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Dr. Kevin McGrew

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The Brain Clock: The brain clock as a “jack-of-all-trades” brain mechanism that can be fine-tuned to improve human performance

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The Brain Clock:  The brain clock as a “jack-of-all-trades” brain mechanism that can be fine-tuned to improve human performance

In my inaugural IM-Home blog post (Brain Clock: My journey to understand the science of mental timing interventions), I concluded with the following statement:

I am now convinced that the IM-effect is impacting a fundamental and critical cognitive mechanism (or set of mechanisms) involved in a wide array of human cognitive and motor performance domains.”

Cognitive and intelligence researchers have long sought for (and argued about) the “holy grail”of intelligence—an underlying core essence or mechanism that plays a role in most all intellectual and human performance situations.  It is typically referred to as g, or general intelligence.   The general consensus touches on the concept of neural efficiency.  Such a general mechanism or process is considered a domain-general cognitive mechanism as it works across multiple domains of human ability, or in other words...if you improve this one area of ability, it in turn improves several areas of ability in the same person like cognitive skills (focus, attention, memory), speech/language abilities (articulation, auditory processing, reading), and motor skills (coordination, gait, balance).   It works across multiple domains of human ability.  Some have referred to such general mechanisms as a “jack-of-all-trade” cognitive mechanism. 

This contrasts with domain-specific cognitive mechanisms, which are compartmentalized (modular) brain-based components.  For example, we all have learned to drive a car.  We have all automatized the act of driving so we can drive with little in the way of deliberate cognitive thinking—the resources of our immediate mind are freed up to listen to the radio, think about work, mull over our plans for the day, etc.  If you practiced your driving one hour a day for four weeks straight, you may improve your driving behavior.  However, you would not expect this practice to transfer to improvement in other domains of your life such as speaking, reading, or golf.  This is an example of a circumscribed set of behaviors that have been learned and that are under the control of a set of narrow domain-specific cognitive mechanisms and brain networks.  Domain-specific mechanisms are important for automatic efficient human performance but, in general, improvement via training or exercise is typically restricted to within the specific set of skills and behaviors.

In contrast, a domain-general mechanism is one that if changed, may result in changes in performance across diverse areas of human functioning.  Improving a domain-general cognitive mechanism via intervention or environmental manipulation should result in improvements across multiple domains.  You get more “bang for your buck”if you can improve multiple areas of human functioning via one general treatment, in contrast to many different treatments for multiple skill domains.  The search for such a magical lever has been pursued for decades by researchers in psychology and learning.  Thus, when I first learned that both empirical research and clinical experience demonstrated that IM could improve (a) motor functioning of individuals strokes or cerebral palsy, (b) speech and language disorders, (c) sports performance [golf and tennis], (d) ADHD behavior, and (e) reading, to name but a few, I concluded that the only viable hypothesis is that IM was impacting a fundamental domain-general brain-based cognitive mechanism (click herefor Brain Clock blog posts and articles related to domain-general mechanisms and research).

Evidence for a domain-general brain clock comes from numerous sources.  Researchers across various disciplines and labs, using different methods and focusing on different aspects of human timing, have consistently demonstrated that humans do have some form of brain clock (or system of clocks) that play a pivotal role in a wide array of human cognitive and motor behaviors.  For those who want to learn more about the foundational research check out the Mental Timing Scholars and Research Labs and the Key Articles in the blog roll sidebar at the Brain Clock blog.  I will be extracting information from these sources in future blog posts.

Another source of research that validates the concept of a domain-general brain clock, and one that I find particularly fascinating, is thatdisorders of the brain clock may be central to a diverse set of clinical disorders (click here for links to more disorder-specific information).  Amy Vega and I summarized a portion of this research in a special white paper (The efficacy of rhythm-based [mental timing] treatments with subjects with a variety of clinical disorders:  A brief review of theoretical, diagnostic, and treatment research).  After a review of four different types of rhythm-based timing treatments, of which IM was just one, we concluded that:

we believe that collectively the preponderance of positive outcomes (across the 23 listed studies) indicates that rhythm-based mental-timing treatments have merit for clinical use and warrant increased clinical use and research attentionpositive treatment outcomes were reported for all four forms of rhythm-based treatment.  Positive outcomes were also observed for normal subjects and, more importantly, across a variety of clinical disorders (e.g., aphasia, apraxia, coordination/movement disorders, TBI, CP, Parkinson's disease, stroke/CVA, Down's syndrome, ADHD)...One notable observation of interest is that 15 of the 23 studies (the RAS, AOS-RRT and SMT treatment studies) all employed some form of auditory-based metronome to pace or cue the subjects targeted rhythmic behavior.  In all other studies, rhythm-pacing used some form of manual tapping or beat sound (e.g., drum).  We conclude that the use of external metronome-based rhythm tools (tapping to a beat, metronome-based rhythmic pacing, rhythmic-cuing via timed pulses/beats) is a central tool to improving temporal processing and mental-timing.”

The convergence of research by mental timing scholars studying normal cognitive processes, when supplemented with research that has implicated the integrity/efficiency of the human brain clock in many clinical disorders, is consistent with the notion of a domain-general master internal brain clock.  As a researcher with an interest in applying theories of intelligence, cognition and information processing to benefit individuals at-risk for, or already diagnosed with, various cognitive or motor disorders, this discovery was exciting. 

The finding that IM-specific, other timing- or rhythm-based treatments, as well as lab experiments that have successfully changed the speed of the human brain clock (slowing it down or speeding it up), suggests that it is possible to “fine tune”the human brain clock and improve the quality of life of individuals.  This is one of the major reasons why I continue my journey to understand the human brain clock.  This is the main reason why I now blog for IM-Homeand continue my separate Brain Clock blog.  This is important and “timely”information.


Kevin McGrew, PhD.

Director of Science and Research, Interactive Metronome

Director of the Institute for Applied Psychometrics (IAP)




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Dr. Kevin McGrew is the Director of the Institute for Applied Psychometrics (IAP). He received a masters degree in school psychology at Moorhead State University and his doctoral degree in Educational Psychology at the University of Minnesota. He was a practicing school psychologist for 12 years. He spent 10 years as a Professor of Applied Psychology at St. Cloud State University. He is currently a Visiting Professor in Educational Psychology at the University of Minnesota. He serves as the Research and Science Director for Interactive Metronome.

Dr. McGrew conducts research in the areas of theories of human intelligence, intelligence testing, school learning, and the application of neurotechnology to cognitive performance and learning. He has published over 60 different journal articles, books or book chapters in his areas of expertise. He is a coauthor of the Woodcock-Johnson Battery III. Detailed information can be found at his the IAP web page. McGrew disseminates information regarding human intelligence and the human brain clock at two professional blogs (IQs Corner; Brain Clock Blog).


  • Erlene
    Erlene Friday, 08 April 2016

    Performance is the best one. It needs lots of focus tho.
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