Temporal Context Effects Research Articles

Normalized value coding explains dynamic adaptation in the human valuation process

The notion of subjective value is central to choice theories in ecology, economics, and psychology, serving as an integrated decision variable by which options are compared. Subjective value is often assumed to be an absolute quantity, determined in a static manner by the properties of an individual option. Recent neurobiological studies, however, have shown that neural value coding dynamically adapts to the statistics of the recent reward environment, introducing an intrinsic temporal context dependence into the neural representation of value. Whether valuation exhibits this kind of dynamic adaptation at the behavioral level is unknown. Here, we show that the valuation process in human subjects adapts to the history of previous values, with current valuations varying inversely with the average value of recently observed items. The dynamics of this adaptive valuation are captured by divisive normalization, linking these temporal context effects to spatial context effects in decision making as well as spatial and temporal context effects in perception. These findings suggest that adaptation is a universal feature of neural information processing and offer a unifying explanation for contextual phenomena in fields ranging from visual psychophysics to economic choice.

Cognitive load makes speech sound fast, but does not modulate acoustic context effects

Abstract In natural situations, speech perception often takes place during the concurrent execution of other cognitive tasks, such as listening while viewing a visual scene. The execution of a dual task typically has detrimental effects on concurrent speech perception, but how exactly cognitive load disrupts speech encoding is still unclear. The detrimental effect on speech representations may consist of either a general reduction in the robustness of processing of the speech signal (‘noisy encoding’), or, alternatively it may specifically influence the temporal sampling of the sensory input, with listeners missing temporal pulses, thus underestimating segmental durations (‘shrinking of time’). The present study investigated whether and how spectral and temporal cues in a precursor sentence that has been processed under high vs. low cognitive load influence the perception of a subsequent target word. If cognitive load effects are implemented through ‘noisy encoding’, increasing cognitive load during the precursor should attenuate the encoding of both its temporal and spectral cues, and hence reduce the contextual effect that these cues can have on subsequent target sound perception. However, if cognitive load effects are expressed as ‘shrinking of time’, context effects should not be modulated by load, but a main effect would be expected on the perceived duration of the speech signal. Results from two experiments indicate that increasing cognitive load (manipulated through a secondary visual search task) did not modulate temporal (Experiment 1) or spectral context effects (Experiment 2). However, a consistent main effect of cognitive load was found: increasing cognitive load during the precursor induced a perceptual increase in its perceived speech rate, biasing the perception of a following target word towards longer durations. This finding suggests that cognitive load effects in speech perception are implemented via ‘shrinking of time’, in line with a temporal sampling framework. In addition, we argue that our results align with a model in which early (spectral and temporal) normalization is unaffected by attention but later adjustments may be attention-dependent.

Short and Sweet: The Persuasive Effects of Message Framing and Temporal Context in Antismoking Warning Labels

Current warning labels on cigarette packages are generally focused on long-term losses that can be incurred if one continues smoking. This study compares the effects of these labels against warning labels that stress short-term losses of smoking as well as labels that stress short- and long-term benefits that can be obtained when one quits smoking. A 2 (message frame: gain vs. loss) × 2 (temporal context: short vs. long term) between-subjects experiment was conducted among 132 smokers, with attitude toward quitting smoking and intention to quit smoking, as well as information-seeking behavior and message recall, as the dependent variables. Findings were in line with theory regarding message framing and temporal discounting, showing enhanced effects of gain over loss frames and short-term over long-term consequences on warning labels for attitudes and intentions. In addition, an interaction between message frame and temporal context was found. Especially, gain-framed messages showed stronger effects on intentions to quit smoking than loss-framed messages when warning labels concerned short-term outcomes. Findings suggest that current warning labels, with an emphasis on long-term negative health outcomes, should be reconsidered.

How previous experience shapes perception in different sensory modalities.

What has transpired immediately before has a strong influence on how sensory stimuli are processed and perceived. In particular, temporal context can have contrastive effects, repelling perception away from the interpretation of the context stimulus, and attractive effects (TCEs), whereby perception repeats upon successive presentations of the same stimulus. For decades, scientists have documented contrastive and attractive temporal context effects mostly with simple visual stimuli. But both types of effects also occur in other modalities, e.g., audition and touch, and for stimuli of varying complexity, raising the possibility that context effects reflect general computational principles of sensory systems. Neuroimaging shows that contrastive and attractive context effects arise from neural processes in different areas of the cerebral cortex, suggesting two separate operations with distinct functional roles. Bayesian models can provide a functional account of both context effects, whereby prior experience adjusts sensory systems to optimize perception of future stimuli.

