TEDS Data Dictionary

Description

The Bricks tests were designed to test two aspects of spatial ability: mental rotation and visualisation. These aspects were measured separately and together, using both 2D and 3D stimuli, to form a battery of six subtests. The subtests were as listed below, and were presented in the order shown:

Each subtest comprises 12 items (plus some example and practice items). All items, in all 6 subtests, have the same format. Each item presents a target stimulus image and four response images (labelled A, B, C and D in the data). Participants are asked to select the response image which shows the same object as shown in the target. A full table of test items, including all the images used, can be found below under the heading Table of Test Items.

In every case, the target stimulus image appears near the top of the screen (centred horizontally), with the four multiple-choice response images arranged in a single row (also centred horizontally) beneath. In the data, the 4 responses are labelled A, B, C and D, from left to right in the order in which they appeared on screen. All stimuli are presented at a size of 200x200 pixels, surrounded by a thin black border.

At the same time as the images appear, a timer appears on screen (top right) showing '20' in a bold, black font, and begins counting down in seconds, turning red if it reaches 5. Measurement of the participant's reaction time (in milliseconds) starts immediately. If the participant clicks on one of the response stimuli before the timer runs out, measurement of their reaction time stops, the border of the clicked image turns green for 500ms, then all stimuli fade away (over 250ms). After a pause of 500ms, the stimuli for the next item fade into view (over 250ms) and the timer begins counting (from 20) once this latter fade is complete. If the timer reaches 0 before the participant makes a response, responses are disabled, all stimuli are faded to a light grey (opacity 0.3), and a 'Next' button appears at the bottom of the screen alongside the message (in red) 'Out of time. Press Next to continue'. Clicking on this button triggers the same fade/replace behaviour described above.

Each subtest started with an explanation of what to expect, with an example item where the correct answer was given. The example item was followed by two practice items, to be attempted by the twin, after each of which feedback was given with an explanation of the correct answer. The example and practice items did not contribute to the subtest score. However, they are shown below in the table of test items.

Web Test Rules

• Item order
  The order of the items is fixed, with no branching. The order is shown in the table of test items below.
• Scoring
  For each item the correct response is given a score of 1, and an incorrect response is given a score of 0. The maximum total score for each subtest is 12 (not including the practice items).
• Discontinue rule
  This rule operates within each subtest independently. If the participant makes four consecutive incorrect responses, they discontinue, scoring 0 for any remaining items and skipping to the beginning of the next subtest. Timeouts are treated as incorrect responses for this purpose. The discontinue rule does not include the initial practice items.
• Timeout rule
  A timeout of 20 seconds applies to each item, as described in detail above. After 20 seconds with no response, the item is forfeited with zero score, and a "next" button appears. On resuming the test, the twin is taken to the next item in sequence as described above.

The tests were designed to be completed in one session. Within each subtest all responses were recorded in the browser (using javascript) and only submitted to the web server at the end of the subtest. Hence, if any subtest was halted part-way through, for example by closing the browser, then all responses were lost for that subtest; in this case, a twin would have to re-start the subtest from scratch on logging in again. If a twin attempted to repeat a question, using the browser's Back or Refresh buttons, then a warning message would appear in a pop-up box; if the twin ignored the message, then the test would be halted, and the twin would have to re-start the entire subtest from scratch.

Dataset Item Variables

The item variables relating to the Bricks subtests, as listed in the table below, were generated automatically by programs on the web server, with a few exceptions. The exceptions (subtest score, subtest status, time spent on the subtest, mean item response time in the subtest) were derived during dataset construction, and are included here to complete the set of variables relating directly to Bricks subtests. The raw subtest scores were included as an item in the raw data (originally with values 0-12), but it was decided to re-compute the score from 9 of the 12 items in each subtest.

Note that the dataset only includes data for successfully completed subtests. If a twin started a subtest but left it unfinished, then the data were not submitted to the web server and were therefore not recorded. If the subtest data were found to be compromised, either through loss of data or through random responding, then the subtest item data have been recoded to missing in the dataset. The start and end dates/times have not been retained in the dataset.

Note that the item response variables have been recoded where appropriate with values -1, -2 and -4 to denote item timeout, discontinued or malfunctioned respectively. See the web data cleaning page for further details.

In the table below, XX refers to the subtest code (2r, 2rv, 2v, 3rv, 3r, 3v) and YY refers to the item number (practice items p1 and p2, main items 01 to 12).

