Old-age deficits in the sense of smell as gauged by thresholds, magnitude matching, and odor identification

Twenty elderly subjects (70-90 years old) and 20 young control subjects (18-24 years old) underwent three kinds of olfactory testing: absolute thresholds to three odorants (d-limonene, iso-amyl butyrate, benzaldehyde), magnitude matching of these odorants to salt tastes, and odor identification of 30 common substances. For all three odorants elderly subjects' mean threshold significantly exceeded that of the young by about ninefold for d-limonene, about threefold for benzaldehyde, and about twofold for iso-amyl butyrate. These threshold differences predict approximate concentration differences necessary to arouse the same estimated odor strength above the threshold for the elderly and the young. Young subjects also scored better than the elderly in odor identification, even when subjects were given four alternatives from which to select the correct label. Unimpaired olfactory functioning is uncommon in the elderly; correlational tests show that as a group the young have better olfactory ability and show more interindividual uniformity.     

Variability of olfactory threshold and its role in assessment of aging

Olfactory thresholds of elderly persons (over 65 years) average one to two orders of magnitude higher than those of young adults (under 30 years). Past studies reveal enormous spreads (typically about three orders of magnitude) of individual thresholds within each age group and extensive overlap between the two groups—enough to question how typically decline in sensitivity characterizes the individual aged person. The present study shows that much of the observed overlap is misleading, because the brief threshold tests usually administered tend to exaggerate individual differences. A more representative assessment of an individual’s threshold (for 1-butanol) was achieved by averaging the thresholds from two to eight separate short tests, spread over 4 days. The spread of each group’s thresholds (12 young and 12 elderly subjects) narrowed strikingly as the number of tests averaged increased from one to four; further tests accomplished no additional narrowing of spread. Based on a single test, thresholds of young and elderly overlapped in the usual way; but based on four or more tests, thresholds of young and elderly overlapped little or not at all. The outcome (1) argues that decline in smell sensitivity seems to be, after all, a common feature of aging, and (2) sheds light on the sourcesof variability of sensory thresholds.     

Effect of masker level on infants’ detection of tones in noise

In adult listeners, the signal-to-noise ratio at masked threshold remains constant with increases in masker level over a wide range of stimulus conditions. This relationship was examined in 7-month-old infants by obtaining masked thresholds for .5- and 4-kHz tones presented in four levels of continuous masking noise. Adults were also tested for comparison. Masker spectrum levels ranged from 5 to 35 dB/Hz for .5-kHz tones, and from ?5 to 25 dB/Hz for 4-kHz stimuli. Thresholds were determined for stimuli of both 10 and 100 msec in duration. The results indicated that infants’ performance was more adultlike for 4-kHz stimuli. Although mean thresholds for both 10- and 100-msec, 4-kHz tones were approximately 7 dB higher in infants than in adults, E/N₀ at threshold remained essentially constant over the 30-dB range of maskers employed. By contrast, infants’ thresholds for .5-kHz tones were exceptionally high at lower levels of the masker. Threshold E/N0 decreased significantly as masker level increased from 5 to 35 dB/Hz, and this decrease was significantly greater for 10- than for 100-msec stimuli. Temporal summation of .5-kHz tones, measured as the difference between thresholds obtained at the two signal durations, was greater for infants than for adults at low levels of the masker. However, because infants’ thresholds improved more rapidly with level for 10- than for 100-msec tones, age differences in temporal summation were no longer significant when masker spectrum level was 35 dB/Hz. These results suggest that the relationship between signal-to-noise ratio at masked threshold and level of the masker is dependent on both signal frequency and duration during infancy.     

Effect of masker level on infants' detection of tones in noise

In adult listeners, the signal-to-noise ratio at masked threshold remains constant with increases in masker level over a wide range of stimulus conditions. This relationship was examined in 7-month-old infants by obtaining masked thresholds for .5- and 4-kHz tones presented in four levels of continuous masking noise. Adults were also tested for comparison. Masker spectrum levels ranged from 5 to 35 dB/Hz for .5-kHz tones, and from -5 to 25 dB/Hz for 4-kHz stimuli. Thresholds were determined for stimuli of both 10 and 100 msec in duration. The results indicated that infants' performance was more adult-like for 4-kHz stimuli. Although mean thresholds for both 10- and 100-msec, 4-kHz tones were approximately 7 dB higher in infants than in adults, E/N0 at threshold remained essentially constant over the 30-dB range of maskers employed. By contrast, infants' thresholds for .5-kHz tones were exceptionally high at lower levels of the masker. Threshold E/N0 decreased significantly as masker level increased from 5 to 35 dB/Hz, and this decrease was significantly greater for 10- than for 100-msec stimuli. Temporal summation of .5-kHz tones, measured as the difference between thresholds obtained at the two signal durations, was greater for infants than for adults at low levels of the masker. However, because infants' thresholds improved more rapidly with level for 10- than for 100-msec tones, age differences in temporal summation were no longer significant when masker spectrum level was 35 dB/Hz. These results suggest that the relationship between signal-to-noise ratio at masked threshold and level of the masker is dependent on both signal frequency and duration during infancy.     