Temporal context manipulations and manual reaction times: The influence of temporal attention on behavioral performance.

Manual reaction times (MRTs) are reduced when a warning signal precedes the onset of an imperative stimulus. The decrease in MRTs is modulated by uncertainty about the moment of stimulus occurrence after the warning stimulus. This modulation is related to preparatory mechanisms that occur during the foreperiod between the warning and imperative stimuli. Hence, manipulations within the range of foreperiods influence preparation and thus response latencies. When the moment of the occurrence of the imperative stimulus is highly predictable, volunteers can allocate resources in time to optimize their performance, a mechanism known as the temporal allocation of attention. In the present study, we evaluated the effects of temporal context (i.e., the duration and arrangement of intervals) on MRTs by conducting 2 experiments with different purposes. The first experiment verified which intervals were more susceptible to variations in the temporal context. The second experiment examined whether learning (i.e., practice) that is acquired by volunteers while in a temporal context affects performance if the temporal contexts are changed. Our data showed that short intervals were more susceptible to contextual influences. Participants could implicitly perceive the temporal context of the experiment and used this to optimize performance. Implicit learning obtained during a temporal context influenced response latencies for a period of time, even when the temporal context was changed. Our results complement many aspects of the results reported by other studies and confirm the importance of temporal attention for organizing and optimizing perception and behavioral performance.

A temporal context repetition effect in rats during a novel object recognition memory task.

Recent research in humans has used formal models of temporal context, broadly defined as a lingering representation of recent experience, to explain a wide array of recall and recognition memory phenomena. One difficulty in extending this work to studies of experimental animals has been the challenge of developing a task to test temporal context effects on performance in rodents. The current study presents results from a novel object recognition memory paradigm that was adapted from a task used in humans and demonstrates a temporal context repetition effect in rats. Specifically, the findings indicate that repeating the first two objects from a once-encountered sequence of three objects incidentally cues memory for the third object, even in its absence. These results reveal that temporal context influences item memory in rats similar to the manner in which it influences memory in humans and also highlight a new task for future studies of temporal context in experimental animals.

Does hearing two dialects at different times help infants learn dialect-specific rules?

Infants might be better at teasing apart dialects with different language rules when hearing the dialects at different times, since language learners do not always combine input heard at different times. However, no previous research has independently varied the temporal distribution of conflicting language input. Twelve-month-olds heard two artificial language streams representing different dialects—a “pure stream” whose sentences adhered to abstract grammar rules like aX bY, and a “mixed stream” wherein any a- or b-word could precede any X- or Y-word. Infants were then tested for generalization of the pure stream’s rules to novel sentences. Supporting our hypothesis, infants showed generalization when the two streams’ sentences alternated in minutes-long intervals without any perceptually salient change across streams (Experiment 2), but not when all sentences from these same streams were randomly interleaved (Experiment 3). Results are interpreted in light of temporal context effects in word learning.

NOCOA+: Multimodal Computer-Based Training for Social and Communication Skills

SUMMARY Non-verbal communication incorporating visual, audio, and contextual information is important to make sense of and navigate the social world. Individuals who have trouble with social situations often have difficulty recognizing these sorts of non-verbal social signals. In this article, we propose a training tool NOCOA+ (Non-verbal COmmuniation for Autism plus) that uses utterances in visual and audio modalities in nonverbal communication training. We describe the design of NOCOA+ ,a nd further perform an experimental evaluation in which we examine its potential as a tool for computer-based training of non-verbal communication skills for people with social and communication difficulties. In a series of four experiments, we investigated 1) the effect of temporal context on the ability to recognize social signals in testing context, 2) the effect of modality of presentation of social stimulus on ability to recognize non-verbal information, 3) the correlation between autistic traits as measured by the autism spectrum quotient (AQ) and non-verbal behavior recognition skills measured by NOCOA+ ,4 ) the effectiveness of computer-based training in improving social skills. We found that context information was helpful for recognizing non-verbal behaviors, and the effect of modality was different. The results also showed a significant relationship between the AQ communication and socialization scores and non-verbal communication skills, and that social skills were significantly improved through computer-based training.

