Intelligence 80 (2020) 101451 Contents lists available at ScienceDirect Intelligence journal homepage: www.elsevier.com/locate/intell Kids These Days! Increasing delay of gratification ability over the past 50 years in children T John Protzko Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, 93101, United States of America ARTICLE INFO ABSTRACT Keywords: Have children's ability to delay gratification decreased since the past? We analyze the past 50 years of data on Self-regulation the Marshmallow test of delay of gratification; where children must wait to get two preferred treats of their Metascience choosing; if they cannot wait, they only get one. Here we provide comprehensive evidence on whether children's Prediction ability to delay gratification has truly been decreasing, as theories of technology or a culture of instant grati- Flynn effects fication have predicted. Before analyzing the data, we polled 260 experts in cognitive development, 84% of who believed children are getting worse or are no different than those of the past. Contrary to this prediction, we show delay of gratification times are increasing over the past 50 years, corresponding to a fifth of a standard deviation increase in ability per decade. This mirrors the magnitude of secular gains in IQ seen over decades. 1. Introduction Menie, 2018). In Iceland, for example, polygenic scores for educational attainment have been declining over eight decades (Kong et al., 2017). A common belief is the children of the present are in decline (Smart, Related abilities such as visual working memory have also shown de- 1767; Freeman, 1907; Kitt, 2013; Protzko & Schooler, 2019; see also clines over time (Wongupparaj, Wongupparaj, Kumari, & Morris, Steenvoorden & Van der Meer, 2017 for general societal pessimism); 2017). Thus, we may expect to see secular declines in the ability to indeed since at least 624bce it has been received as common wisdom delay gratification. that present children are just not as capable as contemporary adults Numerous cognitive domains, however, have been increasing over were when they were children (regardless of the veracity of such time. People's IQ, for example, has been experiencing an increase over claims; e.g. Turchin, 2010). In the modern world, one domain that generations all over the world (Flynn, 1984). The increase generally seems especially vulnerable to deficiencies is children's ability to delay runs between 2.3 and 3 points of overall intelligence per decade, cor- gratification or exert self-control (e.g. Bodrova, Germeroth, & Leong, responding to around 1/5 of a standard deviation (Trahan, Stuebing, 2013; Kelley, Wagner, & Heatherton, 2015; Louv & Charles, 2011). Fletcher, & Hiscock, 2014; see also Pietschnig & Voracek, 2015). Across A child's ability to delay gratification, to forego an immediate re- three separate teams, children's ability to delay gratification has also ward for a better future one, is associated with numerous of positive life shown an increase of nearly the exact same amount over the past outcomes. Children who can delay gratification tend to go to school for 50 years using the same measure in 840 preschoolers (the ‘marsh- longer (Ayduk et al., 2000), have healthier bodyweights (Schlam, mallow test’; Carlson et al., 2018). Therefore, it is entirely possible that Wilson, Shoda, Mischel, & Ayduk, 2013), have higher academic overall there has been an overall increase in children's ability to delay achievement and a lower likelihood of engaging in teenage substance gratification instead of a decrease. The present study provides a larger use (Wulfert, Block, Santa Ana, Rodriguez, & Colsman, 2002; but also range of ages across several countries using meta-regression with nu- see Watts, Duncan, & Quan, 2018; but then see Michaelson & merous studies and sample sizes to further investigate the change in Munakata, 2020). Any changes in children's abilities should surely children's ability to delay gratification on the ‘marshmallow test’. merit considerable attention. The paradigmatic measure of delay of gratification in children is the Some cognitive domains have indeed shown evidence of declining “marshmallow test” (Mischel & Ebbesen, 1970). In this, children are over time. Abilities such as simple visual and auditory reaction times, acquainted with an experimenter, and then seated at a table. They are color acuity, patterns of vocabulary usage, 3D visuospatial ability, asked their preferred treat among an array of possibilities. This is im- working memory, and per capita rates of macroinnovation and creative portant as studies usually use children's preferred treat among an array genius (Woodley of Menie et al., 2017; see also Dutton & Woodley of and not just marshmallows. After the child selects