Where to draw the line?

We often take people's ability to understand and produce line drawings for granted. But where should we draw lines, and why? We address psychological principles that underlie efficient representations of complex information in line drawings. First, 58 participants with varying degree of artistic experience produced multiple drawings of a small set of scenes by tracing contours on a digital tablet. Second, 37 independent observers ranked the drawings by how representative they are of the original photograph. Matching contours between drawings of the same scene revealed that the most consistently drawn contours tend to be drawn earlier. We generated half-images with the most- versus least-consistently drawn contours and asked 25 observers categorize the quickly presented scenes. Observers performed significantly better for the most compared to the least consistent half-images. The most consistently drawn contours were more likely to depict occlusion boundaries, whereas the least consistently drawn contours frequently depicted surface normals.

The Do's and Don'ts of Psychophysical Methods for Interpretability of Psychometric Functions and Their Descriptors.

Many areas of research require measuring psychometric functions or their descriptors (thresholds, slopes, etc.). Data for this purpose are collected with psychophysical methods of various types and justification for the interpretation of results arises from a model of performance grounded in signal detection theory. Decades of research have shown that psychophysical data display features that are incompatible with such framework, questioning the validity of interpretations obtained under it and revealing that psychophysical performance is more complex than this framework entertains. This paper describes the assumptions and formulation of the conventional framework for the two major classes of psychophysical methods (single- and dual-presentation methods) and presents various lines of empirical evidence that the framework is inconsistent with. An alternative framework is then described and shown to account for all the characteristics that the conventional framework regards as anomalies. This alternative process model explicitly separates the sensory, decisional, and response components of performance and represents them via parameters whose estimation characterizes the corresponding processes. Retrospective and prospective evidence of the validity of the alternative framework is also presented. A formal analysis also reveals that some psychophysical methods and response formats are unsuitable for separation of the three components of observed performance. Recommendations are thus given regarding practices that should be avoided and those that should be followed to ensure interpretability of the psychometric function, or descriptors (detection threshold, difference limen, point of subjective equality, etc.) obtained with shortcut methods that do not require estimation of psychometric functions.

Influence of the wearable posture correction sensor on head and neck posture: Sitting and standing workstations.

BACKGROUND: Flexed head and neck postures are associated with the development of neck pain in the office environment. There is little evidence regarding whether a wearable posture sensor would improve the head and neck postures of office workers. OBJECTIVE: The aim of this study was to evaluate the effect of the wearable posture sensor on the posture and physical demands on the head and neck during office work. METHODS: Nineteen participants performed a typing task with and without the wearable sensor in the sitting and standing positions. They were allowed to adjust their workstation during the experiment based on a psychophysical method. The flexion angles of the head and neck, the gravitational moment on the neck, and the positions of the workstation components were measured. RESULTS: On average, participants with the wearable sensor had 8% lower neck flexion angles and 14% lower gravitational moments on the neck than those of participants without the wearable sensor. The effect of the wearable sensor on reducing postural stress of the neck was more significant when using the standing workstation compared to the sitting workstation. CONCLUSIONS: The wearable posture sensor could be an effective tool to alleviate the postural stress of the neck in the office setting.

The do's and don'ts of psychophysical methods for interpretability of psychometric functions and their descriptors

Many areas of research require measuring psychometric functions or their descriptors (thresholds, slopes, etc.). Data for this purpose are collected with psychophysical methods of various types and justification for the interpretation of results arises from a model of performance grounded in signal detection theory. Decades of research have shown that psychophysical data display features that are incompatible with such framework, questioning the validity of interpretations obtained under it and revealing that psychophysical performance is more complex than this framework entertains. This paper describes the assumptions and formulation of the conventional framework for the two major classes of psychophysical methods (single- and dual-presentation methods) and presents various lines of empirical evidence that the framework is inconsistent with. An alternative framework is then described and shown to account for all the characteristics that the conventional framework regards as anomalies. This alternative process model explicitly separates the sensory, decisional, and response components of performance and represents them via parameters whose estimation characterizes the corresponding processes. Retrospective and prospective evidence of the validity of the alternative framework is also presented. A formal analysis also reveals that some psychophysical methods and response formats are unsuitable for separation of the three components of observed performance. Recommendations are thus given regarding practices that should be avoided and those that should be followed to ensure interpretability of the psychometric function, or descriptors (detection threshold, difference limen, point of subjective equality, etc.) obtained with shortcut methods that do not require estimation of psychometric functions

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[Assessment of olfactory and gustatory function with validated tests]. / Beurteilung der chemosensorischen Funktion mit validierten Riech- und Schmecktests.

