Two-interval Forced-choice Task Research Articles

The impact of visually simulated self-motion on predicting object motion.

To interact successfully with moving objects in our environment we need to be able to predict their behavior. Predicting the position of a moving object requires an estimate of its velocity. When flow parsing during self-motion is incomplete-that is, when some of the retinal motion created by self-motion is incorrectly attributed to object motion-object velocity estimates become biased. Further, the process of flow parsing should add noise and lead to object velocity judgements being more variable during self-motion. Biases and lowered precision in velocity estimation should then translate to biases and lowered precision in motion extrapolation. We investigated this relationship between self-motion, velocity estimation and motion extrapolation with two tasks performed in a realistic virtual reality (VR) environment: first, participants were shown a ball moving laterally which disappeared after a certain time. They then indicated by button press when they thought the ball would have hit a target rectangle positioned in the environment. While the ball was visible, participants sometimes experienced simultaneous visual lateral self-motion in either the same or in the opposite direction of the ball. The second task was a two-interval forced choice task in which participants judged which of two motions was faster: in one interval they saw the same ball they observed in the first task while in the other they saw a ball cloud whose speed was controlled by a PEST staircase. While observing the single ball, they were again moved visually either in the same or opposite direction as the ball or they remained static. We found the expected biases in estimated time-to-contact, while for the speed estimation task, this was only the case when the ball and observer were moving in opposite directions. Our hypotheses regarding precision were largely unsupported by the data. Overall, we draw several conclusions from this experiment: first, incomplete flow parsing can affect motion prediction. Further, it suggests that time-to-contact estimation and speed judgements are determined by partially different mechanisms. Finally, and perhaps most strikingly, there appear to be certain compensatory mechanisms at play that allow for much higher-than-expected precision when observers are experiencing self-motion-even when self-motion is simulated only visually.

Aging deteriorates the ability to discriminate the weight of an object during an action observation task.

The ability to predict the weight of objects is important for skilled and dexterous manipulation during activities of daily living. The observation of other people moving objects might represent an important source of information on object features and help to plan the correct motor interaction with it. In aging, an impaired ability to evaluate the object weight might have negative drawbacks in term of the safety of the person. The aim of this study was to investigate the role of aging in the ability to discriminate the object weight during action observation. Twenty older adults (Old) and twenty young subjects (Young) performed a two-interval forced-choice task consisting in the observation of a couple of videos showing an actor moving a box of different weights. The observer had to evaluate which video showed the heavier box. Handgrip strength was acquired from all subjects. Sensitivity analysis was performed and psychometric curves were built on participants' responses. The results showed a diminished sensitivity in the object weight discrimination in Old than in Young group. The analysis of the psychometric curves revealed that this impairment pertained both the light and heavy boxes and the minimum difference to discriminate different weights was greater in Old than in Young. At last, the sensitivity and the discrimination ability significantly correlated with individuals' handgrip strength. These findings allow us to deeply characterize the impairments older adults have in discriminating the weight of an object moved by another individual.

The impact of visually simulated self-motion on predicting object motion-A registered report protocol.

To interact successfully with moving objects in our environment we need to be able to predict their behavior. Predicting the position of a moving object requires an estimate of its velocity. When flow parsing during self-motion is incomplete-that is, when some of the retinal motion created by self-motion is incorrectly attributed to object motion-object velocity estimates become biased. Further, the process of flow parsing should add noise and lead to object velocity judgements being more variable during self-motion. Biases and lowered precision in velocity estimation should then translate to biases and lowered precision in motion extrapolation. We investigate this relationship between self-motion, velocity estimation and motion extrapolation with two tasks performed in a realistic virtual reality (VR) environment: first, participants are shown a ball moving laterally which disappears after a certain time. They then indicate by button press when they think the ball would have hit a target rectangle positioned in the environment. While the ball is visible, participants sometimes experience simultaneous visual lateral self-motion in either the same or in the opposite direction of the ball. The second task is a two-interval forced choice task in which participants judge which of two motions is faster: in one interval they see the same ball they observed in the first task while in the other they see a ball cloud whose speed is controlled by a PEST staircase. While observing the single ball, they are again moved visually either in the same or opposite direction as the ball or they remain static. We expect participants to overestimate the speed of a ball that moves opposite to their simulated self-motion (speed estimation task), which should then lead them to underestimate the time it takes the ball to reach the target rectangle (prediction task). Seeing the ball during visually simulated self-motion should increase variability in both tasks. We expect to find performance in both tasks to be correlated, both in accuracy and precision.