Interrelations of perceptual reports of smell,taste and irritance over the near-threshold range,for members of the N-aliphatic monohydric alcohol series

Many compounds are psychophysically complex because they stimulate all three chemical senses; smell, taste, and irritance.3 Interrelations among these three modalities are reported over the near-threshold range, and comparisons are made for three such compounds; methanol, ethanol, and propanol. Eighteen Ss were tested over 16 sessions each under a range of conditions: a combined task condition that approximated normal drinking, in which thresholds for all three modalities were determined simultaneously, and three conditions, in each of which only one threshold in one modality was determined. Pooled results over Ss gave significant shifts in olfactory thresholds between conditions, whereas changes in gustatory and irritant acuity were less marked. Individual results yielded significant correlations between psychophysical behavior and personality measures. Factor analysis of Ss indicated the existence of subgroups of Ss, each typified by different patterns of relative sensitivity over modalities and over alcohols.     

In defense of the right and left audiograms: a reply to Coren (1989) and Coren and Hakstian (1990)

Coren (1989) noticed that the various air-conduction pure-tone thresholds obtained from one ear of an individual in quiet tend to display a high correlation. In addition, Coren and Hakstian (1990) reported a consistently high correlation between pure-tone thresholds in the two ears of the same individual. On the basis of these observations, these authors proposed that pure-tone thresholds measured at audiometric frequencies in one ear, and those measured in both ears of an individual, be collapsed into a single average threshold value. The present paper disputes the usefulness and the appropriateness of such a proposal.     

Effect of stimulus duration on stereo and vernier displacement thresholds

Stereo and vernier thresholds were determined as a function of stimulus duration in both misalignment and displacement paradigms. All four thresholds increase as stimulus duration decreases. The increase is greatest for the stereo displacement threshold, less for the vernier displacement threshold, and least for the misalignment thresholds. The results are consistent with the hypothesis that depth signals are averaged over time.     

Tracking of nociceptive thresholds using adaptive psychophysical methods

Psychophysical thresholds reflect the state of the underlying nociceptive mechanisms. For example, noxious events can activate endogenous analgesic mechanisms that increase the nociceptive threshold. Therefore, tracking thresholds over time facilitates the investigation of the dynamics of these underlying mechanisms. Threshold tracking techniques should use efficient methods for stimulus selection and threshold estimation. This study compares, in simulation and in human psychophysical experiments, the performance of different combinations of adaptive stimulus selection procedures and threshold estimation methods. Monte Carlo simulations were first performed to compare the bias and precision of threshold estimates produced by three different stimulus selection procedures (simple staircase, random staircase, and minimum entropy procedure) and two estimation methods (logistic regression and Bayesian estimation). Logistic regression and Bayesian estimations resulted in similar precision only when the prior probability distributions (PDs) were chosen appropriately. The minimum entropy and simple staircase procedures achieved the highest precision, while the random staircase procedure was the least sensitive to different procedure-specific settings. Next, the simple staircase and random staircase procedures, in combination with logistic regression, were compared in a human subject study (n = 30). Electrocutaneous stimulation was used to track the nociceptive perception threshold before, during, and after a cold pressor task, which served as the conditioning stimulus. With both procedures, habituation was detected, as well as changes induced by the conditioning stimulus. However, the random staircase procedure achieved a higher precision. We recommend using the random staircase over the simple staircase procedure, in combination with logistic regression, for nonstationary threshold tracking experiments.     

