Does IQ Really Predict Job Performance?

IQ has played a prominent part in developmental and adult psychology for decades. In the absence of a clear theoretical model of internal cognitive functions, however, construct validity for IQ tests has always been difficult to establish. Test validity, therefore, has always been indirect, by correlating individual differences in test scores with what are assumed to be other criteria of intelligence. Job performance has, for several reasons, been one such criterion. Correlations of around 0.5 have been regularly cited as evidence of test validity, and as justification for the use of the tests in developmental studies, in educational and occupational selection and in research programs on sources of individual differences. Here, those correlations are examined together with the quality of the original data and the many corrections needed to arrive at them. It is concluded that considerable caution needs to be exercised in citing such correlations for test validation purposes.     

Does Genetic Diversity Predict Health in Humans?

Genetic diversity, especially at genes important for immune functioning within the Major Histocompatibility Complex (MHC), has been associated with fitness-related traits, including disease resistance, in many species. Recently, genetic diversity has been associated with mate preferences in humans. Here we asked whether these preferences are adaptive in terms of obtaining healthier mates. We investigated whether genetic diversity (heterozygosity and standardized mean d²) at MHC and nonMHC microsatellite loci, predicted health in 153 individuals. Individuals with greater allelic diversity (d²) at nonMHC loci and at one MHC locus, linked to HLA-DRB1, reported fewer symptoms over a four-month period than individuals with lower d². In contrast, there were no associations between MHC or nonMHC heterozygosity and health. NonMHC-d² has previously been found to predict male preferences for female faces. Thus, the current findings suggest that nonMHC diversity may play a role in both natural and sexual selection acting on human populations.     

How Does Spatial Study Design Influence Density Estimates from Spatial Capture-Recapture Models?

When estimating population density from data collected on non-invasive detector arrays, recently developed spatial capture-recapture (SCR) models present an advance over non-spatial models by accounting for individual movement. While these models should be more robust to changes in trapping designs, they have not been well tested. Here we investigate how the spatial arrangement and size of the trapping array influence parameter estimates for SCR models. We analysed black bear data collected with 123 hair snares with an SCR model accounting for differences in detection and movement between sexes and across the trapping occasions. To see how the size of the trap array and trap dispersion influence parameter estimates, we repeated analysis for data from subsets of traps: 50% chosen at random, 50% in the centre of the array and 20% in the South of the array. Additionally, we simulated and analysed data under a suite of trap designs and home range sizes. In the black bear study, we found that results were similar across trap arrays, except when only 20% of the array was used. Black bear density was approximately 10 individuals per 100 km(2). Our simulation study showed that SCR models performed well as long as the extent of the trap array was similar to or larger than the extent of individual movement during the study period, and movement was at least half the distance between traps. SCR models performed well across a range of spatial trap setups and animal movements. Contrary to non-spatial capture-recapture models, they do not require the trapping grid to cover an area several times the average home range of the studied species. This renders SCR models more appropriate for the study of wide-ranging mammals and more flexible to design studies targeting multiple species.     

Does Bipedality Predict the Group-Level Manual Laterality in Mammals?

Background

Factors determining patterns of laterality manifestation in mammals remain unclear. In primates, the upright posture favours the expression of manual laterality across species, but may have little influence within a species. Whether the bipedalism acts the same in non-primate mammals is unknown. Our recent findings in bipedal and quadrupedal marsupials suggested that differences in laterality pattern, as well as emergence of manual specialization in evolution might depend on species-specific body posture. Here, we evaluated the hypothesis that the postural characteristics are the key variable shaping the manual laterality expression across mammalian species.

