Spatial and configural factors in compound stimulus processing by pigeons

Abstract

Three matching-to-sample experiments examined whether spatial or configural factors determined how the element arrangement of compound sample stimuli influenced matehing accuracy in pigeons. Seven types of compound stimuli were tested. The arrangement of color and lineorientation elements in these compounds varied in terms of the spatial separation between the elements, the degree ofconsistency in element spatiallocation, and the number ofbounded areas containing the elements. Matching accuracy was examined upon initial exposure to the compounds, during asymptotic conditions of shared attention, and with variation of sample durations ranging from .04 to 5.935 sec. In all three experiments, when spatial proximity, locational certainty, and the number of lines were precisely controlled or equated, no evidence for the proposed configural processing of"unified" compounds was found (Lamb & Riley, 1981). Element spatial separation, and to a lesser degree perceptuallimitations, determined compound performance. These results question our lab's previous evidence for configural compound processing by pigeons (Lamb, 1988; Lamb & Riley, 1981).They suggest instead that pigeons independently and separately process the individual elements of color/line-orientation compounds, with element separation determining the distribution of processing between the elements.Research on humans has shown that the organization of the elements fonning a compound visual stimulus strongly influences its psychological properties (Ceraso, 1985; Gamer, 1974 Gamer, , 1976. Riley and Leith (1976) similarly proposed that element organization may also influence how pigeons process compound stimuli. Since then, two reports from our lab (Lamb, 1988; Lamb & Riley, 1981) have offered evidence in support of this proposal, obtained in variations of the element/compound delayed matchingto-sample (E/C DMTS) task.In the E/C DMTS task, the pigeon is presented with either an element sample, consisting of one of two color elements (red or green, henceforth R or G) or one oftwo line-orientation elements (vertical or horizontal, henceforth V or H), or a compound sample, consisting ofboth acolor and a lineelement (RH, RV, GH, GV). The sample is followed by a test in which the two values of a single dimension are pitted against one another (R vs. Gor

Limited capacity information processing and pigeon matching-to-sample: Testing alternative hypotheses

“…However, the most common finding is that the element-compound difference persists over long sample durations, as it did in the present research. It seems likely, given the persistent failure to find convergence with extended sample durations (Brown & Morrison, 1990;Cook et al, 1992;Lamb & Riley, 1981;Roberts & Grant, 1978;Santi et al, 1982; but see Maki & Leith, 1973;Maki et aI., 1976), that information overload occurs at some stage of processing later than initial information uptake.…”

“…In addition to the element superiority effect, at least three other findings support a limited capacity interpretation. First, matching accuracy for both element and compound samples improves as sample duration increases (Cook et al, 1992;Lamb & Riley, 1981;Maki & Leith, 1973;Maki & Leuin, 1972). That is, the amount of information proessed prior to sample offset increases as sample duration is increased.…”

“…In an extensive literature on the results of elementcompound delayed matching-to-sample (DMTS) with pigeons, matching performance following a color-or lineelement sample is superior to performance following a compound sample consisting of both color and line elements (Cook 1980;Cook, Riley, & Brown, 1992;Lamb, 1988;Maki & Leith, 1973;Maki & Leuin, 1972;Maki, Riley, & Leith, 1976;Roberts & Grant, 1978;Santi, Grossi, & Gibson, 1982). One interpretation, the limited capacity hypothesis, asserts that the element superiority effect is attributable to information overload during initial encoding of the compound while it is physically present.…”

“…In studies in which overlapping line and color elements were used as compounds, experimenters have controlled for gaze direction effects (Cook et al, 1992;Lamb, 1988;Lamb & Riley, 1981), but the resulting element-compound differences might still be explained by either generalization decrement or coding decrement, since experimental controls for these effects were not included. Conversely, Brown and Morrison (1990) controlled for generalization decrement but used separable compound stimuli, and therefore did not rule out gaze direction effects.…”

Pigeon perception and discrimination of rapidly changing texture stimuli.

“…Such presentation times are generally not sufficient in duration for pigeons to make absolute stimulus identifications. For instance, in element-compound matching-to-sample experiments, testing stimuli of comparable size to the individual elements of the current task, presentation durations of 100 ms or less are generally too short to support the absolute identification of a sample's properties (Cook, Riley, & Brown, 1992;Lamb & Riley, 1981). Further, when we tried to identify the specific individual colors of such dynamic displays we found it quite difficult, requiring many seconds of careful scrutiny to confidently name the colors.…”