Detection models: Experimental tests with electrocutaneous stimuli

Contemporary psychophysical procedures were employed to determine the nature of the process for detecting rectangular electrical pulses delivered to the skin. Earlier experiments had shown that the somatosensory system is exceedingly responsive to small changes in the energy of an electrocutaneous stimulus, suggesting that sensory noise may be relatively unimportant in this modality. However, a rating scale study showed that both the high-threshold theory and Luce’s low-threshold theory cannot describe the detection process. The form of the ROC curve is consistent with a signal-detection model that assumes a greater variance for the signal plus noise distribution than for the noise distribution. Additional support for signal detection theory came from an experiment that examined the likelihood of a correct second choke when the first was incorrect in a four-alternative forced-choice paradigm. Therefore, the sensory excitation caused by internal noise can sometimes be greater than the excitation produced by an added stimulus. Electrocutaneous detection differs from auditory or visual in that d’ increases at a greater rate as stimulus intensity changes.     

Thresholds for detection and awareness of masked facial stimuli

It has been suggested that perception without awareness can be demonstrated by a dissociation between performance in objective (forced-choice) and subjective (yes–no) tasks, and such dissociations have been reported both for simple stimuli and more complex ones including faces. However, signal detection theory (SDT) indicates that the subjective measures used to assess awareness in such studies can be affected by response bias, which could account for the observed dissociation, and this was confirmed by Balsdon and Azzopardi (2015) using simple visual targets. However, this finding may not apply to all types of stimulus, as the detectability of complex targets such as faces is known to be affected by their configuration as well as by their stimulus energy. We tested this with a comparison of forced-choice and yes–no detection of facial stimuli depicting happy or angry or fearful expressions using a backward masking paradigm, and using SDT methods including correcting for unequal variances in the underlying signal distributions, to measure sensitivity independently of response criterion in 12 normal observers. In 47 out 48 comparisons there was no significant difference between sensitivity (d_a) in the two tasks: hence, across the range of expressions tested it appears that the configuration of complex stimuli does not enhance detectability independently of awareness. The results imply that, on the basis of psychophysical experiments in normal observers, there is no reason to postulate that performance and awareness are mediated by separate processes.     

A COGNITIVE THEORY OF PSYCHOPHYSICS. I

The fundamental premise of this paper is that subjects deal with stimulus information when performing psychophysical judgments. The coding strategy employed to manipulate this information depends upon the particular experimental procedure, which leads to unique psychophysical functions. Different methods impose different memory constraints upon the subject, thus producing a variety of sensitivity measures for the same stimulus attribute.     

Evidence of rapid recovery from perceptual odor adaptation using a new stimulus paradigm

By attenuating neural and perceptual responses to sustained stimulation, adaptation enhances the detection of new, transient stimuli. Disadaptation serves a similarly important role as a temporal filter for chemoreceptor cells, producing rapid recovery of sensitivity upon termination of the adapting odorant. Previous research from our laboratory indicated that a rapid form of odor adaptation can be measured using a novel, simultaneous-odorant paradigm. In the present study, we extended the earlier method by measuring recovery from adaptation. Perceptual odor adaptation was measured by estimating psychophysical detection thresholds in a group of college-aged student volunteers (N = 20; 12 females, eight males) for a self-adapting odorant, vanilla extract. To induce adaptation, the time between the onset of the adapting odorant and the onset of the target odorant was systematically varied. By first quantifying adaptation, recovery of sensitivity could therefore be investigated by using different time points following the termination of the adapting odorant. Consistent with our previous work, thresholds estimated in the presence of the simultaneous adapting odorant were significantly increased, reflecting a decrease in sensitivity due to adaptation. Conversely, approximately 100 ms following termination of the adapting stimulus (the briefest delay tested), sensitivity began to rapidly recover. Nevertheless, some residual adaptation was evident at the longest offset delay of 500 ms. These findings suggest that the recovery from adaptation proceeds at least as rapidly as the onset of adaptation, a finding that is consistent with physiological evidence from olfactory receptors. These data also suggest the effectiveness of this new odorant paradigm in characterizing the temporal characteristics underlying these critical olfactory mechanisms.     

