Hierarchical structure is employed by humans during visual motion perception.

In the real world, complex dynamic scenes often arise from the composition of simpler parts. The visual system exploits this structure by hierarchically decomposing dynamic scenes: When we see a person walking on a train or an animal running in a herd, we recognize the individual's movement as nested within a reference frame that is, itself, moving. Despite its ubiquity, surprisingly little is understood about the computations underlying hierarchical motion perception. To address this gap, we developed a class of stimuli that grant tight control over statistical relations among object velocities in dynamic scenes. We first demonstrate that structured motion stimuli benefit human multiple object tracking performance. Computational analysis revealed that the performance gain is best explained by human participants making use of motion relations during tracking. A second experiment, using a motion prediction task, reinforced this conclusion and provided fine-grained information about how the visual system flexibly exploits motion structure.

The reliability and internal consistency of one-shot and flicker change detection for measuring individual differences in visual working memory capacity.

We investigated the psychometric properties of the one-shot change detection task for estimating visual working memory (VWM) storage capacity-and also introduced and tested an alternative flicker change detection task for estimating these limits. In three experiments, we found that the one-shot whole-display task returns estimates of VWM storage capacity (K) that are unreliable across set sizes-suggesting that the whole-display task is measuring different things at different set sizes. In two additional experiments, we found that the one-shot single-probe variant shows improvements in the reliability and consistency of K estimates. In another additional experiment, we found that a one-shot whole-display-with-click task (requiring target localization) also showed improvements in reliability and consistency. The latter results suggest that the one-shot task can return reliable and consistent estimates of VWM storage capacity (K), and they highlight the possibility that the requirement to localize the changed target is what engenders this enhancement. Through a final series of four experiments, we introduced and tested an alternative flicker change detection method that also requires the observer to localize the changing target and that generates, from response times, an estimate of VWM storage capacity (K). We found that estimates of K from the flicker task correlated with estimates from the traditional one-shot task and also had high reliability and consistency. We highlight the flicker method's ability to estimate executive functions as well as VWM storage capacity, and discuss the potential for measuring multiple abilities with the one-shot and flicker tasks.

Age and Species Comparisons of Visual Mental Manipulation Ability as Evidence for its Development and Evolution.

Intelligent behavior is shaped by the abilities to store and manipulate information in visual working memory. Although humans and various non-human animals demonstrate similar storage capacities, the evolution of manipulation ability remains relatively unspecified. To what extent are manipulation limits unique to humans versus shared across species? Here, we compare behavioral signatures of manipulation ability demonstrated by human adults and 6-to-8-year-old children with that of an animal separated from humans by over 300 million years of evolution: a Grey parrot (Psittacus erithacus). All groups of participants completed a variant of the "Shell Game", which required mentally updating the locations of varying set sizes of occluded objects that swapped places a number of times. The parrot not only demonstrated above-chance performance, but also outperformed children across all conditions. Indeed, the parrot's accuracy was comparable to (and slightly better than) human adults' over 12/14 set-size/number-of-swaps combinations, until four items were manipulated with 3-4 swaps, where performance decreased toward that of 6- to 8-year-olds. These results suggest that manipulation of visual working memory representations is an evolutionarily ancient ability. An important next step in this research program is establishing variability across species, and identifying the evolutionary origins (analogous or homologous) of manipulation mechanisms.

Using the flicker task to estimate visual working memory storage capacity.

Studies of visual working memory (VWM) typically have used a "one-shot" change detection task to arrive at a capacity estimate of three to four objects, with additional limits imposed by the precision of the information needed for each object. Unlike the one-shot task, the flicker change detection task permits measurement of VWM capacity over time and with larger numbers of objects present in the scene, but it has rarely been used to assess the capacity of VWM. We used the flicker task to examine (a) whether capacity is close to the typical three to four items when using subtly different stimuli; (b) which dependent measure provides the most meaningful estimate of the capacity of VWM in the flicker task (response time or number of changes viewed); (c) whether capacity remains fixed at three to four items for displays containing many more objects; and (d) how VWM operates over time, with repeated opportunities to encode, retain, and compare elements in a display. Four experiments using grids of simple items varying only in luminance or color revealed a range for VWM capacity limits that was largely impervious to changes in display duration, interstimulus intervals, and array size. This estimate of VWM capacity was correlated with an estimate from the more typical one-shot task, further validating the flicker task as a tool for measuring the capacity of VWM.

Visual working memory capacity increases between ages 3 and 8 years, controlling for gains in attention, perception, and executive control.

Research in adults has aimed to characterize constraints on the capacity of Visual Working Memory (VWM), in part because of the system's broader impacts throughout cognition. However, less is known about how VWM develops in childhood. Existing work has reached conflicting conclusions as to whether VWM storage capacity increases after infancy, and if so, when and by how much. One challenge is that previous studies did not control for developmental changes in attention and executive processing, which also may undergo improvement. We investigated the development of VWM storage capacity in children from 3 to 8 years of age, and in adults, while controlling for developmental change in exogenous and endogenous attention and executive control. Our results reveal that, when controlling for improvements in these abilities, VWM storage capacity increases across development and approaches adult-like levels between ages 6 and 8 years. More generally, this work highlights the value of estimating working memory, attention, perception, and decision-making components together.