The present study investigated how learners use feedback information on their test results. We also examined the effects of the type of feedback and learners’ achievement goals on the manner in which feedback information was reviewed. In an experimental study (N = 42 undergraduate and graduate students), we tracked eye movements of the participants while they took a critical thinking test and received their test results. The results showed that most participants checked feedback for incorrectly-answered questions but not for correctlyanswered questions. This suggests that learners do not use feedback information to judge the adequacy of the process of solving. In addition, these tendencies were not different between feedback conditions. Furthermore, participants’ achievement goals predicted learners’ review activities. Specifically, learners with higher mastery goals tended to check feedback for correctly-answered questions. Therefore, fostering the pursuit of mastery goals may prompt learners to use feedback information to enhance their comprehension.

A mode-locked laser that can produce a broadband spectrum and ultrashort pulse has been applied for many applications in an extensive range of scientific fields. To obtain stable mode-locking during a long time alignment-free, a semiconductor saturable absorber is one of the most suitable devices. Dynamics from noise to a stable mode-locking state in the spectral-domain are known as complex and a non-repetitive phenomenon with the time scale from nanoseconds to milliseconds. Thus, a conventional spectrometer, which is composed of a grating and line sensor, cannot capture the spectral behavior from noise to stable mode-locking. As a powerful spectral measurement technique, a time-stretch dispersive Fourier transformation (TS-DFT) has been recently used to enable a successive single-shot spectral measurement over a couple of milliseconds time span. Here, we experimentally demonstrate real-time spectral evolution of femtosecond pulse build-up in a homemade passive mode-locked Yb fiber laser with a semiconductor saturable absorber mirror using TS-DFT. Capturing 700 consecutive spectra (~ 17 µs time window) in real-time using the time-stretch technique, we are able to resolve the transient dynamics that lead to stable mode-locking. Before setting stable mode-locking, an oscillating or shifting fringe pattern in the consecutive spectra was detected. This signature proves the existence of multiple pulses (including a soliton molecule) which is temporally separated with a different relative phase. The dynamics on multiple pulses is originated from a fast relaxation time of the saturable absorption effect. This study provides novel insights into understanding the pulse behavior during the birth of an ultrafast mode-locked laser pulse and the stable single-pulse operation which is highly stabilized.