Intensity resolution and subjective magnitude in psychophysical scaling

Several successful theories of psychophysical judgment imply that exponents of power functions in scaling tasks should covary with measures of intensity resolution such asd’ in the same tasks, whereas the prevailing metatheory of ideal psychophysical scaling asserts the independence of the two. In a direct test of this relationship, three prominent psychophysical scaling paradigms were studied: category judgment without an identification function, absolute magnitude estimation, and cross-modality matching with light intensity as the response continuum. Separate groups of subjects for each scaling paradigm made repeated judgments of the loudnesses of the pure tones that constituted each of two stimulus ensembles. The narrow- and wide-range ensembles shared six identical stimulus intensities in the middle of each set. Intensity resolution, as measured byd’-like distances, of these physically identical stimuli was significantly worse for the wide-range set for all three methods. Exponents of power functions fitted to geometric mean responses, and in magnitude estimation and cross-modality matching the geometric mean responses themselves, were also significantly smaller in the wide-range condition. The variation of power function exponents, and of psychophysical scale values, for stimulus intensities that were identical in the two stimulus sets with the intensities of other members of the ensembles is inconsistent with the metatheory on which modern psychophysical scaling practice is based, although it is consistent with other useful approaches to measurement of psychological magnitudes.     

Learning from Aesthetic Disagreement and Flawed Artworks

Disagreements about art are considered here for their potential to pose questions about reality beyond the artwork. The project of assessing artistic value is useful for bringing complex questions to light. The ambitiousness of the cognitive stock, in Richard Wollheim's term, that can be relevant to understanding an artwork may mean that confident evaluation will elude us. Thinking about artistic value judgment in this way shifts its centrality as the point of artistic interpretation and evaluation; the goal of judging a work's meaning and value is a useful tool for prompting us to understand a work. But if we fail to reach that goal, that does not mean we have failed to engage with the work appropriately. The artistic value judgment, and achieving consensus on that value, can be secondary in importance to grasping the problems a work poses that are not immediately resolvable. Examples drawn from literary and philosophical imagining, in the work of Grace Paley and Mary Mothersill, and from Toni Morrison's literary criticism are used to illustrate and support the fruitfulness of this approach.     

孤独症谱系障碍者基于运动线索的生命知觉

生命知觉是人们将客体自动加工为可以相互作用的生命体的认知过程。ASD者基于运动线索的生命知觉的研究方法包括追逐检测范式、运动特性参数化范式和因果知觉范例。其生命知觉的异常主要表现为运动信息整合能力不足、社会因果知觉缺陷以及对高复杂度运动的神经追踪较弱。相关理论假设从神经病理、认知加工及脑结构和功能障碍层面进行解释。未来应提升研究方法的生态效度,推进追踪与系统化研究,促进相关干预方案的开发。     

A COGNITIVE THEORY OF PSYCHOPHYSICS. II

The fundamental premise of this paper is that subjects code information in such a way that a variety of psychophysical functions can be obtained with the same stimulus attributes. Four terms must be defined in order to understand psychophysical equations. These terms are: (1) The subject's perceptual channel capacity, (2) the subject's cognitive channel capacity, (3) the experimenter's measure of stimulus information, and (4) the context variables associated with the psychophysical procedure.     

Some functional measurement procedures for determining the psychophysical law

Various statistical procedures are ieveloped for determining the psychophysical law within the context of a functional measurement approach to studying stimulus integration in perception. The specific results are limited to additive or multiplicative psychological laws, but the generalization to alternative cognitive algebras is evident. Estimation of parameters of the hypothesized psychophysical law and test of the hypothesis that the row psychophysical law is the same as the column psychophysical law in a two-factor stimulus design is considered for various possible psychophysicaldaws, including linear, polynomial, and power laws.     

Changes in absolute detection threshold and in subjective intensity of suprathreshold stimuli during olfactory adaptation and recovery

Olfactory adaptation and recovery to methyl isobutyl ketone at a concentration 10 times the absolute detection threshold (I_{t o}) was intensively studied in two human Ss. A combined psychophysical procedure was used that allowed comparisons of changes in threshold (I_t) with changes in the subjective intensity of suprathreshold stimuli. Information was also obtained on the effect of the adapting stimulus on the psychophysical power function for this odorant. A threshold detection procedure was used to estimate changes in I_t; an unstructured magnitude-estimation procedure was used to monitor changes in the subjective intensity of suprathreshold stimuli and the psychophysical power function. The data provided additional information on the behavioral course of olfactory adaptation and recovery and suggested that this combined method can be used profitably for further investigations of this kind. Complementary to the work of Cain and Engen (1969), the results suggested an increase in the exponent of the power function with increasing adaptation.     

