Puppy buyers are often misled that poor temperament is "just a fear period," or "all puppies do that," or "that's normal for this breeding" when in fact it is not "normal" for a pup to show protracted, chronic fearfulness of age-appropriate, common environmental stimuli. (As opposed to assaultive, injurious, or otherwise significantly traumatizing experiences, such as a rough mauling by another dog, which has a higher risk of imprinting a fearful association. Pain matters.)
... a 9-week-old pup shows fear and seizes up the first time it encounters, say, a reflective floor, and this fearful reaction persists unabated on the fifth, tenth, and twenty-third time the pup encounters this same floor -- heads up. This is not the emotional or cognitive wariness of novelty or the unknown as intended by the concept of "fear imprint period." This pup has experienced this non-life threatening stimulus many times, and the pup with well-balanced nerve and cognative function should by now be fully conditioned to co-exist fearlessly with that environmental element.
This is the area of temperamental weakness where we see the term "fear period" most commonly misunderstood and inappropriately applied. The chronically fearful youngster demonstrates a lack of capacity to intellectually categorize a benign environmental element (a reflective floor or the wind or the furnace vent or the toddling child or the wet grass or the car horn or the door closing or . . . .) as something that is not a threat to survival and therefore should not be feared. This pup fails to sequentially resolve and integrate the sensory encounter, even after repeated opportunities to do so. The stimulus is never successfully processed and categorized in the pup's brain as something "known" because of faulty cognitive function and insufficient association with and memory of prior life experience.