Animals in Search of Stimulation and Information: A Review of over 10 years of our Research on Spontaneous Exploration in Rats as a Response to Novelty in Low-Stress Paradigm

This article comprehensively reviews our studies that analyzed novelty-related behaviors in rats. We developed and utilized techniques and equipment during these studies to ensure our findings' high ecological validity. We allowed rats to explore a testing apparatus freely, and after a long habituation phase consisting of multiple trials, we introduced non-emotionally arousing changes. The research shows that rats demonstrate enhanced abilities in processing and responding to heightened environmental complexity, as evidenced across various studies. Conversely, when environmental complexity diminishes, rats exhibit reduced exploratory behaviors and decreased cognitive effort despite the adaptive importance of such behaviors. Of particular interest is the observation that rats exhibit greater sensitivity to emerging opportunities in contrast to their limited responsiveness to diminishing ones, unveiling a novel facet of the animal mind that warrants further investigation. The influence of individual experiences before testing sessions on the processing of sensory input in terms of complexity is also determined. Our studies highlight the noteworthy impact of environmental unpredictability versus stability on cognitive development, affecting behaviors like food neophobia and exploration. Furthermore, the social environment during development holds wide-ranging implications for individual characteristics, necessitating continued research and refinement of our understanding in this domain. Moreover, the studies recognize strain and species differences in novelty-related behavior, primarily characterized by quantitative variations that do not overshadow the animals' coping strategies in response to environmental changes. Additionally, curiosity is portrayed as an active approach to seeking and processing environmental affordances, with exploratory behaviors fulfilling this cognitive and motivational need. The authors underscore the significance of ecological validity in test methodologies, particularly in designing environments that authentically invite and encourage pertinent behavioral responses. In summary, this research enhances our insight into rat cognition, underscores the role of curiosity, and underscores the imperative of ecological validity in experimental design, ultimately advancing our comprehension of animal behavior and cognition

The development of juvenile-typical patterns of play fighting in juvenile rats does not depend on peer-peer play experience in the peri-weaning period

Open access article. Creative Commons Attribution 4.0 International License (CC BY 4.0) appliesPlay fighting in rats involves attack and defense of the nape. To protect the nape, rats use a variety of defensive tactics, with different strains having specific preferences. Targeting of the nape is established before weaning and defense matures over the course of the week preceding and the week proceeding weaning. Thus, it is possible that experience from engaging in immature forms of play is needed to consolidate the nape as the playful target and for the development of the juvenile-typical pattern of defense. Two experiments were conducted to evaluate this possibility. For the first experiment, male rats were reared over the week post-weaning in either pairs or alone, and their play tested with unfamiliar partners when juveniles (31-34 days). For the second experiment, during the week preceding weaning, male and female rats were placed into one of three conditions: (1) with the mother and no peers, (2) with same-sex siblings but no mother, or (3) with both the mother and same-sex siblings. The subjects were tested in same-sex, samecondition pairs when juveniles (31-34 days). Rats from all conditions, in both experiments, attacked the nape during play fighting and developed the same juvenile-typical patterns of playful defense. This suggests that the experience of peer-peer play in the peri-weaning period is not necessary for the development of the attack and defense components of juvenile-typical play.Ye

Pinning in the play fighting of rats: a comparative perspective with methodological recommendations

Open access article. Creative Commons Attribution 4.0 International LIcense (CC BY 4.0) appliesDuring play fighting, rats attack and defend the nape of the neck and during the course of this competitive interaction, they may adopt a configuration in which one animal stands over its supine partner (i.e., pin). Because the pin configuration is typically frequent and relatively easy to identify, it has been widely used as a marker to detect the effects of experimental treatments. In the present study, the frequency of pinning during standardized, 10-min trials in three strains of rats, Long Evans hooded (LE), Sprague-Dawley (SD) and wild (WWCPS), was compared. LE and SD had higher rates than WWCPS rats (#/min: 6.5, 5.5, 1.5, respectively). When adjusted for strain differences in the frequency of attacks, SD as well as WWCPS rats had lower rates of pinning compared to LE rats. Both SD and WWCPS rats were less likely to use tactics of defense that promote pinning. Moreover, while the majority of the pins achieved in LE rats arose from the defender actively rolling over onto its back, the majority of pins in WWCPS rats arose because one partner pushed the other onto its back. SD rats were intermediate in this regard. Finally, once they do adopt the pin configuration, SD rats are less likely to remain supine than LE and WWCPS rats. That is, both SD and WWCPS rats have significantly fewer pins than LE rats, but a different combination of factors account for this. These data highlight the need to use a battery of measures for ascertaining the effects of experimental manipulations on play. Some suggested guidelines are provided.Ye

