The processing speed index, a score devices can move

0 The short answer

The Processing Speed Index (PSI) is a composite built from a small set of timed, low difficulty tasks, usually two, and the version worth getting reports a normed index with a confidence interval, read as cognitive efficiency under simple visual demands and not as a measure of reasoning power. In the Wechsler scales the primary PSI comes from Coding and Symbol Search, and ACIS builds its PSI from the same two task families. A psychologist can give the WAIS-5 in a supervised session, and ACIS returns a PSI in the Optimized form (30 dollars, about 110 minutes), in the Full Scale form (50 dollars, about 175 minutes) or in the Custom Test when both subtests are bought at 5 dollars each (prices read October 29, 2026). The decisive limit is that speeded scores are among the most sensitive in a battery to the device, the response hand and the state of the test taker, so a low PSI beside strong reasoning describes performance on those tasks under those conditions and is not a diagnosis, a verdict on intelligence or a measure of decline.

1 What is the Processing Speed Index?

The Processing Speed Index is the composite score that summarizes how quickly and accurately a person completes simple, repetitive cognitive operations under a time limit, and it is a number about a small sample of tasks, not a general speed of thinking. Most batteries build it from a few subtests that present many easy items, impose a short clock and score the correct work completed. The page on processing speed as an ability covers the ability itself and the page on processing speed tests covers taking one, so this page stays on the index as a score: what it combines, how it is reported and how to read it.

The index sits in a longer tradition. In the Cattell-Horn-Carroll framework the broad ability is processing speed, written Gs, and the page on the CHC model lists it beside the other broad abilities. The Riverside Insights document for the Woodcock-Johnson V cognitive battery (read October 29, 2026) defines Cognitive Processing Speed (Gs) as the ability to quickly perform both simple and complex cognitive tasks, particularly when measured under pressure to sustain controlled attention and concentration, and calls it an aspect of cognitive efficiency. The ACIS technical manual, read on the same date, lists the PSI as the index for speed and accuracy of visual scanning and rapid simple decisions, and says the PSI should be interpreted as cognitive efficiency and not as reasoning power.

Two ideas hold the rest of this page together. The first is that a PSI is a composite of very few subtests. A composite built from two tasks inherits the quirks of both, which the section on what moves a speed score returns to. The second is that the word "speed" in the name does not mean the score measures how fast you solve hard problems. The tasks are easy on purpose, so that the rate of work, not the difficulty, produces the differences between people. The page on what IQ measures places the index among the other abilities and the page on cognitive domains explains how a domain relates to the Full Scale score.

The name also attracts neighbours that are not the same thing. A browser reaction time game reports a response time in milliseconds, and the page on the Human Benchmark IQ test reviews what each of those games tests. A symbol matching task under the name Digit Symbol Substitution Test is one of the two ingredients of a typical PSI, and the sibling page on the Digit Symbol Substitution Test covers its history and scoring. This page takes the next step: what happens when such tasks are combined into an index and reported with norms.

2 Which subtests build a Processing Speed Index?

In the current Wechsler adult scale the PSI is built from two subtests, Coding and Symbol Search, and other batteries and the ACIS battery use two timed tasks of the same family, while extra speed measures such as Cancellation and Naming Speed Quantity sit outside the primary index. The table sets out the composition in the sources read on October 29, 2026. Where a source does not say, the cell reads "not stated".

The WAIS-5 row rests on two Pearson documents. The Pearson WAIS-5 overview brochure lists Coding and Symbol Search as the Processing Speed subtests of the primary index scales, shows Naming Speed Quantity under processing speed in the full list of subtests, and names an Expanded Processing Speed Index and a Motor-Reduced Processing Speed Index among its additional scores. It describes the broader coverage as "Processing speed: verbal and visual." Pearson's WAIS-5 product page says Coding did not change, that the Symbol Search items and the font and spacing are different, and that Cancellation was removed in favor of a new, motor-free Processing Speed subtest, Naming Speed Quantity. It also lists the age range as 16:0 to 90:11 and says both Coding and Symbol Search are administered on paper with a response booklet and are not available digitally on Q-interactive.

