We often hear the phrase, “neurons that fire together, wire together.” It’s the golden rule of Hebbian learning — a concept that has long explained how we form habits, memories, and skills. But a groundbreaking new study from Northwestern University has turned this classic understanding on its head, revealing that our over-reliance on positive reinforcement might be creating a “death spiral” that traps children in rigid, unproductive learning loops.

This research has profound implications for child development, education, and behavioral therapy. When we view these findings through the lens of Dr. Stanley Greenspan’s foundational work, we discover that the key to cognitive flexibility isn’t more training — it’s shifting who is doing the thinking. The answer lies in approaches like The Greenspan Floortime Approach®, which prioritizes internal processing and child-led discovery over externally reinforced compliance.

What Is the “Death Spiral” of Learning?

A study published in Communications Physics by Northwestern University researchers introduced a new theoretical framework for observing how activity spreads across brain networks. Their counterintuitive finding: while positive reinforcement strengthens existing neural connections, it can accidentally trap the brain in a loop — what the researchers call a “death spiral.”

The Record Player Groove: Efficiency vs. Adaptability

Think of a vinyl record player. If a record is scratched, the needle gets caught in the same groove, replaying the same three seconds of music over and over again. No matter how rich the rest of the symphony is, the needle cannot move forward on its own.

In our brains, a similar process occurs. When we consistently use positive reinforcement to reward a specific action, we carve a deep “groove” into neural pathways. Because that pathway is so smooth and efficient, the brain prefers to stay in it. The result: the brain becomes “stuck,” unable to adapt when the environment changes. This is the neurological foundation of rigid thinking in children — not a character flaw or a diagnostic inevitability, but a learned pattern shaped by how we teach.

If a learning environment focuses primarily on repetitive, reinforced success, it may be inadvertently training the brain to stay locked in single, predictable grooves. It becomes incredibly efficient at that one response, but utterly incapable of “skipping to the next track” when the situation changes.

The Hidden Trap: When Adults “Do the Thinking” for Children

This neuroscience insight aligns perfectly with a question Dr. Stanley Greenspan famously asked in his Greenspan Floortime® consultations: “Who’s doing the thinking?”

In many traditional behavioral interventions — including some ABA-based programs and behavior plans in school settings — the goal is often to elicit a specific, “correct” response through high-frequency, adult-led prompts. The adult decides what the target behavior is, and the child is reinforced for “getting it right.” From a neuroscientific perspective, this is the perfect recipe for a Hebbian “death spiral.”

By providing constant, directive feedback, the adult is doing all the cognitive heavy lifting — planning the sequence, predicting the output, and guiding the path. The child’s brain is never required to generate its own solution or navigate the “friction” of a novel, unpredictable situation. They aren’t learning to adapt; they’re learning to execute a pre-programmed script.

Over time, this trains the brain to stay within narrow, reinforced loops, producing the rigid thinking that many therapists and parents eventually find themselves trying to “fix.” Unfortunately, this learned rigidity is often misattributed to a child’s diagnosis — particularly in cases involving Pathological Demand Avoidance (PDA) — when it may actually be a product of the intervention approach itself.

Rigid Thinking in Child Development: Nature or Nurture?

Understanding the roots of rigid thinking in child development is critical for parents and professionals. When a child struggles to shift from one activity to another, insists on rigid routines, or melts down when expectations change, the reflexive explanation is often neurological or diagnostic. But the Northwestern research invites us to ask a harder question: Have our interventions inadvertently reinforced this rigidity?

Breaking the Cycle: How The Greenspan Floortime Approach® Builds Flexibility

If positive reinforcement loops create rigidity, how do we foster flexibility? The answer, as championed by The Greenspan Floortime Approach®, is to stop “teaching to the test” and start engaging in the process of discovery.