How big should this object be? Perceptual influences on viewing-size preferences

When viewing objects depicted in a frame, observers prefer to view large objects like cars in larger sizes and smaller objects like cups in smaller sizes. That is, the visual size of an object that “looks best” is linked to its typical physical size in the world. Why is this the case? One intuitive possibility is that these preferences are driven by semantic knowledge: For example, when we recognize a sofa, we access our knowledge about its real-world size, and this influences what size we prefer to view the sofa within a frame. However, might visual processing play a role in this phenomenon—that is, do visual features that are related to big and small objects look better at big and small visual sizes, respectively, even when observers do not have explicit access to semantic knowledge about the objects? To test this possibility, we used “texform” images, which are synthesized versions of recognizable objects, which critically retain local perceptual texture and coarse contour information, but are no longer explicitly recognizable. To test for visual size preferences, we first used a size adjustment task, and the results were equivocal. However, clear results were obtained using a two-interval forced choice task, in which each texform was presented at the preferred visual size of its corresponding original image, and a visual size slightly bigger or smaller. Observers consistently selected the texform presented at the canonical visual size as the more aesthetically pleasing one. An additional control experiment ruled out alternative explanations related to size priming effects. These results suggest that the preferred visual size of an object depends not only on explicit knowledge of its real-world size, but also can be evoked by mid-level visual features that systematically covary with an object's real-world size.

Duration Comparisons for Vision and Touch Are Dependent on Presentation Order and Temporal Context.

Integrating visual and tactile information in the temporal domain is critical for active perception. To accomplish this, coordinated timing is required. Here, we study perceived duration within and across these two modalities. Specifically, we examined how duration comparisons within and across vision and touch were influenced by temporal context and presentation order using a two-interval forced choice task. We asked participants to compare the duration of two temporal intervals defined by tactile or visual events. Two constant standard durations (700 ms and 1,000 ms in ‘shorter’ sessions; 1,000 ms and 1,500 ms in ‘longer’ sessions) were compared to variable comparison durations in different sessions. In crossmodal trials, standard and comparison durations were presented in different modalities, whereas in the intramodal trials, the two durations were presented in the same modality. The standard duration was either presented first (<sc>) or followed the comparison duration (<cs>). In both crossmodal and intramodal conditions, we found that the longer standard duration was overestimated in <cs> trials and underestimated in <sc> trials whereas the estimation of shorter standard duration was unbiased. Importantly, the estimation of 1,000ms was biased when it was the longer standard duration within the shorter sessions but not when it was the shorter standard duration within the longer sessions, indicating an effect of temporal context. The effects of presentation order can be explained by a central tendency effect applied in different ways to different presentation orders. Both crossmodal and intramodal conditions showed better discrimination performance for <sc> trials than <cs> trials, supporting the Type B effect for both crossmodal and intramodal duration comparison. Moreover, these results were not dependent on whether the standard duration was defined using tactile or visual stimuli. Overall, our results indicate that duration comparison between vision and touch is dependent on presentation order and temporal context, but not modality.

Perceptual amplification following sustained attention: implications for hypervigilance.