The children's scale is built the same way. Pearson's Q-interactive technical report 12 (Raiford and colleagues, 2016) lists Coding and Symbol Search among the ten primary subtests of the WISC-V and treats Cancellation as a separate subtest that could not be adapted for the digital format and remains on paper. Pearson's WISC-V product page gives the age range as 6:0 to 16:11, lists five primary index scores including the Processing Speed Index, and lists a Naming Speed Index as a separate score. That page does not itself name the PSI subtests, so the composition above comes from the technical report.

Why do the batteries keep adding variations? The WAIS-5 additions point to the answer. Pearson's brochure says its Nonverbal, Nonmotor and Motor Reduced Processing Speed Index scores offer improved interpretive clarity and measures of ability not confounded by expressive language or motor problems, and its product page describes Naming Speed Quantity as a motor-free subtest designed to measure numerical processing fluency. The publisher is addressing the problem this page returns to in the section on what moves a speed score. The Riverside document shows a third design. Its Letter-Pattern Matching and Number-Pattern Matching tests ask the examinee to tap pairs of identical items, so the response is a tap and not a pencil stroke, and the narrow ability it names is perceptual speed (search) combined with reading and writing or quantitative knowledge. Different composition means different strengths and weaknesses, so a PSI from one battery is a neighbour of a PSI from another and not a copy of it.

3 What are the options for getting a Processing Speed Index?

You can get a PSI from a psychologist, from a battery that includes the two speed subtests or from a speed game, and only the first two report an index with a norm group, while a reaction time game reports a different quantity. ACIS is a seller in this market, so treat this section as a disclosure. ACIS prices and times were read on October 29, 2026 and can change.

The clinician route is the reference, because a trained examiner can watch the response, the grip and the effort, and can interpret a speed score inside a history. A person who needs a result for a school, a workplace accommodation or a clinical question needs that route. The page on where to take an IQ test lists every option, in person and online, and the page on the best online IQ tests compares the online batteries. A reader who wants a first look across several abilities, with the PSI as one of them, can start from the cognitive ability test page, and the page on the IQ test for adults explains what an adult score can and cannot be used for.

A reaction time game is a legitimate measure of a different thing. It reports how long a response took, including the delay of the screen, the browser and the input device, and it has no key to a norm group unless the page states one. The next sections explain why even a norm referenced PSI carries some of that device sensitivity.

4 What does the ACIS Processing Speed Index consist of?

The ACIS PSI is built from two subtests, Coding and Symbol Search, which sample different narrow speed abilities, and the index is reported only when both are complete. The Coding page describes a task in which the person works from a symbol and number key and matches as many symbols as possible, with the demand being visual scanning, rapid association, steady output and resistance to small errors under time pressure. The Symbol Search page describes a task in which the person scans small visual sets, compares symbols and makes a quick discrimination, so that search efficiency, visual comparison and decision speed become the main demands. In CHC terms both pages relate the task to processing speed (Gs), and the technical manual names the narrow abilities as perceptual speed (compare) for Coding and perceptual speed (search) for Symbol Search.

The instructions on the two pages show how the formats differ. In Coding the person has 120 seconds, uses on-screen buttons to select the number that matches each symbol, sees items in a continuous stream, and earns one point per correct match, with errors counted but not penalized. Three unscored practice items come first, and the test uses a new key after them. In Symbol Search two target symbols are shown, the person decides whether either appears in a search group, a symbol turned a different way is not a match, there can be at most one match, and the person clicks NO when there is none. There are 80 puzzles with a 2 minute limit, three unscored practice puzzles, and a penalty for wrong answers. Neither page discloses items, keys or scoring rules beyond these instructions, and this page adds none.

That difference in the scoring rule matters for interpretation. A penalty for wrong answers in Symbol Search means a cautious style costs speed and a careless style costs points, while Coding records errors without penalty. The manual says as much in other words: Symbol Search measures speed of search under an accuracy constraint, not raw speed. The pair therefore samples both the rate of work and the willingness to trade accuracy for pace, and the manual says that when Symbol Search and Coding agree, the PSI interpretation is stronger.

The report states a rule worth knowing before purchase. When a person completes subtests that do not complete any normed set, the dashboard says each has its own scaled score and percentile but does not change any index score, because an index is only reported for the exact set of subtests it was normed on. The PSI therefore needs both Coding and Symbol Search. Neither reasoning nor memory subtests can stand in for either of them, and a single speed subtest returns a scaled score and no index.