Unlike models that prioritize external reinforcement to shape specific behaviors, Greenspan Floortime® prioritizes internal processing. Here is how it directly counteracts the “death spiral” effect:

1. Following the Child’s Lead

In Greenspan Floortime®, we enter the child’s world. Instead of forcing a specific, “correct” response, we join their interests. This requires the child’s brain to generate its own ideas and responses, rather than relying on an adult’s prompt. This puts the child in the driver’s seat of the thinking process — the very opposite of the adult-directed loop that creates rigid thinking.

2. Embracing “Friction” and Novelty

The Northwestern study highlights that for a system to remain flexible, it must break out of its old paths. Greenspan Floortime® thrives on exactly this. By engaging in spontaneous, reciprocal “circles of communication,” the child must constantly read social cues and generate novel responses. This diversity of experience prevents the brain from falling into a “death spiral” because no two interactions are exactly the same — every exchange is a new problem to solve.

3. Prioritizing Process Over Product in Child Development

When we ask “Who is doing the thinking?”, we remind ourselves that the goal of child development is not about the child giving the right answer — it is about the child figuring out the answer, with our support. By valuing the child’s intent and their manageable struggle to solve a problem over finished, compliant behavior, we build the “hardware” for executive functioning in the prefrontal cortex.

We are strengthening the child’s ability to plan, sequence, and adapt — rather than just repeating a reinforced habit. This is the foundation of genuine cognitive flexibility and the antidote to rigid thinking in children.

What This Means for Parents and Therapists

The implications of this research extend beyond clinical therapy rooms. For parents navigating child development at home, for teachers structuring classroom environments, and for therapists designing intervention plans, the message is the same: efficiency isn’t always the goal of learning. Sometimes, efficiency is just another word for “stuck.”

Re-evaluating our reliance on narrow, adult-led positive reinforcement doesn’t mean abandoning structure or warmth. It means creating environments — at home, in the classroom, and in therapy — that value the process of discovery as much as the result of a behavior.

By embracing The Greenspan Floortime Approach®, we invite children to be the thinkers of their own lives. In doing so, we help build brains that are not just efficient, but truly adaptable, creative, and capable of navigating an ever-changing world. To learn more about how Greenspan Floortime® supports flexible thinking and healthy child development, explore the resources at stanleygreenspan.com.

Frequently Asked Questions

What is the “death spiral” of learning?

The “death spiral” of learning refers to a neurological pattern identified by Northwestern University researchers, in which over-reliance on positive reinforcement carves such deep, efficient neural pathways that the brain becomes trapped in repetitive loops. Rather than adapting to new situations, the brain keeps defaulting to the same reinforced response — leading to rigid thinking and reduced cognitive flexibility in children.

Is positive reinforcement bad for child development?

Not inherently. Positive reinforcement is a powerful tool, but problems arise when it is used as the primary driver of learning — especially in adult-directed, scripted formats. When children are constantly guided toward a predetermined “correct” response, they miss the opportunity to develop their own problem-solving and adaptive thinking. The Greenspan Floortime Approach® balances support with genuine child-led discovery to avoid this trap.

How does Greenspan Floortime® differ from ABA?

Greenspan Floortime® — also known as The Greenspan Floortime Approach®, Dr. Greenspan’s version of DIR/Floortime — differs from ABA primarily in who drives the interaction. ABA typically uses adult-directed prompts and positive reinforcement to shape specific behaviors. Greenspan Floortime®, by contrast, follows the child’s lead, uses spontaneous reciprocal play to build “circles of communication,” and prioritizes the child’s own thinking process over behavioral compliance. This is why Greenspan Floortime® is especially effective at addressing rigid thinking and building genuine flexibility in child development.

Can Greenspan Floortime® help children with rigid thinking?

Yes. The Greenspan Floortime Approach® was specifically designed to build the emotional and cognitive foundations — including flexible thinking — that underlie all learning. By engaging children in spontaneous, child-led interactions and gradually expanding their “circles of communication,” Greenspan Floortime® builds the prefrontal cortex capacity for planning, sequencing, and adapting that is often described as executive function. This directly addresses rigid thinking at its neurological root.

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Due to class action lawsuits that have been filed, there is tremendous interest, especially by parents, in the relationship of autism and Tylenol. We are not lawyers and have no opinion on lawsuits.

