Psychometrics of Odor Quality Discrimination: Method for Threshold Determination

Department of Psychology, Uppsala University, Box 1225, S-751 42 Uppsala, Sweden.
Chemical Senses (Impact Factor: 3.16). 11/2000; 25(5):493-9. DOI: 10.1093/chemse/25.5.493
Source: PubMed


There is no natural physical continuum for odor quality along which an odor quality discrimination (OQD) threshold can be measured. In an attempt to overcome this problem, the substitution-reciprocity (SURE) method defines a framework for the measurement of an OQD threshold. More specifically, it (i) defines a threshold concept for OQD, including the quantification of qualitative change of the stimulus, and (ii) suggests how to avoid perceived intensity as an unwanted cue for discrimination. In doing this, the psychometric properties of odor quality in the case of eugenol and citral are investigated using both discrimination (experiment 1) and scaling (experiment 2). Based on discriminatory responses, a change of approximately one-third in stimulus content was needed to reach the OQD threshold for eugenol and citral.

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Available from: William S. Cain, Mar 21, 2015
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    • "In the olfactory system, simultaneous presentation of two compounds in a 50:50 mixture generally evokes the same intensity as each single compound at 100% concentration. This is true even if both compounds are perceptually relatively different (Olsson and Cain, 2000, Boyle et al., 2009). In the gustatory system, however, a different picture emerges: binary taste mixtures consisting of two stimuli, which each evoke the same taste quality (e.g., sweet), may show effects of enhancement or suppression. "
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    Neuroscience 05/2011; 189:377-83. DOI:10.1016/j.neuroscience.2011.04.065 · 3.36 Impact Factor
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    • "In fact, the average rate of correct identification (i.e., naming) for a set of common odors (e.g., coffee, vanilla, tar) rarely exceeds 50%. Also, the most familiar item in a set does typically fall short of 100% correct identification (Engen 1991; de Wijk et al. 1995; Cain and Potts 1996; Herz and Engen 1996; Cain et al. 1998; Olsson and Cain 2000; Wise et al. 2000). Altogether, this olfactory " agnosia " mirrors the lack of importance of precise identification for the olfactory system and also suggests that verbal codes are not typically an aid to memory. "
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    • "For the mixtures of bourgeonal and undecanal, we employed one weaker and one stronger mixture series of 7 stimuli, each ranging from bourgeonal to an isointense undecanal over a 50/50 mixture (see Table 1). This mixing by substitution has previously been shown to produce roughly isointense series of mixtures (Olsson and Cain 2000; Boyle et al. 2009). The particular concentrations for the unmixed substances for the high and low series were chosen from the functions in Figure 1A–C. "
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