Across four preregistered experiments, we had 1.5- to 8-year-olds play a card-matching game on a tablet or video screen (see Figure 1). The game consisted of three face-down cards that “fly” in. There were two cards on the bottom and one on the top. Each of the two bottom cards flipped over to reveal an image. Then, they flipped face down. Finally, the top card flipped over to reveal a match with one of the two bottom cards. It is there that we looked to see whether children looked at (1.5- to 2.5-year-olds) or tapped (3- to 8-year-olds) the correct matching card. There are four trials of this card-matching game where the images on the cards are all unique, and four trials where the images on the cards are repeated from trial to trial. In this repeated condition, the first trial may have an orange on the left card and a banana on the right card. The second trial may then have the orange on the right and the banana on the left. If toddlers and young children are affected by proactive interference, then on later trials, they may have more trouble picking out which side the matching card was on in the repeated condition compared to the version where they see all new cards in each trial.

Figure 1. The sequence of events in a test trial for the card-matching game.

So how do children do? Our first study² using this card-matching game across three preregistered experiments (N = 245, 111 boys) found that 2.5- to 8-year-old children will, like you, walk to yesterday’s parking spot instead of today’s. Our fourth preregistered experiment^3, tested 1.5- to 2.5-year-olds (N = 34) and found that toddlers also make more memory mistakes when old information (“the orange was on the left last time…”) can interfere with new information (“was the orange on the left or the right this time?”). This may not sound too surprising, as we all know that children make much bigger (and funnier, at times) memory mistakes than getting mixed up in a card-matching game. We indeed expected that children, especially young toddlers, would be more susceptible to something like proactive interference than older children or adults. What’s important about quantifying this is that most measures of memory performance in children and toddlers don’t take proactive interference into account, and thus may be reporting children’s memory as worse than it really is.

Plenty of laboratory and clinical tasks measuring memory performance in toddlers and children involve repeated trials where children have to remember the same or similar information over and over again^4,5,6. Although this is an intuitive way to get an average memory “score”, if children’s memory is disproportionately affected by proactive interference, then their performance will tend to decline across trials and thus lead to an underestimation of their actual memory abilities. For example, in our card-matching game, children must remember (1) the image on the bottom-left card, (2) the image on the bottom-right card, and after they see the top card and need to choose the match, they need to remember (3) where (right or left) the matching card was. Previous work has shown that by 9 months of age, infants can keep track of “what” went “where” for two objects at a time⁷. Yet when we induce proactive interference in our experiment, 1.5- to 2.5-year-olds’ performance drops to chance level at this “what” went “where” task by the 4th trial.

It comes as no surprise that toddlers’ working memory would be sensitive to interference effects. Our research has the following takeaway: through critically assessing old assumptions, we can come to new conclusions that impact how future research is conducted. This is the beauty of scientific progress, and it wouldn’t be possible without the R15 grant from the National Institutes of Health (NIH) we received to help pay for equipment and reimbursing the hundreds of families who volunteered their time to participate in our research. Federal grants not only provide financial stability to research projects, but they also buy time. An awarded NIH grant allows researchers to spend time training and mentoring the future generation of scientists. For example, the current project is co-led by an undergraduate research assistant, Zane Mourad, who is not only a co-author on this blog post, but they are also being fully immersed in research thanks to the time that grants allow faculty and graduate students to train mentees. Therefore, only through this kind of major funding could we tackle our next questions: are some kids more susceptible to proactive interference than others? If so, do cognitive assessments appropriately take this into account? We hope to continue our research into children’s memory and forgetting.