their preferred treat, E-mail address: [email protected]. https://doi.org/10.1016/j.intell.2020.101451 Received 14 May 2019; Received in revised form 16 March 2020; Accepted 27 March 2020 0160-2896/ © 2020 Published by Elsevier Inc. J. Protzko Intelligence 80 (2020) 101451 they are then told the experimenter has to leave the room. If they wait Orsini, 1994; Shoda, Mischel, & Peake, 1990).1 Furthermore, secular until the experimenter gets back, they get two treats. Both treats are in increases for tasks such as working memory may not have changed front of the child during this time. How long the child can wait before appreciably in 85 years, suggesting some abilities are not changing signaling to the experimenter that they submit (usually ringing a bell) (Wicherts et al., 2004; Gignac, 2015; but see Woodley of Menie & or until they eat the treat is the indicator of how well the child can Fernandes, 2015). Another reason there may be no change is both delay gratification. forces moving abilities upwards and forces moving abilities downwards The question becomes, what should we expect in terms of children's may be operating simultaneously. Thus, the cancelling out of secular ability to delay gratification when looked at using the same test (the increases plus pernicious environmental abilities or dysgenic effects ‘Marshmallow test) over the past 50 years? Three possibilities are: 1) may lead to the appearance of no change and stability. A lack of There may be numerous influences on children's delay of gratification changes can also be because environmental forces are just not strong ability, for the worse. Multiple aspects of modern life have been ne- enough to have altered delay of gratification ability in the short (evo- gatively associated with self-regulatory behaviors (reviewed below); as lutionarily speaking) timespan of a few decades. The multiple traits and such, we may expect decreases in children's ability to delay gratifica- processes that may underlie ability to delay gratification may simply tion. 2) Similar to the secular increases in IQ, children's ability to delay not be altered by cultural changes. gratification may be on the rise. 3) The ability to delay gratification Overall, as it was unclear when pursuing this project how the data represents a stable developmental trait that is relatively impervious to would look, we make no pre-commitments to explaining changes, if any environmental moderation; thus children may show no change in their occur, in children's ability to delay gratification. All three possibilities ability to delay gratification over the past 50 years. appeared equally likely. Thus, to answer the question of have children's ability to delay gratification changed over the past 50 years, we took a 1.1. Predicting decreases neutral approach to predicting the pattern of data. Until now, there has been no meta-analytic review of secular changes in young children's' The largest reason to believe in decreases in children's ability to ability to delay gratification. To remedy this, we collected all of the data delay gratification are the widespread use and availability of tech- we could from both published and unpublished studies over the past nology. The mass proliferation of at-home tablets, phones, and com- 50 years. puters being used by infants and children continues to grow (Vandewater et al., 2007). Media use by young children has been as- sociated with lowered executive functioning (Barr, Lauricella, Zack, & 2. Materials and methods Calvert, 2010; Lillard & Peterson, 2011), increased obesity (Krebs et al., 2007), showing developmental impairments in social-emotional skills 2.1. Delay of gratification meta-analysis such as theory of mind (Nathanson, Sharp, Aladé, Rasmussen, & Christy, 2013), attentional problems (Baumgartner, Weeda, van der 2.1.1. Inclusion criteria Heijden, & Huizinga, 2014; Ralph, Thomson, Cheyne, & Smilek, 2014). The standard version of the delay of gratification task we chose was Children being increasingly exposed to more and more screentime, even what we believed would be most familiar to people: children in a room owning their own personal electronics before the age of four (Kabali alone with both rewards present. The first study to administer this et al., 2015), could lead to changes in children's ability to delay grati- procedure was used as our earliest study (Mischel & Ebbesen, 1970). We fication. Furthermore, the lack of children engaging in activities pur- then conducted a forward search of every study citing the first delay of portedly shown to facilitate executive control (Berman, Jonides, & gratification paradigm which also included the words “participants” Kaplan, 2008; Louv & Charles, 2011) may be contributing to secular and “marshmallow”. This left