Formal and informal learning have been talked about in educational fields for years. People have an approximately common understanding of formal learning, which is the learning normally delivered by teachers in a systematic intentional way within a school, academy/college/institute or university. Yet, the definition of informal learning varies from person to person. Two major views exist. One believes that any form of learning occurs outside the academic settings is categorized as informal learning, e.g., life-long learning. While, the other defines informal learning as unintentional, unplanned, and therefore without instruction and instructors, e.g., social interpersonal learning. And, everything between formal and informal learning is called non-formal learning, which takes place outside of the school but involves a certain level of instructional planning and organization, e.g., sports clubs.
When the discussion around informal learning remaining hot, some other terms within the informal learning realm are brought to researchers’ attention. One of them is incidental learning. Schneider first defined it as a form of accidental, indirect, additional, unplanned learning within an informal or formal learning situation. The relationship of incidental learning with informal learning is vague and ambiguous, which make the understanding of informal learning even more confusing.
I came across a literature review in regard to the theories and researches on informal and incidental learning (Marsick, Watkins, Callahan, and Volpe, 2006). The authors basically generated a model about the incidental learning in workplace (see figure below) based on 3 areas of studies: tacit/implicit knowing, whole person learning, and communities of practice. These 
areas shaped the theoretical framework of the authors’ model. Tacit/implicit learning is often tied to studies of expertise. Through this kind of learning, we construct and modify our mental, emotional, and interpersonal schemata for processing all of our experiences into knowledge. Whole-person learning theory emphasizes on the feelings and emotions which also play a critical role in the cognitive function of human beings. Communities of practice brings in the social aspect, which makes a great sense because informal/incidental learning is increasingly socially situated and socially constructed.
Among these 3 areas, what caught most of my attention is the tacit/implicit learning. Tacit and implicit are similar in definition yet mean differently in terms of learning. According to the dictionary, tacit means “understood without being openly expressed”, whereas implicit means “implied, rather than expressly stated”. The slight difference lies in that whether the thing can be implied, which leaves some critical questions for us when we try to understand how people learn in an unintentional and unplanned circumstance. So, what is tacit learning? Can it be passed on from someone else other than the learner himself/herself? Let’s take learning swimming as an example. Can it be taught? You would think “Of course it can!” However, when you think deeply, the actual how to float and keep balance thing is nearly impossible to be articulated. What we, as learners, do is just practice and practice, and finally get the “feeling”. The process of getting that “feeling”, which cannot be written down and passed on, to me is the tacit learning. Here comes another question: if learning how to float is tacit learning, and it is definitely not unintentional, then what exactly tacit learning means?
I can go on and on asking further questions, such as should tacit learning be defined across types of learning, is it possible to measure this unconscious learning, can we design instructions around tacit or implicit learning, etc. Perhaps when we figure out the answers for these questions, we would have a better stance in studying incidental learning and therefore informal learning.
Tacit learning, is a two way process of communication, without words or verbalization. For example, between people, a facial expression of approval or disapproval, for example. The root word is tacere in latin, meaning to be silent. So, any learning you can do without text or words is tacit learning.
You use learning to float in water as tacit learning, and this is a two way communication between a person and their environment, if no one is around to explain or teach. This is likely an incredible natural form of learning. However, the person needs to be cognizant of their body in many complex ways, and the water makes a difference. The salinity level of the water, versus fresh water increases your buoyancy, and reduces the cognizant effort between the body and mind. But does a learner understand this for the first time? The movement of lifting your legs, and leaning back, attempting to elevate your hips, to float on your back, is through experience and hopes of being done in shallow water to prevent drowning. And this is different between men and women, due to the dispersion of body composition. This also, mean a chubby person, because fat cells are composed mostly of water, make floating easier. The type of muscle fibers affect the persons buoyancy also, long or short in density. Learning to express the body movements and senses, is a level of mind body connection and linguistic knowledge. Describing the environment and factors is another level of expression of knowledge. However, people don’t always have the tools of expression through abstract language and text. We learn through our senses.
Incidental comes from incident; or to fall upon, happen to. The latin word is incidere, but this has three meaning, but the logical one is in this context is to affect or influence. This form of learning is a consequence, not of what we are learning, but of the context with which we learn in. Furthermore, the context is multiplied between all the participants of the context.
To use incident from the latin meaning as an example; you have to be standing in the right spot at the right time for something to fall on you from above. But nothing may fall on you in that spot. In learning science we are always trying to be intentional, but we cannot assess all the factors before hand. A good teacher or facilitator will assess continuously and modify what is needed based on what can be recognized, making the process an intentional possibility, but still incidental. If you use the root word “incidere”, the meaning of affect or influence applies to this intentional possibility. Incidental learning a consequence of context. This is why natural and experimental science is so different. Experimental is meant to control factors and context, and repeat. Whereas natural doesn’t control the factors and context, but to understand them.
Well, this is my understanding. What do you think?