Approximately 5 % of the general population is affected by functional anosmia. An additional 15 % exhibit decreased olfactory function. Many of these individuals ask ENT-doctors or neurologists for help. A cornerstone of the counselling process is the assessment of olfactory function. The aim of this work is to give a differentiated overview about the administration of commonly used psychophysical tests for olfactory and gustatory function including their normative data. The use of standardized, reliable and validated tools is mandatory to provide patients with state-of the-art counseling on treatment options.

Heartbeat counting is unrelated to heartbeat detection: A comparison of methods to quantify interoception.

Recent research has identified individual differences in interoceptive sensitivity as a key source of variation in action, cognition, and emotion. This research has relied heavily on a single method for assessing interoceptive sensitivity: the accuracy of counting heartbeats while at rest. The validity of this method was assessed here by comparing the heartbeat counting (HBC) performance of 48 individuals with their heartbeat detection (HBD) performance. The HBC task required participants to report the numbers of heartbeats counted during brief signaled periods and indexed cardioceptive accuracy by the difference between the numbers of reported and actual heartbeats. In the HBD task, participants indicated the temporal location of heartbeat sensations relative to the onset of ventricular contraction. On each trial, they judged whether heartbeat sensations were or were not simultaneous with brief tones presented at one of six fixed delays following R waves of the ECG. In this method, cardioceptive accuracy or precision was indexed by variability in the temporal locations, relative to the R wave, of tones judged to be simultaneous with heartbeat sensations. Although intratask correlations indicated that each method yielded reliable scores, intertask correlations showed that HBC scores were unrelated to HBD scores. These results, which indicate that heartbeat detection and heartbeat counting are distinct processes, raise important questions about the assessment of interoceptive sensitivity and the involvement of this attribute in the psychological processes that have been associated with it on the basis of their correlations with HBC performance.

Estimating Change in Tremor Amplitude Using Clinical Ratings: Recommendations for Clinical Trials.

Tremor rating scales are the standard method for assessing tremor severity and clinical change due to treatment or disease progression. However, ratings and their changes are difficult to interpret without knowing the relationship between ratings and tremor amplitude (displacement or angular rotation), and the computation of percentage change in ratings relative to baseline is misleading because of the ordinal nature of these scales. For example, a reduction in tremor from rating 2 to rating 1 (0-4 scale) should not be interpreted as a 50% reduction in tremor amplitude, nor should a reduction in rating 4 to rating 3 be interpreted as a 25% reduction in tremor. Studies from several laboratories have found a logarithmic relationship between tremor ratings R and tremor amplitude T, measured with a motion transducer: logT  =  α·R + ß, where α ≈ 0.5, ß ≈ -2, and log is base 10. This relationship is consistent with the Weber-Fechner law of psychophysics, and from this equation, the fractional change in tremor amplitude for a given change in clinical ratings is derived: (Tf-Ti)/Ti=10α(Rf-(Ri)-1, where the subscripts i and f refer to the initial and final values. For a 0-4 scale and α  =  0.5, a 1-point reduction in tremor ratings is roughly a 68% reduction in tremor amplitude, regardless of the baseline tremor rating (e.g., 2 or 4). Similarly, a 2-point reduction is roughly a 90% reduction in tremor amplitude. These Weber-Fechner equations should be used in clinical trials for computing and interpreting change in tremor, assessed with clinical ratings.

A Psychophysical Protocol to Develop Ergonomic Recommendations for Sitting and Standing Workstations.