Methodology/Principal Findings

We studied forelimb preferences in a most bipedal marsupial, brush-tailed bettong, Bettongia penicillata in four different types of unimanual behavior. The significant left-forelimb preference at the group level was found in all behaviours studied. In unimanual feeding on non-living food, catching live prey and nest-material collecting, all or most subjects were lateralized, and among lateralized bettongs a significant majority displayed left-forelimb bias. Only in unimanual supporting of the body in the tripedal stance the distribution of lateralized and non-lateralized individuals did not differ from chance. Individual preferences were consistent across all types of behaviour. The direction or the strength of forelimb preferences were not affected by the animals’ sex.

Conclusions/Significance

Our findings support the hypothesis that the expression of manual laterality depends on the species-typical postural habit. The interspecies comparison illustrates that in marsupials the increase of bipedality corresponds with the increase of the degree of group-level forelimb preference in a species. Thus, bipedalism can predict pronounced manual laterality at both intra- and interspecific levels in mammals. We also conclude that quadrupedal position in biped species can slightly hinder the expression of manual laterality, but the evoked biped position in quadrupedal species does not necessarily lead to the enhanced manifestation of manual laterality.     

Does Stream Morphology Predict the Home Range Size in Burbot?

Synopsis To determine whether burbot occupy defined home range in rivers, we radio-tracked individuals in the Ohře River, Czech Republic. We also tested the hypothesis that the size of burbot home range would correlate with the fish mass. Burbot's strong attraction to suitable refuges was the basis for our second hypotheses, that its diurnal behavior would reflect refuge availability in the riverine environment. To test these hypotheses, we analyzed data on fish movements in relation to depth, velocity, substratum size and river slope. During the night, burbot preferred deeper areas with lower slope and finer substrates than during daylight hours. The home range was smaller in areas with low or zero slopes, and significantly increased with increasing river slope. There was no relationship between home range size and fish mass. River slope appeared to be the main predictor of the burbot's home range size.     

Does Chronic Unpredictable Stress during Adolescence Affect Spatial Cognition in Adulthood?

Spatial abilities allow animals to retain and cognitively manipulate information about their spatial environment and are dependent upon neural structures that mature during adolescence. Exposure to stress in adolescence is thought to disrupt neural maturation, possibly compromising cognitive processes later in life. We examined whether exposure to chronic unpredictable stress in adolescence affects spatial ability in late adulthood. We evaluated spatial learning, reference and working memory, as well as long-term retention of visuospatial cues using a radial arm water maze. We found that stress in adolescence decreased the rate of improvement in spatial learning in adulthood. However, we found no overall performance impairments in adult reference memory, working memory, or retention caused by adolescent-stress. Together, these findings suggest that adolescent-stress may alter the strategy used to solve spatial challenges, resulting in performance that is more consistent but is not refined by incorporating available spatial information. Interestingly, we also found that adolescent-stressed rats showed a shorter latency to begin the water maze task when re-exposed to the maze after an overnight delay compared with control rats. This suggests that adolescent exposure to reoccurring stressors may prepare animals for subsequent reoccurring challenges. Overall, our results show that stress in adolescence does not affect all cognitive processes, but may affect cognition in a context-dependent manner.

Highlights

• -Rats were reared with or without chronic unpredictable stress in adolescence.
• -In adulthood, spatial cognitive abilities were tested in a radial arm water maze.
• -Prior-stressed rats began searching faster in the maze after an overnight delay.
• -Prior stress may facilitate faster action in challenging situations.
• -Prior stress did not affect learning, reference or working memory, or retention.

     