It is known that attending to a cutaneous stimulus briefly increases its subjective intensity. The purpose of the present study was to determine whether an extended period of attention would produce a longer-lasting perceptual amplification. Eighty subjects were assigned alternately to experimental and control groups. Members of the two groups received identical series of tactile stimuli (near-threshold von Frey filaments applied to the forearm), but those in the experimental group carried out a two-interval forced-choice detection task that required attention to the filaments, while subjects in the control group attended instead to a video game. After this initial phase, all subjects gave magnitude estimates of the intensity of a wide range of von Frey filaments. The experimental group gave estimates 42% greater than those of the control group, both for filaments used in the initial phase, and others not presented previously; the perceptual amplification did not, however, transfer to a different type of pressure stimulus, a 5mm-diameter rod applied to the skin. The aftereffect of sustained attention lasted for at least 15min. This phenomenon, demonstrated in normal subjects, may have implications for the hypervigilance of some chronic pain patients, which is characterized by both heightened attention to pain and long-lasting perceptual amplification of noxious stimuli.

How big should this object be? Perceptual influences on viewing-size preferences

When viewing objects depicted in a frame, observers prefer to view large objects like cars in larger sizes and smaller objects like cups in smaller sizes. That is, the visual size of an object that looks best is linked to its typical physical size in the world. Why is this the case? One intuitive possibility is that these preferences are driven by semantic knowledge: For example, when we recognize a sofa, we access our knowledge about its real-world size, and this influences what size we prefer to view the sofa within a frame. However, might visual processing play a role in this phenomenon--that is, do visual features that are related to big and small objects look better at big and small visual sizes, respectively, even when observers do not have explicit access to semantic knowledge about the objects? To test this possibility, we used images, which are synthesized versions of recognizable objects, which critically retain local perceptual texture and coarse form information, but are no longer explicitly recognizable. To test for visual size preferences, we used a two-interval forced choice task, in which each texform was presented at the preferred visual size of its corresponding original image, and a visual size slightly bigger or smaller. Observers consistently selected the texform presented at the canonical visual size as the more aesthetically pleasing one. These results suggest that the preferred visual size of an object depends not only on explicit knowledge of its real-world size, but also can be evoked by mid-level visual features that systematically covary with an object9s real-world size.

Probing the effect of the expected-speed violation illusion.

Motion perception is complex for the brain to process, involving interacting computations of distance, time, and speed. These computations can be biased by the context and the features of the perceived moving object, giving rise to several types of motion illusions. Recent research has shown that, in addition to object features and context, lifelong priors can bias attributes of perception. In the present work, we investigated if such long acquired expectations can bias speed perception. Using a two-interval forced-choice (2-IFC) task, we asked 160 participants in different experiments to judge which of two vehicles, one archetypically fast (e.g. a motorbike), and one comparatively slower (e.g. a bike), was faster. By varying the objective speeds of the two-vehicle types, and measuring the participants' point of subjective equality, we observed a consistent bias in participants' speed perception. Counterintuitively, in the first three experiments the speed of an archetypically slow vehicle had to be decreased relative to that of an archetypically fast vehicle, for the two to be judged as the same. Similarly, in the next three experiments, an archetypically fast vehicle's speed had to be increased relative to an archetypically slow vehicle's speed, for the two to be perceived as equal. Four additional control experiments replicated our results. We define this newly found bias as the expected-speed violation illusion (ESVI). We believe the ESVI as conceptually very similar to the size-weight illusion, and discuss it within the Bayesian framework of human perception.

Yes/no and two-interval forced-choice tasks with listener-based vs observer-based responses.

Observer-based procedures are used to assess auditory behavior in infants, often incorporating adaptive tracking algorithms. These procedures are reliable, but effects of modifications made to accommodate infant testing are not fully understood. One modification is that observation intervals are undefined for the listener, introducing signal-temporal uncertainty and increasing the likelihood that listener response bias will influence estimates of performance. The effect of these factors was evaluated by comparing threshold estimates obtained from adults using two tasks: (1) single-interval, yes/no and (2) two-interval, forced-choice. Detection thresholds were estimated adaptively for a 1000-Hz FM tone in quiet and for a word presented in two-talker speech masking. Trials were initiated and judged by the observer (observer-based) or the listener (listener-based). Thus, listening intervals were temporally uncertain in observer-based procedures and temporally defined in listener-based procedures. Thresholds were higher for observer-based relative to corresponding listener-based procedures. The magnitude of this difference was similar across the yes/no and two-interval tasks, and was larger for masked word detection than tone detection in quiet. Listeners adopted a conservative criterion when tested using the observer-based, yes/no procedure, but modeling results suggest that signal-temporal uncertainty accounts for the largest portion of the threshold difference between observer-based and listener-based procedures.

