The following story provides an amusing, though costly example of the real-world importance of JNDs, in this case, for weight. During an extended stay in Italy, a man we know went to the grocery store, taking with him the shopping trolley (an opaque bag on wheels) provided in his rental apartment. Returning from the store, he thought he had taken all his purchases from the bag, but a small bottle of laundry detergent was still inside. The bottle was light enough that the man did not notice that the bag weighed a little more now than when it was empty, and it still “felt” empty when he wheeled it back to the store a few days later. On the second visit, he again used the trolley as a shopping cart, putting new items into it. So imagine his surprise and frustration when he put all those items on the checkout counter and discovered that they included the detergent he had purchased previously. There was no way that, with his minimal Italian language skills, he was going to be able to provide a description of Weber’s law to convince the store clerk that he had already paid for that item, so he ended up buying it twice.

A video found at this link provides an enjoyable and impressive example of illusory motion created by a very skilled drill team.

Here is a nice example of linear perspective in which more distant objects appear to converge toward a single point. It was taken in the hallway of a cruise ship.

Although commonly regarded as a less important sense, human olfaction has been underestimated. Humans can detect some odors better than other animals can, have relatively large olfactory bulbs (which seems to be important in olfactory ability) and the number of olfactory neurons does not vary as much across species as is the case with other physical features. Figures associated with these findings can be found in this article:

McGann, J. P. (2017). Poor human olfaction is a 19th-century myth. Science, 356(6338),
available here