Human information processing

Most of the human visual field falls in the periphery, and peripheral processing is
important for normal visual functioning. Yet, little is known about peripheral object
recognition in naturalistic scenes and factors that modulate this ability. We propose that
a critical function of scene and object memory is in order to facilitate visual object
recognition in the periphery. In the first experiment, participants identified objects in
scenes across different levels of familiarity and contextual information within the scene.
We found that familiarity with a scene resulted in a significant increase in the distance
that objects were recognized. Furthermore, we found that a semantically consistent scene
improved the distance that object recognition is possible, supporting the notion that
contextual facilitation is possible in the periphery. In the second experiment, the preview
duration of a scene was varied in order to examine how a scene representation is built and
how memory of that scene and the objects within it contributes to object recognition in
the periphery. We found that the closer participants fixated to the object in the preview,
the farther on average they recognized that target object in the periphery. However, only a preview duration of the scenes for 5000 ms produced significantly farther peripheral
object recognition compared to not previewing the scene. Overall, these experiments
introduce a novel research paradigm for object recognition in naturalistic scenes, and
demonstrates multiple factors that have systematic effects on peripheral object
recognition.

Transcription and translation of proteins are required for the consolidation of episodic memory. Arc, an effector immediate early gene, has been linked to synaptic plasticity following learning and memory. It is well established that the rodent hippocampus is essential for processing spatial memory, but its role in processing object memory is a point of contention. Using immunohistochemical techniques, hippocampal sections were stained for arc proteins in the CA1 region of the dorsal hippocampus in mice following two variations of the novel object recognition (NOR) task. Results suggest mice that acquired strong object memory showed significant hippocampal activation. In mice that acquired weak object memory, hippocampal activation was not significantly different from controls. Arc expression was also examined in other hippocampal sub-regions, as well as in the perirhinal cortex. These results suggest that the mice must acquire a threshold amount of object information before the hippocampal CA1 region is engaged.

The perception of visual motion is an integral aspect of many organisms' engagement with the world. In this dissertation, a theory for the perception of visual object-motion is developed. Object-motion perception is distinguished from objectless-motion perception both experimentally and theoretically. A continuoustime dynamical neural model is developed in order to generalize the ndings and provide a theoretical framework for continued re nement of a theory for object-motion
perception. Theoretical implications as well as testable predictions of the model are discussed.

Impression formation has in the past always been viewed as an instantaneous one time event. In this experiment impression formation was viewed as a process occurring over time. Subjects received descriptions of a hypothetical individual and then gave trait judgments indicating how they perceived this person. Subjects continued to receive information and make judgments through ten successive trials. Correlations were performed between seven major variables evaluated over the course of the trials. Results showed that the major work of impression formation occurs early in the process and that less is accomplished as time goes on. It was also found that an information processing point of view accommodated much of the results quite nicely.

Previous research has shown that priming of digits is a
function of the ordinal distance of the target digit from
the priming sequence and that under certain conditions this
effect may be automatic. The present experiment, which
employs a choice RT task, was designed to test automaticity
by manipulating subjects' expectancies and the time
available for processing the priming sequence.
Schematically valid primes (e.g., "1,2,3" preceding "4")
were presented on 30%, 50%, or 70% of the trials to a given
subject. Invalid primes (e.g., "5, 6, 7" preceding "4")
were presented on the remaining trials. There was a highly
significant effect of priming modified by interactions with
exposure time and frequency. Employing a cost-benefit
analysis to the frequency factor, it was found that the most
frequently occurring prime resulted in decreased response
latency but the less frequently occurring prime did not
result in an increase in response latency (benefit wihout
cost). On this basis, it is concluded that frequency
influences an automatic process in this experiment. Since
frequency interacts with priming, it is therefore argued
that priming also affects an automatic process.

A category effect of alphanumeric characters in a visual search paradigm
was examined to see whether the effect could be accounted for
by the number of memory comparisons or by an early stage of perceptual
processing. In Experiments 1 and 2, subjects searched for
targets in either a within-category or between-category condition.
The two experiments differed by the point in the trials where "catch
trials" were presented. Experiment 3 used new configurations based
on Gestalt principles which had been shown to influence target detection
times at an early level of perceptual processing. The results
of Experiments 1 and 2 favored a perceptual explanation mediating the
effect. In Experiment 3, the critical interaction of category and
Gestalt factors which would have demonstrated a competition in
perceptually parsing the display fell short of significance.

