Introverted Intuition and Introverted Sensation are alike in the sense that the environment affects the self due to the nature of Introverted Perception functions (contrasted with Extroverted Perception functions, where the self affects the environment)
Introverted Sensation is the realization of how the present environment and concrete observations affect you personally, and accounts for the dynamic features of the present environment. Usually, Introverted Sensors have an excellent memory, which aids them in establishing stability in the environment (for spontaneity can be anxiety-producing to them, and this spontaneity is specifically aimed at hypothetical possibilities postulated not by the environment itself but by what could be in the environment after certain actions are made (a.k.a inferior Ne is scary)), for they are able to remember conditions the environment has inflicted upon them prior and can organize the environment to achieve stability. These people easily know what they like in terms of aesthetics and taste due to the fact that the Si function is always paying attention to the dynamic components of the environment. These people will notice changes in the environment and label them as favorable or unfavorable usually under the concept of comfort, usually taking note of environmental things like temperature, humidity, movements in the environment, noises, etc, in relation to the meaning each of these concrete things create, which is usually in relation to the Si user's memory banks. The sound of a police siren, for instance, might conjure feelings of anxiety and fear in an ex-con Si user due to the fact that he was arrested after a hot pursuit chase where sirens were blaring all over the place (The environment, the police sirens, makes the Si-user, the ex-con, uncomfortable). Ergo, these people will often build attachments to certain objects in the environment due to the meaning they convey, such as a family heirloom and tokens that eschew personal sentiments. Si is the notation and interpretation of the present dynamics of the environment in relation to how the environment affected the individual in the past.
Introverted Intuition, on the other hand, is the realization of dynamic circumstances that are not physically present in the environment, and how they affect you personally. Usually, these dynamic circumstances are not located in the dynamics of the present environment, but how the dynamics of the present environment were arrived at (i.e., It's hot outside right now, which is probably because the sun's out and we are standing on pavement that has been heated since the sun arose) and where the dynamics of the present environment may be leading to in the future (contrasted against Si's dynamic interpretations, which predict immediate outcomes of dynamics in the environment; i.e. If you punch a man, the man will probably punch you back immediately, while Ni is more focused on the possible civil court case that could arise from that action). In a way, Introverted intuition can interpret personal meaning from what isn't present in the physical environment in the present (unlike Si which attaches to that which is in the physical environment), where abstract concepts, omnipresent patterns, and dynamic circumstances are laced with personal meaning, to where the introverted intuitive's concepts and insight is seen in the same fashion as an Si user seeing an object in the environment that conjures personal sentiments. Ideas, Dynamic circumstances, and patterns become the Ni user's heirlooms and memorabilia, allowing the Ni user to build a memory vault much like the Si user's memory bank, except based not on tangible, experienced memories but on previous patterns/circumstances/ideas that have been extrapolated from the environment. As aforementioned with Introverted Sensation, spontaneity still causes anxiety and fear in the Introverted Intuitive, but this is not directed at hypothetical, negative, possibilities that can be induced by the self but by realistic, immediate negative happenings in the present environment that are caused by the self. Ni is the notation and interpretation of the dynamic circumstances of the environment in relation to how the environment probably acted and probably will act.