Visual Predictions Operate on Different Timescales

Humans live in a volatile environment, subject to changes occurring at different timescales. The ability to adjust internal predictions accordingly is critical for perception and action. We studied this ability with two EEG experiments in which participants were presented with sequences of four Gabor patches, simulating a rotation, and instructed to respond to the last stimulus (target) to indicate whether or not it continued the direction of the first three stimuli. Each experiment included a short-term learning phase in which the probabilities of these two options were very different (p = .2 vs. p = .8, Rules A and B, respectively), followed by a neutral test phase in which both probabilities were equal. In addition, in one of the experiments, prior to the short-term phase, participants performed a much longer long-term learning phase where the relative probabilities of the rules predicting targets were opposite to those of the short-term phase. Analyses of the RTs and P3 amplitudes showed that, in the neutral test phase, participants initially predicted targets according to the probabilities learned in the short-term phase. However, whereas participants not pre-exposed to the long-term learning phase gradually adjusted their predictions to the neutral probabilities, for those who performed the long-term phase, the short-term associations were spontaneously replaced by those learned in that phase. This indicates that the long-term associations remained intact whereas the short-term associations were learned, transiently used, and abandoned when the context changed. The spontaneous recovery suggests independent storage and control of long-term and short-term associations.

The Effect of Information Quantity on Distinctive Accuracy and Normativity of Personality Trait Judgments

Information quantity is an important moderator of personality judgment accuracy. Some evidence suggests that the amount of available information is positively related to accuracy. The current study utilized the social accuracy model to investigate the effects of differences in thin slices of information quantity on the distinctive accuracy and normativity of personality trait judgments. It was hypothesized that distinctive accuracy and normativity would increase as information quantity increased. Participants were 431 individuals who participated in an online study that varied the length of stimulus target observations (30 seconds, 1 minute, 3 minutes, and 5 minutes), after which judges rated targets using other–report measures of the Big Five personality traits. For all traits combined, significant levels of accuracy were found for all observation lengths, but distinctive accuracy and normativity did not increase as video length increased. Findings varied for individual traits. For distinctive accuracy, there was a linear increase with information quantity for Extraversion and a non–linear relationship for Conscientiousness, while there was a linear decrease for Openness. For normativity, there was a linear increase with information quantity for Agreeableness and a non–linear relationship for Conscientiousness. There are important differences in how observation length affects distinctive accuracy and normativity for different personality traits. © 2019 European Association of Personality Psychology

Network inference performance complexity: a consequence of topological, experimental and algorithmic determinants

Motivation Network inference algorithms aim to uncover key regulatory interactions governing cellular decision-making, disease progression and therapeutic interventions. Having an accurate blueprint of this regulation is essential for understanding and controlling cell behavior. However, the utility and impact of these approaches are limited because the ways in which various factors shape inference outcomes remain largely unknown. Results We identify and systematically evaluate determinants of performance—including network properties, experimental design choices and data processing—by developing new metrics that quantify confidence across algorithms in comparable terms. We conducted a multifactorial analysis that demonstrates how stimulus target, regulatory kinetics, induction and resolution dynamics, and noise differentially impact widely used algorithms in significant and previously unrecognized ways. The results show how even if high-quality data are paired with high-performing algorithms, inferred models are sometimes susceptible to giving misleading conclusions. Lastly, we validate these findings and the utility of the confidence metrics using realistic in silico gene regulatory networks. This new characterization approach provides a way to more rigorously interpret how algorithms infer regulation from biological datasets. Availability and implementation Code is available at http://github.com/bagherilab/networkinference/. Supplementary information Supplementary data are available at Bioinformatics online.

Modulation of Neuronal Activity in the Monkey Putamen Associated With Changes in the Habitual Order of Sequential Movements