Which forms contain the PSI follows from that. The manual's availability table says the Quick form (15 dollars, about 45 minutes) has no PSI, Optimized (30 dollars, about 110 minutes) includes Coding and Symbol Search and reports the index, and Full Scale (50 dollars, about 175 minutes) includes both and reports it. The Custom Test, at 5 dollars per subtest, states that "any domain you complete returns its full index score, and every subtest returns its scaled score." Both PSI subtests at 5 dollars each is 10 dollars, our arithmetic on the posted price, and at that price a buyer who wants only this index pays less than for Optimized. The free trial needs no card, is limited to one per person, and when started from the Full Scale form opens five subtests including Coding and Symbol Search (read in the published site on October 29, 2026). Whether a trial dashboard shows a PSI is not stated on the pages read for this guide, so this page does not promise it. The technical manual holds the definitions, and this page quotes no statistics from it.

5 How is a Processing Speed Index reported, and how should the number be read?

A PSI is reported as an index with a mean of 100 and a standard deviation of 15, a percentile and a confidence interval, and it should be read as a range built from only two subtest scores, not as a single exact number. In ACIS each subtest first returns a scaled score from 1 to 19 (mean 10, standard deviation 3), and the two together produce the index on the familiar scale. The page on the standard deviation of 15 explains why that scale is used, the page on how IQ scores are normed explains what a norm group does, and the page on IQ score versus percentile explains why the index and the percentile cannot be averaged. A percentile is the share of the norm group that scored at or below the score.

Why does the interval matter more for a PSI than for a Full Scale score? A composite from many subtests averages out the quirks of each task, and a composite from two does not. The Standards for Educational and Psychological Testing (AERA, APA and NCME, 2014) say, in Standard 2.13, that the standard error of measurement should be provided in units of each reported score. The arithmetic of the standard error is simple. For an index with standard deviation 15, the standard error equals 15 times the square root of one minus the reliability coefficient. In a purely hypothetical case with a reliability of .90, that gives about 4.7 points, and a 95 percent interval of roughly 9 points either side of the observed score. Those numbers are our arithmetic on a made up coefficient and describe no real test. The point is the shape: an index whose plausible range is 18 points wide cannot separate two people whose scores differ by five.

Speeded tasks carry a second precision problem that the Standards name. The reliability chapter says that when a test is designed to reflect rate of work, internal consistency estimates of reliability, particularly by the odd-even method, are likely to yield inflated estimates for highly speeded tests. In plain terms, splitting a speed test into halves and correlating them overstates how repeatable the score is, because both halves share the same clock. Evidence for a speed score should therefore come from repeating the measurement, and a reader judging any PSI should ask what kind of reliability evidence its publisher reports. The page on reliability and validity explains the difference, and the technical manual documents the evidence for ACIS without this page quoting it.

The practical reading rules are short:

• Read the index with its interval and not as a point. A difference between a PSI and another index that is smaller than the combined uncertainty is not a finding.
• Read it against age peers. Speed is the part of a profile that shifts most over a lifetime, so a PSI compares you with people of your own age in the norm group.
• Read the two subtest scores. A PSI built from a high Symbol Search and a low Coding describes a different person than the reverse, even if the index is identical.
• Read it with the rest of the battery. The page on index score differences explains how common it is for two indices of the same person to differ by a wide margin.

6 Why are speed scores so sensitive to device, motor and fatigue factors?

A speed score times a response, so anything that changes the response, such as the input device, the hand, the screen or the hour, is built into the score in a way that it is not for a reasoning item. Five lines of evidence show it, and each has a design that limits what can be said.

The first is the device. Passell and colleagues, in Behavior Research Methods in 2021, compared performance on timed and untimed cognitive tests between users of common digital devices among 59,587 (Study 1) and 3,818 (Study 2) visitors to the web platform TestMyBrain.org. Controlling for age, gender, educational background and performance on an untimed vocabulary test, users of mobile devices, particularly Android smartphones, were significantly slower on reaction time tests than users of laptop and desktop computers, which the authors read as device latency affecting measured reaction times. Users of devices that differ in user interface, such as screen size or mouse against touchscreen, also differed significantly (p < 0.001) on tests requiring fast reactions or fine motor movements. The result is about web samples and reaction time and motor tests, not about the Wechsler subtests, but it shows that "same person, different device" is a real source of difference in speeded scores. The sibling page on the IQ test on a phone takes up the device question for the whole battery.

