show a strong preference for grouping, we explored the effect of social contexts on learning. Individually housed fish were assayed in an ‘open-field’ test and then trained to criterion in a task where fish learnt to shoot a novel cue for a food reward—with a conspecific neighbour visible either during training, outside of training or never (full, partial or no visible presence). Time to learn to shoot the novel cue differed across individuals but not across social context. This suggests that social context does not have a strong effect on learning in this non-obligatory social species; instead, it further highlights the importance that inter-individual variation in behavioural traits can have on learning.Significance statementSome individuals learn faster than others. Many factors can affect an animal’s learning rate—for example, its behavioural phenotype may make it more or less likely to engage with novel objects. The social environment can play a big role too—affecting learning directly and modifying the effects of an individual’s traits. Effects of social context on learning mostly come from highly social species, but recent research has focused on less-social animals. Archerfish display high intra-specific competition, and our study suggests that social context has no strong effect on their learning to shoot novel objects for rewards. Our results may have some relevance for social enrichment and welfare of this increasingly studied species, suggesting there are no negative effects of short- to medium-term isolation of this species—at least with regards to behavioural performance and learning tasks.

Financial risk attitudes, demographic profiles, and behavioural traits: Do they interrelate?

Research aim: The paper addressed two objectives: examining the differences in behavioural traits with regard to risk attitudes, and explore the differences in financial risk attitudes with regard to demographic profiles of Malaysian investors.Design/ Methodology/ Approach: Using the t-test and one-way analysis of variance (ANOVA), this paper investigates how differences in behavioural trait bias among 241 master of business administration students in Malaysia affect their financial risk attitudes.Research finding: First, we find that the financial risk takers have higher levels of overconfidence, maximization, happiness, and trust than the risk-averse respondents. Second, in terms of demographics, we find that the following take significantly higher risks: men versus women, singles versus those who are married, and, those with lower income and less work experience. Besides, in terms of race, the Chinese are the greatest financial risk takers.Theoretical contribution/ Originality: Both the behavioural traits and financial risk attitudes are new for a multicultural background market like Malaysia. Reflections on the findings suggest that the financial planners need to take cognisance of such relationships, tendencies and risk preferences so as to understand their client inclination and provide appropriate advice to their investor clients.Research limitation/ Implication: Categories under the research design and sample selection can be further extended by considering more advanced research approach and a bigger size of sample respondents.Keywords: Behavioural Finance, Behavioural Traits, Risk Attitudes, Financial Risk, Demographic ProfilesType of article: Research paperJEL Classifications: D14, D91, G41Received: 31 January 2020Revised: 15 April 2020, 24 April 2020Accepted: 6 May 2020Published online: 29 January 2021

Heritability of animal individuality in fish: Distribution, behavior, metabolism and stress response

Animal individuality is proposed to describe individual differences in behavior. Individuals may exhibit consistent differences in behavioral traits within a population, and these traits are heritable. It has also been known that animal individuality can be attributed to both genetic and environmental effects. We previously observed the presence of bold individuals (BI) and shy individuals (SI) in olive flounder (Paralichthys olivaceus). However, the individuality distribution and the behavioral phenotype of offspring with different individualities remain unclear. In this study, the temperature and acidity challenges of larvae at 25 days-post-hatch (DPH) and juvenile (50 DPH) of bold and shy flounder offspring were investigated at pH = 7.3, 7.7, 8.1 and temperature at 4, 18, 28 °C. On 25 DPH, bold offspring (BO) showed higher survival rates with acidity at pH = 7.3 and 4 °C challenge. Three behavioral phenotypes (bold, middle and shy individuals, BI, MI and SI) were observed in both juvenile (8 MPH) bold and shy flounder offspring. The percentage of SI offspring from the shy maternal line (SS) was higher than BI offspring from the bold maternal line (BB) (0.75 vs. 0.58). BI from both BO (BB) and SO (SB) were more motivated to feed and active during net confinement than SI (BS and SS). Furthermore, BB and SB exhibited higher metabolic rates and actively responded to predator stressor, while BS and SS showed a divergent tendency. However, the metabolism of the offspring seemed to be partially affected by their maternal line. Taken together, our study indicates that screening of animal individuality in population would improve animal welfare and increase the output efficiency of flounder in aquaculture.