The striatum, especially its dorsolateral part, plays a major role in motor skill learning and habit formation, but it is still unclear how this contribution might be mediated at the neuronal level. We recorded single neurons in the posterior putamen of two monkeys performing an overlearned sequence of arm reaching movements to examine whether task-related activities are sensitive to manipulations of the serial order of stimulus-target locations. The monkeys' capacity to learn sequential regularities was assessed by comparing arm movement latencies and saccadic ocular reactions when a fixed repeating sequence was replaced with a random sequence. We examined neurons classified as phasically active projection neurons (PANs) and tonically active presumed cholinergic interneurons (TANs). About one-third of the PANs (35/106, 33%) activated during specific parts of a trial displayed modulations of their level of activation when the sequential structure was changed. This differential activity consisted of either decreases or increases in activity without altering the time period during which task-related activations occurred. In addition, half of the TANs (41/80, 51%) changed their responses to task stimuli with the sequence switch, indicating that the response selectivity of TANs reflects the detection of the context that requires adaptation to changes in the serial order of stimulus presentations. Our findings suggest that task-related changes in activity of projection neurons may be an important factor contributing to the production and adjustment of sequential behavior executed in an automatic fashion, whereas putative interneurons may provide a signal for performance monitoring in specific contexts.

Age Differences in the Functional Field-of-View while Driving: A Preliminary Simulator-Based Study

This study represents an initial exploration of a new technique developed to permit the assessment of age differences in the “useful field of view” (Ball, et al., 1993) while simultaneously operating a motor vehicle. Due to necessary safety precautions, this novel approach was first evaluated using a simulated rather than a real-world driving context. Data was collected from seventeen young (mean age = 19.8) and eight older (mean age = 72.9) adult volunteers. Preliminary data analyses indicated that the technique was sensitive to “tunnel vision” effects resulting from experimentally induced limitations in the time available to process stimulus target “onset” events in the visual periphery. The magnitude and time-course of these effects differed markedly as a function of the age of the observer. Shortcomings in the current implementation of the technique and planned improvements are also discussed.

The Influence of Eccentricity, Contrast, and Angular Extent on the Perception of Peripheral Apparent Motion

Two experiments were performed to investigate the perception of peripherally presented apparent motion as a function of eccentricity of the stimulus, ambient illumination, gender, athletic ability, age, stimuli pattern (diamond, square), and angular extent of stimuli presentation. The experiment task for both studies was to determine the direction of apparent motion for a lighter than background stimulus target presented on a Braumbach perimeter. The results from experiment one indicated main effects for subjects, eccentricity, and age. The results from experiment two indicated main effects for subjects, eccentricity, and angular separation of the apparent motion.

Spatial Awareness with a Helmet-Mounted Display

Two experiments were conducted to determine the human's ability to acquire and memorize the spatial locations of stimulus targets using a helmet-mounted display. The experimental task was a two-phase search and replace task in which the size of the field-of-view (FOV) on the helmet-mounted display and the memory load (number of targets) were manipulated. In Experiment 1, all stimulus targets were removed after the search phase. In Experiment 2, only the three stimulus targets to be replaced were removed, leaving the subjects with some contextual information regarding the overall pattern of targets. Results of both experiments showed that: 1) search time increased significantly as the size of the FOV became smaller, and 2) subjects' ability to replace a stimulus target in its original location in space was adversely affected by increases in memory load. These results indicate that the size of the FOV affects one's ability to acquire spatial information of one's surroundings, but once this information has been mapped into spatial memory, humans can use that information independently of the size of their “window” to the world. However, subjects' spatial memory has some limitations, since the ability to remember precise locations becomes poorer as the amount of information to remember increases. The effects of additional context provided in Experiment 2 resulted in a slight increase in the precision with which subjects could remember specific target locations. The results of these studies have implications in two areas: human spatial cognition, and the design of helmet-mounted displays.

Effects of Room Reflectance and Background Noise on Perceived Auditory Distance

Perceptions of egocentric auditory distance were investigated within an environment for which the reverberation time could be systematically varied without changes in the size or shape of the room. Two levels of wide-band background noise, differing by 20 dB, were used as a masking stimulus. Target sounds were presented from distances between 0.75 and 6.0 m and verbal reports of distance were collected from 288 listeners in two separate experiments. Changes in physical distance produced variation in reported distance in each configuration. Reported distance was generally proportional to real distance, but considerably underestimated when room reflectance was low. When room reflectance was high ( T60 ≈ 1.7 s for the range of frequencies used), initial reports of distance were often overestimates; upon repeated presentation, judgments in the high reflectance room became more nearly veridical. The effect of increasing the background noise level was to decrease the perceived distance. These findings are in accord with expectations based upon the importance of reverberation cue(s) to distance and upon previous analyses from this laboratory.