Form perception

Forster and Lavie (2008) and Lavie, Lin, Zokaei and Thoma (2009) have demonstrated that meaningful stimuli, such as objects, are ignored under conditions of high perceptual load but not low. However, objects are seldom presented without context in the real world. Given that context can reduce the threshold for object recognition (Barenholtz, 2013), is it possible for context to reduce the processing load of objects such that they can be processed under high load? In the first experiment, I attempted to obtain similar findings of the aforementioned studies by replicating their paradigm with photographs of real-world objects. The findings of the experiment suggested that objects can cause distractor interference under high load conditions, but not low load conditions. These findings are opposite of what the perceptual literature suggests (e.g., Lavie, 1995). However, these findings are aligned with a two-stage dilution model of attention in which information is first processed in parallel and then selectively (Wilson, Muroi, and MacLeod, 2011). Experiment 2 assessed if this effect was specific to semantic objects by introducing meaningless, abstract objects. The results suggest that the dilution effect was not due to the semantic features of objects. The third experiment assessed the influence of context on objects under load. The results of the experiment found an elimination of all interference effects in both the high and low load conditions. Comparisons between scene-object congruency revealed no influence of semantic information from scenes. It appears that the presentation of a visual stimuli prior to the flanker task diluted attention such that the distractor effects previously observed in the high load condition were minimized. Thus, it does not appear that context reduced the threshold for object recognition under load. All three experiments have demonstrated strong evidence for the dilution approach of attention over perceptual load models.

This study was a partial replication of one previously
reported by Nash and Michels (1966). The purpose was to investigate
perceptual form discrimination behavior of young
squirrel monkeys as affected by contextual variables of the
stimulus. The variables examined were Redundancy, Position
and, of the form itself, Complexity. In addition, a sequential
method of testing and recording was compared with
the conventional 50-trial block procedure. Two 17 month old monkeys were tested on eight twochoice
problems in a Purdue General Test Apparatus. The
problems each consisted of two slides on which pairs of
random shapes were presented. The shapes within each pair
of slides were held constant on the parameters investigated.
One slide was designated as the positive stimulus and presented
in either the right or left position in random order. The number of correct responses for the 50-trial
blocks, as examined by an analysis of variance, failed to
reach statistical significance for any of the variables
investigated. However, graphic inspection of the data
suggests general agreement with the findings of Nash and
Michels (1966). In comparing the two methods of testing,
the sequential test of performance (STOP) was equally as
effective as the conventional method and could have provided
a substantial savings in test time. Comparison of
scores obtained by the two procedures shows good correlation. Although no strong conclusions can be drawn from the
data, they do lead to the speculation that there is a relationship
between effect and extent of redundancy, and
that failure of S to make a correct response in the test
situation may be the result of cue sampling rather than a
failure to discriminate.

Lower prices of video sensors, security concerns and the need for better and faster
algorithms to extract high level information from video sequences are all factors which
have stimulated research in the area of automated video surveillance systems. In the
context of security the analysis of human interrelations and their environment provides
hints to proactively identify anomalous behavior. However, human detection is a
necessary component in systems where the automatic extraction of higher level
information, such as recognizing individuals' activities, is required. The human detection
problem is one of classification. In general, motion, appearance and shape are the
classification approaches a system can employ to perform human detection. Techniques
representative of these approaches, such us periodic motion detection, skin color
detection and MPEG-7 shape descriptors are implemented in this work. An infrastructure
that allows data collection for such techniques was also implemented.

Rock's procedure for separating the effect of objective
and retinal spatial reference by varying stimulus orientation
and body posture was used in conjunction with the "same-different"
reaction time paradigm. It was predicted that
the individual differences in perceptual processing (analytic
and structural) obtained by Hock (1973) would involve
different determinants of spatial reference, these being
retinal reference for analytic processing and objective
reference for structural processing. The results show that
analytic subjects as hypothesized, referenced perceptual
information to a retinal coordinate system. Structural
subjects however, seemed to reference perceptual information
to both objective and retinal coordinates. The results for
structural subjects were attributed to the unexpected finding
that subjects who were structural while upright, became
analytic when in a reclining position. The latter finding
suggested that Rock's methodology for separating the effects
of retinal and objective orientation relies on the subjects
employing the same mode of processing in all bodily postures.

The central importance of vision to an organism is evident in the anatomical and physiological adaptations within the eye that can be correlated to the organism's behavior and ecology. The goal of this study was to perform a functional analysis of adaptations within the elasmobranch visual system. An integrative approach was used to examine morphological and physiological adaptations in several species and link these adaptations to phylogeny, locomotion, habitat, behavior and ecology. Functional aspects investigated were eye position, pupil shape, spectral sensitivity, temporal resolution, the extent of the visual field and ultimately the integration of the visual and electrosensory systems. The elasmobranch eye adapts to the light environment of its habitat. Sharks from similar habitats had similar spectral sensitivities such as the bonnethead and blacknose sharks, both maximally sensitive to blue light of 480 nm. The spectral sensitivity of the scalloped hammerhead, which lives in a different environment, was maximally sensitive to green light (530 nm). The temporal characteristics of the eye also matched habitat and lifestyle. Species experiencing variable light conditions exhibited increased critical flicker-fusion frequencies, such as the bonnethead (31 Hz) and scalloped hammerhead (27 Hz), in contrast to deeper or more nocturnal species such as the blacknose shark (18 Hz). Elasmobranch visual fields correlated to each species' lifestyle, habitat and foraging strategy. Expansive monocular views, including a 360° panoramic view in the yellow stingray, were measured in species that rely on vision for vigilance against predators.

When interpreting how an animal "learns" discrimination tasks, strain capabilities must be considered, and it should be shown that they comprehend the task in a manner consistent with the given interpretation. A novel visual-discrimination (VD) task for relative-size-relations was used to examine visual cue use in C57BL/6J mice, which are shown to have biologically good vision and neurologically intact memory for VD tasks. Results suggest C57BL/6J strain may not be fully capable of relative cue-size associations or even object recognition-based on a water maze VD task. This is in contrast to previous studies suggesting this mice strain is quite strong in visual skills and on VD tasks. Additionally, cue size and/or cue-pairings do appear to influence specific directional preferences or stereotyped behaviors as trainings continued, and these strategies shifted during novel probes. Future studies should assess how mice discriminate between objects and test rat's capabilities on this task.