1. Hamilton, M., Ross, A., Blaser, E., & Kaldy, Z. (2022). Proactive interference and the development of working memory. Wiley Interdisciplinary Reviews – Cognitive Science, 13(3), e1593.
2. Hamilton, M., Roper, T., Blaser, E., & Kaldy, Z. (2024). Can’t get it out of my head: Proactive interference in the visual working memory of 3- to 8-year-old children. Developmental Psychology, 60(3), 582–594.
3. Koolhaas, C., Hamilton, M., Roper, T., Blaser, E., Kaldy, Z. Proactive interference disrupts 2-year-olds’ working memory. Poster presentation at the Biennial Meeting of the Society for Research in Child Development, May 1 – May 3, 2025, Minneapolis, MN.
4. Fitzpatrick, C., & Pagani, L. S. (2012). Toddler working memory skills predict kindergarten school readiness. Intelligence, 40(2), 205-212.
5. Morra, S., Gandolfi, E., Panesi, S., & Prandelli, L. (2021). A working memory span task for toddlers. Infant Behavior and Development, 63, 101550.
6. Willoughby, M. T., Blair, C. B., Wirth, R. J., & Greenberg, M. (2010). The measurement of executive function at age 3 years: psychometric properties and criterion validity of a new battery of tasks. Psychological Assessment, 22(2), 306.
7. Kaldy, Z., & Leslie, A. M. (2003). Identification of objects in 9‐month‐old infants: integrating ‘and ‘information. Developmental Science, 6(3), 360-373.

About the Author

The big picture

Thanks to modern neonatal care, more preterm babies are surviving than ever before. Yet more than thirteen million babies worldwide are still born early each year, and many spend their first days or weeks in neonatal intensive-care units (NICUs) ([1]; [2]). Being born early can place children at higher risk for long-term challenges with movement, attention, and behavior ([3]; [4]; [5]).

Alongside medicines when they are needed (e.g., [6]), researchers have been testing gentle, non-drug approaches that can soothe and support development – like carefully structured sounds (white noise, heartbeat recordings, and other environmental sounds) that help stabilize sleep and reduce stress ([10]; [11]). Music – whether passively listened to or used in a therapeutic way ([12]-[15]) – has also been linked to better physiological regulation and emotional well-being in infants, with longer-term benefits for mental health and social inclusion ([16]; [17]).

Because premature infants are extra sensitive to noise, sound in the NICU has to be handled with care: average levels outside the incubator should stay around 45–50 dB, with brief peaks below 65 dB ([18]; [19]). And none of this replaces the power of everyday bonding. Early, sensitive parent–infant interactions set the stage for healthy brain development – but those interactions can be harder to achieve after a stressful or traumatic birth ([20]; [21]). With that context in mind, our team asked a simple question with big stakes: Do a caregiver’s relationship to the baby (kinship) and the pitch of their voice (which tends to be lower in men and higher in women) change how a preterm infant’s brain responds to singing? To find out, we created a precision-music medicine protocol designed specifically for fragile newborns [22].

What we did

We ran a small, carefully controlled study in the NICU. 30 very-preterm infants (born at or before 32 weeks gestation) took part. In the experimental group (15 infants), over four consecutive days, each baby experienced the same short, 11.5-minute “listening session”, but the singer changed from day to day: father, mother, a male music therapist, and a female music therapist – in randomized order. That let us tease apart two things at once: kinship (parent vs. non-parent) and voice type (typically lower-pitched male voices vs. higher-pitched female voices). Each session included quiet periods for comparison and two kinds of sounds: a single musical note and a lullaby. While the babies listened, we recorded their brain activity using an infant-friendly electroencephalography (EEG) set up. We focused on the “delta” brainwaves range – slow brain waves linked to cortical maturation in premature infants – because it is a useful window into how the brain is organizing itself at this stage.

What we found

In our preliminary report published in Plos One journal [22], showed that mothers’ singing tended to evoke strong slow-wave responses under most conditions. But during the lullaby – a richer, more complex sound – father’ singing produced the strongest average response, followed by the male music therapist, then the mother, and then the female music therapist.

When we analyzed the full cohort of all 15 infants in the experimental group, the overall pattern held. The lullaby prompted especially robust slow-wave activity, and paternal singing again came out on top. To zero in on whether this had more to do with voice type than the specific people, we grouped male voices (father + male therapist) and female voices (mother + female therapist). Male voices elicited significantly higher slow-wave (delta) activity during the lullaby condition even in this case. In everyday terms: a lower-pitched lullaby seemed to sync more strongly with these babies’ developing brain rhythms.

Of course, this is a small study, so we should be cautious. But the results suggest that both the complexity of the sound (like a full lullaby) and the voice’s pitch can shape how a very-preterm infant’s brain responds.

Why this matters for families

These findings push back on the idea that only a mother’s voice “counts” in early interventions. Certainly, mothers remain essential – their voices reliably supported strong brain responses under simpler sound conditions, but fathers’ singing – especially a real lullaby – may offer a unique boost.

