原文出處： https://explorable.com/top-down-vs-bottom-up-processing
Generally speaking, there are two approaches to understanding the process of perception. These are the top-down processing and the bottom-up processing. What differentiates one from the other? Let's find out.
通俗來講，這里有兩種方法來理解感知的過程。這就是從上到下（top-down processing）和從下到上（bottom-up processing）的處理過程。那么二者之間有什么區別呢？
Top-Down Processing
Top-down processing is defined as the development of pattern recognition through the use of contextual information. For instance, you are presented with a paragraph written with difficult handwriting. It is easier to understand what the writer wants to convey if you read the whole paragraph rather than reading the words in separate terms. The brain may be able to perceive and understand the gist of the paragraph due to the context supplied by the surrounding words.
自上而下的處理過程被定義為：在模式識別的過程中使用了上下文信息。比如，當你看到了一張字跡潦草難以辨認的手寫文本時，你可以利用整個文本來輔助你理解其中含義，而不是每個字單獨辨認。正因為有了周圍字體的上下文信息，大腦可以去感知和理解文本里的意思。
注：
這個比較好理解了，比如學書法時看的字帖，其中有些字單獨看，很難明白其意思，但是如果連起來看，因為有先驗知識的存在，就相對容易理解了。比如正好是一個成語，三個字認識，其中一個不認識，如果知道了這個成語，那這個不認識的古漢字，對你而言也是可以辨認理解的。
Bottom-Up Processing
In the bottom-up processing approach, perception starts at the sensory input, the stimulus. Thus, perception can be described as data-driven. For example, there is a flower at the center of a person's field. The sight of the flower and all the information about the stimulus are carried from the retina to the visual cortex in the brain. The signal travels in one direction.
自下而上的處理可以理解為：將感應器結果作為輸入，也就是激勵。因此自下而上可以被描述為是數據驅動的。例如，在一個人的花園正中有一朵花兒，這個花兒的視覺和所有的激勵信息都從視網膜上通過視神經傳遞到大腦，然后大腦分析后得到圖像。這些信息的傳遞時單方向的。
注：
這個比較好理解了。