How Jersey Numbers Affect Visual Judgments

Source: Tim Mossholder / Unsplash

As a die-hard sports fan, I was surprised to read the headline of a recent Pew Research Study, which stated that the majority of Americans (62%) do not closely follow professional or college sports. This claim seems at odds with the oversized impact of sports on college campuses—where 31 of the 50 highest-paid state employees are college football coaches—and the massive television audience for last year’s Super Bowl, when 115 million viewers made it the most watched U.S.-based telecast in history.

Yet a deeper dive into the Pew results convinced me that it would be premature to conclude that Americans’ obsession with sports and athletes is waning. According to the study, a healthy minority of Americans (37%) cares about sports to some extent—in fact, 16% follow sports extremely or very closely, 10% talk about sports daily, and 7% (known as “super fans”) do both!

What exactly do sports fans like to talk about? That’s where numbers come in! From scores and standings to advanced sabermetrics and jersey numbers, numbers are everywhere in sports. A 2022 Nielsen report even claimed that 51% of people check live stats when watching sports. Specific numbers have become imbued with meaning because they are indelibly linked to celebrated sport-related achievements or milestones.

Take the following numbers: 2,632, 762, 406, and 56. A baseball fan would instantly recognize these numbers on account of their association with four legendary Major League feats: 2,632 is the record number of consecutive games played by Orioles’ “Iron Man” Cal Ripken, 762 is the career record for home runs, a number synonymous with home run king Barry Bonds and the allegations of performance-enhancing drug use that have tarnished his legacy. The batting average .406 belongs to Ted Williams, the last player to hit over .400 in a single season (representing a 40% “success” rate). Williams’ accomplishment took place in 1941, the same year that Yankees slugger Joe DiMaggio hit safely in 56 consecutive games, a record that still remains unbroken.

Given my dual identity as a numerical cognition researcher and a sports aficionado, I thought that other sports fans might be interested to learn about a few cognitive biases that have been shown to affect perceptions, judgments, and behavior in sport-related contexts. In this post, I discuss an intriguing recent paper in PLOS One that examines how jersey numbers affect body-size perceptions. The author team of Leon Shams, Alisha Föry, Achint Sharma, and Ladan Shams, all affiliated with UCLA’s psychology department, conducted two studies in which observers successively encountered computer-generated images of football players wearing jerseys with different numbers. After each football player was displayed, observers rated the player’s body size on a continuous unnumbered scale with anchors at “very slender” to “very husky.” At the end of each study, each rating position was converted into a numerical score from 0 (“very slender”) to 100 (“very husky”).

In one study, observers encountered 120 trials, meaning they rated 120 football players who varied in terms of clothing colors, skin tone, and proportion (i.e., the image’s aspect ratio). The catch was that there were actually only 60 unique football players shown; each of the 60 players was displayed twice, once wearing a jersey randomly selected from the range 10 to 19, and once wearing a jersey randomly selected from the range 80 to 89. This clever design allowed the researchers to compare if body image ratings systematically differed depending on whether the same player was wearing a higher or lower jersey number. Indeed, the mean body size difference score (i.e., high jersey number rating less low jersey number rating) was +1.37, which is a small but significant discrepancy.

In a second study, the authors replicated the same pattern of results using stimuli in which participants saw jerseys with the same numbers, just in a different order (e.g., 71 vs. 17, 81 vs. 18, 91 vs. 19). This design helped ensure that the earlier results did not emerge just because certain numbers (e.g., 8) are themselves broader than visually slim numbers (e.g., 1). The mean body size difference in this second study (i.e., high jersey number rating less low jersey number rating) was +0.55, which is again significantly higher than zero. Taken together, these studies reveal that people think the same player is huskier when he wears a larger jersey number.

What leads people to use accessible but unrelated numerical magnitude information to make size judgments in this way? The authors of the jersey study argue that this effect is based on a learned association. In football, lower jersey numbers (i.e., under 19) were historically reserved for “skilled” position players (i.e., quarterbacks, wide receivers, and kickers), whereas lumbering linemen and defensive ends tended to wear higher numbers. Even though some of these numbering conventions have been modified in recent years, it may not be easy for people to erase the mental association that had developed between slender players and low jersey number magnitudes, or between husky players and high number magnitudes. Beyond football (or even sports altogether), high numbers and large sizes often go hand-in-hand. After all, a 20-pound bag of rice is bigger than a 5-pound bag. As another example, consider photo frames—higher numbers again legitimately correspond with larger sizes; an 11 x 14 frame is bigger than an 8 x 10 frame. If we get used to seeing higher numbers and larger sizes together, this association can affect our expectations and ultimately shape our visual perceptions and judgments. In the case of football jerseys, it can evidently make us see a husky lineman in jersey number 91 and a sleek wide receiver in jersey number 19, even when they are really the same person!