TEDS Data Dictionary

Description of Test

This test was identical to the version of the Picture Completion test that was previously used in the 10 Year study. The items themselves, and the test rules, were unchanged.

The test consisted of a series of pictures of recognisable objects or scenes, each with an essential detail omitted from the picture. (The pictures are shown in a table below.) The twin was asked to click on the relevant part of the picture on screen, to identify the part that is missing. There was a time limit of 20 seconds for each picture (shown pictorially by a moving time bar on screen). If 20 seconds passed before the twin had clicked on the picture, this was treated as an incorrect response (zero score), and then the twin was shown a prompt asking them to continue with the next picture.

In order to determine whether a given click corresponded to a correct or an incorrect response, each picture was divided into a rectangular grid. Each cell of the grid was numbered. When a twin clicked on the picture, the relevant grid number was recorded as the item response. The grid is depicted in the table of items below; the correct grid number(s) for each item are also shown in the table.

There are 30 main picture items, plus one initial 'practice' item which contributes to the branching but not to the test score. Any given twin taking the test may have been presented with fewer than 30 items, because of the branching and discontinue rules, which are described below.

Test Rules

• Scoring
  For each question, a correct response is given a score of 1, and an incorrect response is given a score of 0. Correct and incorrect responses are based on grid numbers corresponding to where each picture was clicked (see table of items below). The maximum total score for the test is 30 (not including the practice item).
• Branching rules
  
  • Start with the practice item p1, and proceed to item 5.
  • If both the practice item and item 5 are correct, give credit for items 1-4 (as though they had been answered correctly, gaining a score of 1 for each item), then proceed upwards from item 6.
  • If either the practice item or item 5 is incorrect (scoring 0), attempt the lower items (1-4) in reverse order. Then:
    • If any two successive items are correct (e.g. 4 and 3), then give credit for any of items 1-4 not yet attempted; then proceed upwards from item 6. Note that if either the practice item or item 5 is correct, while the other is incorrect, and this is followed by a correct answer for item 4, then this results in an upward branch to item 6 (the practice item and item 4 are treated as successive items for this rule, as are item 5 and item 4).
    • If no two successive items are correct, the test ends after item 1 has been attempted.
• Discontinue rule
  Discontinue the test after five scores of zero in any five consecutive items. This rule only applies from item 6 upwards. It does not include the branching items (the practice item and item 5), nor does it include the lower items (1-4) if attempted.
• Timeout rule
  A timeout of 20 seconds applies to each item. After 20 seconds with no response, the item is forfeited with zero score, and a "next item" screen appears. On resuming the test, the twin is taken to the next item in sequence as described above.

Item Variables

The item variables relating to the Picture Completion 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. Note that the variable holding the total test score was also generated automatically on the web server. It is therefore treated as an item variable (it did not have to be derived as at age 10).

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 timed out items, the item response variable is recoded from missing to -1, and the item answer time is recoded from 20 to missing (item scores are 0)
• 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 skipped and credited due to upward branching, the item response variable is recoded from missing to -3 (the item score is already recorded as 1 on the web server).
• 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.
• For instances of crashed or otherwise compromised tests, the 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)
• For twins identified as random responders in this test, the status flag is recoded from 2 to 4, 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 numbering of the items, shown in the table below, equates to the numbering used in the item variables. Note that this is not the same as the order in which items were presented to twins in the test (see branching rules above).

item	picture	correct response (missing part)	correct grid number(s)
(grid)		(the picture is for item 4, but this same grid was used for all items)	(numbers below, in this column, refer to this grid)
p1 (practice item)		lead tip of pencil	73, 74
1		ear of fox	27-29, 40
2		lid flap of box	14-18, 26-30, 38-42, 50-54, 62-66
3		whiskers on one side of cat's face	31, 32
4		finger nail of little finger	32
5		leg of elephant	75-77, 87-89, 99-101
6		strap of watch	92
7		bottom door hinge	52, 64, 76, 88, 100
8		reflection of doll in girl's hand	40, 52, 64
9		number 11 on face of clock	29
10		handle on second drawer from top	44, 45
11		holes in belt	61-62, 73-74, 86-91
12		veins in part of the top leaf	16-17, 27-29
13		second-bottom step	56, 66-69, 78-79
14		eye lashes on one eye	55, 56
15		dot on top of right-hand die (there should be 6 dots)	33
16		plug hole in bath	52-55, 64-66
17		filament of bulb	30-32, 42-44, 54-56, 66-68
18		hole in top of whistle	40-42, 52-56, 67-68
19		black keys on piano keyboard	63-70
20		hinge where scissor blades meet	66-68
21		eye brow	40-42, 53
22		red liquid in thermometer bulb	103
23		slat near top-left of lattice	7, 17-19, 29-30, 39-41, 50-52, 62-63, 73-74
24		pith dividing segments in part of orange	43-45, 55-57
25		gill of fish	52-53, 64-65
26		labels on cans, on top-right shelf	45-48
27		cable attached to phone hand set (on either side)	50-52, 57-58, 62-64, 69-70, 75-76, 81-82
28		spoke of umbrella	30, 43, 55-56, 67-68
29		shadow of tree	62-64, 73-77, 86-88
30		eye hole for lace of shoe	42