OBJECTIVE: The aim of this study was to determine user self-selected setup for both sitting and standing computer workstations and identify major differences. BACKGROUND: No current ergonomic setup guideline for standing computer workstations is available. METHODS: Twenty adult participants completed four 45-min sessions of simulated office computer work with an adjustable sit-stand computer workstation. Placement and relative position of all workstation components, including a cordless mouse, a cordless keyboard, a height-adjustable desk, and a 22-inch monitor mounted on a mechanical-assisted arm were recorded during the four sessions, which alternated between sitting and standing for each session. Participants were interrupted four times within each session, and the workstation was "reset" to extreme locations. Participants were instructed to adjust the location to achieve the most comfortable arrangement and to make as many adjustments during the session to achieve this goal. RESULTS: Overall, users placed the keyboard closer to their body (sternum), set desk height lower than their elbow, and set the monitor lower relative to their eyes with a greater upward tilt while standing compared to sitting. During the 45-min sessions, the number of adjustments participants made became smaller and over the four sessions was consistent, suggesting the psychophysical protocol was effective and consistent. CONCLUSION: Users preferred different workstation setups for sitting and standing computer workstations. Therefore, future setup guidelines and principles for standing computer workstations may not be simply translated from those for sitting. APPLICATION: These results can serve as the first step toward making recommendations to establish ergonomic guidelines for standing computer workstation arrangement.

¿Son efectivos nuestros centros de reconocimiento médico valorando la aptitud psicofísica para permisos de conducción y licencias de armas? / Are our medical centres for fitness to drive and firearms licences effective?

Objetivos. Este artículo se propuso evaluar la efectividad de los centros de reconocimiento médico en la valoración de la aptitud psicofísica para permisos de conducción y licencias de armas, describiendo las diferencias observadas en sendas valoraciones. Método. Mediante un diseño transversal se tomó una muestra representativa de titulares de permisos de conducción y licencia de armas calificados como aptos en la provincia de Málaga durante 2014 (363 informes para permisos de conducción y 626 para licencia de armas), evaluando la concordancia de la aptitud psicofísica informada por los centros con los registros del Servicio Andaluz de Salud. Se estimó la proporción de dichos titulares que no reunirían los requisitos legales de aptitud, analizando el origen de las discordancias en relación con la información de la que dispusieron los centros. Resultados. Se estimó la discordancia en la valoración de la aptitud psicofísica para permisos de conducción en 15,4% (IC 95%: 12,0 a 19,4), proporción 2,7 veces mayor para licencias de armas (41,4%), relacionándose el origen de la discordancia con la información que dispuso el centro más que a la calificación realizada por estos. Conclusiones. Es limitada la efectividad de los centros en la valoración de la aptitud psicofísica para permisos de conducción y, especialmente, para licencias de armas. Podría mejorar con un mayor seguimiento de su actividad, disponiendo de personal sanitario con formación adecuada y acceso a los registros asistenciales de los solicitantes (AU)

Objectives. This article aimed to evaluate the effectiveness of medical centres in the assessment of medical fitness for driving and gun licences, as well as describing the differences between them. Method. Using a crossover design and a representative sample of holders of driving and firearms licences in the province of Malaga during 2014 (363 reports for driving licenses and 626 for firearms licenses), an assessment was made of fitness report issued by the centres by comparing it with the records of the Andalusian public health service. The proportion of those that would not meet the legal eligibility requirements was calculated. An analysis was made of the origin of the disagreements as regards the information made available by the centres. Results. The discordance in the assessment of fitness to drive was estimated as 15.4% (95% CI: 12.0 to 19.4), while for firearms licenses it was 2.7 times higher (41.4%). The origin of the discordance is related to the information provided to the centres, rather than the assessment made by them. Conclusions. The limited effectiveness of the centres in the assessment of fitness for driving and, especially, for firearms licenses, could be improved by increased monitoring of their activity, providing health workers with adequate training and access to healthcare records of applicants (AU)

Psychophysics and the anisotropy of time.

In psychophysics, experimental control over the presented stimuli is an important prerequisite. Due to the anisotropy of time, this prerequisite is not given in psychophysical experiments on time perception. Many important factors (e.g., the direction of perceived time flow) cannot be manipulated in timing experiments. The anisotropy of time is a peculiarity, which distinguishes the time dimension from other perceptual qualities. Here I summarize the anisotropy-related differences between the perception of time and the perception of other qualities. It is discussed to what extent these differences might affect results and interpretations in psychophysical experiments. In conclusion, I argue for a 'view from nowhen' on the psychophysical study of time perception.

The psychophysical assessment of odor valence: does an anchor stimulus influence the hedonic evaluation of odors?