Probing the functions of contextual modulation by adapting images rather than observers.

Countless visual aftereffects have illustrated how visual sensitivity and perception can be biased by adaptation to the recent temporal context. This contextual modulation has been proposed to serve a variety of functions, but the actual benefits of adaptation remain uncertain. We describe an approach we have recently developed for exploring these benefits by adapting images instead of observers, to simulate how images should appear under theoretically optimal states of adaptation. This allows the long-term consequences of adaptation to be evaluated in ways that are difficult to probe by adapting observers, and provides a common framework for understanding how visual coding changes when the environment or the observer changes, or for evaluating how the effects of temporal context depend on different models of visual coding or the adaptation processes. The approach is illustrated for the specific case of adaptation to color, for which the initial neural coding and adaptation processes are relatively well understood, but can in principle be applied to examine the consequences of adaptation for any stimulus dimension. A simple calibration that adjusts each neuron's sensitivity according to the stimulus level it is exposed to is sufficient to normalize visual coding and generate a host of benefits, from increased efficiency to perceptual constancy to enhanced discrimination. This temporal normalization may also provide an important precursor for the effective operation of contextual mechanisms operating across space or feature dimensions. To the extent that the effects of adaptation can be predicted, images from new environments could be "pre-adapted" to match them to the observer, eliminating the need for observers to adapt.

A single mechanism of temporal integration unites neural adaptation and norm-based coding

What information is encoded in a cortical visual representation? That visual representations are distributed across the ventral temporal cortex is well established. fMRI adaptation studies demonstrate these neural codes are modulated by the perceptual similarity of sequential stimuli. Studies investigating prototype-based coding effects propose that neural responses are proportional to distinctiveness from a central reference, or prototype. In existing fMRI work, these two effects are considered independently. Here, we propose that these two effects arise as a consequence of a single mechanism of coding based upon temporal integration over recent stimulus history. Using a carry-over fMRI design, we show significant neural adaptation and prototype-based coding effects in a face-responsive region of interest in the right fusiform gyrus when effects are modeled discretely. By considering these effects as extremes of a single drifting norm model, we find that visual representations tend to encode identity in terms of intermediate stimulus history. Looking beyond the region of interest, we demonstrate that the effect of temporal context varies smoothly across the cortex, with the modulatory effect of recent visual history extending further back in time in a posterior to anterior fashion along the right ventral temporal cortex. These findings reframe two branches of the visual representation literature in terms of a unified encoding model. Importantly, this finding offers a perspective on the cortical topology of visual identity representations. We discuss these advances in terms of prior work related to the temporal qualities of visual stimuli. Meeting abstract presented at VSS 2014

Effect of temporal modification and vowel context on speech perception in individuals with auditory neuropathy spectrum disorder (ANSD)

Objectives: The study aimed to investigate the effect of time-scale modification on consonant perception in individuals with an auditory neuropathy spectrum disorder (ANSD). The study also evaluated the effect of vowel context on consonant perception. Study design: Eight individuals with ANSD in the age range of 15 to 24 years participated in the study. Their perception of eight stops and two liquids in the context of the vowels /a/, /i/ and /u/ were studied. The stimuli were stretched by 25%, 35% and 50% using pitch synchronous overlap and add algorithm. Results: It was found that 25% stretching resulted in significant improvement in perception in all three vowel contexts, while 35% stretching improved perception only in the context of /a/. However, 50% stretching resulted in deterioration in performance in all three vowel contexts. Furthermore, consonant perception in the context of /a/ and /u/ were significantly higher than that of /i/ in all the stretch conditions. Sequential information analysis revealed that perception of place and voicing were lowest in the context of /i/ compared to that of /a/ and /u/. Conclusion: Stretching the entire stimuli by a factor of 25% improves consonant perception in individuals with ANSD. In contrast, stretching beyond 25% resulted in either no improvement or deterioration in consonant perception. This information can be used to create a signal-processing algorithm that stretches the entire speech signal. Hence, without having to laboriously increase only the transition duration manually, improvement in speech perception can be brought about by stretching the whole signal. Additionally, consonant perception in individuals with ANSD is influenced by vowel context and hence two extreme vowels need to be used while studying the vowel context effect.

