The Gordon Diagnostic System (GDS)

The Standard in Computerized Assessment of Attention and Self Control

About The Gordon:

The Gordon is an assessment device that aids in the diagnosis of attention deficits, especially Attention-Deficit / Hyperactivity Disorder (AD/HD). It provides reliable, objective information about an individual’s ability to sustain attention and exert self-control. This practical, reliable, and well-researched device enhances the accuracy and relevance of a comprehensive evaluation for attention deficits and impulsiveness.

The GDS is a microprocessor-based, portable unit which administers a series of game-like tasks. The Vigilance Task yields data regarding an individual’s ability to focus and maintain attention over time and in the absence of feedback. A series of digits flash, one at a time, on an electronic display. The subject is told to press a button every time a “1” is followed by a “9”. The GDS records the number of correct responses, incorrect responses, and failures to respond to the “1/9” combination. A more complicated version of this paradigm designed for older children and adults (the Distractibility Test) flashes irrelevant digits on either side of the column that displays the target stimuli. For the testing of younger children the GDS contains a “1” mode which requires the child to press the button only upon appearance of a “1”.

The GDS also offers parallel forms of each task and a test of impulse control (the Delay Task) which requires a child to inhibit responding in order to earn points. Each task can be administered in less than 9 minutes. The internal microprocessor generates the tasks and records quantitative features of the child’s performance. This data can either be read from the GDS or transmitted to an external printer or computer. The GDS has been cleared as a medical device by the U.S. Public Health Service Food & Drug Administration, and boasts extensive standardization.

The GDS has a secure operator’s panel containing a numeric keypad for task and data selection, a LED data display, programming lights, and mode switches. A serial interface communications port is also provided.

GDS Auditory Module
Because of the interest in testing auditory attention, an auditory module has been developed to operate in conjunction with any GDS. This allows the GDS to “speak” the digits that appear on the front display. An Interference version has also been included, which introduces auditory distraction to the Vigilance Task. The auditory module uses the very latest in digital synthesis to produce remarkably clear and natural speech. Using a GDS with the auditory module, the following new tasks can be administered:

Auditory Vigilance Task – Identical to the standard (visual) Vigilance Task except that the subject responds to numbers that are heard instead of seen. To administer the task, the examiner covers the front display of the GDS (cover supplied) and the subject utilizes headphones (also supplied). All scores for the auditory version are gathered and calculated identically to the standard task.

Auditory Interference Task – Instead of saying the precise number that appears on the front display, this task generates a random number through the headphones. The subject performs on the standard Vigilance (or Distractibility) tasks while having to contend with the confusing auditory input.

Considered in the context of other clinical information, GDS data helps the practitioner evaluate the impulsive subject, generate treatment recommendations, and assess therapeutic outcome. It can be particularly useful in establishing levels of severity and in identifying the “well behaved” child with serious attention deficits. Objective data is also helpful when ratings from parents and teachers are clouded by disagreement or when the credibility of such reports is in doubt. GDS scores have also been found useful in the monitoring of pharmacotherapy.

Questions Often Asked About The GDS:

1. How has the GDS been standardized?

Normative data for the GDS tasks are based upon protocols of over 1,300 non-hyperactive boys and girls aged 4-16 years. The norms are arranged in Threshold Tables which demarcate Normal, Borderline, and Abnormal ranges of performance. The data is broken down by age groups (4-5, 6-7, 8-11, 12-16 years), but not by sex or socioeconomic status because these factors are not correlated with GDS scores. Published norms are also available for adults, college students, geriatric populations, and Puerto Rican children. Dr Gordon and independent research sites have explored the validity and reliability of the GDS with over 20 years of research. A representative selection of relevant journal articles can be provided on request.

2. Why should the GDS be used to evaluate children referred for symptoms of AD/HD / Hyperactivity?

Surveys have shown that practitioners frequently rely almost entirely upon subjective reports or their own clinical judgment when arriving at diagnostic decisions relating to this prevalent disorder. While information from parents and teachers should always be carefully considered, this is often influenced by a host of emotional and perceptual factors. The GDS provides the clinician with objective data based upon the child’s actual behavior and allows for observation in a paradigm likely to elicit inattention and impulsiveness. With adults, GDS data allows for standardized assessment of a critical area of functioning which is often overlooked in formal evaluations.

3. Who can administer and interpret the GDS?

The GDS is extremely easy to use and can be administered by any relevant professional. However, because observation of the child’s performance provides critical information, it is usually advisable for the clinician to test the subject personally. As with any psychological test data, GDS protocols should be interpreted only by qualified professionals.

4. If I purchase a GDS, will I be kept informed of current research findings?

Yes – with the purchase of the GDS, users receive a one-year subscription to the ADHD/Hyperactivity Newsletter, which reviews research projects being conducted internationally. The Newsletter also contains updates of standardization data and articles about developments in the field of AD/HD / Hyperactivity.

