Written by Sandra Michels and the Research Committee
According to researchers Mahmut and Stevenson (2012) there is evidence to suggest that psychopathy may involve the dysfunction of specific areas of the frontal lobe of the brain, including the orbital frontal cortex (OFC) instead of a general frontal lobe deficit. It is thought that individuals higher in psychopathic traits have less effective OFC functioning.
One interesting fact about the OFC is that it is generally accepted that olfactory processing takes place in part in the OFC. When an individual comes in contact with volatile chemicals (odorants) the chemicals interact with olfactory receptor neurons (ORNs) in the nasal vault and information about the odorant travels from the ORNs to the olfactory bulb, then to the primary olfactory cortex, then on to the secondary olfactory cortex (an area in OFC). Previous research has shown that damage to the OFC area is associated with impaired odor discrimination, while showing no association with odor detection impairments. In turn, odor discrimination is needed for odor identification. Considering that psychopathy has been shown to be associated with dysfunction in the OFC and complex olfactory processing most likely involves the OFC, the researchers hypothesized that individuals scoring higher on psychopathic traits would be worse at identifying and discriminating odors, but not worse in odor detection.
Mahmud and Stevenson (2012) tested their hypotheses by administering the Self-Report Psychopathy Scale-4 (SRP-4) and the three Sniffin’ Sticks tests to a group of university students. The SRP-4 was used to measure psychopathic traits (interpersonal manipulation, callous affect, erratic lifestyle, and criminal tendencies) and the Sniffin’ Sticks tests were used to measure three different olfactory abilities, odor threshold, odor discrimination and odor identification. The Sniffin’ Sticks test used were: 1) an olfactory threshold test, which measures odor detection, that is, the lowest concentration of the odor n-butanol that a participant can perceive, 2) an odor discrimination test, which measures an individual’s ability to discriminate between odors by identifying a sample odor that has a different smell than two other sample odors and 3) an odor identification test, which measures an individual’s ability to identify 16 common odors, such as coffee and orange.
Results of the study were consistent with the researchers’ hypotheses, with participants’ SRP-4 total scores significantly predicting how they performed on the odor discrimination test and close to significant for the odor identification test. No association between SRP-4 total scores and odor threshold test scores was found, which makes sense because the process of perceiving an odor is carried out in the primary olfactory cortex located in the piriform cortex, not in the OFC.
Along with examining the predictability of participants’ SRP-4 total scores, the researchers also examined the predictability of participants’ scores on specific SRP-4 traits (traits related to specific components of psychopathy). A significant negative correlation was found between all four of the trait scores and odor discrimination test scores, but none of the trait scores uniquely predicted participants’ odor discrimination test scores. This finding indicates that it is something that is shared among the specific components that is important to this relationship. Also a significant negative correlation was found between scores for two of the traits, callous affect and erratic lifestyle, and odor identification test scores.
In general this study suggests that individuals with a higher degree of psychopathic traits will be worse at identifying and discriminating odors. Individuals characterized by callous affect may be particularly poor at identifying odors while at the same time still have the capacity to be able to detect odors (there were no differences in the odor detection threshold).
Reference: Mehmet, K., & Stevenson, R. J. (2012). Olfactory abilities and psychopathy: Higher psychopathy scores are associated with poorer odor discrimination and identification. Chemosensory Perception, 5, 300-307.
