Three parallel twin studies of early reading development were conducted in Australia, Colorado, and Scandinavia (Norway & Sweden). Investigators Brian Byrne, Richard Olson, and Stefan Samuelsson have committed to creating a unified data set suitable for cross-country comparisons. This study is known by a host of acronyms including:

• RDS: Reading Development Study
• ERDS: Early Reading Development Study
• ILTS:
• LSERD: Longitudinal Study of Early Reading Development (thus the lizard)

Visit Study Public Home Page

Data from each assessment wave from each country is sent to a single location (currently IBG - Robin Corley) for creation of a unified assessment wave data set, e.g., IT (Initial Test) or F1 (Follow-Up 1). Selected variables from the individual waves are then combined into a working individual-level cross-assessment file, and a twin-pair (double-entered) cross-assessment file.

• Combine data from all three sites and creates a unified IT file (Initial Test/Pre-Kindergarten).
• Combine data from all three sites and creates a unified F1 file (Follow-up 1/Post-Kindergarten).
• Combine data from all three sites and creates a unified F2 file (Follow-up 2/Post-1st grade).
• Combine data from all three sites and creates a unified F3 file (Follow-up 3/Post-2nd Grade).
• Combine data from Colorado and Sweden and creates a unified F4 file (Follow-up 4/Post-4th Grade).

The files that are available for download are listed below. They represent SPSS Export (Portable) files that can be opened by either SPSS or SAS. These files represent the test session data collected from each twin.

• IT combined file: IT (pre-school) data
• F1 combined file: F1 (post-K) data
• F2 combined file: F2 (post-1st) data
• F3 combined file: F3 (post-2nd) data
• F4 combined file: F4 (post-4th) data
• IT-F4 combined file: IT-F4 data
• Post-9th grade file: Colorado-only data from post-9th grade follow-up

Additional Information files

• IT-F4 health file: IT-F4 twin health data

ACCESS for non-SPSS users

SPSS files can be read by SAS. If using R, this library package appears to “translate” SPSS .sav files adequately. A similar function is available for .por files, which are soon to be phased out of SPSS.

library(haven)
df <- read_sav('kidpar.sav')

The combined IT-F4 data can also be accessed as an Excel file with the data on one sheet and labeling information on a second. This should allow access to those without ready access to SPSS.

• IT-F4 combined file: IT-F4 data and labels in Excel format

All ERDS collaborators have a responsibility to use the ERDS data responsibly, including restricting access to these files to those colleagues who have requested and received permission to work with the data. Please notify the site manager IMMEDIATELY if information is found in the files that directly identifies families (e.g., date of birth).

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