5. What is your opinion on software versions of vigilance tasks?

Dr Gordon’s group tried this approach, but were concerned about reliable administration and obtaining valid data.

There are a number of computer monitors in use that produce characters of various sizes, colors and intensities. Each computer also has its own keyboard which presents different stimuli to the child. Because these administrative parameters affected performance, Dr Gordon was convinced that offering a GDS on varying hardware would require separate sets of norms for each kind of computer. He felt strongly that test administrators should use equipment carefully calibrated to generate tasks reliably. Experience showed that AD/HD / Hyperactive children, though academic underachievers as a group, were quite deft at disassembling devices placed before them. It was also easy for them to shut off the computer, insert fingers in delicate disk drives, turn brightness knobs, and remove covers.

6. Does the GDS have applications beyond assessing AD/HD?

Although the GDS was developed for the evaluation of AD/HD / Hyperactive children, it can be used in other areas for the assessment of vigilance and behavioral inhibition. For example, neurologists and neuropsychologists use the GDS in the evaluation of Tourette’s Syndrome and to screen for inattention that may follow the administration of anticonvulsive medication. Other professionals have incorporated the GDS into the testing of adults with closed head injury, liver damage, or HIV infection.

GDS Instruction Manual and Interpretive Guide

The GDS is supplied with clearly-written documentation that fully addresses administration and interpretation of the test. The guide presents percentile and threshold tables, sample reports, and answers to common questions about interpretation.

Selected GDS References:

Aylward, G.P.. Verhulst, S.J., & Bell, S. (1990) Individual and combined effects of attention deficits and learning disabilities on computerized ADHD assessment. Journal of Psychoeducational Assessment, 8, 497-508.

Barkley. R.A., Grodzinsky, G. & DuPaul, G.J. (1992). Frontal lobe functions in Attention Deficit Disorder With and Without Hyperactivity: A Review and Research Report. Journal of Abnormal Child Psychology, 20(2), 163-188.

Bauermeister, J.J., Berrios, V, Jimenez, Al. I., Acevedo, L. & Gordon, M. (1990). Some issues and instruments for the assessment of Attention Deficit Hyperactivity Disorder in Puerto Rican Children. Journal of Clinical Child Psychology, 19, 9-16.

Brown, R.T. & Sexson, S.B. (1988). A controlled trial of methylphenidate in black adolescents: Attention, behavioral, and psychological effects. Clinical Pediatrics, 27, 74-81.

Fischer, M., Newby, R.F., & Gordon, M. (1995). Who are the false negatives on continuous performance tests? Journal of Clinical Child Psychology, 24(4), 427-433.

Gordon, M. (1987). How is a computerized attention test used in the diagnosis of Attention Deficit Disorder? In J. Loney (Ed ) The young hyperactive child: Answers to questions about diagnosis, prognosis, and treatment. New York: Haworth Press.

Michael Gordon, Ph.D.
Dr Gordon, a clinical psychologist, is Professor of Psychiatry at S.U.N.Y. Health Science Center in Syracuse, New York. He has extensive experience helping children, adolescents and adults who have problems adjusting to home, school and work. Widely published in academic journals, he is also well-known for his popular books and videos for individuals who have Attention-Deficit / Hyperactivity Disorder. Dr Gordon is director of an AD/HD clinic, and has developed educational texts for professionals in addition to test materials and treatment programmes that are used internationally.

GDS Features:

  • absolute reliability
  • solid psychometrics
  • an extensive scientific database
  • unlimited administrations
  • lightweight and portable
  • tamper-proof and nearly indestructible
  • a mainstay of empirical research and clinical practice
  • cost-effective

Pricing and Availability

The GDS and optional Auditory Module are now available from IPS in the UK. Each instrument is converted electrically for use outside the United States, for specific countries, and is guaranteed 12 months (RTB). Please contact IPS for further details:

17 High Street, Hurstpierpoint, West Sussex, England BN6 9TT

Tel. (44) 1273 832181 Fax (44) 1273 358886 e-mail:


The Gordon Diagnostic System III (GDS) including Delay, Vigilance, Distractibility Tasks, Instruction Manual, Interpretive Guide, package of 50 Record Forms and four issues of the ADHD / Hyperactivity Newsletter, one year warranty, converted for use outside USA, £1,175 (US$1,950) plus taxes and delivery applicable to your country. Units for use in North America can be quoted on request.

GDS Auditory Module, including connecting cable, display cover and headphones £185 (US$275) plus VAT at 17.5% (for purchasers in EU only).

GDS Record Forms, for tabulation and graphic display of GDS data (package of 50) £20 (no VAT)

GDS Interpretive Guide (3rd Edition), included with purchase of GDS £35 (no VAT)

Please note that prices quoted above are for overseas purchasers who are responsible for import duties and other taxes in their own country (if any).