What could this look like in practice? We need to start inviting fathers in NICUs more often and more systematically, where bonding can be interrupted by medical needs. In these terms, structured paternal singing may help spark healthy brain rhythms and strengthen father–infant bonding and later attachment right from the start. Furthermore, when a mother cannot sing on a given day – because of medical recovery, logistics, or simply exhaustion – a father’s lullaby can serve as a powerful stand-in, helping maintain consistent, meaningful sensory input for the baby. For mothers who are singing most often, it can also help to experiment with a slightly lower pitch range or a slower tempo to see whether it better matches the baby’s calm, slow rhythms, especially during lullabies. Remember: sound levels in the NICU must stay gentle and safe, and nothing replaces nurturing contact and responsive caregiving. Singing is one supportive tool among many.

Why public funding also matters

This work was possible because of hospital/state support – the kind of public investment that lets teams build safe, family-centered protocols and bring advanced tools to the bedside. Findings like ours, therefore, do not just refine how we think about early bonding. They point to practical changes that national and international health policies can encourage, such as expanding paternal leave and making room for father-infant co-regulation in the earliest days.

We should also mention that studies like this are careful and resource intensive. We used infant-grade EEG, a data-cleaning process tailored to fragile signals, and a study design where each baby experienced every experimental condition so we could spot real differences with a small group. That approach is efficient – it squeezes more clarity out of fewer participants – but it only works when public funding supports skilled clinician-scientist teams, specialized equipment, and the time needed to do the work right (ideally including follow-up as children grow).

Without that broader public infrastructure, questions at the intersection of sound, relationships, and early brain development would remain unanswered, and precision, family-centered care underpowered. Therefore, our research and findings, we believe, make a strong case for continued public stewardship: even modest investments in precision, family-focused neonatal care can generate knowledge and insights that improve care now and reduce costs later – by lowering the burden of neurodevelopmental difficulties across childhood. In short, public investment pays off twice – first by protecting fragile beginnings and again by strengthening the society those children will help build.

References

[1] Bradley, E., Blencowe, H., Moller, A. B., et al. (2025). Born too soon: Global epidemiology of preterm birth and drivers for change. Reproductive Health, 22(Suppl. 2), 105. https://doi.org/10.1186/s12978-025-02033-x

[2] Cheong, J. L., Spittle, A. J., Burnett, A. C., Anderson, P. J., & Doyle, L. W. (2020). Have outcomes following extremely preterm birth improved over time? Seminars in Fetal & Neonatal Medicine, 25(3), 101114. https://doi.org/10.1016/j.siny.2020.101114

[3] Camerota, M., & Lester, B. M. (2025). Neurobehavioral outcomes of preterm infants: Toward a holistic approach. Pediatric Research, 97(5), 1475–1480. https://doi.org/10.1038/s41390-024-03505-9

[4] Song, I. G. (2023). Neurodevelopmental outcomes of preterm infants. Clinical and Experimental Pediatrics, 66(7), 281–287. https://doi.org/10.3345/cep.2022.00822

[5] Twilhaar, E. S., Wade, R. M., de Kieviet, J. F., van Goudoever, J. B., van Elburg, R. M., & Oosterlaan, J. (2018). Cognitive outcomes of children born extremely or very preterm since the 1990s and associated risk factors: A meta‐analysis and meta‐regression. JAMA Pediatrics, 172(4), 361–367. https://doi.org/10.1001/jamapediatrics.2017.5323

[6] Juul, S. E., Comstock, B. A., Wadhawan, R., Mayock, D. E., Courtney, S. E., Robinson, T., … Heagerty, P. J. (2020). A randomized trial of erythropoietin for neuroprotection in preterm infants. New England Journal of Medicine, 382(3), 233–243.