The simultaneous chain: a new approach to serial learning

Recent advances have allowed the application of behaviorism's rigor to the control of complex cognitive tasks in animals. This article examines recent research on serially organized behavior in animals. 'Chaining theory', the traditional approach to the study of such behavior, reduces intelligent action to sequences of discrete stimulus-response units in which each overt response is evoked by a particular stimulus. However, such theories are too weak to explain many forms of serially organized cognition, both in humans and animals. By training non-human primates to produce arbitrary sequences that cannot be learned as chains of particular motor responses, the simultaneous chaining paradigm has overcome limitations of chaining theory in experiments on serial expertise, the use of numerical rules, knowledge of ordinal position, and distance and magnitude effects.     

Effects of audio-visual integration on the detection of masked speech and non-speech sounds

Integration of simultaneous auditory and visual information about an event can enhance our ability to detect that event. This is particularly evident in the perception of speech, where the articulatory gestures of the speaker's lips and face can significantly improve the listener's detection and identification of the message, especially when that message is presented in a noisy background. Speech is a particularly important example of multisensory integration because of its behavioural relevance to humans and also because brain regions have been identified that appear to be specifically tuned for auditory speech and lip gestures. Previous research has suggested that speech stimuli may have an advantage over other types of auditory stimuli in terms of audio-visual integration. Here, we used a modified adaptive psychophysical staircase approach to compare the influence of congruent visual stimuli (brief movie clips) on the detection of noise-masked auditory speech and non-speech stimuli. We found that congruent visual stimuli significantly improved detection of an auditory stimulus relative to incongruent visual stimuli. This effect, however, was equally apparent for speech and non-speech stimuli. The findings suggest that speech stimuli are not specifically advantaged by audio-visual integration for detection at threshold when compared with other naturalistic sounds.     

The psychometric function: I. Fitting, sampling, and goodness of fit.

The psychometric function relates an observer's performance to an independent variable, usually some physical quantity of a stimulus in a psychophysical task. This paper, together with its companion paper (Wichmann & Hill, 2001), describes an integrated approach to (1) fitting psychometric functions, (2) assessing the goodness of fit, and (3) providing confidence intervals for the function's parameters and other estimates derived from them, for the purposes of hypothesis testing. The present paper deals with the first two topics, describing a constrained maximum-likelihood method of parameter estimation and developing several goodness-of-fit tests. Using Monte Carlo simulations, we deal with two specific difficulties that arise when fitting functions to psychophysical data. First, we note that human observers are prone to stimulus-independent errors (or lapses). We show that failure to account for this can lead to serious biases in estimates of the psychometric function's parameters and illustrate how the problem may be overcome. Second, we note that psychophysical data sets are usually rather small by the standards required by most of the commonly applied statistical tests. We demonstrate the potential errors of applying traditional chi2 methods to psychophysical data and advocate use of Monte Carlo resampling techniques that do not rely on asymptotic theory. We have made available the software to implement our methods.     

Simplicity versus likelihood in visual perception: from surprisals to precisals

The likelihood principle states that the visual system prefers the most likely interpretation of a stimulus, whereas the simplicity principle states that it prefers the most simple interpretation. This study investigates how close these seemingly very different principles are by combining findings from classical, algorithmic, and structural information theory. It is argued that, in visual perception, the two principles are perhaps very different with respect to the viewpoint-independent aspects of perception but probably very close with respect to the viewpoint-dependent aspects which, moreover, seem decisive in everyday perception. This implies that either principle may have guided the evolution of visual systems and that the simplicity paradigm may provide perception models with the necessary quantitative specifications of the often plausible but also intuitive ideas provided by the likelihood paradigm.     

