Subsequent Navigation Research Articles

Effects of varying the amount of preexposure to spatial cues on a subsequent navigation task

In each of two experiments rats were preexposed to four compound landmarks (AX, BX, CX, and DX) one at a time; they were then trained to find a submerged platform located in a fixed position in a swimming pool using these same landmarks. When the preexposure was SHORT (4 sessions) it facilitated subsequent learning (a perceptual learning effect), whereas when rats were given a LONG preexposure phase (8 sessions) this facilitatory effect disappeared. EXTRA-LONG preexposure (16 sessions) reversed the facilitatory effect—that is to say, we observed retarded learning. The results show that rats’ ability to navigate towards an invisible goal is affected by the length of their preexposure to the spatial cues that signal the location of the goal. These data are consistent with an associative analysis of the swimming pool navigation task.

Effects of varying the amount of preexposure to spatial cues on a subsequent navigation task.

In each of two experiments rats were preexposed to four compound landmarks (AX, BX, CX, and DX) one at a time; they were then trained to find a submerged platform located in a fixed position in a swimming pool using these same landmarks. When the preexposure was SHORT (4 sessions) it facilitated subsequent learning (a perceptual learning effect), whereas when rats were given a LONG preexposure phase (8 sessions) this facilitatory effect disappeared. EXTRA-LONG preexposure (16 sessions) reversed the facilitatory effect--that is to say, we observed retarded learning. The results show that rats' ability to navigate towards an invisible goal is affected by the length of their preexposure to the spatial cues that signal the location of the goal. These data are consistent with an associative analysis of the swimming pool navigation task.

A scenario-based object-oriented hypermedia design methodology

This paper defines an object-oriented methodology for developing hypermedia information systems. The methodology consists of six phases: domain analysis; object modeling; view design; navigation design; implementation design; and construction. Users' requirements are analyzed with a responsibility-driven technology using scenarios. Object-oriented views are generated as the result of object modeling, and then used for the subsequent navigation and implementation design. The implementation design phase deals with database schema, page structure and flow, and user interface. This methodology integrates enterprise databases with distributed hypermedia systems via Internet, Intranet, or Electronic Commerce.

The Treatment of Simultaneous Position Data in the Air

The theoretical determination of a fix from a number of simultaneous, or near simultaneous, positional data has attracted considerable attention during the last five years. A problem is presented whenever the amount of information obtained is more than sufficient to determine the fix, the most common case being when a set of three position lines is obtained. In this instance the size of the triangle of intersection can be used to estimate whether or not the position lines are likely to be consistent with each other; if they are, some central point inside the triangle is accepted as the fix. In doing this the influence of the position provided by the vessel's past history (the dead reckoning position) is ignored; once the fix is decided on, however, a comparison between the two estimates of position may be of value either in enabling a blunder to be detected or, possibly, in selecting some intermediate point as a position from which subsequent navigation should be based. Although the determination of a position from a number of data is, mathematically, a single problem whether these data include the dead reckoning estimates or not, it is usual navigational procedure to consider first the latest positional information. It is the study of this problem that is the object of this article.