[7] Rohmah, I., Mukminin, M. A., Hasan, F., Romadlon, D. S., Chang, K. M., Chen, K. H., & Chiu, H. Y. (2025). Comparative effects of nonpharmacological interventions on sleep-wake states among preterm infants in neonatal intensive care units: A systematic review and network meta-analysis. Intensive and Critical Care Nursing, 91, 104168. https://doi.org/10.1016/j.iccn.2025.104168

[8] Shen, Q., Huang, Z., Leng, H., Luo, X., & Zheng, X. (2022). Efficacy and safety of non-pharmacological interventions for neonatal pain: An overview of systematic reviews. BMJ Open, 12(9), e062296. https://doi.org/10.1136/bmjopen-2022-062296

[9] Sofologi, M., Pliogou, V., Bonti, E., Efstratopoulou, M., Kougioumtzis, G. A., Papatzikis, E., … & Papantoniou, G. (2022). An investigation of working memory profile and fluid intelligence in children with neurodevelopmental difficulties. Frontiers in psychology, 12, 773732. https://doi.org/10.3389/fpsyg.2021.773732

[10] Zhang, Q., Huo, Q., Chen, P., Yao, W., & Ni, Z. (2024). Effects of white noise on preterm infants in the neonatal intensive care unit: A meta-analysis of randomised controlled trials. Nursing Open, 11(1), e2094. https://doi.org/10.1002/nop2.2094

[11] Zhang, S., & He, C. (2023). Effect of the sound of the mother’s heartbeat combined with white noise on heart rate, weight, and sleep in premature infants: A retrospective comparative cohort study. Annals of Palliative Medicine, 12(1), 11120–11120.

[12] Jaschke, A. C., Papatzikis, E., & Haslbeck, F. B. (2025). Medical Neurohumanities: Sharing Insights from Medicine, Neuroscience, and Music in Paediatric Care. Frontiers in Neuroscience, 19, 1648030. https://doi.org/10.3389/fnins.2025.1648030

[13] Papatzikis, E., Agapaki, M., Selvan, R. N., Hanson-Abromeit, D., Gold, C., Epstein, S., … Pandey, V. (2024). Music medicine and music therapy in neonatal care: A scoping review of passive music listening research applications and findings on infant development and medical practice. BMC Pediatrics, 24(1), 829.

[14] Yakobson, D., Gold, C., Beck, B. D., Elefant, C., Bauer-Rusek, S., & Arnon, S. (2021). Effects of live music therapy on autonomic stability in preterm infants: A cluster-randomized controlled trial. Children, 8(11), 1077. https://doi.org/10.3390/children8111077

[15] Haslbeck, F. B., Jakab, A., Held, U., Bassler, D., Bucher, H. U., & Hagmann, C. (2020). Creative music therapy to promote brain function and brain structure in preterm infants: A randomized controlled pilot study. NeuroImage: Clinical, 25, 102171. https://doi.org/10.1016/j.nicl.2020.102171

[16] Agapaki, M., Pinkerton, E. A., & Papatzikis, E. (2022). Music and neuroscience research for mental health, cognition, and development: Ways forward. Frontiers in Psychology, 13, 976883. https://doi.org/10.3389/fpsyg.2022.976883

[17] Papatzikis, E., & Rishony, H. (2022). What is music for neuroplasticity?: Combined value on infant development and inclusion. In Rethinking inclusion and transformation in special education (pp. 160-177). IGI Global Scientific Publishing. https://doi.org/10.4018/978-1-6684-4680-5.ch010

[18] Almadhoob, A., & Ohlsson, A. (2020). Sound reduction management in the neonatal intensive care unit for preterm or very low birth weight infants. The Cochrane Database of Systematic Reviews, 1(1), CD010333. https://doi.org/10.1002/14651858.CD010333.pub3

[19] Smith, S. W., Ortmann, A. J., & Clark, W. W. (2018). Noise in the neonatal intensive care unit: A new approach to examining acoustic events. Noise & Health, 20(95), 121–130. https://doi.org/10.4103/nah.NAH_53_17

[20] Shaw, R. J., Givrad, S., Poe, C., Loi, E. C., Hoge, M. K., & Scala, M. (2023). Neurodevelopmental, mental health, and parenting issues in preterm infants. Children, 10(9), 1565. https://doi.org/10.3390/children10091565

[21] Boissel, L., Pinchaux, E., Guilé, M., Corde, P., Crovetto, C., Diouf, M., Mariana, C., Meynier, J., Picard, C., Scoury, D., Cohen, D., Benarous, X., Viaux-Savelon, S., & Guilé, J. M. (2022). Development and reliability of the coding system evaluating maternal sensitivity to social interactions with 34- to 36-week postmenstrual age preterm infants. Frontiers in Psychiatry, 13, 938482. https://doi.org/10.3389/fpsyt.2022.938482

