TEDS Data Dictionary

Description of Test

This was a modified version of the PIAT web test that was previously used in the 10 Year study. A few of the initial practice items in the 10 Year version were removed, but the main items (numbered 19 to 100) remained unchanged. The 'correct' response to item 79 was changed (from 3 to 1). The branching and discontinue rules were simplified.

This was a test of reading ability. In each item of the test, the twin was first presented with a sentence of written text to read on the screen; when the twin clicked on "OK", or after a 20 second time limit (whichever happened sooner), the text was replaced on screen with four pictures. The twin was then required to select (by clicking) the picture that most accurately matched the sentence they had just read; there was another 20 second time limit for the twin to do this. For further details, see the test rules and the table of test items further down this page.

The test included 85 items, as follows:

• 3 "practice" items (P3, P4, P5), in which the text consists of simple short sentences. These form part of the branching mechanism, as described below, but do not contribute to the overall score of the test.
• 82 main items (numbered 19 to 100).

In practice, most twins attempted fewer than 85 items, because of the branching and discontinue rules (see below). The items are numbered in increasing order of difficulty, with item 100 intended to be the most difficult item.

Test Rules

• Scoring
  For each question, the correct response is given a score of 1, and any of the three incorrect responses is given a score of 0.
  The maximum total score for the test is 82: this score only includes the main items (19-100) not the practice items (p3-p5).
  If at any point a twin branches up, and does not subsequently branch down again, any lower items skipped due to branching are credited towards the total score, as though they had been answered correctly.
• Branching rules
  The branching rules for this test are tabulated in full below. The general principles of the branching are as follows:
  • There are 2 branch points in the test. The first branch point consists of the three practice items (p3-p5). The second branch point consists of the five consecutive items 55-59.
  • Depending on the number of correct responses to the branch point items, move up or down as shown in the table below. The move up from the first branch point goes directly to the second branch point; other branching movements go to a basal point.
  • At a basal point, the twin proceeds upwards either until the end of the test is reached (item 100), or until the twin discontinues (see below). There are four basal points, at items 19, 40, 60 and 75 respectively.
  The exact branching rules are tabulated below. For all twins, the test starts with branch point items P3-P5.

  Branch	Branch point items	Branching rule	Move to:
  1	P3,P4,P5	All three items incorrect	Basal point 1: item 19
  		At least one item correct	BRANCH point 2: item 55
  2	55,56,57,58,59	All 5 items incorrect	Basal point 1: item 19
  		1 or 2 items correct, with any 3 consecutive items incorrect	Basal point 2: item 40
  		1, 2, 3 or 4 items correct, with no 3 consecutive items incorrect	Basal point 3: item 60
  		All 5 items correct	Basal point 4: item 75

  No item is presented more than once, and no further branching occurs after a basal point has been reached. Here is an example sequence of items: items p3-p5 (branch up to branch point 2), then items 55-59 (branch down to basal point 2), then items 40-54, then from item 60 upwards until discontinuing.
• Discontinue rule
  Discontinue the test after four scores of zero in four consecutive items. This rule only applies after a "basal point" has been reached (it does not apply within branch points).
• Timeout rules
  Each item has two time limits: 20 seconds for reading the initial sentence, then 20 seconds for choosing an answer (by clicking on a picture). On both the text screen and the picture screen, a moving time bar is displayed to shown the passing of the 20 second limit. The timeouts are enforced as follows.
  • In the text screen, if 20 seconds passes before the twin has clicked on "OK", then the text screen is automatically replaced by the picture screen. It is not possible for the twin to return from the pictures to the text.
  • In the picture screen, if 20 seconds passes before the twin has clicked on a picture, then the item is forfeited (with zero score). The pictures are removed from the screen, and replaced by a link to the next item, allowing the twin to continue with the test.
• Come Back Later restriction
  The "Come Back Later" button was only provided on the text page for each item, not on the pictures page. This was to prevent twins from looking at the pictures then going back to the text to double-check before answering. If a twin ended a session (for example by closing the browser) while on a pictures page, then the item would be forfeited with zero score; on resumption, the twin would be presented with the text for the next item.