The role of acceleration and jerk in perception of above-threshold surge motion

Inertial motions may be defined in terms of acceleration and jerk, the time-derivative of acceleration. We investigated the relative contributions of these characteristics to the perceived intensity of motions. Participants were seated on a high-fidelity motion platform, and presented with 25 above-threshold 1 s forward (surge) motions that had acceleration values ranging between 0.5 and 2.5 text {m/s}^2 and jerks between 20 and 60 text {m/s}^3, in five steps each. Participants performed two tasks: a magnitude estimation task, where they provided subjective ratings of motion intensity for each motion, and a two-interval forced choice task, where they provided judgments on which motion of a pair was more intense, for all possible combinations of the above motion profiles. Analysis of the data shows that responses on both tasks may be explained by a single model, and that this model should include acceleration only. The finding that perceived motion intensity depends on acceleration only appears inconsistent with previous findings. We show that this discrepancy can be explained by considering the frequency content of the motions, and demonstrate that a linear time-invariant systems model of the otoliths and subsequent processing can account for the present data as well as for previous findings.

Neurophysiological correlates of collective perceptual decision-making.

Humans frequently perform tasks collaboratively in daily life. Collaborating with others may or may not result in higher task performance than if one were to complete the task alone (i.e., a collective benefit). A recent study on collective benefits in perceptual decision-making showed that dyad members with similar individual performances attain collective benefit. However, little is known about the physiological basis of these results. Here, we replicate this earlier work and also investigate the neurophysiological correlates of decision-making using EEG. In a two-interval forced-choice task, co-actors individually indicated presence of a target stimulus with a higher contrast and then indicated their confidence on a rating scale. Viewing the individual ratings, dyads made a joint decision. Replicating earlier work, we found a positive correlation between the similarity of individual performances and collective benefit. We analyzed event-related potentials (ERPs) in three phases (i.e., stimulus onset, response and feedback) using explorative cluster mass permutation tests. At stimulus onset, ERPs were significantly linearly related to our manipulation of contrast differences, validating our manipulation of task difficulty. For individual and joint responses, we found a significant centro-parietal error-related positivity for correct versus incorrect responses, which suggests that accuracy is already evaluated at the response level. At feedback presentation, we found a significant late positive fronto-central potential elicited by incorrect joint responses. In sum, these results demonstrate that response- and feedback-related components elicited by an error-monitoring system differentially integrate conflicting information exchanged during the joint decision-making process.

Amygdala-prefrontal cortex connectivity increased during face discrimination but not time perception.

Time sensitivity is affected by emotional stimuli such as fearful faces. The effect of threatening stimuli on time perception depends on numerous factors, including task type and duration range. We applied a two-interval forced-choice task using face stimuli to healthy volunteers to evaluate time perception and emotion interaction using functional magnetic resonance imaging. We conducted finite impulse response analysis to examine time series for the significantly activated brain areas and psycho-physical interaction to investigate the connectivity between selected regions. Time perception engaged a right-lateralised frontoparietal network, while a face discrimination task activated the amygdala and fusiform face area (FFA). No voxels were active with regard to the effect of expression (fearful versus neutral). In parallel with this, our behavioural results showed that attending to the fearful facesdid not cause duration overestimation. Finally, connectivity of the amygdala and FFA to the middle frontal gyrus increased during the face processing condition compared to the timing task.Overall, our results suggest that the prefrontal-amygdala connectivity might be required for the emotional processing of facial stimuli. On the other hand, attentional load, task type and task difficultyare discussed as possible factors that influence the effects of emotion on time perception.