[22] Papatzikis E., Dimitropoulos K., Tataropoulou K., Kyrtsoudi M., Pasoudi E., O’Toole JM., et al. (2025) The father’s singing voice may impact premature infants’ brain more than their mother’s: A NICU single-arm exploratory study protocol and preliminary data on a singing and EEG framework based on the fundamental frequency of voice and kinship. PLoS One 20(8): e0328211. https://doi.org/10.1371/journal.pone.0328211

About the Author

Humor perception is widely considered to occur when a person is confronted with a benign but unexpected event – and incongruity – which they then resolve (Pien & Rothbart, 1976). In other words, they develop sudden insight into the incongruity so that it makes sense. Wearing a cup as a hat becomes funny when it is resolved as intentional; a face that reappears during Peekaboo becomes funny when it is resolved as having been hidden rather than truly gone. Additionally, the playful context signals the incongruity is not only interesting, but safe. These moments of insight are often marked by laughter indicating a little cognitive puzzle has been solved.

The scant literature on infants’ laughter toward incongruity is contrasted with another body of literature showing that infants consistently gaze at unexpected events (Margoni et al., 2024). In a recent study, we explored this intriguing question: why do infants laugh at some incongruities and gaze at others? Both kinds of incongruities share key qualities: they are novel, slightly surprising, and safe. The key differentiating feature may be that babies stare at incongruities that cannot be resolved (i.e., magic tricks) and laugh at those that can (i.e., jokes). Problematic to this idea however is that, although infants have been credited with all kinds of capacities, including for example, some knowledge of natural physical laws (e.g., solidity, gravity; Baillargeon, 2004), they have not been credited with the ability to resolve incongruities because that question has not been directly tested.

Importantly, studies that find infants stare at magical incongruities tend to present those events in nonsocial contexts in which objects act in odd ways, all on their own. On the other hand, studies that find infants laugh at humorous incongruities tend to present those events in social contexts where people behave in strange ways with objects. The latter events are also often repeated, potentially giving infants an opportunity to make sense of or resolve them. We set out to determine whether these features – social context and repetition – are what allow infants to make sense of unexpected incongruous events. In other words, would infants laugh at magic if given a chance to resolve it? 

To do this, we took two magical incongruities used in the research: one in which a ball disappears by sleight of hand, and other in which a ball turns into a cube. We presented these incongruities to 6-month-old infants (N=88) in an nonsocial context where only the researcher’s hands were visible, or in a social context where infants could see the researcher “magician”. Importantly, the researcher did not look at, speak to, or interact with the infant and maintained a neutral downward gaze throughout. Each magical incongruity was paired with a corresponding control (i.e., ordinary) event, and both were presented 6 times allowing us to compare infants’ reactions to their first vs. repeated exposures to each event. We used a within-subjects design wherein all infants saw both magical incongruous events and their respective controls. Infants were randomized to one of four possible orders in which the event (control/incongruity) and social context (nonsocial/social) were counterbalanced, meaning that we systematically controlled for the order of events that infants saw. Infants were videoed while watching the events so that research assistants blind to the hypotheses could later code infants’ behavior which included looking, smiling/laughing, looks to the caregiver, and looks away. We also explored whether infants differentiated events based on reaching as recent work suggests this may shed additional insight on infants’ reactions to magical incongruity (Köster et al., 2020). Research assistants traveled to infants’ homes with a portable Blackbox theater allowing infants to be tested in their familiar environments and allowing us to capture their most natural reactions.

Importantly, and corroborating prior studies, infants looked more often at magical incongruous than ordinary events and were also more likely to reach toward the former suggesting an attempt to explore those events more closely, perhaps to make sense of them (Köster et al., 2020).

Crucially, when magical incongruities were placed in a social context, infants expanded their appraisal, initially smiling or laughing at them compared to ordinary events, and hinting at an early capacity for incongruity resolution. In contrast, those same events became uninteresting when repeated, especially in a nonsocial context, evoking neither gazing nor smiling and suggesting these events quickly lost their novelty perhaps as they became too predictable. Repetition alone, therefore, was insufficient to evoke amusement. It could be that repetition results in amusement only when embedded in a playful frame (e.g., chase games, peekaboo; Hoicka, 2014) where it predicts arousing social interaction even as novelty diminishes.