Does Childhood Sexual Abuse Predict Young Adult's BMI? A Birth Cohort Study

Objective: The objective was to identify the extent to which childhood sexual abuse (CSA) is associated with BMI and overweight status in young adulthood and to examine whether any associations differ by gender. Research Methods and Procedures: The Mater‐University of Queensland Study of Pregnancy is a prospective birth cohort from a population‐based sample involving 7223 singletons whose mothers were enrolled in the 1980s at the first antenatal visit. The present cohort consisted of a subgroup of 2461 young adults who had both self‐reported CSA data and measured BMI at 21 years. Results: Of 1273 men, 10.5% reported non‐penetrative and 7.5% reported penetrative CSA before age 16 years. Of 1305 women, 20.6% reported non‐penetrative and 7.9% reported penetrative CSA by age 16 years. We found young women's BMI and the prevalence of overweight at age 21 were greater in those who experienced penetrative CSA. This association was robust to adjustment for a variety of potential confounders. However, there was no association between non‐penetrative CSA and BMI in women and no association between either category of CSA and BMI in men. There was statistical evidence for a gender difference in the association of CSA with mean BMI at age 21 (p value for statistical interaction <0.01 in all models). Discussion: These findings suggest that among women, penetrative CSA is associated with greater BMI and increased odds of being overweight in later life, whereas in men, this association does not hold. This gender difference may reflect differences between women and men in the relationship between psychological trauma and body image or may be a chance subgroup finding.     

Does Microorganism Stoichiometry Predict Microbial Food Web Interactions After a Phosphorus Pulse?

Knowledge of variations in microbial food web interactions resulting from atmospheric nutrient loads is crucial to improve our understanding of aquatic food web structure in pristine ecosystems. Three experiments mimicking atmospheric inputs at different nitrogen/phosphorus (N/P) ratios were performed in situ covering the seasonal biological succession of the pelagic zone in a high-mountain Spanish lake. In all experiments, abundance, biomass, algal cell biovolume, P-incorporation rates, P-cell quota, and N/P ratio of algae strongly responded to P-enrichment, whereas heterotrophic bacteria remained relatively unchanged. Ciliates were severely restricted when a strong algal exploitation of the available P (bloom growth or storage strategies) led to transient (mid-ice-free experiment) or chronic (late ice-free experiment) P-deficiencies in bacteria. In contrast, maximum development of ciliates was reached when bacteria remained P-rich (N/P < 20) and algae approached Redfield proportions (N/P approximately 16). Evidence of a higher P-incorporation rate supports the proposition that algae and bacteria shifted from a mainly commensalistic-mutualistic to a competitive relationship for the available P when bacterial P-deficiency increased, as reflected by their unbalanced N/P ratio (N/P > 20-24). Hence, the bacterial N/P ratio proved be a key factor to understand the algae-bacteria relationship and microbial food web development. This study not only demonstrates the interdependence of life history strategies, stoichiometric nutrient content, and growth but also supports the use of bacterial N/P thresholds for diagnosing ciliate development, a little-studied aspect worthy of further attention.     

Does an Oblique/Slanted Perspective during Virtual Navigation Engage Both Egocentric and Allocentric Brain Strategies?

Perspective (route or survey) during the encoding of spatial information can influence recall and navigation performance. In our experiment we investigated a third type of perspective, which is a slanted view. This slanted perspective is a compromise between route and survey perspectives, offering both information about landmarks as in route perspective and geometric information as in survey perspective. We hypothesized that the use of slanted perspective would allow the brain to use either egocentric or allocentric strategies during storage and recall. Twenty-six subjects were scanned (3-Tesla fMRI) during the encoding of a path (40-s navigation movie within a virtual city). They were given the task of encoding a segment of travel in the virtual city and of subsequent shortcut-finding for each perspective: route, slanted and survey. The analysis of the behavioral data revealed that perspective influenced response accuracy, with significantly more correct responses for slanted and survey perspectives than for route perspective. Comparisons of brain activation with route, slanted, and survey perspectives suggested that slanted and survey perspectives share common brain activity in the left lingual and fusiform gyri and lead to very similar behavioral performance. Slanted perspective was also associated with similar activation to route perspective during encoding in the right middle occipital gyrus. Furthermore, slanted perspective induced intermediate patterns of activation (in between route and survey) in some brain areas, such as the right lingual and fusiform gyri. Our results suggest that the slanted perspective may be considered as a hybrid perspective. This result offers the first empirical support for the choice to present the slanted perspective in many navigational aids.     

