David C. Hubbard

Does attention have different effects on line orientation and line arrangement discrimination

Visual search and texture segregation studies have led to the inference that stimuli differing in the orientation of their component line segments can be distinguished without focal attention, whereas stimuli that differ only in the arrangement of line segments cannot. In most of this research, the locus of attention has not been explicitly manipulated. In the first experiment presented here, attention was directed to a relevant peripheral target by a cue presented near the target location or at the fovea. Effects of attention on orientation discrimination were assessed in a two-alternative forced-choice task with targets that were either: (1) lines that slanted obliquely to the right or left, or were horizontal or vertical, or (2) Y-like targets that had a short arm leading obliquely right or left of a vertical line. In some groups, a four-alternative forced-choice test with lines at 0°, 45°, 90°, and 135° orientations was used. Discrimination of these targets (i.e. targets that differ in the orientation of component line segments) was only minimally facilitated as the time between the onset of the valid cue and the onset of the target (cue-target stimulus onset asynchrony, SOA) was increased from 0 or 17 msec to 267 msec. In contrast, discrimination of targets that did not differ in the orientation of component line segments but differed in line arrangement (T-like characters), was greatly facilitated by longer cue-target SOAs. In Experiment 2, a cue misdirected attention on 20% of the trials. A decrement occurred on incorrectly cued trials in comparison to correctly cued trials for both types of stimuli used (lines and Ts). The results from these experiments suggest that discrimination of line orientation benefits less from focal attention than does discrimination of line arrangement, but that both discriminations suffer when attention must be disengaged from an irrelevant spatial location.

EFFECTS OF THREE TYPES OF FLIGHT SIMULATOR VISUAL SCENE DETAIL ON DETECTION OF ALTITUDE CHANGE.

The effects of three types of flight simulator visual scene detail on detection of altitude change were evaluated in three experiments. Across all experiments and with a variety of tasks and display conditions, speed and accuracy of detecting altitude change improved with increases in the density of vertical objects in scenes. Adding detail to individual objects to increase their natural appearance produced no consistent effects on performance. In Experiment 3 complex texture distributed globally on terrain surfaces improved detection of altitude change but did not alleviate the need for high object density. These results indicate that available computer image generator processing capacity would be used more effectively by increasing the density of objects in scenes, rather than by increasing the complexity and detail of individual objects. Complex texture is used more effectively when distributed globally on terrain surfaces, rather than when allocated to individual objects.

EFFECT OF THREE-DIMENSIONAL OBJECT TYPE AND DENSITY IN SIMULATED LOW-LEVEL FLIGHT

Three-dimensional objects placed on simulated terrain surfaces are particularly effective as cues for altitude in simulated low-level flight. To conserve the limited edge processing capacity of computer image generators (CIGs), objects have typically been simple in shape and therefore fairly abstract in appearance. The present investigation sought to determine whether the apparent size of more detailed and familiar appearing objects (e.g., trees and bushes) serves as an additional cue for altitude in simulated low-level flight. Results showed no differences in performance between abstract objects and familiar objects. However, performance did improve with increases in object density, at least for some performance measures. These results suggest that CIG processing capacity may be most effectively utilized by increasing object density rather than individual object detail.

Utility and Utilization of Aircrew Training Device Advanced Instructional Features

The utility and utilization of the Advanced Instructional Features (AIFs) capabilities of USAF Aircrew Training Devices (ATDs) was explored by means of a survey of 534 Simulator Instructors from Air Training Command, Military Airlift Command, Strategic Air Command, and Tactical Air Command training sites. The primary purpose of the survey was to provide a database that could be used in defining the requirements for ATD procurements and in developing future ATD training programs. In general, the features that were rated highest in utility and utilization were those used for training management, variation of task difficulty/fidelity, and monitoring student performance. The level of AIF use was affected somewhat by hardware and/or software deficiencies; however, the presumed training value of an AIF was the most important determiner of its use.

Performance of Three Visual Approach Landing Light Systems

This report documents the methodology and experimental approach taken to evaluate the effectiveness of the three visual approach landing light systems: Visual Approach Slope Indicator (VASI), Precision Approach Path Indicator (PAPI), and Pulse Light Approach Slope Indicator (PLASI). Performance measures were taken inflight in the Air Force T-37 jet trainer, which produced objective determinations of deviations from glideslope on final approach, for each system. The subjects were experienced Air Force Instructor Pilots. Results showed that PAPI and PLASI were statistically equivalent, but that both were superior to VASI. Some subjective pilot evaluations of the three systems are also described.