Second Guessing in Perceptual Decision-Making.

Human subjects of both sexes were asked to make a perceptual decision between multiple directions of visual motion. In addition to reporting a primary choice, they also had to report a second guess, indicating which of the remaining options they would rather bet on, assuming that they got their primary choice wrong. The second guess was clearly informed by the amounts of sensory evidence that were provided for the different options. A single computational integration-to-threshold model, based on the assumption that the second guess is determined by the rank ordering of accumulated evidence at or shortly after the time of the decision, was able to explain the distribution of primary choices, associated response times, and the distribution of second guesses. This suggests that the decision-maker has access to how well supported unchosen options are by the sensory evidence.SIGNIFICANCE STATEMENT Perceptual decisions require conversion of sensory evidence into a discrete choice. Computational models based on the accumulation of evidence to a decision threshold can explain the distribution of choices and associated decision times. Subjects are also able to report the level of confidence in their decision. Here we show that, when making decisions between more than two alternatives, the decision-maker can even report a second guess that is clearly informed by the sensory evidence. These second guesses show a distribution that is consistent with subjects having access to how much sensory evidence was accumulated for the unchosen options. The decision-maker therefore has knowledge about the outcome of the decision process that goes beyond just the choice and an associated confidence

I, NEURON: the neuron as the collective

Purpose – In the last half-century, individual sensory neurons have been bestowed with characteristics of the whole human being, such as behavior and its oft-presumed precursor, consciousness. This anthropomorphization is pervasive in the literature. It is also absurd, given what we know about neurons, and it needs to be abolished. This study aims to first understand how it happened, and hence why it persists. Design/methodology/approach – The peer-reviewed sensory-neurophysiology literature extends to hundreds (perhaps thousands) of papers. Here, more than 90 mainstream papers were scrutinized. Findings – Anthropomorphization arose because single neurons were cast as “observers” who “identify”, “categorize”, “recognize”, “distinguish” or “discriminate” the stimuli, using math-based algorithms that reduce (“decode”) the stimulus-evoked spike trains to the particular stimuli inferred to elicit them. Without “decoding”, there is supposedly no perception. However, “decoding” is both unnecessary and unconfirmed. The neuronal “observer” in fact consists of the laboratory staff and the greater society that supports them. In anthropomorphization, the neuron becomes the collective. Research limitations/implications – Anthropomorphization underlies the widespread application to neurons Information Theory and Signal Detection Theory, making both approaches incorrect. Practical implications – A great deal of time, money and effort has been wasted on anthropomorphic Reductionist approaches to understanding perception and consciousness. Those resources should be diverted into more-fruitful approaches. Originality/value – A long-overdue scrutiny of sensory-neuroscience literature reveals that anthropomorphization, a form of Reductionism that involves the presumption of single-neuron consciousness, has run amok in neuroscience. Consciousness is more likely to be an emergent property of the brain

Blind insight: metacognitive discrimination despite chance task performance

Blindsight and other examples of unconscious knowledge and perception demonstrate dissociations between judgment accuracy and metacognition: Studies reveal that participants’ judgment accuracy can be above chance while their confidence ratings fail to discriminate right from wrong answers. Here, we demonstrated the opposite dissociation: a reliable relationship between confidence and judgment accuracy (demonstrating metacognition) despite judgment accuracy being no better than chance. We evaluated the judgments of 450 participants who completed an AGL task. For each trial, participants decided whether a stimulus conformed to a given set of rules and rated their confidence in that judgment. We identified participants who performed at chance on the discrimination task, utilizing a subset of their responses, and then assessed the accuracy and the confidence-accuracy relationship of their remaining responses. Analyses revealed above-chance metacognition among participants who did not exhibit decision accuracy. This important new phenomenon, which we term blind insight, poses critical challenges to prevailing models of metacognition grounded in signal detection theory

Backwards is the way forward: feedback in the cortical hierarchy predicts the expected future

Clark offers a powerful description of the brain as a prediction machine, which offers progress on two distinct levels. First, on an abstract conceptual level, it provides a unifying framework for perception, action, and cognition (including subdivisions such as attention, expectation, and imagination). Second, hierarchical prediction offers progress on a concrete descriptive level for testing and constraining conceptual elements and mechanisms of predictive coding models (estimation of predictions, prediction errors, and internal models)

Higher-order thoughts in action : Consciousness as an unconscious re-description process

Peer reviewedPostprin

Waiting is the Hardest Part: Comparison of Two Computational Strategies for Performing a Compelled-Response Task

The neural basis of choice behavior is commonly investigated with tasks in which a subject analyzes a stimulus and reports his or her perceptual experience with an appropriate motor action. We recently developed a novel task, the compelled-saccade task, with which the influence of the sensory information on the subject's choice can be tracked through time with millisecond resolution, thus providing a new tool for correlating neuronal activity and behavior. This paradigm has a crucial feature: the signal that instructs the subject to make an eye movement is given before the cue that indicates which of two possible choices is the correct one. Previously, we found that psychophysical performance in this task could be accurately replicated by a model in which two developing oculomotor plans race to a threshold and the incoming perceptual information differentially accelerates their trajectories toward it. However, the task design suggests an alternative mechanism: instead of modifying an ongoing oculomotor plan on the fly as the sensory information becomes available, the subject could try to wait, withholding the oculomotor response until the sensory cue is revealed. Here, we use computer simulations to explore and compare the performance of these two types of model. We find that both reproduce the main features of the psychophysical data in the compelled-saccade task, but they give rise to distinct behavioral and neurophysiological predictions. Although, superficially, the waiting model is intuitively appealing, it is ultimately inconsistent with experimental results from this and other tasks