Does Seed‐Caching Experience Affect Spatial Memory Performance by Pinyon Jays?

Food‐storing birds use spatial memory to find previously cached food items. Throughout winter, pinyon jays (Gymnorhinus cyanocephalus) rely heavily on cached pinyon pine (Pinus edulis) seeds. Because of a recent severe drought, pinyon pine trees had not produced a significant seed crop for several years. Therefore, 1‐ and 2‐yr‐old birds never had the opportunity to cache and recover seeds and birds 4 or more years of age had not recovered seeds in 3 yr. This study examined whether natural but extreme variability in experience might result in differences in abstract spatial memory ability during a non‐cache recovery test of spatial memory. Three groups of jays were tested for spatial memory ability in an open room analog of the radial arm maze. Two of the groups were 8 mo old: young/minimally experienced birds which had 2 mo of experience in the wild, while young/experienced birds had 5 mo of experience in their natural habitat. The third group, adult, consisted of birds more than 3 yr old, with at least 3 yr of experience in their natural habitat. This was the only group with experience caching pine seeds. All three groups performed equally and well above chance. This suggests that spatial memory is fully developed by 8 mo of age and is not affected by extensive experience in the wild.     

Does Social Isolation and Low Societal Participation Predict Disability Pension? A Population Based Study

Purpose

The aim was to examine the potential influence of social isolation and low societal participation on the future risk of receiving disability pension among individuals in Sweden. A specific aim was to describe differences depending on disability pension diagnoses, and how the results were modified by sex and age.

Method

The study comprised representative samples of Swedish women and men, who had been interviewed in any of the annual Swedish Surveys of Living Conditions between 1990 and 2007. Information on disability pension and diagnoses was added from the Swedish Social Insurance Agency’s database (1991-2011). The mean number of years of follow-up for the 53920 women and men was twelve years (SD 5.5), and the study base was restricted to the ages 20 to 64 years of age. The predictors were related to disability pension by Cox’s proportional hazards regression.

Results

Social isolation and low societal participation were associated with future disability pension also after control for age, year of interview, socio demographic conditions and self reported longstanding illness. Lone individuals were at increased risk of disability pension, and the effect of living without children was modified by sex and age. An increase in risk was particularly noticeable among younger women who reported that they had sparse contacts with others, and no close friend. Both women and men who reported that they did not participate in political discussions and who could not appeal on a decision by a public authority were also at increased risk. The effects of social isolation were mainly attributed to disability pension with mental diagnoses, and to younger individuals.

Conclusions

The study suggests that social isolation and low societal participation are predictors of future disability pension. Social isolation and low societal participation increased particularly the risk of future disability pension in mental diagnoses among younger individuals.     

Factors Driving Potential Ammonia Oxidation in Canadian Arctic Ecosystems: Does Spatial Scale Matter?

Ammonia oxidation is a major process in nitrogen cycling, and it plays a key role in nitrogen limited soil ecosystems such as those in the arctic. Although mm-scale spatial dependency of ammonia oxidizers has been investigated, little is known about the field-scale spatial dependency of aerobic ammonia oxidation processes and ammonia-oxidizing archaeal and bacterial communities, particularly in arctic soils. The purpose of this study was to explore the drivers of ammonia oxidation at the field scale in cryosols (soils with permafrost within 1 m of the surface). We measured aerobic ammonia oxidation potential (both autotrophic and heterotrophic) and functional gene abundance (bacterial amoA and archaeal amoA) in 279 soil samples collected from three arctic ecosystems. The variability associated with quantifying genes was substantially less than the spatial variability observed in these soils, suggesting that molecular methods can be used reliably evaluate spatial dependency in arctic ecosystems. Ammonia-oxidizing archaeal and bacterial communities and aerobic ammonia oxidation were spatially autocorrelated. Gene abundances were spatially structured within 4 m, whereas biochemical processes were structured within 40 m. Ammonia oxidation was driven at small scales (<1m) by moisture and total organic carbon, whereas gene abundance and other edaphic factors drove ammonia oxidation at medium (1 to 10 m) and large (10 to 100 m) scales. In these arctic soils heterotrophs contributed between 29 and 47% of total ammonia oxidation potential. The spatial scale for aerobic ammonia oxidation genes differed from potential ammonia oxidation, suggesting that in arctic ecosystems edaphic, rather than genetic, factors are an important control on ammonia oxidation.     