Two experimental designs generate contrasting patterns of behavioral differentiation along a latitudinal gradient in Lestes sponsa-Common-garden not so common after all?

Understanding why and how behavioral profiles differ across latitudes can help predict behavioral responses to environmental change. The first response to environmental change that an organism exhibits is commonly a behavioral response. Change in one behavior usually results in shifts in other correlated behaviors, which may adaptively or maladaptively vary across environments and/or time. However, one important aspect that is often neglected when studying behavioral expressions among populations is if/how the experimental design might affect the results. This is unfortunate since animals often plastically modify their behavior to the environment, for example, rearing conditions. We studied behavioral traits and trait correlations in larvae of a univoltine damselfly, Lestes sponsa, along its latitudinal distribution, spreading over 3,300 km. We compared behavioral profiles among larvae grown in two conditions: (a) native temperatures and photoperiods or (b) averaged constant temperatures and photoperiods (common‐garden). We hypothesized latitudinal differences in behavioral traits regardless of the conditions in which larvae were grown, with northern populations expressing higher activity, boldness, and foraging efficiency. When grown in native conditions, northern larvae were bolder, more active and more effective in prey capture than central and low latitude populations, respectively, as well as showed the strongest behavioral correlations. In contrast, larvae reared in common‐garden conditions showed no differences between regions in both individual traits and trait correlations. The results suggest different selective pressures acting on the studied traits across populations, with environment as a central determinant of the observed trait values. Common‐garden designed experiments may evoke population‐dependent levels of plastic response to the artificial conditions and, hence, generate results that lack ecological relevance when studying multi‐population differences in behavior.

Successful mating and hybridisation in two closely related flatworm species despite significant differences in reproductive morphology and behaviour

Reproductive traits are some of the fastest diverging characters and can serve as reproductive barriers. The free-living flatworm Macrostomum lignano, and its congener M. janickei are closely related, but differ substantially in their male intromittent organ (stylet) morphology. Here, we examine whether these morphological differences are accompanied by differences in behavioural traits, and whether these could represent barriers to successful mating and hybridization between the two species. Our data shows that the two species differ in many aspects of their mating behaviour. Despite these differences, the species mate readily with each other in heterospecific pairings. Although both species have similar fecundity in conspecific pairings, the heterospecific pairings revealed clear postmating barriers, as few heterospecific pairings produced F1 hybrids. These hybrids had a stylet morphology that was intermediate between that of the parental species, and they were fertile. Finally, using a mate choice experiment, we show that the nearly two-fold higher mating rate of M. lignano caused it to mate more with conspecifics, leading to assortative mating, while M. janickei ended up mating more with heterospecifics. Thus, while the two species can hybridize, the mating rate differences could possibly lead to higher fitness costs for M. janickei compared to M. lignano.

Cocaine-induced changes in behaviour and DNA methylation in rats are influenced by inter-individual differences in spontaneous exploratory activity.

Individual differences in behavioural traits influence susceptibility to addictive disorders. Drug addiction involves changes in gene expression, proposed to occur via DNA methylation (DNAm). To investigate DNAm changes in reward-related brain structures (nucleus accumbens (NAc), lateral habenula (LHb)) in response to cocaine exposure in rats differing in spontaneous exploratory activity. Rats were observed in the exploration box and categorised as high- (HE) or low explorers (LE). Rats were administered vehicle or cocaine (12 mg/kg, i.p.) for 7 days, followed by a 14-day withdrawal period and cocaine challenge (7 mg/kg); horizontal locomotor activity was recorded. Brain tissue was dissected after 24 h; we analysed messenger RNA (mRNA) and activity levels of epigenetic DNA modifiers (DNMTs and TETs) as well as mRNA and promoter methylation levels at selected genes previously linked to addictive behaviours. The cocaine challenge dose stimulated locomotor activity in both LE- and HE rats only when administered after a repeated cocaine schedule, suggesting development of behavioural sensitisation. Quantitative polymerase chain reaction analyses demonstrated higher basal expression of Dnmt3a, Tet2 and Tet3 in the LHb of HE- vs. LE rats, and we observed differential effects of cocaine exposure on the expression and activity of epigenetic DNA modifiers in the NAc and LHb of HE- and LE rats. Furthermore, cocaine exposure differentially altered promoter methylation levels of A2AR, Ppp1cc, and Taar7b in the NAc and LHb of HE- and LE rats. DNAm might play a role in the HE- and LE phenotypes as well as mediate behavioural effects of LE- and HE rats in response to drugs of abuse.

