Deep learning as an alternative to global optimization in diffusion model for conflict tasks

To apply mathematical models of decision making in psychological research, researchers need ways to extract model parameters from behavioural studies. The expansion of the drift diffusion model to con ict tasks (DMC) (Ulrich, Schroter, Leuthold, & Birngruber, 2015) resulted in the model being non-differentiable, which means that the parameters of DMC can only be estimated. The current methods for recovering parameters from DMC rely on comparing reaction time (RT) distributions. Such methods will struggle to recover all DMC parameters well due to the of the solution space of DMC, which means that some parameters can be confused with others when RT distributions are compared. Following that, five global optimization algorithms from different optimization families were compared to create a benchmark for parameter recovery from DMC. The results revealed that differential evolution outperformed the other four optimization algorithms in recovery of parameters from both distributions with high and low trial numbers. Even though differential evolution is capable of recovering parameters well, it is very expensive in computational time, which means that researchers who do not have access to vast computational resources cannot apply DMC in their research. Due to this, deep learning was investigated in application of parameter recovery from DMC. The results showed that deep learning recovered all model parameters exceptionally well from RT distributions with large trial numbers, and as well as differential evolution from RT distributions with low trial numbers, which allows application of deep learning models in deployment pipelines that take seconds rather than months. Finally, deep learning models were applied in several experimental studies investigating the effects of speed-accuracy trade-off (SAT) in response inhibition and perceptual decision making tasks, and how the performance relates between the tasks and over two different testing sessions, and demonstrated the effects of SAT on DMC parameters in different tasks

The Role of Attention in Ambiguous Reversals of Structure-From-Motion

Multiple dots moving independently back and forth on a flat screen induce a compelling illusion of a sphere rotating in depth (structure-from-motion). If all dots simultaneously reverse their direction of motion, two perceptual outcomes are possible: either the illusory rotation reverses as well (and the illusory depth of each dot is maintained), or the illusory rotation is maintained (but the illusory depth of each dot reverses). We investigated the role of attention in these ambiguous reversals. Greater availability of attention – as manipulated with a concurrent task or inferred from eye movement statistics – shifted the balance in favor of reversing illusory rotation (rather than depth). On the other hand, volitional control over illusory reversals was limited and did not depend on tracking individual dots during the direction reversal. Finally, display properties strongly influenced ambiguous reversals. Any asymmetries between ‘front’ and ‘back’ surfaces – created either on purpose by coloring or accidentally by random dot placement – also shifted the balance in favor of reversing illusory rotation (rather than depth). We conclude that the outcome of ambiguous reversals depends on attention, specifically on attention to the illusory sphere and its surface irregularities, but not on attentive tracking of individual surface dots

Effect of attentional focus on the outcome of FAS.

<p>Mean ± standard error.</p

Spatial and temporal attention revealed by microsaccades

We compared the spatial and temporal allocation of attention as revealed by microsaccades. Observers viewed several concurrent “rapid serial visual presentation” (RSVP) streams in the periphery while maintaining fixation. They continually attended to, and discriminated targets in one particular, cued stream. Over and above this continuous allocation, spatial attention transients (“attention shifts”) were prompted by changes in the cued stream location and temporal attention transients (“attentional blinks”) by successful target discriminations. Note that the RSVP paradigm avoided the preparatory suppression of microsaccades in anticipation of stimulus or task events, which had been prominent in earlier studies. Both stream changes and target discriminations evoked residual modulations of microsaccade rate and direction, which were consistent with the presumed attentional dynamics in each case (i.e., attention shift and attentional blink, respectively). Interestingly, even microsaccades associated with neither stream change nor target discrimination reflected the continuous allocation of attention, inasmuch as their direction was aligned with the meridian of the target stream. We conclude that attentional allocation shapes microsaccadic activity continuously, not merely during dynamic episodes such as attentional shifts or blinks

Effect of availability of spatial attention on the outcome of FAS.

<p>A) Experimental procedure (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037734#s4" target="_blank">Methods</a> for details). A set of four letters was presented around the time of FAS, “bracketing” it by ±100 ms and was followed shortly by a mask. The response was collected after the stimulus presentation. B) Performance for the letter task in a single task (observers responded on letter task only) and dual task conditions. C) For all observers (near) absence of attention resulted in a highly significant drop of illusory motion reversal reports.</p

Effect of the colour patch.

<p>A) If the interpolated sphere is not symmetric relative to the zero depth plain at the time of FAS (e.g. as in a single patch condition), the <i>constant illusory motion reversal</i> outcome results in depth inversion for both individual dots (middle column) and the interpolated illusory sphere (right column). Compare to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037734#pone-0037734-g001" target="_blank">Figure 1D</a>. B) Example sphere with a single patch, snapshot taken at the time of FAS. C) Presence of a single colour patch results in significantly more frequent illusory motion reversals.</p

Illusory motion and depth of a rotating band.

<p>Illustrated are the instants just before and after FAS, with identical spatial distributions but opposite directions of motion. Top row: frontal views with two highlighted example dots (red and green). Middle and bottom rows: top views of the interpolated shapes, resulting from different combinations of illusory motion and illusory depth, again with two highlighted example dots (red and green). The arrows depict spontaneous reversals (green), reversals of illusory depth only (blue, constant illusory motion outcome of FAS), and reversals of illusory rotation only (red, illusory motion reversal outcome of FAS).</p

Volitional control over ambiguous illusory sphere during trials with (A) and without (B) forced ambiguous switch.

<p>Mean ± standard error. C) Strength of the volitional control defined as a difference in the percentage of illusory motion reversals between Switch and Hold conditions (see text for details).</p