by Brendan Gwynn
The sense of smell can be powerful. While each of the senses can provide a nostalgic effect, research has shown that smell is perhaps the strongest of the five when it comes to triggering emotional memories.
You may recall a time when you passed somebody on the street whose deodorant reminded you of a past boyfriend or girlfriend. Perhaps a whiff of chlorine brings to mind swimming lessons from your youth. Maybe the smell of homemade bread makes you think of your mother baking.
Whatever your nostalgic scents are, they can produce vivid images in your mind that are directly connected to emotional memories.
Such an experience happened to Arthur Hasler in 1946, which not only triggered an emotional memory, but also led to a significant scientific discovery.
Hasler recalled: “As I hiked along a mountain trail in the Wasatch Range of the Rocky Mountains where I grew up, my reflections. . . were interrupted by wonderful scents that I had not smelled since I was a boy. So impressive was this odor that it evoked a flood of memories of boyhood chums and deeds long since vanished from my conscious memory.”
The association was so strong that Hasler quickly applied it to his field. He wondered if it was the answer to salmon homing, the phenomenon by which salmon wondrously return to their home stream to spawn after migrating to the ocean. Hasler hypothesized that specific scents from streams could be imprinted on the fish before they make their migration, which would then enable them to use olfactory memory to identify their home when returning from the sea.
After heading back to the University of Wisconsin where he was working as a professor, Hasler and zoology graduate student Warren Wisby went to work on the olfactory hypothesis. They ingeniously designed special tanks for the study, which were used to see if minnows could identify dilute solutions of chemicals and tell the difference between various lake waters.
The tests proved to be successful, supporting the idea that salmon were able to “home” using their sense of smell. Hasler and Wisby then needed to try their hypothesis in an actual river.
In 1953, the men traveled to the Seattle area, where they built two fish traps along the Issaquah Creek and its East Fork. They trapped 322 fish as they entered their native branch, plugging the nasal sacs of half of them with cotton to impair their olfactory sense and leaving the other half unplugged to act as controls. The men also tagged each fish to indicate which test group it belonged to and from which branch it had been caught. The fish were then taken one mile downstream, where they were released below the fork and allowed to continue their migration.
Afterward, the fish were recaptured and results were recorded, where Hasler noted that “all but 8 of 73 control fish returned to the branch where they were originally captured, [while] 28 out of the 70 fish that had been deprived of their sense of smell entered the wrong branch of the stream.”
The success of the field test was certainly worth noting, as it seemed to confirm the olfactory hypothesis among salmon. However, because their research had been done with adult fish, Hasler and Wisby were unsure if the outcomes truly related to long-term olfactory memory, or if the fish were simply relying on recent exposure prior to testing. In order to prove their theory, they realized they would need to work with both adult fish and smolts.
Unfortunately, the salmon required for the experiment were only found on the west coast, nearly 2,000 miles from where Hasler and Wisby were working in Wisconsin. The men decided to publish their plans, hoping that somebody else would take the reins and conduct the research. In spite of expressed interest from several professors and scientists, the experiment was never performed.
In the late 1960s, a miracle occurred when salmon were introduced into the Great Lakes to reduce the population of alewife (a species of fish). The fish required to complete the experiment were now in Hasler’s backyard.
Hasler took on the experiment with undergraduate assistant Al Scholz in 1968. The two men then worked on the project for 15 years, completing the experiment by publishing a book on imprinting and homing in salmon. They ultimately confirmed that salmon rely on long-term olfactory memory to find their way back to their birth stream.
In order to reach this conclusion, Hasler and Scholz exposed salmon smolts to synthetic chemicals (rather than home-stream odors) to determine if they would then be attracted to a stream or lake scented with that chemical as adults. After brief exposure, the smolts made their migration, returning to the lake scented with the chemical 18 months later. This confirmed that the smolts had been able to learn and remember the scent, using the sense of smell to return to their home.
Hasler’s efforts were significant not only because of his monumental discoveries, but also because of his great example of determination. Not surprisingly, the salmon homing finding was only one of Hasler’s many contributions to science.
Prior to his success in the scientific realm, Hasler attended and graduated from BYU. He was the recipient of the 1986 Alumni Achievement Award from the BYU College of Biology and Agriculture for his significant contributions in scientific research. Hasler’s story illustrates academic excellence and perseverance, which inspires students. As BYU students and faculty, we are honored to walk in the footsteps of so many impressive and influential alumni.