Understanding the Complexity of Ambivalence Toward Pregnancy: Does It Predict Inconsistent Use of Contraception?

Ambivalence towards future pregnancy is common and may increase the risk of unprotected sex and unintended pregnancy. We propose that ambivalent attitudes toward pregnancy consist of subtypes that are differentially associated with contraceptive use. Using data from a nationally representative survey of unmarried young adults (N = 1,147), we constructed four categories of ambivalence based on attitudes toward a hypothetical pregnancy. Multivariate analyses examined characteristics of ambivalence and the association between ambivalence and contraceptive use. Approximately one third of sexually active unmarried young adults are ambivalent about pregnancy. Having positive ambivalence (important to avoid a pregnancy but would be happy if it occurred) is associated with age, gender, education, and Hispanic origin. Although ambivalence toward pregnancy is associated with lower contraceptive use, this is true only among women with negative ambivalence (not important to avoid a pregnancy but would be unhappy if a pregnancy occurred). Attitudes toward pregnancy are multifaceted, and a more nuanced understanding of women’s attitudes toward pregnancy can help target prevention programs and related policies for women at risk of unintended pregnancy.     

Orientation and Navigation in Elasmobranchs: Which Way Forward?

Elasmobranchs possess a multiplicity of mechanisms controlling posture and short distance orientation. Visual–vestibular contributions to posture and locomotion are well documented. So too, are the contributions of vision, olfaction and the octavolateralis senses to short distance orientation, particularly orientation to specific environmental stimuli such as those generated by prey. Less well understood are the mechanisms guiding orientation over longer distances. Anecdotal and systematic observations of behaviour show tidal, daily, repeat long distance, and even seasonal movement patterns. True navigation has not been demonstrated in elasmobranchs and the sensory mechanisms underlying the above movement patterns remain largely speculative. However, they are likely to include responses to water currents, and physical parameters such as temperature, pressure, and the geomagnetic field. Of particular interest in elasmobranchs is that geomagnetic orientation could be mediated directly via a magnetite based sensory system, or indirectly via the electrosensory system. Systematic studies of movement patterns and experimental studies of the underlying mechanisms of orientation are required to gain an increased understanding of orientation and navigation in this intriguing group.     

Does Sedentary Behavior Predict Academic Performance in Adolescents or the Other Way Round? A Longitudinal Path Analysis

This study examined whether adolescents’ time spent on sedentary behaviors (academic, technological-based and social-based activities) was a better predictor of academic performance than the reverse. A cohort of 755 adolescents participated in a three-year period study. Structural Equation Modeling techniques were used to test plausible causal hypotheses. Four competing models were analyzed to determine which model best fitted the data. The Best Model was separately tested by gender. The Best Model showed that academic performance was a better predictor of sedentary behaviors than the other way round. It also indicated that students who obtained excellent academic results were more likely to succeed academically three years later. Moreover, adolescents who spent more time in the three different types of sedentary behaviors were more likely to engage longer in those sedentary behaviors after the three-year period. The better the adolescents performed academically, the less time they devoted to social-based activities and more to academic activities. An inverse relationship emerged between time dedicated to technological-based activities and academic sedentary activities. A moderating auto-regressive effect by gender indicated that boys were more likely to spend more time on technological-based activities three years later than girls. To conclude, previous academic performance predicts better sedentary behaviors three years later than the reverse. The positive longitudinal auto-regressive effects on the four variables under study reinforce the ‘success breeds success’ hypothesis, with academic performance and social-based activities emerging as the strongest ones. Technological-based activities showed a moderating effect by gender and a negative longitudinal association with academic activities that supports a displacement hypothesis. Other longitudinal and covariate effects reflect the complex relationships among sedentary behaviors and academic performance and the need to explore these relationships in depth. Theoretical and practical implications for school health are outlined.     