Sex differences and personality factors in responsivity to pain

This study investigated the relationship between measured levels of masculinity-femininity, social desirability, and responsivity to pain in men and women. The literature suggests that the two personality variables might provide an explanation for the common findings of higher pain thresholds and tolerances in men than in women. A significant interaction was found between masculinity-femininity and sex for pain thresholds. Analysis of this interaction indicated that for men, but not women, there was a significant correlation between masculinity-femininity and pain, where higher masculinity was associated with higher pain thresholds. However, this finding did not account for the sex difference in pain threshold. The sex of the subject remained a significant predictor of both pain thresholds and tolerances after allowing for the influence of masculinity-femininity, social desirability, and their associated interactions.     

Olfactory detection thresholds in man under conditions of rest and exercise

Detection thresholds for seilen odorants were measured under conditions of rest and exercise. The test panel comprised six males with previous experience in odor detection. Exercise was maintained constant by using a modified bicycle positioned within the context of an air-dilution olfactometer. The effects of exercise were idiosyncratic for Ss: odor sensitivity was increased in some Ss, decreased in some, and not changed in others. Results of these experiments are discussed in terms of intra-subject variance within sessions and from session to session. In addition, two test techniques—one a fixed series and the other a tracking procedure—were evaluated for rapid estimation of an odor threshold. The tracking procedure facilitated prompt detection of changes in sensitivity for individual Ss.     

Manifest anxiety and two-point threshold sensitivity.

The present study utilized 27 college students (14 females, 13 males) to investigate the effects of anxiety upon the ability to attend to detail (two-point threshold sensitivity). It was hypothesized that subjects both low and high in anxiety would have a smaller threshold than mild or moderately anxious subjects. A curvilinear correlation of .83 (p less .01) was obtained between anxiety scores and two-point threshold sensitivity. There was no significant difference between mean thresholds for those scoring above or below the median on the anxiety scale. Suggestions for further research are discussed.     

A comparison of thresholds for 1/3-octave filtered clicks and noise bursts in infants and adults

Behavioral thresholds of 6-month-old infants and adults were determined for 1/3-octave filtered clicks and 300-msec noise bursts with center frequencies ranging from .5 to 8 kHz. For noise bursts, differences between infant and adult thresholds were largest at low frequencies and smallest at 8 kHz. For clicks, infants’ thresholds were most like adults’ at 4 kHz, and age differences increased at both lower and higher frequencies. Differences between click and noise thresholds were significantly larger for infants than for adults at .5, 1, and 8 kHz, but not at 2 and 4 kHz. These results suggest that improvements in threshold for long-duration stimuli during infancy may not be accompanied by comparable changes in threshold at short durations. The delayed development of sensitivity to low- and high-frequency clicks appears consistent with maturational trends recently described for the auditory brainstem response.     

Spectral, intensive, and temporal factors influencing overshoot

Threshold was measured for a 10-msec, 4.0-kHz signal presented near the onset or in the temporal centre of a 400-msec noise masker. Overshoot, the difference (in dB) between these two thresholds, was seen only for masker bandwidths wider than a critical band. The threshold near masker onset, and hence overshoot, could be reduced by the presence of an additional noise that was presented continuously or gated on and off prior to masker onset. The spectral, intensive, and temporal properties of this effect were studied. When the additional noise was continuous and either bandpass filtered with a variable bandwidth or notch filtered with a variable notchwidth, the results indicated that energy both near and remote from the signal frequency contributed to the reduction in overshoot. The effect of this additional noise was highly dependent upon its relative level. When the additional noise was 400 msec in duration and the delay between its offset and the onset of the masker was varied, overshoot “recovered” to its maximum value within about 50 msec. Finally, as the duration of the additional noise was varied from 3 to 400 msec while the time between its offset and masker onset was fixed, the reduction in overshoot was virtually complete for durations of about 25-50 msec. The results are consistent with the notion that overshoot at least partly reflects peripheral adaptation, and that this adaptation is not restricted to the signal frequency channel but, rather, extends in both directions over several channels.     

Odor intensity: Differences in the exponent of the psychophysical function

A series of five experiments showed that there are reliable differences among the exponents of the psychophysical power functions for odorants. There was virtually a perfect rank-order correlation between the size of the exponent and the water-solubility of the odorants. The exponents for odorants that are completely soluble in water (n-propanol and acetone) were approximately 2.5 times the size of the exponents for odorants that are insoluble in water (n-octanol and geraniol). For n-aliphatic alcohols, the size of the exponent and solubility in water decrease as a function of carbon chain-length. Although the exponents were higher when the stimuli were delivered with an air-dilution olfactometer than when they were sniffed from cotton swabs, the relative values among odorants were independent of the method of stimulus presentation.     