Infants have already been credited with differentiating impossible from possible events (Baillargeon et al., 2009; Margoni et al., 2024); the added value of these findings is to further credit them with being able to resolve those impossible events if given the context to do so. Social context may help infants make a different appraisal of magical incongruities as amusing, possibly because the simple presence of a person acting on the objects allows infants to infer the events as caused by that person (i.e., the magician), thereby resolving them (Reddy & Uithol, 2016). These findings require replication but suggest infants may be more sophisticated in their ability to appraise unexpected, highly unusual events when the context allows the opportunity.

This study shows that infants do more than passively watch incongruities—they actively engage with them, laughing at and reaching for them when the context affords it. Infants’ curiosity, humor, and social engagement toward and with novelty, suggests they treat surprising events not just as puzzles to watch, but as opportunities to explore and engage. Knowing this can shape how we think about supporting cognitive and social-emotional development in the earliest months of life, and in the most effortless, joyful ways. 

Of particular relevance given today’s political climate, this work was supported by an NIH R16 (SuRE) grant. The R16 mechanism has two objectives. One is to produce meritorious research that contributes meaningfully to the field. The other is to provide science training opportunities to undergraduates at teaching-focused institutions, enabling them to participate directly in hands-on research, strengthening both the science and the scientific workforce. Federal investment in infant research is essential, not only because it advances our scientific understanding of how babies think, feel, and learn, but also because it provides training for the next generation of scientists. At a time when federal research funding faces heightened scrutiny, sustaining these programs is critical for ensuring that developmental science continues to thrive. Funding ensures that discoveries about the earliest months of life — and the students who will carry the field forward — are not left to chance.

References

Baillargeon, R. (2004). Infants’ physical world. Current Directions in Psychological Science, 

13(3), 89-94. https://doi.org/10.1111/j.0963-7214.2004.00281.x

Baillargeon, R., Li, J., Ng, W., & Yuan, S. (2009). An account of infants’ physical reasoning. In A. Woodward & A. Needham (Eds.), Learning and the infant mind (pp. 66–116). Oxford University Press.

Hoicka, E. (2014). The pragmatic development of humor. In D. Matthews (Ed.), Pragmatic

development in first language acquisition (pp. 119–237). John Benjamins Publishing Company. https://doi.org/10.1075/tilar.10.13hoi

Köster, M., Kayhan, E., Langeloh, M., & Hoehl, S. (2020). Making sense of the world: Infant 

learning from a predictive processing perspective. Perspectives on Psychological Science, 15(3), 562–571. https://doi.org/10.1177/1745691619895071

Margoni, F., Surian, L., & Baillargeon, R. (2024). The violation-of-expectation paradigm: A 

conceptual overview. Psychological Review, 131, 716-748. https://doi.org/10.1037/rev0000450

Pien, D., & Rothbart, M. K. (1976). Incongruity and resolution in children’s humor: A 

reexamination. Child Development, 47(4), 966–971. https://doi.org/10.2307/1128432

Reddy, V., & Uithol, S. (2016). Engagement: Looking beyond the mirror to understand action 

understanding. British Journal of Developmental Psychology, 34, 101–114. https://doi.org/10.1111/bjdp.12106

About the Author

The truth is, screens are nearly impossible to avoid, even for infants, which means it is difficult to offer realistic guidance for how to manage it within a household. The proliferation of mobile and on-demand media has changed the digital media landscape rapidly, which also changes the ways in which children engage with it and the impact it has on their development. Here, I offer guidance based on research for both tempering these expectations and supporting children’s language development in a digital world.

Researchers have been trying to keep up with the fast changing digital world, but given how widespread media use is and how critical the first few years of life are, advancing this research depends on large-scale funding support such as that from the National Institutes of Health (NIH) and National Science Foundation (NSF). My lab and I have been fortunate to be awarded some of this funding–we worked on what is called an R15 AREA (Academic Research Enhancement Award) award, which is specifically focused on solving key scientific questions (for us, that was the impact of digital media on language development) while also training the next generation of students in how to conduct this research. Our lab (the SMU KID Lab) has trained over 50 students in the course of this work, many of whom now have the skills and knowledge to work directly with families and improve children’s lives. But more importantly, we discovered that while digital media use is rapidly rising, it is not solely the amount of media that matters, but how and why it is being used that has both negative and positive effects on children’s language outcomes.