The second is the format of the speed task itself. When Pearson moved the WISC-V Coding and Symbol Search subtests from paper to a tablet, its technical report 12 says the digital formats involved substantive changes to the examinee and tablet interaction, including onscreen touch responses, scrolling stimuli and the elimination of writing, so new data had to be collected. The first pilot version, in which children used a stylus, did not correspond closely enough to the paper format to support equating: some correlations did not reach .7, and the correlation between the two formats of Coding for ages 6 to 7 was less than .4. The released digital format was redesigned and then met the publisher's equivalence standard of an effect size of 0.2 or smaller. The lesson is not about children or tablets. It is that the response mode of a speed task is part of the construct, and a publisher that changes it re-establishes the score instead of assuming it carries over. Standard 5.17 of the Standards is written for this situation: when scores on tests that cannot be equated are linked, direct evidence of score comparability should be provided, and its comment lists tests administered in different formats, such as paper-and-pencil and computer-based tests, among the examples.

The third is the hand. Kreiner and Ryan, in The Clinical Neuropsychologist in 2001, examined the motor skill and memory components of the WAIS-III Digit Symbol-Coding subtest in a clinical sample. A large proportion of the variance in the subtest was explained by Copy scores, which measure motor skill, with the incidental learning memory scores controlled, while the memory scores explained little additional variance when the copy scores were controlled. The same Pearson report adds that prior research with children with motor impairment found large mean differences on Coding, Symbol Search and the PSI relative to matched controls, with no significant differences on Similarities, Vocabulary or the Verbal Comprehension Index. Both findings describe groups and a pencil response. The WAIS-5 offers a Motor-Reduced Processing Speed Index, and the ACIS manual makes the matching caution that Coding is often sensitive to motor fluency and automaticity and is not a pure cognitive reasoning task. ACIS answers with on-screen buttons, which changes the motor demand without removing it.

The fourth is the state of the test taker. Lim and Dinges, in Psychological Bulletin in 2010, meta-analyzed 70 articles with 147 cognitive tests on short-term total sleep deprivation, defined as under 48 hours. Effect sizes ranged from small and nonsignificant for reasoning accuracy (g = -0.125) to large for lapses in simple attention (g = -0.776). The study is about total sleep loss in experiments, not about an ordinary short night, and its abstract gives no figure for processing speed alone. It supports the narrower point that impaired alertness does not cost every kind of task equally, and that simple attention is where it shows most. The page on sleep and IQ reviews what ordinary sleep loss does to test scores.

The fifth is practice. Estevis, Basso and Combs, in The Clinical Neuropsychologist in 2012, gave the WAIS-IV twice to 54 participants (mean age 20.9, initial Full Scale IQ mean 111.6) at an interval of 3 or 6 months. The Full Scale IQ, Verbal Comprehension, Working Memory, Perceptual Reasoning, Processing Speed and General Ability indices improved approximately 7, 5, 4, 5, 9 and 6 points, and the authors interpret the gains as practice effects and not as genuine intellectual change. The Processing Speed gain was the largest, in a small, young and above average sample. A person who takes a speed task twice in a short period should expect the second score to carry some familiarity.

None of these findings makes a PSI worthless. They say that the conditions of the session belong in the interpretation, and the section on practical conditions below turns them into steps.

7 What does a low PSI next to strong reasoning mean?

A low PSI beside strong reasoning scores means efficiency on simple timed tasks is lower than reasoning on harder tasks, which is a common profile shape, and it does not mean that reasoning is weaker than it looks or that anything is wrong. The ACIS manual states the reading directly: a low Coding score with strong FRI and VCI may indicate weaker speeded response execution rather than weak reasoning. It adds that processing speed is a legitimate part of a broad profile but should not dominate the interpretation of reasoning ability.

