Why does the ULAT only use the target language in its instructional videos?

There are a number of very important reasons for only using the target language in the instructional videos:

SPEAKING TO THE INSTRUCTOR
The instructor who uses the ULAT in class must understand that the ULAT instructor by no means expects the students to understand him at all time (and classroom teachers do well to let their students understand this as well when the year begins regarding their own speech). That which is essential will be made overwhelmingly obvious through repetition and association with a visual representation of its meaning. Exclusive use of the target language, over the course of months, is the only way to attain the exciting conclusion mentioned last in this list. In many cases, that which the ULAT instructor is saying in the instructional videos, if beyond the scope of the students' comprehension, is intended for the classroom instructor with the comments existing as language teaching tips or explanations as to the contents of the ULAT lesson.

SETTING THE STANDARD
By refusing to use the students' native language and by only using the target language, the ULAT is setting the standard for what should be the norm in any effective language classroom. The students thereby understand that the use of the target language is to be expected.

PICKING UP SECONDARY VOCABULARY AND PRONUNCIATION
By refusing to use the students' native language and by only using the target language, the ULAT is setting the standard for what should be the norm in any effective language classroom. The students thereby understand that the use of the target language is to be expected. The importance of becoming accustomed to the sounds of the language, and consequently to authentic pronunciation, should not be overlooked as well.

DEVELOPMENT OF THE HABIT OF LISTENING, OBSERVING AND HYPOTHESIS
Anyone who has learned a second language in a natural fashion, particularly while living in the target culture, knows that they need to do far more active listening than speaking initially, that is to say, listening in which they are carefully observing for clues as to meaning and constantly formulating and reformulating hypotheses as to the meaning of what they are hearing. Students who are "spoon fed" information, always in close relationship to their native language, do not acquire this skill and thereby find their language development stunted when placed in the target culture or with native speakers of the target language in their own culture.

EMPATHY
Whereas the goal of the ULAT instruction is not to make things hard for the learner, language learning done right is difficult. Learning to use a second language, without the dubious benefit of any recourse to one's native language, is a challenging intellectual exercise, however it is the only approach that will produce lasting, worthy results. As a by-product of the natural language learning challenge, students learn empathy and gain respect for non-native speakers in their own culture who are having to learn the students' native language in the same fashion.

SURPRISED BY COMPREHENSION!
Forgive me if I try to wax poetic here a moment. I cannot help myself because I am talking about one of the most beautiful things that can occur in the life of the world language teacher. At what point, hidden in the depths of the crysalis does the caterpillar become a butterfly? At what moment, while we are entirely unconscious of the event, does a shoot emerge from a cold seed that has lain dormant under a layer of snow and frozen earth all winter? Likely while we are asleep, as the winds begin to blow from out of the south, for those of us in the upper reaches of the northern hemisphere, does the long, hard winter soften into an early spring and surprise us with an almost unspeakable joy when we first step outside. (You can tell that I'm writing these words in the midst of a Michigan winter.) The world language teacher who has steadfastly employed only the target language from Day 1, often likely wondering if it is serving any purpose other than to make his or her life more dificult, experiences something very much akin to the three natural phenomena I've described. Invariably, along about the month of March each year, not surprisingly as springtime promises to awake, I have a serendipitous experience. I find myself speaking at the beginning of a class period in the target language at a natural conversational pace, possibly giving instructions as to what we will be doing during that day's class, and I suddenly grow aware that every eye is not only on me, but that there is a look of total comprehension on each face. Breaking with my usual habit, I suddenly switch to English and ask my students: "What am I telling you?" Without pause, they immediately give me a very accurate summary in English of what I have just been saying to them. At that moment, I often sit down for a moment, pause in my presentation, take a deep breath, as you might do upon completing a long and arduous journey through a wilderness area. (Frankly, I also tend to tear up at such a moment, though I try to hide it.) I am overwhelmed by a feeling of gratitude and contentment, as though finally seeing a road marker that confirms that we are indeed on the right path after many months of uncertainty. Probably many of you have experienced the same phenomenon. If not, I covet that for you as well, but posit that total target language immersion is the only way you will ever know that experience. And, by the way, the students' sense of self-esteem skyrockets when I tell them on those occasions how pleased I am with them. Therefore...be perseverant and patient and press on!