Our research discovered that by the time children are just two-years-old, they use some form of screen media an average of nearly 2 hours per day, nearly double the rate of book reading (Kucker et al., 2024). The amount of time spent in front of a screen was, in general, correlated with a child’s overall vocabulary–more screen time was related to lower vocabulary. However, the impact on language was not universal–- it varied based on what type of screen was used, what the activity was, and potentially based on why it was being used. It turns out that the majority of kids’ screen time is spent watching television shows or movies, which tend to be more passive and associated with lower language. Children spend much less time using video chat, reading e-books, or playing educational games, and these particular media activities are not associated with lower language. There is some evidence that when media is used for educational purposes or to socially connect, it might buffer against some of the negative impacts. This is very consistent with other work showing that educational, interactive, and joint use of media (such as Facetime or Zoom, or educational apps that require a real-life partner) may not hinder language (Jing et al., 2023). Likewise, high quality media in which the characters interact with children and follow a narrative story have less negative effects on language development than fast-paced, disjointed stories (Krcmar & Cingel, 2019).

But why do screens impact children’s language development? For two reasons: 1) it is harder for children to generalize what they learn from media to real-life scenarios and 2) time spent on screens could replace opportunities for face-to-face, real-world interactions, which are critical for language learning. When children learn information from a digital source, they have a hard time processing the information in the same way until they are at least 3-4 years-old and they struggle to transfer such information and remember it in a different context (Barr, 2010). This means we should not be relying on television shows to teach very young children concepts, but if we use the media as a launchpad for children to apply those concepts to real life, it may be ok. For instance, if your child learns about bananas while watching Ms. Rachel, don’t stop with that, but have a banana for a snack, make some banana bread, and ask them to find a banana when grocery shopping. Or, if screentime is inevitable – you let your child watch a few minutes of video so you can finish making dinner, which can be offset by co-viewing and talking to your child as they watch (Strouse et al., 2018), or by giving them a few minutes of rich face-to-face time talking with real people (Kucker & Schneider, 2024). That short video will not derail your child’s development, especially if it’s periodic and supplemented with an abundance of rich social interactions.

Because media is so prevalent, it is critical to keep in mind that we cannot plausibly avoid all screens for our children, nor might we want to– being able to FaceTime with Grandma for instance, can actually be good for helping your child bond with family members (Strouse et al., 2021). Our argument, based on empirical data and research supported by federal funds, is that the goal should not be to eliminate all media, or even try to measure it down to the minute. Caregivers cannot realistically do this and, in most cases, it is not needed. However, caregivers should be mindful of their children’s screen time, especially when they are younger. There is not a one-size-fits-all approach and no black-and-white “rule” for how much or when children can or cannot use media. Rather, thanks to the federal funding supporting this work, we know that it is not the amount of screen time that matters so much as how, when and why.

References

Barr, R. (2010). Transfer of learning between 2D and 3D sources during infancy: Informing theory and practice. Developmental Review, 30(2), 128–154. https://doi.org/10.1016/j.dr.2010.03.001

Jing, M., Ye, T., Kirkorian, H. L., & Mares, M. (2023). Screen media exposure and young children’s vocabulary learning and development: A meta‐analysis. Child Development, cdev.13927. https://doi.org/10.1111/cdev.13927

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About the Author

In a recent paper (Campbell et al, 2025), we wanted to look at the kind of tension highlighted above: how language and direct sensory experience interact. We were especially interested in how likely toddlers and preschoolers (roughly, 2- to 3-year-olds) were to produce words for things they could or couldn’t perceive. We zoomed in on sets of words that were highly visual (e.g., see, green), auditory (e.g., hear, meow), or abstract (e.g., good, pretend). We recruited 6 groups of young children, primarily paired into 3 sets of comparisons: blind and sighted children; deaf children who had cochlear implants and were learning spoken English, and hearing children; and early and late  learners of ASL (American Sign Language; early learners were exposed to ASL from birth, late learners not until around age 2). This let us get at several interesting comparisons: while none of the groups directly perceived the abstract words, the deaf groups (both ASL groups and English-learners) and the blind group had different access to the visual and auditory words than their hearing or sighted peers.

