Alex Filipowicz

Statistical and perceptual updating: correlated impairments in right brain injury

Abstract It has been hypothesized that many of the cognitive impairments commonly seen after right brain damage (RBD) can be characterized as a failure to build or update mental models. We (Danckert et al. in Neglect as a disorder of representational updating. NOVA Open Access, New York, 2012a; Cereb Cortex 22:2745–2760, 2012b) were the first to directly assess the association between RBD and updating and found that RBD patients were unable to exploit a strongly biased play strategy in their opponent in the children’s game rock, paper, scissors. Given that this game required many other cognitive capacities (i.e., working memory, sustained attention, reward processing), RBD patients could have failed this task for various reasons other than a failure to update. To assess the generality of updating deficits after RBD, we had RBD, left brain-damaged (LBD) patients and healthy controls (HCs) describe line drawings that evolved gradually from one figure (e.g., rabbit) to another (e.g., duck) in addition to the RPS updating task. RBD patients took significantly longer to alter their perceptual report from the initial object to the final object than did LBD patients and HCs. Although both patient groups performed poorly on the RPS task, only the RBD patients showed a significant correlation between the two, very different, updating tasks. We suggest these data indicate a general deficiency in the ability to update mental representations following RBD.

Learning what from where: Effects of spatial regularity on nonspatial sequence learning and updating

The current study examined the influence of redundant stimulus features on our ability to build and update representations of our environment. We hypothesized that our ability to process redundant spatial features would speed our ability to adapt to changing nonspatial regularities. Using a computerized version of the childrens game “rock–paper–scissors”, undergraduates were instructed to win as often as possible against a computer opponent. The computers plays were repeating sequences of five choices that were presented either with spatial regularity (i.e., “rock” would always appear on the left, “paper” in the middle, and “scissors” on the right) or without spatial regularity (i.e., the items were equally likely to appear in any of the three locations). Once participants learned a sequence, the computer switched to a different sequence without participants being informed that a switch had occurred. Redundant spatial regularity improved a participants ability both to learn sequences of plays and to update their plays to reflect new computer sequences. Our results suggest that our perceptual system is sensitive to redundant spatial stimulus features and that this information can improve learning and updating.

Tuned by experience: How orientation probability modulates early perceptual processing

ABSTRACT Probable stimuli are more often and more quickly detected. While stimulus probability is known to affect decision‐making, it can also be explained as a perceptual phenomenon. Using spatial gratings, we have previously shown that probable orientations are also more precisely estimated, even while participants remained naive to the manipulation. We conducted an electrophysiological study to investigate the effect that probability has on perception and visual‐evoked potentials. In line with previous studies on oddballs and stimulus prevalence, low‐probability orientations were associated with a greater late positive ‘P300’ component which might be related to either surprise or decision‐making. However, the early ‘C1’ component, thought to reflect V1 processing, was dampened for high‐probability orientations while later P1 and N1 components were unaffected. Exploratory analyses revealed a participant‐level correlation between C1 and P300 amplitudes, suggesting a link between perceptual processing and decision‐making. We discuss how these probability effects could be indicative of sharpening of neurons preferring the probable orientations, due either to perceptual learning, or to feature‐based attention.

Knowing where is different from knowing what: Distinct response time profiles and accuracy effects for target location, orientation, and color probability

When a location is cued, targets appearing at that location are detected more quickly. When a target feature is cued, targets bearing that feature are detected more quickly. These attentional cueing effects are only superficially similar. More detailed analyses find distinct temporal and accuracy profiles for the two different types of cues. This pattern parallels work with probability manipulations, where both feature and spatial probability are known to affect detection accuracy and reaction times. However, little has been done by way of comparing these effects. Are probability manipulations on space and features distinct? In a series of five experiments, we systematically varied spatial probability and feature probability along two dimensions (orientation or color). In addition, we decomposed response times into initiation and movement components. Targets appearing at the probable location were reported more quickly and more accurately regardless of whether the report was based on orientation or color. On the other hand, when either color probability or orientation probability was manipulated, response time and accuracy improvements were specific for that probable feature dimension. Decomposition of the response time benefits demonstrated that spatial probability only affected initiation times, whereas manipulations of feature probability affected both initiation and movement times. As detection was made more difficult, the two effects further diverged, with spatial probability disproportionally affecting initiation times and feature probability disproportionately affecting accuracy. In conclusion, all manipulations of probability, whether spatial or featural, affect detection. However, only feature probability affects perceptual precision, and precision effects are specific to the probable attribute.

Rejecting Outliers: Surprising Changes Do Not Always Improve Belief Updating.

An important human skill is the ability to update one’s beliefs when they are no longer supported by the environment. Current models of dynamic decision-making suggest that more unexpected, or “surprising,” events lead to quicker belief updating. The current article tests the ubiquity of the notion that surprising environmental changes are always positively related to updating. Using a novel task based on the game Plinko, we tracked participants’ beliefs as they learned distributions of ball drops. At an unannounced point during the task, the distribution of ball drops changed and we computed how surprising these changes were relative to participants’ beliefs and compared how this surprise factor influenced their ability to update their beliefs to reflect the change. We found that, consistent with current models, there were some situations in which belief updating was positively related to the surprise of a change. However, we also found a situation in which highly surprising changes were negatively related to updating—situations where participants tended to update less with increasingly surprising changes. This negative relationship seems due to participants’ treating highly surprising events as “outliers” and choosing not to integrate them in their current beliefs. Our results provide a novel and more nuanced representation of the relationship between surprise and updating that should be considered in models of dynamic decision-making.