Spatial memory in foraging games.

Foraging and foraging-like processes are found in spatial navigation, memory, visual search, and many other search functions in human cognition and behavior. Foraging is commonly theorized using either random or correlated movements based on Lévy walks, or a series of decisions to remain or leave proximal areas known as "patches". Neither class of model makes use of spatial memory, but search performance may be enhanced when information about searched and unsearched locations is encoded. A video game was developed to test the role of human spatial memory in a canonical foraging task. Analyses of search trajectories from over 2000 human players yielded evidence that foraging movements were inherently clustered, and that clustering was facilitated by spatial memory cues and influenced by memory for spatial locations of targets found. A simple foraging model is presented in which spatial memory is used to integrate aspects of Lévy-based and patch-based foraging theories to perform a kind of area-restricted search, and thereby enhance performance as search unfolds. Using only two free parameters, the model accounts for a variety of findings that individually support competing theories, but together they argue for the integration of spatial memory into theories of foraging.

Patterns of interaction-dominant dynamics in individual versus collaborative memory foraging.

The extent to which a cognitive system's behavioral dynamics fit a power law distribution is considered indicative of the extent to which that system's behavior is driven by multiplicative, interdependent interactions between its components. Here, we investigate the dynamics of memory processes in individual and collaborating participants. Collaborative dyads showed the characteristic collaborative inhibition effect when compared to nominal groups in terms of the number of items retrieved in a categorical recall task, but they also generate qualitatively different patterns of search behavior. To categorize search behavior, we used multi-model inference to compare the degree to which five candidate models (normal, exponential, gamma, lognormal, and Pareto) described the temporal distribution of each individual and dyad's recall processes. All individual and dyad recall processes were best fit by interaction-dominant distributions (lognormal and Pareto), but a clear difference emerged in that individual behavior is more power law, and collaborative behavior was more lognormal. We discuss these results in terms of the cocktail model (Holden et al. in Psychol Rev 116(2):318-342, 2009), which suggests that as a task becomes more constrained (such as through the necessity of collaborating), behavior can shift from power law to lognormal. This shift may reflect a decrease in the dyad's ability to flexibly shift between perseverative and explorative search patterns. Finally, our results suggest that a fruitful avenue for future research would be to investigate the constraints modulating the shift from power law to lognormal behavior in collaborative memory search.

Recalling items from a category for 1 hour: an inquiry into power-law behavior and memory foraging.

There are two complementary approaches to characterizing performance in a free recall task (retrieving items from a specified category). The historic, or top down approach, considers the overall structure of the produced responses, generally as the parameters of a fitted cumulative recall curve. Alternatively, free recall can be considered as a time series of recalls or inter-recall intervals. Earlier work employing this approach (Rhodes & Turvey, 2007) suggested power law behavior. Long trial durations (1 hour) are employed to more rigorously test for the presence of power law behavior and more generally, the hypothesis that the dynamics of free recall reflect complex, multiplicative processes. The outlined empirical methods are also employed to test predictions about the relative structure of differently sized categories. Consequences for an asymptotic curve based understanding of free recall and foraging metaphors of retrieval are discussed.

Drawing from memory: hand-eye coordination at multiple scales.

Eyes move to gather visual information for the purpose of guiding behavior. This guidance takes the form of perceptual-motor interactions on short timescales for behaviors like locomotion and hand-eye coordination. More complex behaviors require perceptual-motor interactions on longer timescales mediated by memory, such as navigation, or designing and building artifacts. In the present study, the task of sketching images of natural scenes from memory was used to examine and compare perceptual-motor interactions on shorter and longer timescales. Eye and pen trajectories were found to be coordinated in time on shorter timescales during drawing, and also on longer timescales spanning study and drawing periods. The latter type of coordination was found by developing a purely spatial analysis that yielded measures of similarity between images, eye trajectories, and pen trajectories. These results challenge the notion that coordination only unfolds on short timescales. Rather, the task of drawing from memory evokes perceptual-motor encodings of visual images that preserve coarse-grained spatial information over relatively long timescales as well.

The diffusion of novel signs beyond the dyad.

We present a study aimed at investigating how novel signs emerge and spread through a community of interacting individuals. Ten triads of participants played a game in which players created novel signs in order to communicate with each other while constantly rotating between the role of interlocutor and that of observer. The main result of the study was that, for a majority of the triads, communicative success was not shared by the three dyads of players in a triad. This imbalance appears to be due to individual differences in game performance as well as to uncooperative behaviors. We suggest that both of these are magnified by the social dynamics induced by the role rotations in the game.

Scaling laws in cognitive sciences.

Scaling laws are ubiquitous in nature, and they pervade neural, behavioral and linguistic activities. A scaling law suggests the existence of processes or patterns that are repeated across scales of analysis. Although the variables that express a scaling law can vary from one type of activity to the next, the recurrence of scaling laws across so many different systems has prompted a search for unifying principles. In biological systems, scaling laws can reflect adaptive processes of various types and are often linked to complex systems poised near critical points. The same is true for perception, memory, language and other cognitive phenomena. Findings of scaling laws in cognitive science are indicative of scaling invariance in cognitive mechanisms and multiplicative interactions among interdependent components of cognition.