Brian Maniscalco

Publications of Brian Maniscalco

• Does response interference depend on the subjective visibility of flanker distractors?

  Authors: Brian Maniscalco, Joo Won Bang, Laila Iravani, Franc Camps-Febrer, Hakwan Lau

  Attention, perception & psychophysics. 04/2012;

  Response interference (or response conflict) refers to the phenomenon whereby response times to a target stimulus are longer in the presence of distractor stimuli that indicate contrary motorResponse interference (or response conflict) refers to the phenomenon whereby response times to a target stimulus are longer in the presence of distractor stimuli that indicate contrary motor responses. Response interference has been observed even when the distractor stimuli cannot be discriminated above chance levels. These results raise the question of whether response interference might be driven automatically by the physical distractor stimuli, independently of one's subjective perception of the distractors. Using a modified version of the Eriksen flanker task, we applied metacontrast masks to the flanker stimuli and measured their subjective visibility after each trial. We found converging lines of evidence that the subjective perception of flankers contributed to response interference, over and above the contribution of automatic processing of the stimulus itself. A factorial analysis revealed that the objective, physical congruency of target and flankers and the subjective, perceptual congruency of target and flankers make additive, noninteracting contributions to target response interference, suggesting that the two interference effects originate from independent levels or stages of cognitive processing.

• Direct injection of noise to the visual cortex decreases accuracy but increases decision confidence.

  Authors: Dobromir Asenov Rahnev, Brian Maniscalco, Bruce Luber, Hakwan Lau, Sarah H Lisanby

  Journal of neurophysiology. 12/2011;

  The relationship between accuracy and confidence in psychophysical tasks has been traditionally assumed to be mainly positive, i.e. the two typically increase or decrease together. However, recentThe relationship between accuracy and confidence in psychophysical tasks has been traditionally assumed to be mainly positive, i.e. the two typically increase or decrease together. However, recent studies have reported examples of exceptions where confidence and accuracy dissociate from each other. Explanations for such dissociations often involve dual-channel models in which a cortical channel contributes to both accuracy and confidence, while a sub-cortical channel only contributes to accuracy. Here we show that a single-channel model derived from signal detection theory (SDT) can also account for such dissociations. We applied transcranial magnetic stimulation (TMS) to the occipital cortex to disrupt the internal representation of a visual stimulus. The results showed that, consistent with previous research, occipital TMS decreased accuracy. However, counter-intuitively, it also led to an increase in confidence ratings. The data were predicted well by a single-channel SDT model which posits that occipital TMS increased the variance of the internal stimulus distributions. A formal model comparison analysis that used information theoretic methods confirmed that this model was preferred over single-channel models in which occipital TMS changed the signal strength, or dual-channel models which assume two different processing routes. Thus, our results show that dissociations between accuracy and confidence can, at least in some cases, be accounted for by a single-channel model.

• Attention induces conservative subjective biases in visual perception.

  Authors: Dobromir Rahnev, Brian Maniscalco, Tashina Graves, Elliott Huang, Floris P de Lange, Hakwan Lau

  Nature neuroscience. 12/2011; 14(12):1513-5.

  Although attention usually enhances perceptual sensitivity, we found that it can also lead to relatively conservative detection biases and lower visibility ratings in discrimination tasks. TheseAlthough attention usually enhances perceptual sensitivity, we found that it can also lead to relatively conservative detection biases and lower visibility ratings in discrimination tasks. These results are explained by a model in which attention reduces the trial-by-trial variability of the perceptual signal, and we determined how this model led to the observed behavior. These findings may partially reflect our impression of 'seeing' the whole visual scene despite our limited processing capacity outside of the focus of attention.

• A signal detection theoretic approach for estimating metacognitive sensitivity from confidence ratings.

  Authors: Brian Maniscalco, Hakwan Lau

  Consciousness and cognition. 11/2011; 21(1):422-30.

  How should we measure metacognitive ("type 2") sensitivity, i.e. the efficacy with which observers' confidence ratings discriminate between their own correct and incorrect stimulus classifications?How should we measure metacognitive ("type 2") sensitivity, i.e. the efficacy with which observers' confidence ratings discriminate between their own correct and incorrect stimulus classifications? We argue that currently available methods are inadequate because they are influenced by factors such as response bias and type 1 sensitivity (i.e. ability to distinguish stimuli). Extending the signal detection theory (SDT) approach of Galvin, Podd, Drga, and Whitmore (2003), we propose a method of measuring type 2 sensitivity that is free from these confounds. We call our measure meta-d', which reflects how much information, in signal-to-noise units, is available for metacognition. Applying this novel method in a 2-interval forced choice visual task, we found that subjects' metacognitive sensitivity was close to, but significantly below, optimality. We discuss the theoretical implications of these findings, as well as related computational issues of the method. We also provide free Matlab code for implementing the analysis.

• Awareness-related activity in prefrontal and parietal cortices in blindsight reflects more than superior visual performance.

  Authors: Navindra Persaud, Matthew Davidson, Brian Maniscalco, Dean Mobbs, Richard E Passingham, Alan Cowey, Hakwan Lau

  NeuroImage. 09/2011; 58(2):605-11.

  Many imaging studies report activity in the prefrontal and parietal cortices when subjects are aware as opposed to unaware of visual stimuli. One possibility is that this activity simply reflectsMany imaging studies report activity in the prefrontal and parietal cortices when subjects are aware as opposed to unaware of visual stimuli. One possibility is that this activity simply reflects higher signal strength or the superior task performance that is associated with awareness. To find out, we studied the hemianope GY who has unilateral destruction of almost all primary visual cortices. He exhibits 'blindsight', that is, he claims to have no conscious visual phenomenology (i.e., no visual qualia), for stationary stimuli presented to his right visual field (the blind field), although he can press keys to distinguish between different stimuli presented there. We presented to him a visual discrimination task, and equated performance for stimuli presented to the left or right visual field by presenting low contrast stimuli to his normal (left) field and high contrast stimuli to his blind (right) field. Superior accuracy can be a serious confound, and our paradigm allows us to control for it and avoid this confound. Even when performance was matched, and the signal strength was lower, visual stimulation to the normal (conscious) field led to higher activity in the prefrontal and parietal cortices. These results indicate that the activity in the prefrontal and parietal areas that has been reported in previous studies of awareness is not just due to a (signal strength or performance) confounds. One possibility is that it reflects the superior 'metacognitive' capacity that is associated with awareness, because GY was better able to distinguish between his own correct and incorrect responses for stimuli presented to his normal field than to his blind field.

• Neuroscience. Should confidence be trusted?

  Authors: Hakwan Lau, Brian Maniscalco

  Science (New York, N.Y.). 09/2010; 329(5998):1478-9.