Critically, for blind children learning spoken English and deaf learners of ASL, the sense they are missing is not the one that carries the linguistic signal (i.e., blind children have intact hearing, and deaf ASL learners have intact vision). In contrast, deaf children with cochlear implants (i.e. children with severe to profound hearing loss) learning spoken English have no access to language until they get their cochlear implant (around age 1), and after implantation, the input they hear is degraded (a cochlear implant does not transmit all of the detailed auditory signal that the cochlea of hearing children receives). These groups of participants also let us explore the roles of early vs. late language access, for both spoken English and ASL. For all the groups, parents filled out a vocabulary checklist indicating which words their child said (spoken English) or signed (ASL).

Distilling a complex set of findings (where we controlled for things like overall vocabulary size, age, word frequency, etc.), we found 3 key results. (1) Blind children were just as likely to produce abstract and auditory words as sighted peers, but less likely to produce visual words. (2) In contrast, deaf children with cochlear implants learning spoken English were less likely to produce all three types of words than hearing peers, with the largest difference for abstract words. (3) The late vs. early ASL learners did not differ in their likelihood of producing signs for any of the three word types. In an exploratory follow-up analysis, we tried to figure out whether we could home in on the role of language access by combining our early groups into an early language access group (hearing + early ASL) and a late language access group (deaf spoken English learners + late ASL). When we did that, we found that later language access corresponded with lower word production.

So how do those results come together to help us better understand the link between sensory experience and early word production? These results help support an important idea sparked by seminal work by Landau and Gleitman (1985): language itself carries a ton of information we all use to represent our world (and fictional worlds as well). On the one hand, across the board and unsurprisingly, our young child participants were more likely to produce words for things they could perceive versus those they couldn’t. That is, what drove word production was whether children could, given their sensory access, perceive it.

However, the language access story is a bit more complicated: deaf spoken English learners weren’t uniquely less likely to produce auditory words, and early vs. late ASL learning didn’t seem to matter for rates of word production here. While later language access did link to later word production in our pooled analysis, this wasn’t uniquely or more strongly true for our abstract words, where we’d predicted language access may be particularly relevant. There is more work to be done to better understand how sensory experience and language access and learning come together.

It’s also worth highlighting though that we had blind participants and deaf participants producing highly visual and auditory words and signs by age 1.5, words like “green” and “hear” that they don’t directly experience. So just like the alien planets I envisioned without visiting, the children in our studies learn and produce words for things they don’t directly perceive. How specifically perceptual experiences leave their fingerprints on learning is also a question in need of further study. But in short, blind babies and deaf babies provide a fascinating window into a learning process we all take part in: learning language from language. Direct perceptual input is not—in any sense—strictly required.

Coda: I’d be remiss to not mention the current funding climate in a post on work funded by federal grants in the U.S. The NSF CAREER grant that funded the work above ended at the end of April, just before all the grant cuts to Harvard. My NIH grant was not so lucky; it was terminated in May (as were virtually all DHHS grants to Harvard). Our work is not controversial or politically-charged: it’s basic science asking how babies get better at understanding language. It was vetted by a rigorous and transparent review process at the NIH by specialists in language and communication, and funded by federal funds appropriated by Congress to the NIH. It is, in my view (and many others’) completely unethical and of extremely questionable legality for the NIH (at the President’s behest) to withhold these funds in the way they have. This termination is the subject of ongoing litigation between Harvard and the U.S. Government with, at this point, an unclear future.

Fortunately, our infant participants are not being harmed by this grant termination (which is more than can be said for terminated grants on drug trials, medical devices, etc.). But our trainees are: the future scientists of the U.S. are actively losing opportunities to engage in cutting-edge research, both in a practical sense of fewer funded opportunities, and in the broader opportunity costs that arise when basic science research falls victim to political arrow-slinging. I encourage interested scientists at any career stage to engage with efforts like Science Homecoming to help highlight the importance of science for everyone. Anyone who’s seen the wonders (or struggles!) of babies as they develop, think, and grow can appreciate the importance of better understanding this process. We would all benefit in being more babylike in our approach to scientific inquiry and human health: led by a deep-seated curiosity about how the world works above all else.

About the Author