Item Variables

The item variables relating to the PIAT 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 reading, 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	text	correct picture	pictures
P3	It is a red duck	3
P4	The bird is in the tree	2
P5	See the boy with the hat.	3
19	There is the sun.	3
20	A boy is on a bike.	4
21	Here is a fire.	2
22	The can is going into a bag.	1
23	The puppy is in the pan.	2
24	Some kittens are in the bed.	3
25	The pony has a big hat on its head.	4
26	In the window is a toy.	4
27	A bird is on the horse’s back.	1
28	A cake is sitting on the step.	3
29	The animal has put the people into a cage.	2
30	A cookie is running out of the store.	4
31	The tiger has a feather in its mouth.	4
32	It is a surprise to see a bus bringing chickens to school.	1
33	The monkey is holding a rocket with its tail.	3
34	Grandmother finds a lion in the garden.	3
35	Inside the basket is a pair of skates.	2
36	The woman on television is smiling.	4
37	A pie is burning so the kitchen is full of smoke.	1
38	The clown is throwing paper aeroplanes at the family.	4
39	A kite string is caught on the telephone line.	3
40	A bull has chased the farmer up the ladder and onto the roof.	4
41	A wheel of the tractor is stuck in the pond.	2
42	Whoever built this kennel made many mistakes.	3
43	A strange creature from a faraway planet is ringing the doorbell.	2
44	The tired giraffe has put its pillow on the cabin and is taking a nap.	3
45	While leaning against a log, the elf is taking a bite out of a banana.	4
46	These crows are not frightened by the scarecrow in the cornfield.	3
47	A ghost is practising the flute beneath a balcony.	2
48	The lost girl found large tracks in the sand.	1
49	Dusty spider webs have given the unused castle a scary look.	2
50	The eagle floats on its wings as it travels in search of a feast.	3
51	The fallen branch caused the runner to stumble.	2
52	The windscreen on the wrecked taxi was not destroyed.	1
53	His foolish costume delights everyone except his daughter.	1
54	Swooping off its perch, the thief seized the sausages in its claws.	4
55	A scarf and cane are hanging from the closet rod.	4
56	Postage stamps may be created to remind us of historical military occasions.	2
57	Its ivory horn outlined against the sky, the unicorn poses on the horizon.	3
58	The weary hikers stagger through the rugged passage.	4
59	The aquarium provides an entertaining display in the barbershop.	4
60	The delightful scenery is scarred with rusting junk and machinery.	2
61	The wretched villain is confined to the dingy dungeon.	2
62	The knight in armour steers the rickety raft over the waterfall.	3
63	A peasant attempts to wrestle his heavy cabinet into a wheelbarrow.	3
64	An octopus is in a panic over a painful visit from a hornet.	1
65	Awaiting the safety of twilight, the vampire crouches in the corncrib.	4
66	The barefoot acrobat, showing tremendous grace, stirs the audience to applause.	4
67	The gorilla is fascinated by its deformed image in the mirror.	1
68	The stranger hesitates because the ancient building appears haunted.	2
69	The bulldozer did not detour but invaded the banquet area.	3
70	A robot monitors the radar terminal while operating the throttle of the aircraft.	1
71	The cargo is being hauled down the wharf to a waiting barge.	1
72	The vacant kennels are overgrown with briars and saplings.	2
73	The inexperienced senator was now being bombarded with numerous inquiries.	1
74	The barricade, which encircles the fortress, contributes an effective obstacle to intruders.	4
75	The residence has been essentially reduced to rubble, the remainder being only the foundation.	4
76	Binoculars on a tripod can be exploited to contemplate constellations in a galaxy.	1
77	From the belfry, a raven spies on a heifer grazing near the quarry.	3
78	This beast has devoured such a quantity of lush fodder that it is now inactive.	1
79	The lecturer is distributing pamphlets to an unruly faculty.	1
80	The wispy seeds are so downy that, once relinquished, they soar off with the slightest disruption.	2
81	The barrier that is interfering with entry to the motorway is a sedan.	2
82	The displeased chauffeur had to remove the luggage prior to replacing the punctured tyre.	4
83	After a dazzling performance, the successful athlete is suffering from exhaustion.	1
84	A sturdy muskrat is mowing countless thistles.	3
85	Because of a collision in the intersection, the constable has veered into the pedestrian zone.	2
86	Heedless of the precipitation, the residents of the community evacuated as the volcano erupted.	3
87	Complete with gala decorations, the buffet is the occasion for a raucous reunion of exuberant alumni.	1
88	Disregarding his responsibility, the barker fends off the Doberman pinscher that is harassing him.	3
89	This cypress, once vigorous and magnificent, now is decomposing among the vegetation.	4
90	Through the protracted, seemingly interminable tempest, one can perceive disarray: the trellis askew and the conifers bowed.	4
91	Light radiating through the playhouse portal projects elongated silhouettes of the belated patrons onto the adjoining facility.	2
92	Because of the contrasting physical images and preferred pursuits of these juveniles, others are astonished when informed that they are twins.	3
93	The valise is disreputable – antiquated, crammed imprudently with apparel, and secured with frayed twine.	2
94	The adolescent, survivor of an unavoidable calamity, applies antiseptic to a limb to eliminate possible infection.	4
95	A forlorn politician ascends the escalator to the privacy of her capitol suite.	1
96	The verdant countryside is prodigiously arable; however, a squalid domicile sullies the otherwise exquisite panorama.	4
97	The pollster is perturbed by the flippant observations of the minstrel she is interrogating.	3
98	The immaculately attired socialite was staggered by ascertaining that she had inadvertently exchanged her shampoo for a nostrum that eradicated her locks.	2
99	A raconteur, the picture of sartorial resplendence, has a ponderous and histrionic barrister cajoling an adjudicator for clemency.	3
100	When the official signified the transgression, anguished zealots hurled acrimonious invectives and engendered pandemonium.	2