Olfactory stimuli are experienced primarily in terms of their hedonic tone and the assessment of olfactory hedonic estimates is a prevalent task in scientific and industrial contexts. However, measuring conditions are poorly standardized. Our study aims to fill this gap, focusing on the influence of anchor stimuli on olfactory hedonic evaluations, frequency of anchor presentation, and temporal stability of results. In n = 31 subjects, hedonic estimates for the 16 odors of the Sniffin' Sticks identification task were assessed on a visual analog rating scale under 4 measuring conditions (nonanchor, pleasant anchor, neutral anchor, unpleasant anchor). To test for stability over time, n = 10 subjects were reassessed 2, 4, and 6 months after original testing. To analyze for possible effects of single versus repeated anchor presentation, n = 15 subjects were retested 2 months after the original session in a multiple anchor presentation format. Statistical analysis revealed significant differences between the 4 anchor conditions, thus highlighting the necessity of specifying assessment methods in scientific research. No significant differences between timepoints were observed, indicating a high temporal stability of olfactory hedonic evaluations, especially from timepoint T2 onward. No overall significant effects of single versus multiple anchor presentation were detected. Findings might help to further standardize testing procedures.

Reproducibility of psychophysics and electroencephalography during offset analgesia.

BACKGROUND: Offset analgesia (OA) is a pain-inhibiting mechanism, defined as a disproportionately large decrease in pain perception in response to a discrete decrease in noxious stimulus intensity. Hence, the aims were (1) to investigate whether psychophysics and electroencephalography (EEG) can be assessed simultaneously during OA and (2) to assess whether OA is reproducible within the same day as well as between different days. METHODS: Two separate studies investigated OA: Study I (13 healthy volunteers; seven men; 25.5 ± 0.65 years) aimed at determining the feasibility of recording psychophysics and EEG simultaneously during OA. Study II (18 healthy volunteers; 12 men; 34 ± 3.15 years) assessed reproducibility of OA in terms of psychophysics and EEG. Subjects were presented to a 30-s OA heat stimulus paradigm on the volar forearm and psychophysics, and EEG recordings were obtained throughout the procedure. Reproducibility was assessed within the same day and between different days, using intraclass correlation coefficients (ICCs). Additionally, the reproducible psychophysical parameters were correlated to relevant EEG frequency bands. RESULTS: Simultaneous recording of psychophysics and EEG affects the frequency distribution in terms of alpha suppression. Reproducibility was proven for the psychophysics and EEG frequency bands both within the same day (all ICCs > 0.62) and between different days (all ICCs > 0.66, except for the delta band). Correlations between psychophysics and EEG were found in the theta (4-8 Hz), alpha (8-12 Hz) and gamma (32-80 Hz) bands (all p < 0.01). CONCLUSION: OA is a robust and reproducible model for experimental pain research, making it suitable for future research.

Linking hypotheses underlying Class A and Class B methods.

Class A psychophysical observations are based on the linking hypothesis that perceptually distinguishable stimuli must correspond to different brain events. Class B observations are related to the appearance of stimuli not their discriminability. There is no clear linking hypothesis underlying Class B observations, but they are necessary for studying the effects of context on appearance, including a large class of phenomena known as "illusions." Class B observations are necessarily measures of observer bias (Fechner's "constant error") as opposed to Class A measures of sensitivity (Fechner's "variable error"). It is therefore important that Class B observations distinguish between response biases, decisional biases, and perceptual biases. This review argues that the commonly used method of single stimuli fails to do this, and that multiple-alternative forced choice (mAFC) methods can do a better job, particularly if combined with a roving pedestal.

A "view from nowhen" on time perception experiments.

Systematic errors in time reproduction tasks have been interpreted as a misperception of time and therefore seem to contradict basic assumptions of pacemaker-accumulator models. Here we propose an alternative explanation of this phenomenon based on methodological constraints regarding the direction of time, which cannot be manipulated in experimental settings. In two experiments, we demonstrate the influence of the direction of a dimensional change for pitch and brightness estimates. The results support the assumption that errors in time reproduction tasks do not reflect a systematic temporal misperception, but rather a methodological artifact. Implications for contemporary models of time perception are discussed.