Can Dreams During Pregnancy Predict Postpartum Depression?

Postpartum depression (henceforth PPD) is an emotional disturbance which occurs in as much as 20% of the childbearing population. This study attempted to ascertain whether dreams, offering unconscious expression of internal emotional processes, could help to identify early signs of PPD. It was hypothesized that differences would be found in the emotional dream work of pregnant women who either later developed or did not develop PPD. 166 women participated in the two stages of the study. During stage I, the women were interviewed in the last trimester of their first pregnancies. The interview included a demographic questionnaire and an account of a dream. During stage II, the women were interviewed 6–10 weeks after giving birth. The second interview included only the EPDS scale for affirming or denying the occurrence of PPD. The findings of the study confirm the hypothesis that dreams of pregnant women can differentiate among women who are or are not at-risk for PPD. It was found that more unpleasant dreams and dreams expressing apprehension were found among women who did not later develop PPD, than among women who did develop PPD.     

Community Functional Responses to Soil and Climate at Multiple Spatial Scales: When Does Intraspecific Variation Matter?

Despite increasing evidence of the importance of intraspecific trait variation in plant communities, its role in community trait responses to environmental variation, particularly along broad-scale climatic gradients, is poorly understood. We analyzed functional trait variation among early-successional herbaceous plant communities (old fields) across a 1200-km latitudinal extent in eastern North America, focusing on four traits: vegetative height, leaf area, specific leaf area (SLA), and leaf dry matter content (LDMC). We determined the contributions of species turnover and intraspecific variation to between-site functional dissimilarity at multiple spatial scales and community trait responses to edaphic and climatic factors. Among-site variation in community mean trait values and community trait responses to the environment were generated by a combination of species turnover and intraspecific variation, with species turnover making a greater contribution for all traits. The relative importance of intraspecific variation decreased with increasing geographic and environmental distance between sites for SLA and leaf area. Intraspecific variation was most important for responses of vegetative height and responses to edaphic compared to climatic factors. Individual species displayed strong trait responses to environmental factors in many cases, but these responses were highly variable among species and did not usually scale up to the community level. These findings provide new insights into the role of intraspecific trait variation in plant communities and the factors controlling its relative importance. The contribution of intraspecific variation to community trait responses was greatest at fine spatial scales and along edaphic gradients, while species turnover dominated at broad spatial scales and along climatic gradients.     

Does Prison Crowding Predict Higher Rates of Substance Use Related Parole Violations? A Recurrent Events Multi-Level Survival Analysis

Objective

This administrative data-linkage cohort study examines the association between prison crowding and the rate of post-release parole violations in a random sample of prisoners released with parole conditions in California, for an observation period of two years (January 2003 through December 2004).

Background

Crowding overextends prison resources needed to adequately protect inmates and provide drug rehabilitation services. Violence and lack of access to treatment are known risk factors for drug use and substance use disorders. These and other psychosocial effects of crowding may lead to higher rates of recidivism in California parolees.

Methods

Rates of parole violation for parolees exposed to high and medium levels of prison crowding were compared to parolees with low prison crowding exposure. Hazard ratios (HRs) with 95% confidence intervals (CIs) were estimated using a Cox model for recurrent events. Our dataset included 13070 parolees in California, combining individual level parolee data with aggregate level crowding data for multilevel analysis.