Several reasons make this profile unremarkable. The first is that the PSI is the loosest fit to the rest of the battery. In the Pearson technical report for the WISC-V digital format, the correlations between the Processing Speed subtests and all other primary subtests are low, and the PSI is less correlated with the Full Scale IQ than the other primary index scores (samples of children aged 6 to 16). The ACIS technical manual makes the same point in words, saying that the PSI should be interpreted as processing speed and cognitive efficiency and not as a direct proxy for general reasoning. The second is that the tasks work differently. A reasoning item can be hard for everyone, while a speed item is easy for everyone and differs only in rate, so a person who is careful, who checks, or who is slowed by the response device loses points that a reasoning task would not take away.

The ACIS pages list the causes that a speed subtest cannot separate on its own. For Coding the page lists motor speed, visual tracking, perfectionism, distraction and unfamiliarity with timed work, and for Symbol Search it lists slow scanning, a cautious style, visual discrimination difficulty and reduced tolerance for time pressure. Add the device, fatigue and practice effects from the previous section and a low PSI has many possible explanations. The manual's own guidance is to compare Coding with Symbol Search, to separate the transcription and output demand from the visual decision speed.

Wechsler batteries have a standard way of handling a speed score that is out of line with reasoning. The WAIS-5 brochure lists a General Ability Index and a Cognitive Proficiency Index among its summary scores, and the ACIS manual describes its General Ability Index as higher order reasoning and knowledge with reduced working memory and processing speed emphasis. The page on the General Ability Index explains when to use it, and the next sections explain the companion Cognitive Proficiency Index. An adult who is comparing a reasoning score with a speed score can read the pair as a profile and does not have to average them.

Is a low PSI evidence of ADHD, a learning difference or anything else? On this page the answer is no, and it is a sourced no. Frazier, Demaree and Youngstrom, in Neuropsychology in 2004, meta-analyzed intellectual and neuropsychological test performance in ADHD and report that overall cognitive ability (Full Scale IQ) was significantly lower among the groups with ADHD than among healthy participants, with a weighted d of .61. That is a difference between group means, and it says nothing about one person's PSI, so a PSI cannot screen for or diagnose ADHD or any other condition. The page on ADHD and IQ reviews the group evidence, and the page on the IQ test for adults with ADHD explains how an adult who already has a diagnosis can use a score. A person who is worried about attention or learning should talk to a qualified clinician, who can use history and a supervised battery.

Adults also ask whether an uneven profile counts for or against a high ability claim. The honest reading is that a strong reasoning index beside a lower PSI is common and says little about either. The page on gifted tests for adults explains what a profile can and cannot support, and the PSI is not the index to rely on for that question.

8 How does the Processing Speed Index change with age?

On average, speed of processing is lower at older ages, and research places the start of some age-related decline in the 20s and 30s, so a PSI is always read against age peers and the shape of that average says nothing certain about one person. The theory behind the construct comes from aging research. Salthouse, in Psychological Review in 1996, proposed that increased age in adulthood is associated with a decrease in the speed with which many processing operations can be executed, and that this reduction impairs other cognitive functioning through a limited time mechanism and a simultaneity mechanism. The evidence he assembled was considerable shared age-related variance across measures of speed and a large attenuation of age-related influences on cognitive measures after statistical control of speed. It is a theory of group averages and of fluid cognition.

How early does it start? Salthouse, in Neurobiology of Aging in 2009, reports that cross-sectional comparisons consistently show lower performance with increased age even in the range from 18 to 60, and concludes from three methods of estimating retest effects that some aspects of age-related cognitive decline begin in healthy educated adults when they are in their 20s and 30s. He also writes that longitudinal comparisons can mask declines because of large positive effects of prior test experience. That is the same practice effect as in the previous section, and it is one reason the two kinds of studies disagree. A cross-sectional average compares different people at different ages and so mixes aging with generational differences, which the page on how IQ changes with age explains in full.

For a test taker, the useful consequences are practical. An adult norm table for ages 16 to 90 compares a score with people of the same age, so a PSI that is average for a 55 year old reflects lower absolute speed than the same index at 25. The ACIS Symbol Search page says it directly: absolute speed falls across adulthood while rank order among age peers stays comparatively stable, which is why a speed result is interpretable only against an age reference. A reader past middle age will find the wider picture, including what holds and what slips, on the page about the IQ test for adults over 40.