Correlation between catch method, condition, and diet patterns in Atlantic cod (Gadus morhua)

AbstractWith seal populations increasing significantly in the Baltic Sea, the conflict between seals and fisheries is growing. The most sustainable method for mitigating the seal–fishery conflict is to develop and use seal-safe fishing gear. Although pots have been shown to be a promising alternative to gillnets for catching cod (Gadus morhua), there are indications that cod caught in pots are in poorer condition than those caught in gillnets, potentially making the pots a less-economical alternative. This study investigates whether this difference in condition is consistent over larger spatial scales. Gear-specific cod condition was related to both short-term (determined from stomach contents) and long-term (determined by stable isotope analysis) diet composition. Results indicate that differences in fish condition between gear types are consistent over large areas, possibly due to temporal and spatial differences in feeding strategies. We argue that condition differences between pot- and gillnet-caught cod may be driven by differences in behavioural traits. Consequently, fishing with a certain gear type may have ecological consequences affecting population characteristics, with implications for fisheries management. From the perspective of the seal–fisheries conflict, pots may ultimately have consequences on the catch value of fish.

Why are some personalities less plastic?

Individuals from the same population typically show consistent differences in behavioural traits that are frequently associated with differences in contextual plasticity. Yet such a correlation might arise either because some individuals are better able than others to detect environmental changes or because the benefits of being plastic are condition-dependent. To discriminate between these two competing hypotheses, I developed an individual-based model that simulates a population in which individuals of varying fighting ability compete by pairwise interactions using either the fixed hawk (aggressive) or dove (peaceful) strategies or a conditional assessment strategy. As anticipated, the model predicts that only individuals with low (and/or intermediate) fighting ability should use the assessment strategy, giving rise to a negative (or dome-shaped) relationship between aggressiveness and plasticity. The proportion of plastic individuals, however, should be affected not only by the environmental conditions in which individuals live but also by the mechanism that would maintain variation in the traits that determine the benefits of plasticity. In particular, if individual differences in fighting ability may be eroded by natural selection, it predicts that ecological conditions that cause assortative interactions (e.g. high predation risks) would contribute in maintaining variation among individuals in their fighting ability, thereby favouring greater plasticity.

Behavioural tendencies associated with microhabitat use in a clonal gecko species living in the wild

Individual differences in behavioural traits influence habitat choice, and in turn, differences in used habitats shape different behavioural tendencies through plasticity. Here, I investigated the relationship between personality and microhabitat use in a free-living population of the clonal gecko Lepidodactylus lugubris. The study site is a small beachfront forest facing two environments with contrasting levels of human disturbance. I conducted a mark-recapture survey to assess the geckos’ spacing pattern and evaluated their boldness and exploration scores in the laboratory. The geckos exhibited a small range of movement and a high consistency in their perch height. Boldness was related to two microhabitat features, but exploration was not. Relatively shy geckos were found in trees near the roadside and on low branches, whereas relatively bold geckos were found on both the beachside and the roadside and on low to high branches. These patterns suggest that geckos in high-disturbance microhabitats may have frequently experienced artificial stimuli and become shy. However, the present results cannot exclude the possibility that individual differences are caused by other factors and that different personality types prefer and settle in different microhabitats. Although the actual mechanisms are unclear, my findings highlight that behaviour-related habitat use emerges even in clonal animals. Individuals within conspecifics show different spacing patterns and different behavioural tendencies. If clonal animals live in a spatially diverse environment, it is predicted that different microhabitats may gradually shape different personality types through developmental plasticity. Here, I investigated the association between the personality of clonal geckos and their microhabitat use in different levels of human disturbance. In contrast to the prediction, both juveniles and adults showed a similar pattern of boldness-related microhabitats; relatively shy individuals were found in putatively high-disturbance sites. This result suggests that the association between boldness and microhabitats is not gradually formed through a long-time scale but is likely generated within their early ontogenetic stage.

