Skip to content


Switch branches/tags

Name already in use

A tag already exists with the provided branch name. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Are you sure you want to create this branch?

Latest commit


Git stats


Failed to load latest commit information.
Latest commit message
Commit time

Effect sizes from one hundred years of social psychology

A total of 474 effect sizes from meta-analyses from social psychology during one hundred years extracted from the study by Richard et al. (2003) into a tab-separated CSV file.

Thanks to @richarddmorey we now have year as well.

Magnitude of meta-analytic effect sizes in social psychology


  • originalorder is the order of the effect size as in Richard et al. (2003).
  • field is one of 18 research fields the effect sizes are grouped into, as in Richard et al. (2003).
  • description is a short description of the effect size in question.
  • k is the number of studies.
  • r is the mean effect size (Pearson's r).
  • sd is the standard deviation of the mean effect size. This is the only field with missing values, denoted by NA.
  • documentnumber refers to the document number of the specific meta-analysis. See appendix in Richard et al. (2003).
  • reference is the reference to the specific meta-analysis.
  • year is when the meta-analysis was published (extracted from reference).


  • Aggression
  • Attitudes
  • Attribution
  • Expectancy effects
  • Gender roles
  • Group processes
  • Health psychology
  • Helping behavior
  • Intergroup relations
  • Law
  • Leadership
  • Methodology
  • Motivation
  • Nonverbal communication
  • Personality
  • Relationships
  • Social cognition
  • Social influence

Import into R

df <- read.csv("",
               header=TRUE, sep="\t", stringsAsFactors=FALSE)

df$field <- factor(df$field)

# What is the mean effect size from all meta-analyses?

# What is the mean effect size from all meta-analyses in aggression research?
mean(subset(df$r, df$field == "Aggression"))

# Histogram of all effect sizes.
hist(df$r, breaks = 30)


# Reproduce graph in Richard et al. (2003), but use density instead.
df %>%
  ggplot(aes(r)) +
  geom_density(fill="grey") + 
  scale_x_continuous(limits=c(0, 1), breaks=seq(0, 1, 0.1)) +
  theme_minimal() +
  labs(title="Magnitude of meta-analytic effect sizes in social psychology",
       x="Mean correlation coefficient",

# Plot all effect sizes by field.
df %>% 
  ggplot(aes(year, r, color=factor(field))) +
  geom_point() + 
  theme_minimal() +
  labs(title="All effect sizes by year", color="Field", x="Field", y="Effect size (r)")

# Plot mean effect size by year.
df %>%
  group_by(year) %>%
  summarize(meanr = mean(r)) %>%
  ggplot(aes(year, meanr)) +
  geom_point() + 
  theme_minimal() +
  labs(title="Mean effect size by year", x="Year", y="Effect size (r)")

Import into Python

import pandas as pd
import numpy
import matplotlib.pyplot as plt

data = pd.read_csv("", sep="\t")

# What is the mean effect size from all meta-analyses?

# Histogram.
plt.hist(data["r"], bins="auto")
plt.title("Magnitude of meta-analytic effect sizes in social psychology")

See also


Richard, F. D., Bond, C. F., & Stokes-Zoota, J. J. (2003). One Hundred Years of Social Psychology Quantitatively Described. Review of General Psychology, 7(4), 331–363.


One hundred years of social psychology quantitatively described