Psychophysical and cerebral responses to heat stimulation in patients with central pain, painless central sensory loss, and in healthy persons.

Patients with central pain (CP) typically have chronic pain within an area of reduced pain and temperature sensation, suggesting an impairment of endogenous pain modulation mechanisms. We tested the hypothesis that some brain structures normally activated by cutaneous heat stimulation would be hyperresponsive among patients with CP but not among patients with a central nervous system lesion causing a loss of heat or nociceptive sensation with no pain (NP). We used H(2)(15)O positron emission tomography to measure, in 15 healthy control participants, 10 NP patients, and 10 CP patients, increases in regional cerebral blood flow among volumes of interest (VOI) from the resting (no stimulus) condition during bilateral contact heat stimulation at heat detection, heat pain threshold, and heat pain tolerance levels. Both patient groups had a reduced perception of heat intensity and unpleasantness on the clinically affected side and a bilateral impairment of heat detection. Compared with the HC group, both NP and CP patients had more hyperactive and hypoactive VOI in the resting state and more hyperresponsive and hyporesponsive VOI during heat stimulation. Compared with NP patients, CP patients had more hyperresponsive VOI in the intralaminar thalamus and sensory-motor cortex during heat stimulation. Our results show that focal CNS lesions produce bilateral sensory deficits and widespread changes in the nociceptive excitability of the brain. The increased nociceptive excitability within the intralaminar thalamus and sensory-motor cortex of our sample of CP patients suggests an underlying pathophysiology for the pain in some central pain syndromes.

Testing equivalence with repeated measures: tests of the difference model of two-alternative forced-choice performance

Solving theoretical or empirical issues sometimes involves establishing the equality of two variables with repeated measures. This defies the logic of null hypothesis significance testing, which aims at assessing evidence against the null hypothesis of equality, not for it. In some contexts, equivalence is assessed through regression analysis by testing for zero intercept and unit slope (or simply for unit slope in case that regression is forced through the origin). This paper shows that this approach renders highly inflated Type I error rates under the most common sampling models implied in studies of equivalence. We propose an alternative approach based on omnibus tests of equality of means and variances and in subject-by-subject analyses (where applicable), and we show that these tests have adequate Type I error rates and power. The approach is illustrated with a re-analysis of published data from a signal detection theory experiment with which several hypotheses of equivalence had been tested using only regression analysis. Some further errors and inadequacies of the original analyses are described, and further scrutiny of the data contradict the conclusions raised through inadequate application of regression analyses (AU)

Resolver problemas teóricos o empíricos requiere en ocasiones contrastar la equivalencia de dos variables usando medidas repetidas. El mero planteamiento de este objetivo supone un desafío para la lógica subyacente a los métodos de contraste de hipótesis estadísticas, que están diseñados para evaluar la magnitud de la evidencia contraria a la hipótesis nula y de ningún modo permiten evaluar la evidencia a favor de ella. En algunos contextos aplicados se ha abordado el problema utilizando métodos de regresión y contrastando la hipótesis de que la pendiente es 1 y la hipótesis de que la ordenada en el origen es 0 (o simplemente la primera de ellas cuando se fuerza la regresión «por el origen»). Este trabajo muestra que esa estrategia conlleva tasas empíricas de error tipo I muy superiores a las tasas nominales bajo cualquiera de los modelos de muestreo más comúnmente implicados en estudios de equivalencia. Como alternativa, se propone una estrategia basada tanto en pruebas tipo ómnibus que incluyen contrastes de medias y varianzas como en análisis sujeto a sujeto (cuando la situación lo permita). Un estudio de simulación con estas pruebas muestra que la tasa empírica de error tipo I se ajusta a la tasa nominal y que la potencia de los contrastes es adecuada. A modo de ilustración, se aplican estos contrastes para re-analizar los datos de un experimento psicofísico sobre detección de contraste que originalmente sólo fueron analizados mediante regresión por parte de los autores del estudio, pese a que todas las hipótesis consideradas implicaban equivalencia con medidas repetidas. Nuestro reanálisis permite una inspección más minuciosa de los datos que revela contradicciones entre las características empíricas de los datos y las conclusiones extraídas mediante la aplicación inadecuada de métodos de regresión. Los resultados de este re-análisis también invalidan las conclusiones extraídas en la publicación original (AU)

Bayesian adaptive estimation of the contrast sensitivity function: the quick CSF method.

