Purpose
We aim to identify the possible sources for age-related differences in the perception of emotion in speech, focusing on the distinct roles of semantics (words) and prosody (tone of speech) and their interaction.
Method
We implement the Test for Rating of Emotions in Speech (
Ben-David, Multani, Shakuf, Rudzicz, & van Lieshout, 2016
). Forty older and 40 younger adults were presented with spoken sentences made of different combinations of 5 emotional categories (anger, fear, happiness, sadness, and neutral) presented in the prosody and semantics. In separate tasks, listeners were asked to attend to the sentence as a whole, integrating both speech channels, or to focus on 1 channel only (prosody/semantics). Their task was to rate how much they agree the sentence is conveying a predefined emotion.
Results
(a) Identification of emotions: both age groups identified presented emotions. (b) Failure of selective attention: both age groups were unable to selectively attend to 1 channel when instructed, with slightly larger failures for older adults. (c) Integration of channels: younger adults showed a bias toward prosody, whereas older adults showed a slight bias toward semantics.
Conclusions
Three possible sources are suggested for age-related differences: (a) underestimation of the emotional content of speech, (b) slightly larger failures to selectively attend to 1 channel, and (c) different weights assigned to the 2 speech channels.
Emotional prosody and semantics are separate but not separable channels, and it is difficult to perceive one without the influence of the other. Our findings indicate that the Test for Rating of Emotions in Speech can reveal specific aspects in the processing of emotional speech and may in the future prove useful for understanding emotion-processing deficits in individuals with pathologies.
Selective attention, an essential part of daily activity, is often impaired in people with Alzheimer's disease (AD). Usually, it is measured by the color-word Stroop test. However, there is no universal agreement whether performance on the Stroop task changes significantly in AD patients; or if so, whether an increase in Stroop effects reflects a decrease in selective attention, a slowing in generalized speed of processing (SOP), or is the result of degraded color-vision. The current study investigated the impact of AD on Stroop performance and its potential sources in a meta-analysis and mathematical modeling of 18 studies, comparing 637 AD patients with 977 healthy age-matched participants. We found a significant increase in Stroop effects for AD patients, across studies. This AD-related change was associated with a slowing in SOP. However, after correcting for a bias in the distribution of latencies, SOP could only explain a moderate portion of the total variance (25%). Moreover, we found strong evidence for an AD-related increase in the latency difference between naming the font-color and reading color-neutral stimuli (r2 = 0.98). This increase in the dimensional imbalance between color-naming and word-reading was found to explain a significant portion of the AD-related increase in Stroop effects (r2 = 0.87), hinting on a possible sensory source. In conclusion, our analysis highlights the importance of controlling for sensory degradation and SOP when testing cognitive performance and, specifically, selective attention in AD patients. We also suggest possible measures and tools to better test for selective attention in AD.
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