TEDS Data Dictionary

Description of Test

In each item of this test, a set of "blocks" is represented on screen using this diagram:

A sequence of some of the blocks is then represented on screen by highlighting blocks one by one as shown below:

During this stimulous sequence, each block is highlighted for exactly 1 second, followed by a pause of 1 second during which no blocks are highlighted.

When the stimulous sequence has been presented in full, the prompt "start now" appears above the diagram on the screen, and the twin is invited to repeat the sequence by clicking on the blocks in sequence.

In the introduction to the test, twins are asked to attempt a simple practice item (a sequence of 3 blocks), and are given feedback to tell them whether they responded correctly (no feedback is given in the main test). Twins may repeat the practice item before they start the main test if they wish.

The first two items of the main test consist of sequences of 4 blocks. These are followed by two sequences of 5 blocks, and so on up to sequences of 9 blocks. The item sequences are shown in full in the table of items below.

A twin may not respond during the stimulous sequence: clicks on screen are only recorded after the "start now" prompt appears. During the response, each clicked block is highlighted, as shown in the diagram above, and remains highlighted until the next block is clicked. The response for each item ends when the twin has clicked the required number of blocks, e.g. after clicking 4 blocks in the first item.

At the end of each item response, when the twin has clicked on the required number of blocks, an intermediate screen appears and twins can choose either to "come back later" or to "continue" with the next item.

The stimulous sequence for each item is only shown once, and may not be repeated. If a twin attempts to repeat an item using the browser's Back or Refresh buttons, the item is forfeited with zero score.

Items are presented in numerical item number order, without branching. The test is discontinued if both items at any level are answered incorrectly. There is no time limit for responding to each item, so item timeouts do not occur. A "come back later" button is presented on the intermediate screen between items.

Test Rules

• Scoring
  For each item, the correct response (correct sequence of blocks) is given a score of 1, and any other response is given a score of 0. Any question omitted due to the discontinue rule is given a score of 0. The total test score is the sum of the item scores. The maximum total score for the test is 12.
• Discontinue rule
  Discontinue the test after two consecutive items at the same level are answered incorrectly (with zero score), e.g. if incorrect responses are given for items 51 and 52. Note that this rule does not apply to consecutive items at different levels, e.g. items 52 and 61.

Item Variables

The item variables relating to the Corsi Block test, as listed in the table below, were generated automatically by programs on the web server during the course of the test. Note that the dataset only includes data for completed tests. If a twin started the test but left it unfinished, then the data for the test were not used.

In most cases the values of these variables have been left unaltered, although some have been recoded during data cleaning as follows. See the web data cleaning page for further details.

• For items skipped due to the discontinue rule, the item response variable is recoded from missing to -2, and the item score is recoded from missing to 0.
• For items that crashed or malfunctioned in any way, the item response variable is recoded from missing to -4, and the item score is recoded from missing to 0.
• In rare cases when the test crashed repeatedly in a series of items, so that insufficient data were collected for a meaningful test score, the test status flag is recoded from 2 to 3, the data flag is recoded from 1 to 0, and all item variables are recoded to missing (test data deleted)

The test start and end dates and times, and item answer and download times, have not been retained in the dataset.

Test Items

The blocks are numbered as shown in the image below:

Note that these numbers are not visible to twins taking the test; the numbers are presented here for reference purposes only.

In the table below, each test item is described using a sequence of numbers representing the sequence of blocks as numbered above.