How informative are first impressions? The thin-slices technique as a method for video-based assessment of instruction

A drawback of video-based analysis of teaching lies in its high cost in terms of time and money. The present study examines the possibility of assessing instructional features on the basis of very short observations, respectively first impressions. We applied the so-called thin-slices technique: This procedure which uses judgements based on first impressions has shown high reliability and validity in the assessment of various psychological constructs. In two studies untrained raters judged 37 elementary school teachers regarding three dimensions of instructional quality based on 30-second randomly selected sequences from full classroom videos. Both showed very high interrater reliabilities. While descriptive analyses indicate a rather undifferentiated judging process, multilevel regression analyses predicting students' achievement gain via ratings of instructional quality indicate a certain predictive validity of first impressions.