Selected Psychological Aspects of Meat Consumption—A Short Review

Eating meat is deeply entrenched in Western culture. It is often associated with wealth and a highly nutritional diet; and for many people it is also an established habit that is difficult to change. The second half of the 20th century was a period of rapid growth in meat consumption, which resulted in intensified meat production. At the same time, eating meat has recently become subject to criticism for health-related, environmental or humanitarian reasons. This review aims to signal the potential consequences of a change of diet or switching to diets that are rich/poor in certain ingredients on the functioning of the hormonal and nervous system, which translates into changes in mood and behavior. This paper discusses the psychological phenomena which underlie the difficulty of changing one’s food preferences and problems encountered while adding new products to the daily diet. Finally, this study summarizes the limitations of modifying eating habits that have resulted from established attitudes and habits

Exploratory Analysis of the Links among Food Consumption Profiles, Prenatal Androgens, and Selected Measures of Quality of Life

Prenatal sex steroids play a vital role in the development of the whole organism, and therefore also the brain. Exposure of the fetus to testosterone seems to be of special importance both for typical development and pathology. The key factor impacting offspring development (including prenatal androgen levels) appears to be diet, both in terms of shortage and excessive intake of certain food products. Prenatal steroid levels are measured using the ratio of the lengths of the second and fourth fingers (2D:4D). So far the digit ratio (2D:4D) has been shown to correlate negatively with prenatal testosterone and positively with prenatal estrogen. Numerous correlational studies found relationships between the 2D:4D phenotype and differences in magnitude of many psychological traits. Certain social and demographic variables also correlate with the digit ratio. The present paper offers a preliminary analysis of correlations between diet, prenatal hormones' levels (established based on the digit ratio) and selected social variables. One of the findings is that countries with high meat consumption present the so-called masculine digit ratio, while countries with plant-based diets – a feminine digit ratio

Median latency (the decimal logarithms of median values) of picking food off novel food pellets on consecutive days of the experiment.

<p>Median latency (the decimal logarithms of median values) of picking food off novel food pellets on consecutive days of the experiment.</p

Food Neophobia in Wild Rats (Rattus norvegicus) Inhabiting a Changeable Environment—A Field Study

<div><p>Food neophobia is a reaction to novel food observed in many animal species, particularly omnivores, including <i>Rattus norvegicus</i>. A neophobic reaction is typically characterised by avoidance of novel food and the necessity to assess both its potential value and toxicity by the animal. It has been hypothesised that this reaction is not observed in rats inhabiting a changeable environment with a high level of variability with regard to food and food sources. This study was conducted in such changeable conditions and it aims to demonstrate the behaviour of wild rats <i>R</i>. <i>norvegicus</i> in their natural habitat. The rats were studied in a farm setting, and the experimental arena was demarcated by a specially constructed pen which was freely accessible to the rats. At regular intervals, the rats were given new flavour- and smell-altered foods, while their behaviour was video-recorded. The results obtained in the study seem to confirm the hypothesis that rats inhabiting a highly changeable environment do not exhibit food neophobia. The observed reaction to novel food may be connected with a reaction to a novel object to a larger extent than to food neophobia. The value of the results obtained lies primarily in the fact that the study was conducted in the animals’ natural habitat, and that it investigated their spontaneous behaviours.</p></div

View of the pen with the location of the bowl in which the food was placed.

<p>The detail shows a magnified outline of the bowl with the distribution of the food pellets (F).</p

An outline of experimental area.

<p>A and B indicate bowls in which food pellets were placed on a daily basis.</p

Can the Hole–Board Test Predict a Rat’s Exploratory Behavior in a Free-Exploration Test?

This study focuses on the rat activity in a hole–board setting that we considered a type of exploratory behavior. The general hypothesis is based on the claim that a motivational mechanism is central to both the response to novelty in a highly familiarized environment and the activity in the hole–board apparatus. Our sample consisted of 80 experimentally naive Lister Hooded rats. All rats were tested in the hole–board apparatus. Twenty individuals with the highest hole-board scores and twenty subjects with the lowest hole–board scores subsequently underwent an established free-exploration test. In our study, the scores obtained in the hole–board test had little predictive value for the rats’ activity in the free-exploration test. Based on our previous experience in studying exploratory behavior in the free-exploration test and the data presented in this paper, we suggest that the hole–board test is not an appropriate tool for measuring exploratory behavior in laboratory rodents