This is a presentation of my master thesis on the olfactory capacity of the spider monkey. More specifically, their sensitivity to aromatic aldehydes, a class of odorant with a pleasant floral scent.   All in all six different odorants were tested, bourgeonal, helional, lilial, canthoxal, cyclamal and 3-phenyl-propionic aldehyde (3-PPA), all of them with similar structures. Some of them, f ex. bourgeonal is used in the perfume industry, with its Lilly-of-the-Valley fragrance. In recent years it has also been discovered that bourgeonal elicits chemotaxis in human sperm cells.

Primates are often thought to be animals that rely more on their vision than their other senses. However, this does not mean that they do not have a sensitive nose.

By teaching them to discriminate between odors, their sensitivity can be assessed depending on when they no longer can discriminate between two samples.

Several factors affect the olfactory capacity of a species. Evolutionary history shapes the physiological characteristics such as brain structures and nasal structures with a varying number of receptors for reacting with odorant molecules. If high sensitivity to a smell has been beneficial to a species survival, their sensitivity to it will most likely be high. However, if the odorant is not beneficial to survival or absent in their environment, they may not be as sensitive.

Other studies have time and again showed that small changes in the molecular structure of an odorant molecule can greatly affect how sensitive an animal is to it. By using odorants with similar structures it is possible to investigate how much of an impact the changes have, and how the aromatic aldehydes compare to other classes tested.