Physiological differences between winter phenotypes of Siberian hamsters do not correlate with their behaviour

Living in a seasonally changing environment requires periodic, reversible changes in animals' phenotypes to match variations in their abiotic and biotic environments. These changes may relate to temperature regulation, torpor use, basal metabolic rate, body mass or behaviour, all acting in concert to ensure the best adjustment to the environmental challenges. As winter approaches, many small mammals develop a winter phenotype that is qualitatively and quantitatively different from a summer one. However, there is a significant within-population polymorphism in winter phenotype. We hypothesized that winter phenotype is correlated with consistent between-individual differences in animal behaviour, i.e. animal personality, and energy metabolism. We measured basal metabolic rate (BMR) and behavioural traits in three winter phenotypes of Siberian hamsters, Phodopus sungorus, which were acclimated to summer-like and then to winter-like conditions: fully responding, nonresponding and partially responding to a short photoperiod. We found no differences in behavioural traits between hamsters of different winter phenotypes, but the seasonal increase in activity was lowest in full responders indicating their lower behavioural flexibility than partial responders and nonresponders. The same was true for BMR. While nonresponders and partial responders increased their BMR from summer to winter, full responders did not change it. We argue that different winter phenotypes are maintained in the population because they could be beneficial under different environmental conditions. We also suggest that within a population there is a continuum of winter phenotypes, which is not related to differences in animal personalities. This continuum allows for population maintenance despite environmental conditions changing over short and long timescales.

A modelling approach to evaluate the impact of fish spatial behavioural types on fisheries stock assessment

Abstract Spatial behavioural types (SBTs) arise from between-individual differences in behavioural traits that foster spatial behavioural patterns that are consistent over time and ecological contexts. Fish stocks are regularly assessed using catch per unit effort (CPUE) as input data that may non-linearly co-vary with the underlying abundance (N) of the exploited stock when SBT affect catchability. We hypothesized that SBT promote characteristic changes in catchability within harvesting seasons that affect catch rates and in turn catch-based fish stock assessments. To test this hypothesis, we developed a spatially explicit agent-based simulation where we measured encounters between fish and fishers and estimated the shape of the CPUE–N relationship. We ran the simulation in a prototypical fish–fisher encounter-leads-to-catch-type fishery and systematically studied outcomes in the presence or absence of SBTs. It was revealed that the existence of SBTs leads to CPUE inevitably declining faster than N (a process known as hyperdepletion) when compared with a simulation lacking SBTs. This finding was consistent in a wide range of fishing effort scenarios. The emergent hyperdepletion of catch rates was caused by fast and behavioural-selective exploitation of vulnerable SBT that encompassed the mobile component of the fish stock. The theoretical predictions received support from field data from a coastal recreational fishery. Our work suggests that the consideration of SBT when interpreting trends in CPUE data may notably improve stock assessments by providing a more reliable CPUE–N relationship.

More eggs but less social and more fearful? Differences in behavioral traits in relation to the phylogenetic background and productivity level in laying hens

Different lines of laying hens have undergone a strong selection pressure for productivity traits, which has been proposed as a potential cause of undesirable side effects like behavioural disorders. One reason for such behavioral changes might be due to energy trade-offs, as high productive laying hens may conserve energy expenditure on activity in order to sustain the high level of egg production. However, beside the level of egg production, also phylogenetic origin has potential implications on differences in fearfulness, stress reactivity and sociality in layers. In this study, we compared four purebred layer lines differing in egg laying productivity and phylogenetic origin on their fearfulness and sociality prior to the start of laying. We used 77 chickens in a 2 x 2 group design, with two layer lines with white egg shell color and two lines with brown color which differed in laying performance (∼200 versus ∼300 egg / y, respectively, within colors). We measured fearfulness and sociality using five different behavioral tests (visual cliff, social approach, novel-object, mirror approach and tonic immobility). The data from the tests were analyzed using a principle component analysis revealing that our data were best explained by two components representing the dimension social behavior (PC1) and fear (PC2), respectively, which were further analyzed by a linear model (LM). The high productive lines showed a lower social motivation (lower values on PC1social, LM: p < 0.0001) than the less productive lines and the white hens had a higher social motivation than brown hens (higher values on PC1social, LM: p = 0.0004). Our results indicated that phylogeny and level of egg production affected the two dimensions of behavior differently with sociality but not fearfulness likely linked to the level of egg productivity. The decreased engagement in social behavior is consistent with the notion of energy trade-offs due to intense selection on egg productivity. The unintentional impacts of selection on behavior deserves further research, especially with regard to potential effects on welfare.