Results

Comparing parolees exposed to high crowding with those exposed to low crowding, the effect sizes from greatest to least were absconding violations (HR 3.56 95% CI: 3.05–4.17), drug violations (HR 2.44 95% CI: 2.00–2.98), non-violent violations (HR 2.14 95% CI: 1.73–2.64), violent and serious violations (HR 1.88 95% CI: 1.45–2.43), and technical violations (HR 1.86 95% CI: 1.37–2.53).

Conclusions

Prison crowding predicted higher rates of parole violations after release from prison. The effect was magnitude-dependent and particularly strong for drug charges. Further research into whether adverse prison experiences, such as crowding, are associated with recidivism and drug use in particular may be warranted.     

Das Orientierungssystem der V?gel II. Heimfinden und Navigation

Zusammenfassung Die Analyse des Navigationssystems der Vögel bezieht sich meist auf Versuche mit Brieftauben. Kramers Karte-Kompaß-Prinzip geht davon aus, daß die Heimrichtung zunächst als Kompaßkurs bestimmt wird. Dies wurde durch zahlreiche Zeitumstimmungsversuche bestätigt. Damit erscheinen nur zwei Navigationsstrategien möglich: (1) Benutzen von Weginformation, die auf einem Richtungsreferenzsystem beruht, und (2) Benutzen von Ortsinformation, deren Richtungsbeziehung zum Ziel bekannt ist.Junge Tauben, denen während der Verfrachtung der Zugang zu magnetischer Information verwehrt worden war, flogen ungerichtet ab. Dies spricht für eine Navigationsstrategie, bei der die Richtung des Hinwegs mit dem Magnetkompaß gemessen wird. Diese Art von Wegintegration stellt aber nur eine erste Strategie sehr junger, unerfahrener Tauben dar; sobald wie möglich benutzen die Tauben Ortsinformation, denn diese erlaubt Nachbestimmung des Heimkurses und damit das Korrigieren von Fehlern.Navigation anhand von Ortsinformation bedeutet, daß Vögel den Heimkurs aufgrund von Faktoren am Auflaßort bestimmen. Die modernen Vorstellungen berücksichtigen die zentrale Rolle eines äußeren Referenzsystems und gehen von einer Navigationskarte aus, die einer kompaßmäßig ausgerichteten mentalen Repräsentation des Verlaufs der Navigationsfaktoren entspricht. Der Heimkurs wird aus den Unterschieden zwischen den Werten am Auflaßort und denen am Heimatort abgeleitet. Da es sich bei den Navigationsfaktoren um Gradienten handelt, können die Vögel deren Verlauf extrapolieren und ihren Heimkurs auch in unbekanntem Gelände bestimmen. Unregelmäßigkeiten im Gradientenverlauf führen zu Abweichungen von der Heimrichtung, sogenannten Ortsmißweisungen. In der Nähe des Heimatorts wird die Navigationskarte durch eine entsprechende Mosaik-Karte von Landmarken ergänzt.Beide Karten werden durch Lernvorgänge erstellt. Junge Tauben verschaffen sich die notwendige Information auf spontanen Flügen, indem sie Information über den zurückgelegten Weg mit Ortsinformation verknüpfen und gemeinsam in den Karten abspeichern. Bei Tauben wird die Navigationskarte etwa im dritten Lebensmonat funktionstüchtig, aber sie wird auch später noch ständig erweitert und verbessert. Ihre Größe hängt von der Erfahrung der Vögel ab. Die Karte enthält offenbar Entfernungsangaben und erlaubt freie Flüge zwischen beliebigen Zielen. In einigen Punkten entspricht sie der in der psychologischen Literatur diskutierten kognitiven Karte.Das Navigationssystem der Vögel ist dadurch gekennzeichnet, daß sie sich mit Hilfe eines einfachen angeborenen Mechanismus, des Magnetkompaß, viele andere Faktoren durch Lernvorgänge nutzbar machen und diese in komplexe Mechanismen wie die Karten integrieren.

