The implied motion aftereffect changes decisions, but not confidence

Motion After-Effects Induced by Dynamic Illumination in Crab Vision

Motion detection is an elementary aspect of most animal visual systems. However, many environments are prone to background motion, which might disrupt the ability of visual systems to detect relevant motion cues. While in humans, background motion can disrupt the detection of visual cues even after the moving background component has ceased, it remains unknown whether natural forms of background motion might also affect other animal visual systems. Here, we test whether prior exposure to naturally occurring 'caustics', a form of dynamically moving light patterns commonly found in shallow aquatic environments, can have a persisting effect on an animal's motion detection abilities even after the caustic exposure has stopped. To do this, we established the response probability of the shore crab Carcinus maenas to computer-generated expanding disc stimuli mimicking an approaching predator after exposure to either static or moving caustic scenes. Prior exposure to moving caustics had a short-term persisting effect on visual perception in C. maenas, reducing crabs' likelihood to respond to an approaching predator for at least 2 s after the moving caustics had ceased. Our study shows that even after an exposure period to background motion has ended, the visual response rates in C. maenas can still be reduced for a short period owing to the prior exposure. While this so-called 'historical effect' may derive from an adaptation of the crab's visual system to the caustic background motion, we discuss whether it may have survival consequences for this crustacean species.

An entropy model of decision uncertainty

Studying metacognition, the introspection of one's own decisions, can provide insights into the mechanisms underlying the decision. Here we show that observers' uncertainty about their decisions incorporate both the entropy of the stimuli and the entropy of their response probability across the psychometric function. Being able to describe uncertainty data with a functional form permits the measurement of internal parameters not measurable from the decision responses alone. To test and demonstrate the utility of this novel model, we measured uncertainty in 11 participants as they judged the relative contrast appearance of two stimuli in several experiments employing implicit bias or attentional cues. The entropy model enabled an otherwise intractable quantitative analysis of participants' uncertainty, which in one case distinguished two comparative judgments that produced nearly identical psychometric functions. In contrast, comparative and equality judgments with different behavioral reports, yielded uncertainty reports that were not significantly different. The entropy model was able to successfully account for uncertainty in these two different types of decisions that resulted in differently shaped psychometric functions, and the entropy contribution from the stimuli, which were identical across experiments, was consistent. An observer's uncertainty could therefore be measured the total entropy of the inputs and outputs of the stimulus-response system, i.e. the entropy of the stimuli plus the entropy of the observer's responses.

Dynamics of sensory and decisional biases in perceptual decision making: Insights from the face distortion illusion

Bias in perceptual decision making can have both sensory and decisional origins. These distinct sources of bias are typically seen as static and stable over time. However, human behavior is dynamic and constantly adapting. Yet it remains unclear how sensory and decisional biases progress in distinct ways over time. We addressed this question by tracking the dynamics of sensory and decisional biases during a task that involves a visual illusion. Observers saw multiple pairs of peripherally presented faces that induce a strong illusion making the faces appear distorted and grotesque. The task was to judge whether one of the last two faces had true physical distortion (experimentally introduced in half of the trials). Initially, participants classified most faces as distorted as exemplified by a liberal response bias. However, over the course of the experiment, this response bias gradually disappeared even though the distortion illusion remained equally strong, as demonstrated by a separate subjective rating task without artificially distorted faces. The results suggest that the sensory bias was progressively countered by an opposite decisional bias. This transition was accompanied by an increase in reaction times and a decrease in confidence relative to a condition that does not induce the visual illusion. All results were replicated in a second experiment with inverted faces. These findings demonstrate that participants dynamically adjust their decisional bias to compensate for sensory biases, and that these two biases together determine how humans make perceptual decisions.

The role of attention in eliciting a musically induced visual motion aftereffect

Previous studies have reported visual motion aftereffects (MAEs) following prolonged exposure to auditory stimuli depicting motion, such as ascending or descending musical scales. The role of attention in modulating these cross-modal MAEs, however, remains unclear. The present study manipulated the level of attention directed to musical scales depicting motion and assessed subsequent changes in MAE strength. In Experiment 1, participants either responded to an occasional secondary auditory stimulus presented concurrently with the musical scales (diverted-attention condition) or focused on the scales (control condition). In Experiment 2 we increased the attentional load of the task by having participants perform an auditory 1-back task in one ear, while the musical scales were played in the other. Visual motion perception in both experiments was assessed via random dot kinematograms (RDKs) varying in motion coherence. Results from Experiment 1 replicated prior work, in that extended listening to ascending scales resulted in a greater likelihood of judging RDK motion as descending, in line with the MAE. In contrast, the MAE was eliminated in Experiment 2. These results were internally replicated using an in-lab, within-participant design (Experiment 3). These results suggest that attention is necessary in eliciting an auditory-induced visual MAE.

