Absence of overshadowing between a landmark and geometric cues in a distinctively shaped environment: A test of Miller and Shettleworth (2007).

Abstract

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Overshadowing of geometry learning by discrete landmarks in the water maze: Effects of relative salience and relative validity of competing cues.

“…If the argument presented above is correct, it naturally leads to a question as to why previous studies failed to show overshadowing of learning based on the geometry by non--geometric cues, especially by discrete landmarks or beacons (Hayward et al, 2003;Hayward et al, 2004;McGregor et al, 2009;Pearce et al, 2001). Based on the findings from the present study, we can point out several potential variables that may account for the lack of overshadowing in the previous studies.…”

“…The question is important as many previous studies employed just such a condition in which the predictive validity of the landmarks and geometric features were matched, and they failed to demonstrate overshadowing (e.g., Hayward et al, 2003;McGregor et al, 2009).…”

“…If the same principle can apply to navigation tasks, then it is possible to argue that the geometric cues, such as walls and corners, are more salient for animals than discrete landmarks, and therefore it is more difficult for the latter to overshadow the former, without necessitating the additional assumption on the special status of geometric cues. Although McGregor et al (2009) were aware of this possibility and demonstrated in separate experiments that the landmark they employed was salient enough to overshadow learning based on other non--geometric cues (the room cues, but not colours of the walls; Experiment 3 and 4, McGregor et al, 2009), they did not explicitly manipulate the salience of the target geometric cues, which leaves the possibility that overshadowing can still be observed when the landmark is put in conjunction with a less salient geometric stimulus.…”

“…McGregor et al, 2009). It might be argued that these colour cues are integrated into a representation of geometry in a way not possible for discrete landmarks, whereas learning about discrete landmarks is indeed independent of the process responsible for geometry learning as envisaged by those theories mentioned above.…”

“…A number of studies so far have found that learning about the location of a goal based on the geometry of an enclosed arena is not restricted by the concurrent presence of other types of cues, such as a discrete landmark located near the platform Hayward, Good, & Pearce, 2004;Hayward, McGregor, Good, & Pearce, 2003;McGregor, Horne, Esber, & Pearce, 2009;Pearce, Ward--Robinson, Good, Fussell, & Aydin, 2001;Wall, Botly, Black, & Shettleworth, 2004;see Pearce, 2009 for a review). McGregor et al (2009), for example, trained rats to find a hidden platform in one of the base corners of an isosceles triangular arena. An experimental group of rats was trained with a single landmark always suspended above the platform, whereas a control group of rats was trained in the same way except that a second, identical landmark was also suspended at the other base corner.…”