Letter Cancellation Task

Background

The Letter Cancellation Task (LCT) is a widely used neuropsychological assessment tool of selective attention and scanning speed. George Talland is credited with the first formal description and implementation of the LCT in 1965. His original work used the task as a general psychological probe to study how people search for visual targets amidst distractors.

The d2 Test of Attention, developed by Rolf Brickenkamp, is a highly popular commercialized paper and pencil variant of the LCT. The simple letters 'd' and 'p' function as perceptually similar yet different base stimuli. The goal of the task is to find as many d-stimuli with 2 vertical marks (positioned above or/and below the letter) as possible. These target stimuli are hidden within 14 rows of distractor letters on each page consisting of d-letters with 1,3 or 4 marks and p-letters with any number of marks.

Millisecond's LCT procedure is inspired by the 'UCancellation Letters Task' published by Anja Pahor and colleagues in 2022 as a simple, modern, computerized alternative to the d2 Test of Attention and its variants using similar target and distractor stimuli. Instead of presenting participants with many rows as is done with pencil and paper variant, the computerized version presents one row of 8 items at a time. Each row contains about 3-5 targets and needs to be worked on from left to right. Millisecond's procedure is optimized and primarily intended for use on touch-screen devices (tablets), but can also be completed using the mouse on regular Windows / Mac desktop or laptop computers.

Task Procedure

Rows of 8 letters are presented on-screen. Letters are either targets ("d"s with two marks) or distractors ("d"s with fewer or more than two marks, "p"s with any number of marks). Participants are instructed to select the targets in each row from left to right and to ignore the distractors. An animated demonstration illustrates the task. This is followed by a guided practice phase consisting of 3 rows. Detailed feedback is provided during this practice phase. The practice phase is repeated if participants make errors in more than one of the 3 practice rows.

During the test phase, the number of target letters in each row varies between 3 and 5, with exactly 40 targets in each set of 10 rows. Each row is presented on-screen for a maximum of 6 seconds, after which the next row is presented after a 1-second blank period. Participants may advance to the next row early via a Next button (green arrow) at the right side of the screen. The goal is to complete as many rows as possible within a set time limit of 3.5 minutes, as indicated by a countdown timer displayed in the upper left corner of the screen. At the conclusion of the test phase, feedback on the number of "perfect" rows completed is provided.

What it Measures

The LCT is a measure of selective attention and scanning speed.

Psychological domains

• Selective Attention: Ability to focus on target-relevant features
• Sustained Attention: Ability to keep focused attention over a duration of time
• Inhibitory Control / Response Inhibition: Ability to ignore distractors and not select them
• Visual Scanning: The efficiency of the eyes moving across a line of text.

Main Performance Metrics

• Total Items Processed: The total number of items the participant was exposed to as a measure of "Processing Speed"
• Total Performance: The total number of correct items processed
• Concentration Performance: The difference in number of hits and commission errors as a measure of "Pure Concentration"

Psychiatric Conditions

Performance tends to be impaired in patients with the following conditions.

• Attention Deficit Hyperactivity Disorder (ADHD)
• Traumatic Brain Injury (TBI)
• Dementia
• Schizophrenia
• Depressive Disorders
• Sleep Deprivation