That noted, we are experts at treating autism and other developmental delays in children and adults. So, as an aid to parents and other autism therapy professionals, we have developed this guide to understanding the ongoing published peer-reviewed research on autism and Tylenol. We will continuously update this autism and Tylenol research guide as further studies are published.

What is Tylenol?

Tylenol is a brand name for the drug commonly known as acetaminophen in the United States and Canada and known as paracetamol in the rest of the world. Chemically, it is N-acetyl-p-aminophenol and is sometimes referred to in academic journals as APAP. The name Tylenol comes from its chemical name (aceTYL-p-aminophENOL).

Back in 1884 Germany, two physicians used acetanilide, a derivative of aniline, a compound that had been isolated from coal tar and used in the production of the novel synthetic dyes that were all the rage, to treat a patient with a raging fever and intestinal worms. Acetanilide did nothing for the worms but did reduce the fever. They began marketing acetanilide as Antifebrin (medical-speak for anti-fever).

They would soon learn acetanilide’s nasty methemoglobinemia side-effect when the skin color of users turned a blueish color because of its inhibition of oxygen transport by hemoglobin. This led to a search for a way to make acetanilide safer by modifying its molecular structure to remove this nasty side-effect.

In 1887, the German pharmaceutical company Bayer did just that, producing phenacetin. That same year a Johns Hopkins chemistry professor, Harmon Morse, synthesized acetaminophen, which accomplished the same thing, but physicians at the time wrongly reported that it could sometimes still produce that nasty methemoglobinemia side-effect. Consequently, acetaminophen was shelved until 1947 when it was discovered that both acetanilide and phenacetin actually convert to acetaminophen in the body and that acetaminophen is the active fever-reducing compound in both drugs.

About Autism and Floortime Therapy

When a parent or caregiver hears the words “Your child has autistic spectrum disorder” from a psychologist or physician, it can often sound to that parent or caregiver like a life sentence. They believe that their child will always be autistic. That autism diagnosis, however, is dynamic not static.

What does it mean that your child’s diagnosis is dynamic? It means that it can change. Dr. Stanley Greenspan says that an autism diagnosis is dynamic. Floortime therapy can help in the development of children with autism spectrum disorder diagnoses.

There were three key developments in Dr. Greenspan’s research on children with autism and other developmental issues. The first of these is the importance of affect and relationships for the growth of the brain and mind. The second is the recognition that there are significant variations in the underlying processing capacities of children. The third is the recognition of what the integrated early stages of development actually are. You can learn more about Floortime therapy at our introduction to Floortime.

Associating Tylenol with Safety for Children and Pregnant Moms

Whereas Floortime is an autism treatment for children after they are born, the autism and Tylenol connection happens before the child is born. Why is this? This connection happens because for many years, and unlike aspirin and ibuprofen, Tylenol, including generic forms of acetaminophen or paracetamol, was considered a safe pain killer and fever reducer during pregnancy. After all, around 20% of the adult American population uses products containing Tylenol each week.

Tylenol has been considered the safest over-the-counter option for pregnant mothers. For years, its use within the recommended dosage was not thought to be harmful to developing in utero children. That view has more recently begun to change. Nevertheless, Tylenol and its generic formulations are among the most commonly used medications during pregnancy across the planet.

Why does acetaminophen have such a strong association with safety compared to other analgesics? Recall that phenacetin, discussed in the ‘What Is Tylenol?’ section above, was used instead of acetaminophen during the first half of the twentieth century. Phenacetin was eventually found to be associated with developing kidney problems. Another alternative, aspirin, was associated with stomach irritation and with Reye’s syndrome, a rare but serious children’s disease.

In the Spring of 1955, McNeil Laboratories launched TYLENOL Elixir for Children with acetaminophen as the active ingredient. McNeil Laboratories marketed Tylenol to physicians as a prescription-only safer alternative to aspirin and phenacetin. Their marketing campaign was wildly successful. The global acetaminophen market is now worth about $9.5 billion. In America, it’s estimated that about 65% of pregnant women use acetaminophen. It is the most commonly used over-the-counter medicine used during pregnancy.