---

The orientation system of birds — II. Homing and navigation

Summary The analysis of the navigational system of birds is largely based on experiments with displaced homing pigeons. Kramer's map-and-compass model assumes that the home direction is first established as a compass course. This is confirmed by numerous clock-shift experiments. Consequently, only two types of navigational strategy appear possible: (1) the use of route-specific information based on an external reference or (2) the use of site-specific information whose directional relationship is familiar to the birds.The use of route-specific information is indicated by the finding that young birds deprived of magnetic information during displacement were disoriented, whereas birds receiving the same treatment at the release site were not. This suggests that birds navigate by recording the direction of the outward journey with their magnetic compass, determining the home course by reversing it. This strategy of path integration with the help of an external reference, however, is used only by very young, inexperienced pigeons during an early phase in the development of the navigational system. As soon as birds become more experienced and are able to use site-specific information, they give up route-specific information in favor of the former. The reasons for this change in strategy lie in the fact that using site-specific information enables birds to redetermine their home course as often as necessary, thus allowing the correction of initial mistakes.Site-specific information means that birds can derive their home course from factors perceived at the release site. The present models on navigation acknowledge the crucial role of an external reference system by proposing the navigational map to be a directionally oriented mental representation of the spatial distribution of at least two navigational factors, which are assumed to be environmental gradients. The birds determine their home course by comparing the local values of these factors with the remembered home values. Gradients can be extrapolated beyond the range of direct experience, which explains the birds' ability to home from distant, unfamiliar sites. Deviations from the true home direction, so-called release site biases, as frequently observed in pigeons and other bird species, may be attributed to unforeseen irregularities in the distribution of the navigational factors, which cause birds to misinterpret their position. Near home, the navigational or grid map is supplemented by the mosaic map, which is supposed to be a directionally oriented mental representation of the distribution of familiar landmarks.Both maps are based on experience. Young birds obtain the relevant information during spontaneous flights by combining information on the route travelled with information on the location of prominent landmarks and the direction of environmental gradients. In pigeons, the maps become functional during the third month of life. They are continuously enlarged and updated also in later years. The total size of the navigational map appears to depend on the spatial range of the birds' experience. The maps seem to include information on distance; they are not restricted to homing, but allow free movements between arbitrary goals. In several respects, the model of the avian navigational map is similar to the concept of the cognitive map discussed in psychological literature, the main differences being the larger distances involved, the representation of continuous environmental gradients instead of separate entities, and the essential role of an external reference.The navigational system of birds is thus characterized as utilizing a wide variety of environmental cues. Learning processes, which are based on a simple, innate mechanism, the magnetic compass, integrate these cues and form complex, experience-based mechanisms, such as the maps.

     

Does Absence Matter?

This paper examines the effects of three different types of father absence on the timing of life history events among women in rural Bangladesh. Age at marriage and age at first birth are compared across women who experienced different father presence/absence conditions as children. Survival analyses show that daughters of fathers who divorced their mothers or deserted their families have consistently younger ages at marriage and first birth than other women. In contrast, daughters whose fathers were labor migrants have consistently older ages at marriage and first birth. Daughters whose fathers died when they were children show older ages at marriage and first birth than women with divorced/deserted fathers and women with fathers present. These effects may be mediated by high socioeconomic status and high levels of parental investment among the children of labor migrants, and a combination of low investment, high psychosocial stress, and low alloparental investment among women with divorced/deserted fathers. Our findings are most consistent with the Child Development Theory model of female life history strategies, though the Paternal Investment and Psychosocial Acceleration models also help explain differences between women in low paternal investment situations (e.g., father divorced/abandoned vs. father dead). Father absence in and of itself seems to have little effect on the life history strategies of Bangladeshi women once key reasons for or correlates of absence are controlled, and none of the models is a good predictor of why women with deceased fathers have delayed life histories compared with women whose fathers are present.