CogAT Grade 3 common mistakes
CogAT Grade 3 · Understand the traps and how to avoid them.
Treating an analogy as a general 'these words are related' match and picking any pair that shares a topic, instead of checking that the relationship runs the same direction between both pairs.
Third graders often compare the two pairs by overall meaning rather than by the exact relation (part-to-whole, worker-to-tool, young-to-adult). A pair about the same subject feels correct even when the arrow points the wrong way, as in 'puppy is to dog' versus 'dog is to puppy'.
What to do instead
Have the child say the first pair aloud as a full sentence with a blank: 'A puppy is a young ___ .' Then test each answer by dropping it into the same sentence, keeping the order fixed. Practise with deliberately reversed distractors so the direction check becomes automatic.
Choosing a classification answer that fits only one of the listed words, or fits them only loosely, rather than finding the one category that covers every word in the group.
Young readers latch onto the first familiar word and pick a category that suits it, then stop reading the rest of the row. They also accept broad labels like 'things you can buy' that technically include everything but do not capture what the group has in common.
What to do instead
Teach a three-step routine: read all the words first, name one thing each shares, then check the chosen answer against every word before marking it. Give practice sets where two answers fit one word each, so the child learns that a partial fit is a trap.
Answering a sentence-completion item with a word that is grammatical but does not match the meaning clue, such as picking 'cold' for a sentence that signals heat because the sentence contains the word 'winter'.
Children grab a word that is merely associated with a keyword in the sentence instead of using the logic words ('because', 'but', 'so', 'although') that determine what the blank must mean. The association feels strong enough to override the sentence's actual logic.
What to do instead
Train the child to circle the connective and the key noun, then ask 'does the blank need to agree with this or oppose it?' Before looking at options, have them predict a word in their own head, then choose the option closest to that prediction.
Spending a long time on one hard verbal item and then rushing the final items in the section, leaving several unanswered.
Third graders have limited time-monitoring skill and often believe they must finish every question in order. One unfamiliar vocabulary word can absorb two or three minutes, and the child does not notice the section clock.
What to do instead
Practise with a visible timer and a rule: if no answer comes within about 45 seconds, mark the best guess and move on. Do timed mini-sets of ten items so the child builds a feel for pace, and rehearse returning to skipped items only if time remains.
Adding or subtracting the wrong quantities in a two-step word problem because the child computes with the first two numbers seen rather than the numbers the question asks about.
The question is read once for gist, not for the specific quantity requested, and extra numbers are included as distractors. Working memory is still developing, so the last number read tends to dominate the operation chosen.
What to do instead
Require a written 'plan line' before any arithmetic: what is asked, which numbers are needed, and which operation. Cross out unused numbers in the problem. Use two-step problems with one irrelevant number so the child must justify each number's role.
Solving number-pattern and number-series items by looking only at the difference between the first two terms and assuming that rule continues, without checking it against the rest of the sequence.
Third-grade pattern work is usually simple addition, so children expect a constant step. They do not yet test alternating rules, doubling, or steps that change size, and they stop verifying after one successful guess.
What to do instead
Make 'predict, then check every gap' a habit: write the differences under each pair and confirm the same change holds throughout. Introduce sequences with changing steps and alternating operations so the child learns to look for two interleaved rules.
Confusing 'how many more than' with 'how many altogether', or treating a comparison question as an addition problem.
The phrase 'more than' contains the word 'more', which children associate with addition, even though comparison subtraction requires finding the difference. The linguistic cue overrides the underlying model of the situation.
What to do instead
Draw two bars of different lengths and label the missing part as the difference. Say the comparison sentence both ways ('A has 4 more than B' and 'B has 4 fewer than A') and connect each to subtraction. Mix comparison and total problems so the child must classify before computing.
Guessing the next figure in a figural sequence from the last figure only, without tracking how the figure changed across all the earlier steps.
The items are visual and tempting to answer quickly. Children notice a salient feature such as colour or size and extrapolate from it, missing a rotation, a count change, or an alternating pattern that only appears when the whole row is compared.
What to do instead
Have the child describe each transition in words ('it turned a quarter, then a quarter again') and write the rule down before choosing. Cover the answer choices while studying the sequence, then predict the next figure and only then look.
Matching a figure to an answer choice by overall outline or by one shared feature, ignoring differences in internal details such as number of dots, line orientation, or filled versus open regions.
Visual comparison in young children is holistic and fast; the eye registers the general shape before the details. Answer choices are designed with near-miss figures that share the silhouette but differ in a small, rule-relevant attribute.
What to do instead
Teach a feature checklist to run on every figure: shape, size, orientation, number of parts, shading. Count or point to each feature aloud. Use paired-figure practice where the wrong options differ by exactly one feature so the child must name the difference.
Losing track of the rule in paper-folding or figure-transformation items and answering from how the picture looks rather than mentally reversing the fold or turn.
These items demand spatial working memory and mental rotation, which are still developing at age eight or nine. The child holds the first fold in mind, then the second fold displaces it, and the final choice reflects only the last step.
What to do instead
Have the child act it out with a real piece of paper or trace the folds with a finger on the page, marking where holes or marks land at each stage. Work backwards from the answer choices, unfolding each one mentally, until the habit of reversing the operation is established.