Contextual effects in interval-duration judgements in vision, audition and touch

We examined the effect of temporal context on discrimination of intervals marked by auditory, visual and tactile stimuli. Subjects were asked to compare the duration of the interval immediately preceded by an irrelevant "distractor" stimulus with an interval with no distractor. For short interval durations, the presence of the distractor affected greatly the apparent duration of the test stimulus: short distractors caused the test interval to appear shorter and vice versa. For very short reference durations (≤ 100 ms), the contextual effects were large, changing perceived duration by up to a factor of two. The effect of distractors reduced steadily for longer reference durations, to zero effect for durations greater than 500 ms. We found similar results for intervals defined by visual flashes, auditory tones and brief finger vibrations, all falling to zero effect at 500 ms. Under appropriate conditions, there were strong cross-modal interactions, particularly from audition to vision. We also measured the Weber fractions for duration discrimination and showed that under the conditions of this experiment, Weber fractions decreased steadily with duration, following a square-root law, similarly for all three modalities. The magnitude of the effect of the distractors on apparent duration correlated well with Weber fraction, showing that when duration discrimination was relatively more precise, the context dependency was less. The results were well fit by a simple Bayesian model combining noisy estimates of duration with the action of a resonance-like mechanism that tended to regularize the sound sequence intervals.

Simultaneous Pursuit of Innovation and Efficiency in Complex Engineering Projects—A Study of the Antecedents and Impacts of Ambidexterity in Project Teams

Projects, as the common unit of organizing complex tasks, often feature unique challenges that require both radical innovation and incremental improvements to processes and solutions in order to deliver the project within constraints. Both exploration and exploitation are likely to be needed for complex engineering projects to succeed. This study, through an in-depth case study of a complex infrastructure project facing unique challenges and tight budget and schedule, investigates the antecedents of ambidexterity and the effect of ambidexterity on project performance. The main contributions of this research include finding: (1) ambidexterity at the project team level to be a significant contributor to project performance; (2) the effects of temporal separation and project context on project performance are mediated by the project team's degree of ambidexterity; and (3) contrary to the prediction from organizational literature, structural separation has not contributed to the case project team's ambidexterity. The authors believe that among the three antecedents for ambidexterity at the project level as predicted by organizational literature, structural separation is rendered ineffective by the natural cycling between exploration and exploitation in the project environment and by the need to integrate the two under time pressure and resource constraints. The development of an effective project context can facilitate the temporal cycling between exploration and exploitation by creating awareness that overcomes the inertia in transitioning between the two by setting performance expectations and appropriate social context. Implications for theory development and practice are discussed.

Auditory stream segregation impairments in schizophrenia

We used behavior and event-related potentials (ERPs) to examine auditory stream segregation in people with schizophrenia and control participants. During each trial, a context pattern was presented, consisting of low (A) and high (B) tones and silence (-) in a repeating ABA- pattern, with a frequency separation (Δf) of 3, 6, or 12 semitones. Next, a test ABA-pattern was presented that always had a 6-semitone Δf. Larger Δf during the context resulted in more perception of two streams and larger N1 and P2 ERPs, but less perception of two streams during the test pattern. These effects of Δf were smaller in schizophrenia. Individuals with schizophrenia also showed a reduced effect of prior perceptual judgments. Overall, the findings demonstrate that people with schizophrenia have abnormalities in segregating sounds. These abnormalities result from difficulties utilizing frequency cues in addition to reduced temporal context effects.

Effects of temporal and spatial context on colour appearance

Effects of temporal and spatial context on colour appearance

Short article: Forgotten but not gone: Context effects on recognition do not require explicit memory for context

Context effects on recognition memory provide an important indirect assay of associative learning and source memory. Neuropsychological studies have indicated that such context effects may obtain even if the contexts themselves are not remembered--for example, in individuals impaired on direct tests of memory for contextual information. In contrast, a recent study indicated that the effects of temporal context reinstatement on visual recognition obtain only when the contextual information itself was explicitly recollected. Here we report that the effects of reinstatement of spatial-simultaneous context on visual object recognition memory obtain irrespective of whether those context stimuli are explicitly recognized. We suggest that spatial-simultaneous context effects might be based on ensemble unitization of target and context stimuli at encoding, whereas temporal context effects may require recollective processes.

