Nonverbal Concept Formation Test
— Experimental

What the task measures

Concept formation and categorical reasoning tasks — most famously the Wisconsin Card Sorting Test (Heaton et al. 1993) and the Halstead Category Test (Reitan & Wolfson 1985) — assess your ability to infer an unstated classification rule from feedback, apply it consistently, and then flexibly abandon it once it stops working. These constructs sit at the core of executive function: nonverbal concept formation, selective attention to relevant stimulus dimensions, and inhibitory control / set-shifting.

This task presents two "target" items and asks which of four options shares the hidden rule linking them. The rule is always either a shared colour or a shared object category (e.g. headwear, food, vehicle, clothing). After every response you get immediate Correct / Incorrect feedback. The rule changes seven times across the 35-trial run, in fixed 5-trial blocks, without warning.

From your trials we compute four scores, all derived server-side from your raw response sequence — never from client-reported numbers:

• Total Correct — primary accuracy index, 0–35.
• Perseverative Errors — errors where your choice would have been correct under the immediately preceding, now-superseded rule. This is the classic WCST perseveration index: failure to inhibit an old response set after negative feedback.
• Non-perseverative Errors — all other errors, reflecting more generic attentional or reasoning lapses rather than rule-specific stickiness.
• Failure to Maintain Set (FTMS) — an error occurring after three or more consecutive correct responses within the same rule block, indexing an attentional lapse after the rule was apparently already learned.

Per-block accuracy (x/5 for each of the 7 rule blocks) is also reported, letting you see exactly where in the sequence the rule shifts cost you the most.

Why “experimental”?

The task is clearly marked experimental for three specific reasons:

1. Novel item set. The specific stimuli (emoji-based items spanning colour and object-category dimensions), trial sequence, and rule-block ordering are original to this implementation — not a licensed or published WCST/Category Test card deck.
2. No normative data. No published reference sample has been run on this exact 35-item form, so no percentile or T-score can be reported without fabrication. Every figure is a raw, within-person count.
3. Fixed-order pilot form. This is a fixed-order 35-trial experimental form designed for pilot psychometric evaluation (item discrimination, internal consistency, convergent validity with WCST / Halstead Category Test), not a finalized clinical instrument.

The underlying constructs — concept formation, categorical reasoning, and set-shifting — are not experimental; they are among the most established targets in clinical neuropsychology. What is experimental is this particular item set and its unvalidated scoring thresholds.