Rapid Estimation of Gustatory Sensitivity Thresholds with SIAM and QUEST

Adaptive methods provide quick and reliable estimates of sensory sensitivity. Yet, these procedures are typically developed for and applied to the non-chemical senses only, i.e., to vision, audition, and somatosensation. The relatively long inter-stimulus-intervals in gustatory studies, which are required to minimize adaptation and habituation, call for time-efficient threshold estimations. We therefore tested the suitability of two adaptive yes-no methods based on SIAM and QUEST for rapid estimation of taste sensitivity by comparing test-retest reliability for sucrose, citric acid, sodium chloride, and quinine hydrochloride thresholds. We show that taste thresholds can be obtained in a time efficient manner with both methods (within only 6.5 min on average using QUEST and ~9.5 min using SIAM). QUEST yielded higher test-retest correlations than SIAM in three of the four tastants. Either method allows for taste threshold estimation with low strain on participants, rendering them particularly advantageous for use in subjects with limited attentional or mnemonic capacities, and for time-constrained applications during cohort studies or in the testing of patients and children

Nonlinear response speedup in bimodal visual-olfactory object identification

Multisensory processes are vital in the perception of our environment. In the evaluation of foodstuff, redundant sensory inputs not only assist the identification of edible and nutritious substances, but also help avoiding the ingestion of possibly hazardous substances. While it is known that the non- chemical senses interact already at early processing levels, it remains unclear whether the visual and olfactory senses exhibit comparable interaction effects. To address this question, we tested whether the perception of congruent bimodal visual-olfactory objects is facilitated compared to unimodal stimulation. We measured response times (RT) and accuracy during speeded object identification. The onset of the visual and olfactory constituents in bimodal trials was physically aligned in the first and perceptually aligned in the second experiment. We tested whether the data favored coactivation or parallel processing consistent with race models. A redundant-signals effect was observed for perceptually aligned redundant stimuli only, i.e., bimodal stimuli were identified faster than either of the unimodal components. Analysis of the RT distributions and accuracy data revealed that these observations could be explained by a race model. More specifically, visual and olfactory channels appeared to be operating in a parallel, positively dependent manner. While these results suggest the absence of early sensory interactions, future studies are needed to substantiate this interpretation

PsychoPy2: experiments in behavior made easy

PsychoPy is an application for the creation of experiments in behavioral science (psychology, neuroscience, linguistics, etc.) with precise spatial control and timing of stimuli. It now provides a choice of interface; users can write scripts Python if they choose, while those that prefer to construct experiments graphically can use the new Builder interface. Here we describe the features that have been added over the last 10 years of its development. The most notable addition has been that Builder interface, allowing users to create studies with minimal or no programming, while also allowing the insertion of Python code for maximal flexibility. We also present some of the other new features, including further stimulus options, asynchronous timestamped hardware polling, and better support for open science and reproducibility. Tens of thousands of users now launch PsychoPy every month and more than 90 people have contributed to the code. We discuss the current state of the project, as well as plans for the future

Rapid Estimation of Gustatory Sensitivity Thresholds.

The ability to taste enables detection of nutrients and toxins in the oral cavity and is therefore a crucial determinant for decisions as to whether to consume or reject a food. The assessment of taste function is pertinent to identify selective (for one taste) or generalized (for all tastes) taste impairment, as it may lead to deviant eating behavior and malnutrition. Sensory sensitivity is a good measure of the overall function of a sensory system. It can be most efficiently assessed with adaptive algorithms that have been, however, methods (QUEST, SIAM, quickYes-No) to rapidly estimate taste thresholds for 4 basic taste qualities in a yes-no-task. We compared thresholds obtained with QUEST and SIAM (study 1) and QUEST and quickYes-No (study 2) using within-subject test-retest designs and assessed further QUEST thresholds (studies 3 and 4) resulting in an overall sample of N=163. Tastants were dilutions series of aqueous solutions of sodium chloride, quinine, sucrose, and citric acid presented via spray bottles to anterior taste bud fields. We found that gustatory thresholds can be obtained fastest with QUEST (Mean 6.5 min). All methods yield acceptable (SIAM) to good (quickYes-no, QUEST) test-retest correlations (0.4–0.8). Thresholds were highly correlated between QUEST and quickYes-No (r>0.63) indicating that the procedures measure similar perceptual properties. Notably, quickYes-No can detect fluctuations of the response criterion (at the expense of testing time). Our data indicate, however, that participants were able to maintain a relatively stable criterion even in QUEST through instructions alone. Together, the findings suggest that adaptive methods are suitable for the quick and reliable measurement of gustatory sensitivity

A bittersweet symphony: Evidence for taste-sound correspondences without effects on taste quality-specific perception