Effects of message framing and temporal context on college student drinking behavior

This study evaluated the interactive effects of message framing and temporal context on college student alcohol use. Participants (n=228) were randomly assigned to read an alcohol prevention message that varied by message frame (gains vs. losses) and temporal context (short- vs. long-term consequences). Participants returned to the lab one month later to report their drinking behavior over the past month. As predicted, students exposed to the gain-framed message reported lower alcohol use (drank less frequently, drank fewer alcoholic beverages per drinking occasion, and engaged in less binge drinking) as compared to students exposed to the loss-framed message, but only if they read about short-term consequences of alcohol use. Message frame had no effect when participants were exposed to long-term consequences. This investigation extends previous research by demonstrating the effectiveness of message framing for reducing health-damaging behaviors and by identifying temporal context as a moderator of framing effects.

Effects of temporal context and temporal expectancy on neural activity in inferior temporal cortex

Timing is critical. The same event can mean different things at different times and some events are more likely to occur at one time than another. We used a cued visual classification task to evaluate how changes in temporal context affect neural responses in inferior temporal cortex, an extrastriate visual area known to be involved in object processing. On each trial a first image cued a temporal delay before a second target image appeared. The animal's task was to classify the second image by pressing one of two buttons previously associated with that target. All images were used as both cues and targets. Whether an image cued a delay time or signaled a button press depended entirely upon whether it was the first or second picture in a trial. This paradigm allowed us to compare inferior temporal cortex neural activity to the same image subdivided by temporal context and expectation. Neuronal spiking was more robust and visually evoked local field potentials (LFP's) larger for target presentations than for cue presentations. On invalidly cued trials, when targets appeared unexpectedly early, the magnitude of the evoked LFP was reduced and delayed and neuronal spiking was attenuated. Spike field coherence increased in the beta-gamma frequency range for expected targets. In conclusion, different neural responses in higher order ventral visual cortex may occur for the same visual image based on manipulations of temporal attention.

Picking up the pace: Effects of global temporal context on sensitivity to the tempo of auditory sequences

This article continues a line of research examining factors affecting listeners' auditory tempo sensitivities. Of particular interest is the question of whether listeners are sensitive to the overall (global) pace of their auditory environment and how this sensitivity may affect their perceptions of sequence timing. To address this question, we manipulated the set of sequence tempi (between 300 and 700 msec) that listeners experienced over the course of a 1-h period (i.e., the global temporal context) while they performed a tempo-discrimination task involving standard-comparison pairs of isochronous tone sequences. Overall findings show systematic distortions in perceived tempo that are consistent with the view that listeners adapt to the global pace of their auditory environments. Moreover, general support was found for the hypothesis that increasing the number of equal intervals in a standard sequence produces greater improvements in tempo sensitivity when the standard sequence tempo is different from the global pace than when it is at the global pace. Implications of these findings for models of timing and temporal processing are discussed.

Effects of spatial and temporal context on color categories and color constancy

Color constancy is the ability to assign a constant color to an object independent of changes in illumination. Color constancy is achieved by taking context information into account. Previous approaches that have used matching paradigms to quantify color constancy found degrees of constancy between 20% and 80%. Here, we studied color constancy in a color-naming task under different conditions of surround illumination and patch size. Observers categorized more than 400 patches for each illumination condition. This allows one to overcome inherent limitations in color naming and to study the changes in color categories under illumination changes. When small central test patches with a full context illumination were categorized, observers followed the illumination shift almost completely, showing a high degree of constancy (99%). Reducing the available context information or increasing the patch size decreased the degree of constancy to about 50%. Moderate degrees of constancy (66%) occurred even when the test patches were never viewed simultaneously but only in temporal alternation with the illumination. Boundaries between color categories were largely stable within and across observers under neutral illumination. Under changing illumination, there were small but systematic variations in the color category boundaries. Color category boundaries tended to rotate away from the illumination color. This variation was largest under full context conditions where highest degrees of color constancy were obtained.