Size of critical band in infants, children, and adults

Masked thresholds at two signal frequencies (0.8 and 4 kHz) were obtained from listeners aged 6.5 months, 2 years, 5 years, and 20.5 years in the presence of constant spectrum level, narrowband maskers of differing bandwidths. Consistent with the classical results of Fletcher (1940), masked threshold for all age groups increased with bandwidth up to a critical width, beyond which further increases in bandwidth were ineffective in increasing threshold. These critical widths (estimates of critical band size) did not change substantially with age (critical widths for infants were no more than 50% larger than those of adults) despite substantial changes in masked thresholds with age. Thus, contrary to previous claims, changes in auditory filter width cannot account for developmental changes in masked or absolute thresholds.     

Comparison of the methods of limits and electrodermal response for determination of lingual vibrotactile thresholds.

Lingual vibrotactile thresholds were obtained from 30 adult Ss by the method of limits and operant conditioning of the electrodermal response. Sensitivity of the tongue was measured at 250 Hz. Comparisons of lingual threshold data showed that thresholds obtained by the method of limits were significantly lower than those obtained by the electrodermal response technique. There was a moderate positive correlation between methods however, indicating a substantial relationship. It was concluded that consistent lingual vibrotactile indexes of sensitivity can be obtained using an electrodermal response approach.     

Olfactory working memory: exploring the differences in n-back memory for high and low verbalisable odorants

ABSTRACT

We describe four experiments each examining n-back performance for high and low verbalisable odorants. Participants were presented with a sequence of odorants and were required to state if the current odorant was the same or different to the odorant presented two items earlier. Experiment 1 reported superior performance for high, relative to low, verbalisable odorants and was evident despite above-chance memory performance for the low verbalisable odorants. Experiment 2 showed that such superiority persisted with a concurrent articulation condition, suggesting that the memory benefit was not a consequence of verbal recording and rehearsal. Experiment 3 employed metacognitive judgments and showed that correct 2-back responses for high verbalisable odorants received more recollection responses compared to low verbalisable odorants. Experiment 4 compared n-back performance across different stimulus types and showed that, for high verbalisable odorants, performance correlated with both letters and abstract shapes, but such correlations were absent for low verbalisable odorants. Taken together, these findings show differences in n-back performance between high and low verbalisable odorants, and show that high verbalisable odorants exhibit performance similarities with both verbal and visual stimuli. We further argue that n-back performance for low verbalisable odorants operates differently to that of high verbalisable odorants.     

Decrements in olfactory sensitivity due to ozone exposure.

Approximate olfactory thresholds were determined in an exploratory study in which subjects were exposed to ozone (O3). The odorants were butyl alcohol (BA) and acetic acid (AA). Preliminary data suggest (1) temporary increases in thresholds due to O3 exposure, (2) diminution of O3 effects with repeated exposures, and (3) greater and more reliable effects for BA than for AA.     

Auditory threshold,signal-to-noise ratio and signal detection theory

The use of Signal Detection Theory has demonstrated that there is not an auditory threshold at the level supposed by classical psychophysics, but has not disproved the existence of an auditory threshold at a lower level. Following the recommended signal detection theory procedure fairly closely, an experiment obtained evidence either of the existence of a signal-to-noise ratio audi tory threshold, or a nonlinear relationship between stimulus and response which could not be statistically distiguished from such a threshold , Using the same apparatus and subjects, audi tory thresholds were also obtained using the classical method of limits. The acoustic pressure for the classical thresholds was about five times as great as for the signal detection theory method.     

Alone but feeling no pain: Effects of social exclusion on physical pain tolerance and pain threshold, affective forecasting, and interpersonal empathy

Prior findings of emotional numbness (rather than distress) among socially excluded persons led the authors to investigate whether exclusion causes a far-reaching insensitivity to both physical and emotional pain. Experiments 1-4 showed that receiving an ostensibly diagnostic forecast of a lonesome future life reduced sensitivity to physical pain, as indicated by both (higher) thresholds and tolerance. Exclusion also caused emotional insensitivity, as indicated by reductions in affective forecasting of joy or woe over a future football outcome (Experiment 3), as well as lesser empathizing with another person's suffering from either romantic breakup (Experiment 4) or a broken leg (Experiment 5). The insensitivities to pain and emotion were highly intercorrelated.