6. Results
We test the hypotheses using ordinary least squares (OLS) regression. Table 3 reports the results explaining respectively growth action speed (Models 1 to 4) and joint action speed (Models 7 to 10). In addition to the full model, as a robustness test, we also report a parsimonious model (Armstrong, 2012) that only includes the postulated predictors and those control variables that are significant in the full regression model (Model 4 and Model 10). These models enhance predictive power over the full model (Model 3 and Model 9), but hypothesis tests may be subject to omitted variable biases.