The impact of self-selection on performance

kids-runningOur behavior is strongly influenced by comparisons with others. These “others” are not usually assigned to us, but we choose who we interact and compare ourselves with. Or, as economists put it, individuals self-select into certain environments and into specific peer groups within given environments. However, little is known about the consequences of these self-determined choices.

In a recent discussion paper, Lukas Kiessling, IZA Resident Research Affiliate Jonas Radbruch and Sebastian Schaube (all University of Bonn) study how different peer assignment rules – self-selection or random assignment of peers – affect individual performance, and how self-selection itself alters interactions between peers.

The research team conducted a field experiment with over 600 students (aged 12 to 16) in physical education classes of German secondary schools. The students took part in two running tasks (“suicide” runs) – first alone, then with a peer. After the first run they filled out a survey that elicited preferences for peers, personal characteristics, and the social network within each class. Across treatments the researchers exogenously varied the peer assignment in the second run using three different matching rules.

In a first treatment, the authors implemented a random matching of pairs. This was contrasted with two matching rules using the elicited preferences to implement self-selected peers. The specific setup of their experiment allowed for the implementation of two notions of self-selection, based on either the identity or the relative ability of one’s classmates:

  • Conducting the experiment in classroom environments makes it possible for students to state preferences for known peers (name-based preferences).
  • A running task yields direct measures of performance than can be used to select peers based on their relative ability in the first run (performance-based preferences).

dp11365-fig1The results show that the two peer-assignment mechanisms with self-selected peers improve average performance by 1.27–1.67 percentage points or .14–.15SD relative to randomly assigned peers.

A natural explanation would be that students interact with different peers and react differently to them, which mediates the effects. While self-selection indeed changes the peer composition in a way that students interact predominantly with friends (name-based) or students with a similar ability (performance-based), this cannot explain the observed improvements.

Rather, when accounting for these changes in the peer composition, the effects remain constant or even become more pronounced. Combined with additional evidence on how students perceive the task in the different conditions, these findings provide evidence that the opportunity to self-select peers has a direct effect on performance. The authors argue that the process of self-selection seems to provide an additional motivation to students leading to performance improvements.

While the impact of a peer and the resulting quantitative effect might be specific to the setting analyzed in their study, the underlying mechanisms are valid in more general settings. The results show that the direct effects of self-selecting peers may be even more important than those induced by exogenous group assignment. Additionally, these effects take place even within exogenously formed groups.

Download the complete paper (IZA DP No. 11365):

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