Cognitive Enhancement through Stimulation of the Chemical Senses (2005)

Finding a non-pharmacological adjunct to enhance cognitive processing in humans would be beneficial to numerous individuals. Past research has consistently noted a significant interplay between odors and human behavior; for example, the administration of particular odorants enhances athletic performance, mood, and sleep quality. In addition, odorants have a differential effect on human behavior, dependent upon route of administration (retronasal vs. orthonasal). The following study examined the differential effects of odorants on cognition based upon route of administration. During Phase I, 31 participants completed cognitive tasks on a computer-based program (Impact[c]) under five chewing gum conditions (no gum, flavorless gum, peppermint gum, cinnamon gum, and cherry gum). During Phase II, 39 participants completed the cognitive tasks under four odorant conditions (no odor, peppermint odor, jasmine odor, and cinnamon odor). Results revealed a task-dependent relationship between odors and the enhancement of cognitive processing. Specifically, cinnamon, administered retronasally and orthonasally, improved participants' scores on tasks related to attentional processes, virtual recognition memory, working memory, and visual-motor response speed. Implications are discussed in relation to providing a non-pharmacological adjunct to enhance cognition in the elderly, individuals with test-anxiety, and those with symptoms of dementia. Finding a non-pharmacological adjunct to enhance cognitive processes in humans would be both groundbreaking and readily accepted by society. Attempting to enhance cognitive processing by such measures could ultimately reduce a person's perceived cognitive effort for a task, while still allowing for an enhancement of his or her overall performance on that task. Since pleasant odors induce positive affective reactions, some have argued that the mere presence of such odors may also lead to cognitive, social, psychological, physiological, and physical performance enhancements, and evidence does exist to support this position. For example, Knasko (1992) found that a lemon odor led to fewer reports of health symptoms, and Rottman (1989) noted that jasmine odor enhanced individuals' performance on problem-solving tasks and led the participants to indicate higher levels of interest and motivation to the task. Raudenbush, Koon, Meyer, and Flower (2002a) found that peppermint odor reduced ratings of pain over time and increased participants' overall pain tolerance, as measured by a cold pressor test. Participants also reported reduced mental, physical, and temporal workload requirements, lower effort and frustration, and increased performance and vigor in the presence of peppermint odor. Peppermint odor significantly increased oxygen saturation and blood pressure, providing evidence for its ability to physiologically arouse the human body. Raudenbush, Meyer, and Eppich (2002b) found that during a treadmill stress test peppermint odor reduced measures of workload, effort, fatigue, and frustration, while increasing self-evaluated performance and vigor. Raudenbush, Corley, and Eppich (2001) found peppermint odor increases running speed, handgrip strength, and the number of push-ups performed during a physical workout session. Despite the numerous reports that support the notion of odor-enhanced performance, however, some research has revealed the converse. For instance, research has shown that the presence of a pleasant lavender odor significantly undermines the performance of working memory, reaction time for memory and attention based tasks, and arithmetic reasoning (Ludvigson & Rottman, 1989; Moss, Cook, Wesnes, & Duckett, 2003). Thus, it would seem that it is not the mere presence of a pleasant odor that enhances performance, but rather something specific to the odorant itself. Recent research has compared the effects of orthonasal and retronasal odorants on human behavior. …