The effect of symbolic meaning of speed on time to contact

The effects of moving task-irrelevant objects on time-to-contact (TTC) judgments are examined in six experiments. In particular, we investigated the effects of the symbolic meaning of speed on TTC by presenting images of objects recalling the symbolic meaning of high speed (motorbike, rocket, formula one, rabbit, cheetah and flying Superman) and low speed (bicycle, hot-air balloon, tank, turtle, elephant and static Superman). In all experiments, participants judged the TTC of these moving objects with a black line, indicating the end of the occlusion. Experiment 7 was conducted to disambiguate whether the effects on TTC, found in the previous experiments, were either a by-product of a speed illusion or they were rather elicited by the implicit timing task. In a two-interval forced choice task, participants were instructed to judge if “high-speed objects” moved actually faster than “slow-speed objects”. The results revealed no consistent speed illusion.Taken together the results showed shorter TTC estimated with stimuli recalling the meaning of high compared to low speed, but only with the long occlusion duration (3.14 s). At shorter occlusion durations, the pattern was reversed (participant tend to have shorter TTC with stimuli recalling the meaning of low speed). We suggest that the symbolic meaning of speed works mainly at low speed and long TTC, because the semantic elaboration of the stimulus needs a deeper cognitive elaboration. On the other hand, at higher speeds, a small erroneous perceptual judgment affects the TTC, perhaps due to a speed expectancy violation of the expected “slow object”.

Working Memory Maintenance Modulates Serial Dependence Effects of Perceived Emotional Expression.

The stability of face perception is vital in interpersonal interactions. Recent studies have revealed the mechanism of the stability in the perception of stable attributes of faces (such as facial identity) by serial dependence, a phenomenon in which perception of current stimuli is pulled toward recently viewed stimuli. However, whether serial dependence of perceived emotional expression (a changeable attribute of faces) exists remains controversial, and its exact nature has not been examined yet. To address these issues, we used the methods of constant stimuli and two-interval forced choice tasks in three psychophysical experiments. Participants compared two successive facial expressions selected from a continuum with 50 morphed faces ranging from sad to happy. Experiment 1a and 1b showed that a perceived facial expression pulled toward previously seen facial expressions (i.e., a significant serial dependence effect), independent of response instructions. Furthermore, a stronger serial dependence effect was found when the first facial expression was retained in working memory for a longer delay duration (Experiment 2), and yet a weaker serial dependence effect was observed when a longer delay between decision and response was performed (Experiment 3). These findings indicate that serial dependence facilitates the stability of facial expression perception and is modulated by working memory representations.

Do target detection and target localization always go together? Extracting information from briefly presented displays.

The human visual system is capable of processing an enormous amount of information in a short time. Although rapid target detection has been explored extensively, less is known about target localization. Here we used natural scenes and explored the relationship between being able to detect a target (present vs. absent) and being able to localize it. Across four presentation durations (~ 33-199 ms), participants viewed scenes taken from two superordinate categories (natural and manmade), each containing exemplars from four basic scene categories. In a two-interval forced choice task, observers were asked to detect a Gabor target inserted in one of the two scenes. This was followed by one of two different localization tasks. Participants were asked either to discriminate whether the target was on the left or the right side of the display or to click on the exact location where they had seen the target. Targets could be detected and localized at our shortest exposure duration (~ 33 ms), with a predictable improvement in performance with increasing exposure duration. We saw some evidence at this shortest duration of detection without localization, but further analyses demonstrated that these trials typically reflected coarse or imprecise localization information, rather than its complete absence. Experiment 2 replicated our main findings while exploring the effect of the level of "openness" in the scene. Our results are consistent with the notion that when we are able to extract what objects are present in a scene, we also have information about where each object is, which provides crucial guidance for our goal-directed actions.

