scholarly journals Do Peers Affect Student Achievement? Evidence from Canada Using Group Size Variation

2010 ◽  
Author(s):  
Vincent Boucher ◽  
Yann Bramoulle ◽  
Habiba Djebbari ◽  
Bernard Fortin
Keyword(s):  
Student Achievement ◽  
Group Size ◽  
Size Variation

scholarly journals DO PEERS AFFECT STUDENT ACHIEVEMENT? EVIDENCE FROM CANADA USING GROUP SIZE VARIATION

2012 ◽  
Vol 29 (1) ◽  
pp. 91-109 ◽  
Author(s):  
Vincent Boucher ◽  
Yann Bramoullé ◽  
Habiba Djebbari ◽  
Bernard Fortin
Keyword(s):  
Student Achievement ◽  
Group Size ◽  
Size Variation

scholarly journals Do Peers Affect Student Achievement? Evidence from Canada Using Group Size Variation

2010 ◽  
Author(s):  
Vincent Boucher ◽  
Yann Bramoulle ◽  
Habiba Djebbari ◽  
Bernard Fortin
Keyword(s):  
Student Achievement ◽  
Group Size ◽  
Size Variation

scholarly journals Fluctuating survival selection explains variation in avian group size

2016 ◽  
Vol 113 (18) ◽  
pp. 5113-5118 ◽  
Author(s):  
Charles R. Brown ◽  
Mary Bomberger Brown ◽  
Erin A. Roche ◽  
Valerie A. O’Brien ◽  
Catherine E. Page
Keyword(s):  
Group Size ◽  
Colony Size ◽  
Information Transfer ◽  
Size Variation ◽  
Directional Selection ◽  
Net Benefit ◽  
First Case ◽  
Survival Selection ◽  
Wide Range ◽  
Directional Change

Most animal groups vary extensively in size. Because individuals in certain sizes of groups often have higher apparent fitness than those in other groups, why wide group size variation persists in most populations remains unexplained. We used a 30-y mark–recapture study of colonially breeding cliff swallows (Petrochelidon pyrrhonota) to show that the survival advantages of different colony sizes fluctuated among years. Colony size was under both stabilizing and directional selection in different years, and reversals in the sign of directional selection regularly occurred. Directional selection was predicted in part by drought conditions: birds in larger colonies tended to be favored in cooler and wetter years, and birds in smaller colonies in hotter and drier years. Oscillating selection on colony size likely reflected annual differences in food availability and the consequent importance of information transfer, and/or the level of ectoparasitism, with the net benefit of sociality varying under these different conditions. Averaged across years, there was no net directional change in selection on colony size. The wide range in cliff swallow group size is probably maintained by fluctuating survival selection and represents the first case, to our knowledge, in which fitness advantages of different group sizes regularly oscillate over time in a natural vertebrate population.

Group size and activity patterns of belugas (Delphinapterus leucas) and narwhals (Monodon monoceros) during spring migration in Lancaster Sound

1991 ◽  
Vol 69 (6) ◽  
pp. 1630-1635 ◽  
Author(s):  
Susan E. Cosens ◽  
Larry P. Dueck
Keyword(s):  
Group Size ◽  
Predator Avoidance ◽  
Additional Data ◽  
Activity Patterns ◽  
Size Variation ◽  
Spring Migration ◽  
Delphinapterus Leucas ◽  
Interspecific Differences ◽  
Monodon Monoceros ◽  
Grouping Patterns

Aerial surveys of belugas (Delphinapterus leucas) and narwhals (Monodon monoceros) were conducted in Lancaster Sound and northern Admiralty Inlet, N.W.T., during spring migration in 1987. Interspecific differences in grouping patterns and associated behaviour were observed. Group size and behaviour varied with ice type and state of breakup but patterns of variation differed between species. Behaviour of narwhals but not of belugas varied significantly with group size. Variation in group size and activity suggests that aggregation patterns are not related to predator avoidance strategies. Additional data are needed to test hypotheses about grouping patterns and behaviour in relation to prey distribution.

scholarly journals The Goldilocks Effect: Female geladas in mid-sized groups have higher fitness

2018 ◽  
Author(s):  
Elizabeth Tinsley Johnson ◽  
Noah Snyder-Mackler ◽  
Amy Lu ◽  
Thore J. Bergman ◽  
Jacinta C. Beehner
Keyword(s):  
Group Size ◽  
Size Variation ◽  
Group Living ◽  
Mortality Rates ◽  
Female Mortality ◽  
Individual Fitness ◽  
The Cost ◽  
Large Groups ◽  
The Relationship ◽  
Insight Into

AbstractThe cost-to-benefit ratio of group-living is thought to vary with group size: individuals in “optimal” groups should have higher fitness than individuals in groups that are too large or small. However, the relationship between group size and individual fitness has been difficult to establish, a gap we address here in the gelada. We demonstrate group size effects on the production of surviving offspring and on female mortality rates, which are largely explained by group-size variation in infanticide risk and foraging competition. We also identify a mechanism by which females may alter group size: in large groups, females groomed with less than half of their group, increasing the likelihood of fissions. Our findings provide insight into how and why group size shapes fitness in long-lived species.

scholarly journals Epidemiological effects of group size variation in social species

2013 ◽  
Vol 10 (83) ◽  
pp. 20130206 ◽  
Author(s):  
Damien Caillaud ◽  
Meggan E. Craft ◽  
Lauren Ancel Meyers
Keyword(s):  
Group Size ◽  
Disease Transmission ◽  
Size Variation ◽  
Disease Outbreaks ◽  
Structured Populations ◽  
Epidemic Threshold ◽  
Homogeneous Population ◽  
Contact Patterns ◽  
Animal Populations ◽  
Effective Group

Contact patterns in group-structured populations determine the course of infectious disease outbreaks. Network-based models have revealed important connections between group-level contact patterns and the dynamics of epidemics, but these models typically ignore heterogeneities in within-group composition. Here, we analyse a flexible mathematical model of disease transmission in a hierarchically structured wildlife population, and find that increased variation in group size reduces the epidemic threshold, making social animal populations susceptible to a broader range of pathogens. Variation in group size also increases the likelihood of an epidemic for mildly transmissible diseases, but can reduce the likelihood and expected size of an epidemic for highly transmissible diseases. Further, we introduce the concept of epidemiological effective group size , which we define to be the group size of a hypothetical population containing groups of identical size that has the same epidemic threshold as an observed population. Using data from the Serengeti Lion Project, we find that pride-living Serengeti lions are epidemiologically comparable to a homogeneous population with up to 20 per cent larger prides.

scholarly journals Identification of Peer Effects Using Group Size Variation

2006 ◽  
Author(s):  
Laurent Davezies ◽  
Xavier d'Haultfoeuille ◽  
Denis Fougere
Keyword(s):  
Group Size ◽  
Peer Effects ◽  
Size Variation
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