Direction-selective adaptation from implied motion in infancy

We investigated whether adaptation from implied motion (IM) is transferred to real motion using optokinetic nystagmus (OKN) in infants. Specifically, we examined whether viewing a series of images depicting motion shifted infants' OKN responses to the opposite direction of random dot kinematograms (RDKs). Each RDK was presented 10 times in a pre-test, followed by 10 trials of IM adaptation and test. During the pre-test, the signal dots of the RDK moved left or right. During IM adaptation, 10 randomly selected images depicting leftward (or rightward) IM were presented. In the test, the RDK was presented immediately after the last IM image. An observer, blinded to the motion direction, assessed the OKN direction. The number of matches in OKN responses for each RDK direction was calculated as the match ratio of OKN. We conducted a two-way mixed analysis of variance, with age group (5-6 months and 7-8 months) as the between-participant factor and adaptation (pre-test and test) as the within-participant factor. Only in 7-8 months the OKN responses were shifted in the opposite direction of RDK by viewing a series of images depicting motion, and these infants could detect both IM and RDK motion directions in the pre-test. Our results indicate that detecting the IM and RDK directions might induce direction-selective adaptation in 7-8 months.

Introspective inference counteracts perceptual distortion

Introspective agents can recognize the extent to which their internal perceptual experiences deviate from the actual states of the external world. This ability, also known as insight, is critically required for reality testing and is impaired in psychosis, yet little is known about its cognitive underpinnings. We develop a Bayesian modeling framework and a psychophysics paradigm to quantitatively characterize this type of insight while people experience a motion after-effect illusion. People can incorporate knowledge about the illusion into their decisions when judging the actual direction of a motion stimulus, compensating for the illusion (and often overcompensating). Furthermore, confidence, reaction-time, and pupil-dilation data all show signatures consistent with inferential adjustments in the Bayesian insight model. Our results suggest that people can question the veracity of what they see by making insightful inferences that incorporate introspective knowledge about internal distortions.

Predictive extrapolation effects can have a greater impact on visual decisions, while visual adaptation has a greater impact on conscious visual experience

Human vision is shaped by historic and by predictive processes. The lingering impact of visual adaptation, for instance, can act to exaggerate differences between past and present inputs, whereas predictive processes can promote extrapolation effects that allow us to anticipate the near future. It is unclear to what extent either of these effects manifest in changes to conscious visual experience. It is also unclear how these influences combine, when acting in concert or opposition. We had people make decisions about the sizes of inputs, and report on levels of decisional confidence. Tests were either selectively subject to size adaptation, to an extrapolation effect, or to both of these effects. When these two effects were placed in opposition, extrapolation had a greater impact on decision making. However, our data suggest the influence of extrapolation is primarily decisional, whereas size adaptation more fully manifests in changes to conscious visual awareness.

Confidence in consciousness research

To study (un)conscious perception and test hypotheses about consciousness, researchers need procedures for determining whether subjects consciously perceive stimuli or not. This article is an introduction to a family of procedures called "confidence-based procedures," which consist in interpreting metacognitive indicators as indicators of consciousness. I assess the validity and accuracy of these procedures, and answer a series of common objections to their use in consciousness research. I conclude that confidence-based procedures are valid for assessing consciousness, and, in most cases, accurate enough for our practical and scientific purposes. This article is categorized under: Psychology > Perception and Psychophysics Philosophy > Consciousness.

A metacognitive approach to the study of motion-induced duration biases reveals inter-individual differences in forming confidence judgments

Our ability to estimate the duration of subsecond visual events is prone to distortions, which depend on both sensory and decisional factors. To disambiguate between these two influences, we can look at the alignment between discrimination estimates of duration at the point of subjective equality and confidence estimates when the confidence about decisions is minimal, because observers should be maximally uncertain when two stimuli are perceptually the same. Here, we used this approach to investigate the relationship between the speed of a visual stimulus and its perceived duration. Participants were required to compare two intervals, report which had the longer duration, and then rate their confidence in that judgment. One of the intervals contained a stimulus drifting at a constant speed, whereas the stimulus embedded in the other interval could be stationary, linearly accelerating or decelerating, or drifting at the same speed. Discrimination estimates revealed duration compression for the stationary stimuli and, to a lesser degree, for the accelerating and decelerating stimuli. Confidence showed a similar pattern, but, overall, the confidence estimates were shifted more toward higher durations, pointing to a small contribution of decisional processes. A simple observer model, which assumes that both judgments are based on the same sensory information, captured well inter-individual differences in the criterion used to form a confidence judgment.