The sound of beauty: How complexity determines aesthetic preference

Stimulus complexity is an important determinant of aesthetic preference. An influential idea is that increases in stimulus complexity lead to increased preference up to an optimal point after which preference decreases (inverted-U pattern). However, whereas some studies indeed observed this pattern, most studies instead showed an increased preference for more complexity. One complicating issue is that it remains unclear how to define complexity. To address this, we approached complexity and its relation to aesthetic preference from a predictive coding perspective. Here, low- and high-complexity stimuli would correspond to low and high levels of prediction errors, respectively. We expected participants to prefer stimuli which are neither too easy to predict (low prediction error), nor too difficult (high prediction error). To test this, we presented two sequences of tones on each trial that varied in predictability from highly regular (low prediction error) to completely random (high prediction error), and participants had to indicate which of the two sequences they preferred in a two-interval forced-choice task. The complexity of each tone sequence (amount of prediction error) was estimated using entropy. Results showed that participants tended to choose stimuli with intermediate complexity over those of high or low complexity. This confirms the century-old idea that stimulus complexity has an inverted-U relationship to aesthetic preference.

A Two-interval Forced-choice Task for Multisensory Comparisons.

We provide a procedure for a psychophysics experiment in humans based on a previously described paradigm aimed to characterize the perceptual duration of intervals within the range of milliseconds of visual, acoustic, and audiovisual aperiodic trains of six pulses. In this task, each of the trials consists of two consecutive intramodal intervals where the participants press the upward arrow key to report that the second stimulus lasted longer than the reference, or the downward arrow key to indicate otherwise. The analysis of the behavior results in psychometric functions of the probability of estimating the comparison stimulus to be longer than the reference, as a function of the comparison intervals. In conclusion, we advance a way of implementing standard programming software to create visual, acoustic, and audiovisual stimuli, and to generate a two-interval forced-choice (2IFC) task by delivering stimuli through noise-blocking headphones and a computer's monitor.

A Two-interval Forced-choice Task for Multisensory Comparisons

A Two-interval Forced-choice Task for Multisensory Comparisons

Perceptual processing in the ventral visual stream requires area TE but not rhinal cortex.

There is an on-going debate over whether area TE, or the anatomically adjacent rhinal cortex, is the final stage of visual object processing. Both regions have been implicated in visual perception, but their involvement in non-perceptual functions, such as short-term memory, hinders clear-cut interpretation. Here, using a two-interval forced choice task without a short-term memory demand, we find that after bilateral removal of area TE, monkeys trained to categorize images based on perceptual similarity (morphs between dogs and cats), are, on the initial viewing, badly impaired when given a new set of images. They improve markedly with a small amount of practice but nonetheless remain moderately impaired indefinitely. The monkeys with bilateral removal of rhinal cortex are, under all conditions, indistinguishable from unoperated controls. We conclude that the final stage of the integration of visual perceptual information into object percepts in the ventral visual stream occurs in area TE.

Continuous flash suppression and monocular pattern masking impact subjective awareness similarly.

Peters and Lau (eLife, 4, e09651, 2015) found that when criterion bias is controlled for, there is no evidence for unconscious visual perception in normal observers, in the sense that they cannot directly discriminate a target above chance without knowing it. One criticism of that study is that the visual suppression method used, forward and backward masking (FBM), may be too blunt in the way it interferes with visual processing to allow for unconscious forced-choice discrimination. To investigate this question, we compared FBM directly to continuous flash suppression (CFS) in a two-interval forced-choice task. Although CFS is popular, and may be thought of as a more powerful visual suppression technique, we found no difference in the degree of perceptual impairment between the two suppression types. To the extent that CFS impairs perception, both objective discrimination and subjective awareness are impaired to similar degrees under FBM. This pattern was consistently observed across three experiments in which various experimental parameters were varied. These findings provide evidence for an ongoing debate about unconscious perception: normal observers cannot perform forced-choice discrimination tasks unconsciously.