A paired-comparisons procedure was used to obtain
relative duration judgements of identical pairs of normal
(e.g. A vs. A) or rotated (e.g.V vs.V) letters. Each
pair of letters was presented simultaneously for a duration
of 50msec, with one letter in the LVF (left visual field,
right hemisphere), and one in the RVF (right visual field,
left hemisphere). It was hypothesized that LVF presentations
of rotated letters would have a greater apparent
duration . This was based on Hock, Kronseder, and Corcoran's
(1975) demonstration that rotated letters presented in the
LVF produce longer reaction times than RVF presentations on
a visual comparisons task. The results were that subjects' "left" vs. "right"
responses did not differ significantly for any of the
conditions. Methodological considerations were cited as a
possible reason for the failure to confirm the present
hypo thesis.

There are certain properties of the human mind which allow abstract thought. These properties are responsible for the ability to create myth (or explanations of the unknown), cosmology, and culture. They are the seeds of all human phenomena not attributable to instinct. These properties can be isolated as the capacity for numeric logic and the mind functioning in terms of binary oppositions. The long held paradigm sees the human species as unique in possessing these qualities and well as the phenomena they yield. In order to challenge this paradigm, a two experiments are conducted on a chimpanzee to see if she possessed these properties. She successfully completed the cognitive tests on both experiments, thus implicating the human species as not unique in its abstractions.

A total of 96 adults (mean age 23.5 years) solved simple arithmetic problems in digit and verbal format, using Siegler's choice, no-choice method. In the choice condition, they produced the answer and gave a self report of how they solved it. In the no-choice condition, they were asked to use only retrieval. Naming latencies of numerals in both formats were assessed. Verbal problems were solved more slowly than digit problems in all conditions but format did not interact with problem size effect for reaction times. This latter result does not support an effect of presentation format on calculation processes. Participants also named faster digits than verbal numerals. Smaller reaction times and three times as many errors were associated with the no-choice compared to the choice condition. Mathematical aptitude also had an effect. High arithmetic skill was related to smaller reaction times, more retrieval use and fewer errors.

Can a distributed anatomical and functional architecture serve as the basis for sufficiently complex perceptual phenomena? In addressing this question, the conceptual notion of dynamical system and its relation to other paradigms is considered including its definition. The principal goal is to develop a dynamical framework on which to ground the theoretical study of perception and other physical phenomena. As an entry point, the perceptual dynamics of auditory streaming are modeled using a neurally inspired dynamical model of auditory processing. Traditional approaches view streaming as a competition of streams, realized within a tonotopically organized neural network. In contrast, streaming can be viewed as a dynamic integration process involving locations (information convergence zones) other than the sensory specific neural subsystems. This process finds its realization in the synchronization of neural ensembles. Consequently, the model employs two interacting dynamical systems. The first system responds to incoming acoustic stimuli and transforms them into a spatiotemporal neural field dynamics. The second system is a classification system coupled to the neural field and evolves to a stationary state in the absence of input. The states of the classification system at any time t are identified with a single perceptual stream or multiple streams. Several results in human perception are modeled including temporal coherence and fission boundaries (van Noorden, 1975), and crossing of motions (Bregman, 1990). The model predicts phenomena such as the existence of two streams with the same pitch. So far, this has not been explained by the traditional stream competition models. A psychophysical study provides proof of existence of this phenomenon. Using set theoretical expressions on fMRI data, evidence was found showing that the percept of auditory streaming involves regions (convergence zones) other than just the primary auditory areas. This is a necessary condition for the existence of the network architecture proposed in the auditory streaming model. Networks specific and common to both amplitude and frequency streaming were identified. This lends support to models of perception conceived as interacting neural subnetworks acting as functional differentiation areas and information convergence zones for the classification of the perceptual world as suggested by the introductory question.