Endogenicity and awareness in voluntary action

The idea that we can trigger and control our actions at will is central to our experience as agents. Here, we investigated different cognitive mechanisms involved in voluntary action control. In the first part of the thesis, we investigated the relationship between motor preparation and awareness of intention. To do so, we used spontaneous action paradigms and combined them with novel random and real-time EEG probing techniques. We investigated two main questions. First, do people know that they are about to do something before they do it? Second, to what extent are delayed intention judgements informed by prospective motor preparation rather than retrospective reconstruction? Our findings suggest that people have some feeling of motor intention before acting and can use it to voluntarily control action initiation in real-time. However, their recall-based intention judgements are strongly influenced by overt events happening after the time of probing. Because most daily-life voluntary actions occur in interaction with the environment, in the second part of the thesis we embedded self-paced actions in a decision-making context. We investigated two ways in which endogenous factors can contribute to action selection. First, as a symmetry-breaking mechanism in contexts of external ambiguity. Second, by top-down modulating decision-making processes. We identified the neural correlates of an internal decision-variable that tracks perceptual decisions and also indexes dynamic changes in endogenous goals. Further, we show that the readiness potential can be found not only preceding spontaneous actions, but also in contexts where actions are informed by evidence but preserve a self-paced nature. In sum, this thesis provides new insights into the cognitive mechanisms underlying conscious experience of intention and provides new tools to investigate voluntary control over action initiation and selection processes

Somatic salience and sensory precision in persistent depression

Persistent depression is a debilitating health condition with a poor prognosis even in the context of current gold-standard pharmacological and psychological interventions. A better understanding of the mechanisms contributing to its maintenance is needed to facilitate the development of more targeted psychological interventions. Bayesian predictive processing models of depression propose that negative emotional and physiological outcomes arise in depressive illness as a result of disturbed interoceptive precision estimation in depressed individuals; however, evidence from the clinical and cognitive neuroscience literatures suggests the hypothesis that sensory precision is attenuated in persistent depression across sensory modalities in general. A series of studies was designed to index sensory precision across somatic and auditory modalities and to identify the level at which any disruption manifested in persistently-depressed participants relative to controls. Study 1 (Chapter 3) measured baseline signal discriminability under conditions of focused attention. Study 2 (Chapter 4) measured the impact of failures of voluntary attention on signal discriminability. Study 3 (Chapter 5) used a simulation approach to model sensory precision in the first two studies and to identify mechanisms which could successfully predict the data. Studies 4 (Chapter 6) and 5 (Chapter 7) measured attentional capture by task-irrelevant and predictive sensory cues respectively. Study 6 (Chapter 8) partially replicated Studies 4 and 5 and used the resulting data to estimate the group-level sensory precision and salience parameters of a predictive processing model of precision optimization. The results suggest that sensory precision is attenuated in persistent depression across sensory modalities, and that this attenuation results from disturbances of voluntary and involuntary attention rather than baseline perceptual sensitivity. Under conditions of voluntary attention, reduced sensory precision may result from efforts at resource conservation; and under conditions of involuntary attentional capture, it may be related to a loss of target discriminability and salience. Conversely, the bottom-up salience of somatic stimuli was uniquely enhanced among depressed participants and was predicted by high anxiety and by low interoceptive sensibility. These findings open up new avenues for investigation of the mechanisms underlying persistent forms of depression, and have direct implications for clinical practice with respect to psychological intervention.Medical Research Council Studentshi

Uncovering contextual biases in human decision-making. A multivariate analysis approach for patterns of functional magnetic resonance imaging data and event-related potentials

Decision-making is a fundamental aspect of human cognition and behaviour. Every day, we make a multitude of decisions, ranging from rather simple perceptual choices to complex financial decisions. The underlying cognitive and neural mechanisms appear to directly deploy external information, gathered by our senses, as well as internal information, such as preferences and beliefs. Ideally, this results in well-informed decisions and successful goal-directed behaviour. In reality, however, we are often faced with decision situations in which we do not have clear preferences, or access to all information. In these situations, contextual factors appear to have a strong influence on decision-makers. This work highlights recent research supporting the hypothesis that contextual information can exert significant biases on a variety of decision processes outside decision-makers’ awareness. These studies further exemplify a content-based cognitive neuroscience approach to human decision-making research, building on multivariate analysis techniques for brain imaging data to directly predict the content of decision outcomes and other decision-related variables from brain activity

Valence-Specific Modulation in the Accumulation of Perceptual Evidence Prior to Visual Scene Recognition

Visual scene recognition is a dynamic process through which incoming sensory information is iteratively compared with predictions regarding the most likely identity of the input stimulus. In this study, we used a novel progressive unfolding task to characterize the accumulation of perceptual evidence prior to scene recognition, and its potential modulation by the emotional valence of these scenes. Our results show that emotional (pleasant and unpleasant) scenes led to slower accumulation of evidence compared to neutral scenes. In addition, when controlling for the potential contribution of non-emotional factors (i.e., familiarity and complexity of the pictures), our results confirm a reliable shift in the accumulation of evidence for pleasant relative to neutral and unpleasant scenes, suggesting a valence-specific effect. These findings indicate that proactive iterations between sensory processing and top-down predictions during scene recognition are reliably influenced by the rapidly extracted (positive) emotional valence of the visual stimuli. We interpret these findings in accordance with the notion of a genuine positivity offset during emotional scene recognition