Table of Test Items

The table below lists the test items, showing all the item target and response images from all 6 sub-tests. The images are shown the same size as they appeared in the web test (200 x 200 pixels).

Subtest	item	target image	response A	response B	response C	response D	correct response
2D rotation (2r)	Introductory text: This part of the study tests your ability to recognise 2D objects in different orientations. Each question will appear like this example: [example item images as below] For each question, please identify which of the four options shows the same object as the one depicted at the top. Only one option is correct in each case, showing the same object, rotated but not flipped over. Each of the other three objects is different. In the example above, the correct answer is A.
	example item						A
	p1 (practice item)						C
	p2 (practice item)						D
	1						B
	2						A
	3						C
	4						D
	5						A
	6						C
	7						C
	8						B
	9						D
	10						B
	11						C
	12						A
2D rotation and visualisation (2rv)	Introductory text: This part of the study tests your ability to recognise 2D objects in different orientations, when parts of them are hidden from view. You will have to use the available information about the sizes and shapes of each part of the object, and use this to eliminate the impossible answers. Each question will appear like this example: [example item images as below] For each question, please identify which of the four options shows the same object as the one depicted at the top. Only one option is correct in each case, showing the same object, rotated but not flipped over. Each of the other three objects is different. In the example above, the correct answer is A, as this is the only one which could be the same as the target object.
	example item						A
	p1 (practice item)						A
	p2 (practice item)						D
	1						C
	2						D
	3						C
	4						B
	5						B
	6						D
	7						A
	8						D
	9						A
	10						A
	11						D
	12						B
2D visualisation (2v)	Introductory text: This part of the study tests your ability to recognise 2D objects in different orientations, when parts of them are hidden. You will have to use the available information about the sizes and shapes of each part of the object, and use this to eliminate the impossible answers. Each question will appear like this example: [example item images as below] For each question, please identify which of the four options shows the same object as the one depicted at the top. Only one option is correct in each case, showing the same object in the same orientation (not rotated) - only the occlusion (the black shape hiding part of the object) has moved. Each of the other three objects is different. In the example above, the correct answer is B, as this is the only one which could be the same as the target object.
	example item						B
	p1 (practice item)						A
	p2 (practice item)						B
	1						B
	2						B
	3						A
	4						D
	5						A
	6						D
	7						C
	8						D
	9						B
	10						A
	11						C
	12						C
3D rotation and visualisation (3rv)	Introductory text: This part of the study tests your ability to recognise 3D objects in different orientations - in other words, imagine that you have stayed still, but the object has been rotated. Each question will appear like this example: [example item images as below] For each question, please identify which of the four options shows the same object as the one depicted at the top. Only one option is correct in each case, showing the same object from a different viewpoint. Each of the other three objects is different. In the example above, the correct answer is B.
	example item						B
	p1 (practice item)						D
	p2 (practice item)						B
	1						D
	2						B
	3						A
	4						C
	5						A
	6						A
	7						C
	8						C
	9						B
	10						D
	11						D
	12						A
3D rotation (3r)	Introductory text: This part of the study tests your ability to recognise 3D objects when they stay still, but your viewpoint has rotated on the spot. Each question will appear like this example: [example item images as below] For each question, please identify which of the four options shows the same object as the one depicted at the top. Only one option is correct in each case, showing the same viewpoint of the same object, just rotated in place - imagine that you are looking at the object through a camera which can be rotated on the spot. In the example above, the correct answer is D - in this image, the only change is that the camera has rotated in place, so you can see all the same parts of the object which were visible in the original image.
	example item						D
	p1 (practice item)						B
	p2 (practice item)						C
	1						C
	2						D
	3						A
	4						A
	5						B
	6						C
	7						B
	8						C
	9						A
	10						A
	11						A
	12						D
3D visualisation (3v)	Introductory text: In this part of the study, you will be asked to look at wireframe drawings of objects, and predict what the solid object will look like (from the same viewpoint). Each question will appear like this example: [example item images as below] For each question, please identify which of the four options shows the same object as the one depicted at the top. Only one option is correct in each case, showing the same object in the same orientation - nothing has moved, you are just looking at the 'solid' version of the wireframe drawing. Each of the other three objects is different. In the example above, the correct answer is C, because the studs shown in the wireframe are underneath the object (and therefore hidden, from this viewpoint).
	example item						C
	p1 (practice item)						B
	p2 (practice item)						C
	1						A
	2						C
	3						C
	4						B
	5						A
	6						B
	7						D
	8						D
	9						D
	10						B
	11						A
	12						B