This page makes no claim about decline in a person. A PSI taken once, online and unsupervised, is a single measurement under uncertain conditions, and a single measurement cannot show change. It is not a test of memory health, brain age or dementia, and a person who notices changes in thinking should speak to a clinician and not rely on any online score.

9 What can a Processing Speed Index be used for, and what can it not?

A PSI is useful for seeing one part of a cognitive profile against age peers and for spotting a gap between speed and reasoning, and it cannot stand in for a diagnosis, a measure of brain health or a number to compare across batteries. The uses that hold up are modest and concrete.

• Seeing the profile. A PSI placed beside the verbal, fluid, quantitative, visual spatial and working memory indices shows whether efficiency on simple timed work is in line with the rest of the battery. A gap between indices is common, and the table earlier in this page shows why a profile is easier to read when the same two tasks feed the index.
• Comparing two speed demands. The ACIS pairing of a symbol matching task and a visual search task lets a reader see whether the lower of the two is search or matching, which is the comparison the manual recommends.
• Understanding a reasoning score. If the Full Scale IQ is lower than a reasoning composite and the PSI is low, the speed index is part of the explanation, and the General Ability Index shows the same person without it.

The uses that do not hold up are just as concrete. A PSI is not a screening test for any condition, which is the point of the sourced sentence in the section on a low PSI beside strong reasoning. It is not a measure of memory health or of brain age, and the age section explains why one measurement cannot show change. It is not comparable across batteries without care, because the composition table shows that the Wechsler scales, the Woodcock-Johnson V and ACIS use different tasks, response modes and norm groups, and the Pearson technical report shows that even a change from paper to tablet within one battery needed its own evidence. It is not comparable across devices within one battery either, for the reasons in the Passell study. And it is not a result for a decision about a person's schooling, employment or eligibility, because those decisions need a supervised assessment and professional judgment.

The Standards for Educational and Psychological Testing (AERA, APA and NCME, 2014) put the same idea in testing language, in the form of a general principle that the section on where ACIS sits returns to: the evidence behind a score should match the use made of it. For a PSI, the evidence supports description of performance on specific timed tasks under the conditions of the session, and anything beyond that is inference. A reader who treats the number accordingly gets what it is good for: a precise, age referenced picture of one narrow ability, sitting among five others.

10 How does the Processing Speed Index relate to working memory, cognitive proficiency and the General Ability Index?

The PSI is one half of the cognitive proficiency pairing and the index that general ability composites set aside, so it is the score to compare with working memory and the one to leave out when the question is reasoning and knowledge. The ACIS manual describes its Cognitive Proficiency Index as one that combines working memory and processing speed as cognitive proficiency, and it describes its General Ability Index as the composite that emphasizes higher order reasoning and knowledge while reducing the influence of working memory and processing speed. The WAIS-5 brochure lists both of those composites among its summary index scores. The same logic runs in Wechsler batteries and in ACIS: three kinds of question, three kinds of composite.

If the question is broad cognitive standing, the answer is the Full Scale IQ. If it is reasoning and knowledge without the effect of speed or memory, the manual points to the General Ability Index. If the question is how efficiently a person handles simple, timed, held-in-mind work, the manual points to the cognitive proficiency composite. The pages on the Working Memory Index and on the Cognitive Proficiency Index cover the other ingredient and the composite, and the page on the General Ability Index explains the reverse view. Used together, they let an adult ask a sharper question than "is my speed low": is the efficiency pairing lower than the reasoning pairing, and is the gap in speed, in memory or in both?

The manual adds a caution that applies to this pairing. It says working memory and processing speed form a cognitive proficiency cluster but remain clearly distinct, which means a low PSI does not imply a low Working Memory Index, and the reverse. An adult who reads one as a stand-in for the other is making a claim the evidence does not support. The profile is informative only when each index is read with its own interval, which the earlier section on reading the number explained.

