Use of landmark configuration in pigeons and humans: II. Generality across search tasks.

Abstract

Pigeons and humans searched for a goal that was hidden in varied locations within a search space. The goal location was fixed relative to an array of identical landmarks. Pigeons searched on the laboratory floor, and humans searched on a table top or an outdoor field. In Experiment 1, the goal was centered in a square array of 4 landmarks. When the spacing between landmarks was increased, humans searched in the middle of the expanded array, whereas pigeons searched in locations that preserved distance and direction to an individual landmark. In Experiment 2, the goal was centered between and a perpendicular distance away from 2 landmarks aligned in the left-fight dimension. When landmark spacing was increased, humans, but not pigeons, shifted their searching away from the landmarks along the perpendicular axis. These results parallel those obtained in touch-screen tasks. Thus, pigeons and humans differ in how they use landmark configuration. Many creatures remember places to return to by the use of visual landmarks. In this spatial search strategy, some kinds of spatial relationships between the goal and its surrounding landmarks are encoded and are later used to find the goal again (for reviews, see Collett, 1992; GaUistel, 1990). In many studies of landmark-based spatial memory, the landmarks defining the goal are shifted about from one trial to the next, thus forcing the subject to use the experimentally specified landmarks to locate the target. This method has demonstrated the use of landmarks in studies with insects (e.g.,

Searching by rules: Pigeons' (Columba livia) landmark-based search according to constant bearing or constant distance.

“…Although pigeons acquired the task, their search behavior appeared to be considerably less accurate and more variable than that found in previous studies in which the absolute distance and bearing from the goal to the landmarks was fixed during training (e.g., Cheng, 1989;Spetch et al, 1997). Numerous procedural differences between this study and previous ones, including a much larger average landmark-to-goal distance, could account for the lower accuracy in the present study.…”

“…On trials in which the food and food cup were absent (no-goal trials), the baited finish-box door was opened after 10 sweeping movements were recorded or after a maximum of 10 min. Sweeping movements rather than pecking were used as the index of searching because previous research (e.g., Spetch et al, 1997) indicated that pigeons typically sweep away the bedding first and then peck only upon exposing the food. The sweeping movements were operationally defined as a sideways movement of the beak that resulted in visible displacement of bedding material.…”

“…When the landmarks were spread apart on a transformation test, the pigeons did not search in the middle of the expanded array but instead searched in locations that maintained the approximate training distances and directions from individual landmarks. A similar tendency to search on the basis of individual landmarks rather than using the spatial rela-tionship of the goal to the whole array was found for gerbils (Collett, Cartwright, & Smith, 1986) and monkeys (Sutton, Olthof, & Roberts, 2000), whereas adult humans show the opposite tendency (Spetch et al, 1996(Spetch et al, , 1997. Transformation tests like those described above are useful for revealing an animal's typical or preferred encoding strategy, but they do not indicate how flexible that strategy is.…”

Integration of spatial maps in pigeons

“…Pigeons have been shown to acquire separate landmark-goal vectors independently even in situations involving multiple landmarks (Spetch and Mondloch 1993;Spetch et al 1996Spetch et al ,1997. For example, after learning to find a hidden food goal in the presence of an array of landmarks, search locations on probe tests involving transformations of the landmark array (e.g., expansions of landmark locations or removal of individual landmarks) indicate that pigeons had encoded the vector between one or more individual landmarks and the goal.…”

Geometric determinants of human spatial memory

“…One paradigm examines the locus of search for an object presented in a location equidistant to 2, 3 or 4 landmarks, how it changes after expansion of the array of landmarks, and how responses vary between different species. Gerbils (Collett, Cartwright, & Smith, 1986) and pigeons (Spetch, Cheng, & MacDonald, 1996;Spetch et al, 1997) tend to search in locations that maintain the distance and angle to individual landmarks consistent with a model in which the vectors from the landmarks to the objects' locations are stored. Experiments probing a location nearer to one of two landmarks show that the vector from the landmark nearer to the target location is more influential than that from the farther landmark.…”