Autism and Tylenol Research

This widespread commonality of Tylenol usage across the globe shapes our understanding of research findings about autism and Tylenol. It means that because Tylenol (acetaminophen or paracetamol) is used so much during pregnancy, even a small effect size on autism from using Tylenol will have significant effects on autism rates globally.

Autism and Tylenol Research Study 1: Paracetamol use during pregnancy–a call for Precautionary Action

We will begin with the 2021 Consensus Statement “Paracetamol use during pregnancy–a call for precautionary action” published in the prestigious scientific journal Nature Reviews Endocrinology. Unlike the other papers, this is not primary or scholarly medical research. This is a set of recommendations by 91 medical experts based on scholarly medical research. It’s a good starting point for us because it helpfully summarizes the meaning and implications of recent research findings.

Their assertion is that even though the FDA has long considered Tylenol safe for use during pregnancy, increasing experimental and epidemiological research suggests that prenatal exposure to acetaminophen increases the risks of neurodevelopmental, reproductive and urogenital disorders in children. For our purposes, we will focus on the neurodevelopmental risks.

Observational studies in kids suggest an association between prenatal exposure to acetaminophen and increased risk of attention deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), language delay in girls, and decreased intelligence quotient (IQ). Experimental studies in animals have found that fetal exposure to acetaminophen induced brain changes that affected cognitive function, behavior, and even movement. These effects depend on the timing, duration, and dosage of prenatal acetaminophen exposure.

These medical experts recommend that pregnant women be given the following advice:

1. Forego using acetaminophen unless medically indicated.
2. Consult with their doctor if they are uncertain if using acetaminophen is indicated and before using on a long-term basis.
3. Minimize risk by using the lowest effective acetaminophen dose for the shortest possible time.

Autism and Tylenol Research Study 2: Association of cord plasma biomarkers of in utero acetaminophen exposure with risk of attention deficit/hyperactivity disorder and autism spectrum disorder in childhood

This important 2020 study that the National Institutes of Health (NIH) funded measured the amount of acetaminophen found in the umbilical cord blood of 996 births. These researchers wanted to find out whether the amount of acetaminophen found within that umbilical cord blood was associated with a diagnosis of ADHD or autism by the time these children reached 9 years of age. They classified the children by the amount of acetaminophen within their umbilical cord blood into three groups–lowest, middle, and highest.

Compared to the lowest third, kids in the middle third for acetaminophen concentration were at 2.26 times the risk for ADHD and 2.14 times the risk for autism. Kids in the highest third for acetaminophen concentration were at 2.86 times the risk for ADHD and 3.62 times the risk for autism compared to the lowest third of children.

In summary, fetal exposure to acetaminophen was associated with significantly increased risk of childhood ADHD and autism spectrum disorder. Their takeaway is that in utero exposure to acetaminophen is associated with increased risk of ADHD and autism in kids.

Their findings indicate that fetal exposure to acetaminophen is associated with a significantly increased risk of childhood autism in a “dose-response fashion.” This association of autism and Tylenol continued to hold during their sensitivity and subgroup analyses “across strata of potential confounders, including maternal indication, substance use, preterm birth, and child age and sex.”

This is a significant research paper and possibly the most powerful evidence about autism and Tylenol because its study design is quasi-experimental. A quasi-experimental study design is the next most powerful research design after an experimental or randomized controlled trial research design. Practically speaking for this topic, this is effectively the most powerful study design, because, for ethical reasons, scientists cannot conduct an experiment with pregnant mothers and randomly assign them different doses of acetaminophen. Instead, by using previously collected umbilical cord blood, researchers were able to compare naturally occurring acetaminophen dosage effects on ADHD and autism diagnoses without having to conduct such an experiment themselves. They could not control the acetaminophen doses ahead of time as they would in an experiment, but given an existing historical record of acetaminophen dosages, they could determine acetaminophen dosage effects on ADHD and autism diagnoses.

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