11 What practical conditions give an unsupervised PSI a fair chance?

An unsupervised speed task is fair only when the conditions that move speed are controlled by the test taker, so the same device, a steady surface, a rested hour and a single sitting matter more here than on any other index. The Standards for Educational and Psychological Testing (AERA, APA and NCME, 2014) cover the conditions in Standard 6.4, which says the testing environment should furnish reasonable comfort with minimal distractions to avoid construct-irrelevant variance, and whose comment names noise, disruption, poor lighting and malfunctioning computers. Standard 6.5 says test takers should be given appropriate instructions, practice and other support necessary to reduce construct-irrelevant variance, and its comment adds that instructions should cover the use of equipment likely to be unfamiliar and that practice opportunities should be given when equipment is involved.

Those standards translate into a short checklist:

• Use one device and one input method for the whole session. The device studies in the earlier section describe differences between devices, so a switch halfway through adds a source of difference.
• Choose a screen and a pointer you control well. The Coding and Symbol Search pages both state that no external aids are allowed, and the Coding page says it stays locked horizontally on mobile, asking the person to rotate the device to landscape.
• Do the practice items. Each of the two ACIS pages begins with three unscored practice items or puzzles before the clock starts, which is the practice the Standards describe for unfamiliar interfaces.
• Test when rested. The sleep evidence shows that alertness is not equal across tasks, and a speed task depends on sustained attention for its full duration.
• Expect a quiet room to help, though neither speed subtest needs sound. The three subtests that present items as audio are Digit Span, Alphanumeric Sequencing and Arithmetic, and none of them is a PSI subtest.
• Take the battery in the sessions you are given and do not repeat a speed task to chase a higher number. The retake evidence shows that familiarity raises the score.

Breaks are allowed between subtests and progress is saved, so a person who is tired after the reasoning subtests can take the speed subtests at another time with the same device. Nothing about those conditions makes an unsupervised score equal to a supervised one. They narrow the gap, and the next section states what remains.

12 Where ACIS sits, and what a buyer should do

ACIS offers a normed PSI from two subtests, Coding and Symbol Search, in an online and unsupervised setting, so it is a reasonable way to see a speed index beside the other five indices and it is not a clinical instrument or a substitute for a supervised assessment. The limits are plain. The test is taken online without an examiner. It is not a clinical or diagnostic instrument, so its PSI cannot screen for ADHD, a learning difference, a motor condition or cognitive decline. It is not for hiring, school accommodations or admission to high IQ societies. It is in English only. The same limits apply to every online speed index, and the device and motor effects described above apply to it as they do to any speeded task that is answered with a pointer.

The Standards for Educational and Psychological Testing (AERA, APA and NCME, 2014) give the frame for using the score. They say standard errors of measurement should be reported in units of each reported score (Standard 2.13), that evidence for speeded tests needs more than a split-half estimate, that scores moved to a new format need direct evidence of comparability (Standard 5.17), and that administration conditions should be controlled (Standard 6.4). A person who holds ACIS to those questions should also hold any other provider to them. The APA is a co-publisher of the Standards, and the rule that follows for a reader is the one they set for professionals: a score is an estimate, and its use should match the evidence behind it. The technical manual is the place to check how ACIS answers them.

What should a buyer do? Decide first what the PSI is for. If the purpose is curiosity about a profile, the Optimized form gives the PSI with 13 subtests across five domains for 30 dollars, and the Full Scale form gives all six indices for 50 dollars. If the purpose is only the speed index, the Custom Test with Coding and Symbol Search costs 10 dollars, our arithmetic on the posted price. If the purpose needs a supervised result, such as a school or workplace decision, a clinical question or a diagnosis, book a psychologist. The free trial needs no card and one is allowed per person. When started from the Full Scale form it opens five subtests, including Coding and Symbol Search, and finished trial subtests are kept if the person later unlocks a form that includes them. The guarantee reads: "Full refund within 5 days if the report does not deliver the features described at checkout or a technical issue prevents you from accessing your results." Prices were read on October 29, 2026 and can change.

13 Sources Behind This Page

Every figure above is traceable to one of the following, and each is linked at the point where it is used. Web pages and PDFs were read on October 29, 2026. The 4.7 point standard error, the 10 dollar Custom Test total and the interval width are our arithmetic and are labeled as such in the text. The APA Ethics Code could not be opened and is not cited.

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14 Frequently Asked Questions