The effect of stimulus delivery technique on perceived intensity functions for taste stimuli: Implications for fMRI studies

Classic psychophysical studies have provided significant information on the psychophysical functions for taste stimuli. With the advent of fMRI, studies are being conducted that provide insight into central processing of gustation in humans. However, fMRI experiments impose physical limitations on stimulus delivery. In the present study, we compared psychophysical functions relating perceived intensity to concentration, derived from previous studies that used the traditional sip-and-spit and dorsal flow delivery techniques, to psychophysical functions generated in this study using a simulated stimulus delivery technique (SSDT). The SSDT delivered minute quantities of taste stimuli to the dorsal surface of the tongue, just as in an fMRI scanner. As was hypothesized, the results indicated that slopes of intensity functions were dependent on the type of stimulus delivery technique. The SSDT resulted in slopes that were more similar to those generated by dorsal flow than by sip-andspit stimulus delivery techniques, suggesting the importance of considering the influence of stimulus delivery on psychophysical response in designing and interpreting experiments.     

Synchronous Information Presented in 40-Hz Flicker Enhances Visual Feature Binding

Recent neurophysiological studies have encouraged speculation that the synchronization of spatially distributed neural assemblies (at around 40 Hz in the neocortex) is responsible for the binding of discrete stimulus components into coherent wholes during visual object perception. Using a novel paradigm, we demonstrated specific figural priming under 40-Hz stimulus modulation conditions. Further, under these conditions, observers were not aware of the prime"s existence, nor did the prime act as a stimulus-driven attentional cue. These findings provide the first psychophysical support for a theory of preattentive coding of visual objects, based on an externally entrained and thereby synchronized 40-Hz feature-binding mechanism.     

The magical number seven: Making a “bit” of “sense”

The maximum number of categories distinguishable in making an absolute judgment was estimated by Miller to be “seven plus or minus two,” corresponding to about 3 bits of information transmitted per stimulus. Later work extended this range to include at least 2 to 4 bits of information, which reached 16 categories. In contrast, the number of distinguishable differences between two stimuli is in the order of 100. Why is this so? It is shown here that an answer to these questions can be obtained by constructing anentropy function, Hs, which is a measure of the uncertainty of a subject (or a sensory receptor) as it perceives the magnitude of an applied stimulus. Using this function, it is demonstrated that the ubiquitous 3 bits of information per stimulus can be approximated from the expression \(\log _2 \sqrt {{{\tau _2 } \mathord{\left/ {\vphantom {{\tau _2 } {\tau _1 }}} \right. \kern-0em} {\tau _1 }}} \) , where τ₁ and τ₂ are known time constants. The same entropy function can be used to derive various other psychophysical laws, such as the Weber-Fechner law, Stevens’ law, and the Bunsen-Roscoe law.     

The selective action of Cfunc control

According to relational frame theory Cfunc stimuli select which stimulus properties are transformed via derived stimulus relations. To date there has been no demonstration of the selective action of Cfunc control. We provide an analysis of the requirements for such a demonstration, and describe the results from four experiments employing a paradigm consistent with these requirements. We employed a paradigm based on virtual car races. The paradigm had two components: i) a sample racecar screen which showed the performance of a sample racecar, and used experimentally engineered symbols to communicate how the performance of each real racecar would compare with that of the sample racecar, and ii) a car race screen showing other racecars race. Two symbols were established as Crels for the relations of same and different, and two symbols were established as Cfuncs for the functional properties of speed and direction. The results from these experiments demonstrate Cfunc stimuli can select which functions transform via derived stimulus relations, a central component of relational frame theory. The study has implications for the study of relational responding in complex settings and for applied work aimed at refining repertoires of relational responding.     

Using contextual effects to derive psychophysical scales

This paper presents a functional measurement analysis of Parducci’s range-frequency theory. The theory provides a basis for (1)finding context-invariant psychophysical scales, (2)establishing the validity of rating scales, and (3) explaining contextual effects in judgment. In an experimental illustration, Ss judged the magnitude of numerals in nine different distributions. All data were used to obtain the psychophysical function for numerals and also to test the model. The large contextual effects were consistent with the model. Quantitative tests of fit supported the equal-interval assumption of the category scale. The psychophysical function appeared nearly linear but with a significant negative acceleration. The data were shown to be qualitatively inconsistent with generalizations of Helson’s theory of adaptation level and Johnson’s correlation-regression theory. They supported Parducci’s range-frequency theory and illustrated how it could be used to factor out contextual effects from effects of stimulus magnitude. Extensions of the range-frequency approach are also discussed.