The contrast sensitivity function (CSF) predicts functional vision better than acuity, but long testing times prevent its psychophysical assessment in clinical and practical applications. This study presents the quick CSF (qCSF) method, a Bayesian adaptive procedure that applies a strategy developed to estimate multiple parameters of the psychometric function (A. B. Cobo-Lewis, 1996; L. L. Kontsevich & C. W. Tyler, 1999). Before each trial, a one-step-ahead search finds the grating stimulus (defined by frequency and contrast) that maximizes the expected information gain (J. V. Kujala & T. J. Lukka, 2006; L. A. Lesmes et al., 2006), about four CSF parameters. By directly estimating CSF parameters, data collected at one spatial frequency improves sensitivity estimates across all frequencies. A psychophysical study validated that CSFs obtained with 100 qCSF trials ( approximately 10 min) exhibited good precision across spatial frequencies (SD < 2-3 dB) and excellent agreement with CSFs obtained independently (mean RMSE = 0.86 dB). To estimate the broad sensitivity metric provided by the area under the log CSF (AULCSF), only 25 trials were needed to achieve a coefficient of variation of 15-20%. The current study demonstrates the method's value for basic and clinical investigations. Further studies, applying the qCSF to measure wider ranges of normal and abnormal vision, will determine how its efficiency translates to clinical assessment.

Tests of rating models

The study reports empirical tests of Anderson’s, Haubensak’s, Helson’s, and Parducci’s rating models when two end anchors are used for rating. The results show that these models cannot predict the judgment effect called here the Dai Prà effect. It is shown that an extension of Anderson’s model is consistent with this effect. The results confirm the main contention of each model that ratings are linear measures of mental magnitude(AU)

The precision of temporal judgement: milliseconds, many minutes, and beyond.

The principle that the standard deviation of estimates scales with the mean estimate, commonly known as the scalar property, is one of the most broadly accepted fundamentals of interval timing. This property is measured using the coefficient of variation (CV) calculated as the ratio between the standard deviation and the mean. In 1997, John Gibbon suggested that different time measurement mechanisms may have different levels of absolute precision, and would therefore be associated with different CVs. Here, we test this proposal by examining the CVs produced by human subjects timing a broad range of intervals (68 ms to 16.7 min). Our data reveal no evidence for multiple mechanisms, but instead show a continuous logarithmic decrease in CV as timed intervals increase. This finding joins other recent reports in demonstrating a systematic violation of the scalar property in timing data. Interestingly, the estimated CV of circadian judgements fits onto the regression of decreasing CV, suggesting a link between short interval and circadian timing mechanisms.

Macular blood flow measured by blue-field entoptoscopy and Heidelberg retinal flowmetry: comparison of two techniques in type 1 diabetes women during pregnancy.

PURPOSE: This study compared macular capillary leucocyte velocity values measured with a psychophysical blue-field entoptic simulation (BFS) technique and confocal scanning laser Doppler flowmetry. METHODS: A cross-sectional study was performed where macular capillary leucocyte velocity was measured by BFS using an Oculix BFS-2000 V2.1 psychophysical system and by confocal scanning laser Doppler flowmetry using Heidelberg retinal flowmetry (HRF) in 35 type 1 diabetes women during the second trimester. RESULTS: The macular leucocyte velocities measured with BFS correlated significantly with the 50th percentile (r = 0.345, p = 0.042, n = 35, Spearman's non-parametric correlation), the 75th percentile (r = 0.432, p = 0.009) and the 90th percentile (r = 0.373, p = 0.027) of HRF flow values during the second trimester. However, there was no correlation between BFS velocity and the 25th percentile of HRF measurements. CONCLUSIONS: Blue-field simulation is known to be an experimental technique that provides a quantitative measure of flow in the perifoveal capillary network. By contrast, HRF imaging reflects quantitative, multispectral, objective and non-invasive measurements in a two-dimensional projection of a three-dimensional retinal capillary bed. Our study showed that BFS velocity was correlated with HRF values in a group of women with diabetes during pregnancy. The positive correlation between BFS and HRF values suggests that the psychophysical BFS and scanning laser-based HRF measure similar functions in the retina.