Music has been associated with taste and shown to influence the dining experience. We asked whether sound that is associated with taste affects taste perception of food. In two studies (study 1: N = 20, 13 women; study 2: N = 20, 17 women), participants evaluated the taste of cinder toffee while listening to either of two soundscapes associated with sweet and bitter taste, respectively, or no sound. In study 1, participants rated the taste on a visual‐analog scale (VAS) anchored with “bitter” and “sweet”, aiming to replicate a previous study (Crisinel et al., 2012). In contrast, four separate scales were used in study 2 to report the extent of bitter, sweet, sour, and salty taste to test whether taste qualities were influenced by sound differentially. Additionally, taste intensity and pleasantness were rated in both studies. Taste intensity was increased in the presence of a sound, while pleasantness was not affected. In study 1, sound shifted bitter‐sweet ratings in the direction of the congruent sound, i.e. samples tasted sweeter with “sweet” sound and more bitter with “bitter” sound, replicating Crisinel et al.'s (2012) results. However, this effect was abolished when a “no‐sound” control was included in the statistical model. Taste ratings in study 2 showed no effect of sound on any specific taste quality, suggesting that the influence of sound on taste in study 1 reflects an artifact of the scale rather than an actual shift in perception. Together, the data provide evidence for taste‐sound correspondences without effects on taste‐quality specific perception

Repeatability of Taste Recognition Threshold Measurements with QUEST and Quick Yes–No

Taste perception, although vital for nutrient sensing, has long been overlooked in sensory assessments. This can, at least in part, be attributed to challenges associated with the handling of liquid, perishable stimuli, but also with scarce efforts to optimize testing procedures to be more time-efficient. We have previously introduced an adaptive, QUEST-based procedure to measure taste sensitivity thresholds that was quicker than other existing approaches, yet similarly reliable. Despite its advantages, the QUEST procedure lacks experimental control of false alarms (i.e., response bias) and psychometric function slope. Variations of these parameters, however, may also influence the threshold estimate. This raises the question as to whether a procedure that simultaneously assesses threshold, false-alarm rate, and slope might be able to produce threshold estimates with higher repeatability, i.e., smaller variation between repeated measurements. Here, we compared the performance of QUEST with a method that allows measurement of false-alarm rates and slopes, quick Yes–No (qYN), in a test–retest design for citric acid, sodium chloride, quinine hydrochloride, and sucrose recognition thresholds. We used complementary measures of repeatability, namely test–retest correlations and coefficients of repeatability. Both threshold procedures yielded largely overlapping thresholds with good repeatability between measurements. Together the data suggest that participants used a conservative response criterion. Furthermore, we explored the link between taste sensitivity and taste liking or which we found, however, no clear association

Estimation of Olfactory Sensitivity Using a Bayesian Adaptive Method

The ability to smell is crucial for most species as it enables the detection of environmental threats like smoke, it fosters social interactions, and it contributes to the sensory evaluation of food and eating behavior. The high prevalence for smell disturbances throughout the life span call for a continuous effort to improve tools for the quick and reliable assessment of the ability to smell. Odor-dispensing pens, called Sniffin' Sticks, are an established tool to test olfactory function. We tested the suitability of a Bayesian adaptive algorithm (QUEST) to estimate olfactory sensitivity using Sniffin' Sticks by comparing its results with those obtained via the established standard protocol, which relies on a staircase procedure. Thresholds were measured according to both procedures in two sessions (Test and Retest). The staircase successfully yielded threshold estimates in more cases than QUEST. Yet, Test-Retest correlations showed stronger reliability for QUEST (ρ = 0.70) than for staircase thresholds (ρ = 0.50). A strong correlation (ρ = 0.80) between the results of both procedures indicated good validity of QUEST. We conclude that the QUEST procedure may offer quicker convergence and reduced testing time in some cases, but fail to yield a threshold estimate in others

Delta activity encodes taste information in the human brain

The categorization of food via sensing nutrients or toxins is crucial to the survival of any organism. On ingestion, rapid responses within the gustatory system are required to identify the oral stimulus to guide immediate behavior (swallowing or expulsion). The way in which the human brain accomplishes this task has so far remained unclear. Using multivariate analysis of 64-channel scalp EEG recordings obtained from 16 volunteers during tasting salty, sweet, sour, or bitter solutions, we found that activity in the delta-frequency range (1–4 Hz; delta power and phase) has information about taste identity in the human brain, with discriminable response patterns at the single-trial level within 130 ms of tasting. Importantly, the latencies of these response patterns predicted the point in time at which participants indicated detection of a taste by pressing a button. Furthermore, taste pattern discrimination was independent of motor-related activation and encoded taste identity rather than other taste features such as intensity and valence. On comparison with our previous findings from a delayed taste-discrimination task (Crouzet et al., 2015), taste-specific neural representations emerged earlier during this speeded taste-detection task, suggesting a goal-dependent flexibility in gustatory response coding. Together, these findings provide the first evidence of a role of delta activity in taste-information coding in humans. Crucially, these neuronal response patterns can be linked to the speed of simple gustatory perceptual decisions – a vital performance index of nutrient sensing