Timothy P. McNamara

Mental representations of spatial relations

Abstract Three classes of theories of the mental representation of spatial relations were tested. Nonhierarchical theories propose that spatial relations among objects in an environment are mentally represented in networks or in imagelike, analog formats. The distinctive claim of these theories is that there is no hierarchical structure to the mental representation. Hierarchical theories , on the other hand, propose that different “regions” of an environment are stored in different branches of a graph-theoretic tree. These theories can be divided into two classes of subtheories depending on the kinds of relations encoded in memory: Strongly hierarchical theories maximize storage efficiency by encoding only those spatial relations needed to represent a layout accurately; partially hierarchical theories predict redundancy in the representation, such that many spatial relations that can be computed also will be stored explicitly. These three classes of theories were tested by having subjects learn the locations of actual objects in spatial layouts or the locations of objects on maps of those layouts. Layouts and maps were divided into regions with transparent boundaries (for the layouts, string on the floor; for the maps, lines). After learning the layouts or maps, subjects participated in three tasks: item recognition, in which the variable of interest was spatial priming; direction judgments; and euclidean distance estimation. Results from all three tasks were sensitive (a) to whether objects were in the same region or in different regions and (b) to the euclidean distances between pairs of objects. These findings were interpreted as supporting partially hierarchical theories of spatial representations. Computer simulations supported this conclusion.

Intrinsic Frames of Reference in Spatial Memory

Three experiments investigated the frames of reference used in memory to represent the spatial structure of the environment. Participants learned the locations of objects in a room according to an intrinsic axis of the configuration; the axis was different from or the same as their viewing perspective. Judgments of relative direction using memory were most accurate for imagined headings parallel to the intrinsic axis, even when it differed from the viewing perspective, and there was no cost to learning the layout according to a nonegocentric axis. When the shape of the layout was bilaterally symmetric relative to the intrinsic axis of learning, novel headings orthogonal to that axis were retrieved more accurately than were other novel headings. These results indicate that spatial memories are defined with respect to intrinsic frames of reference, which are selected on the basis of egocentric experience and environmental cues.

Viewpoint Dependence in Scene Recognition

Two experiments investigated the viewpoint dependence of spatial memories In Experiment 1, participants learned the locations of objects on a desktop from a single perspective and then took part in a recognition test, test scenes included familiar and novel views of the layout Recognition latency was a linear function of the angular distance between a test view and the study view In Experiment 2, participants studied a layout from a single view and then learned to recognize the layout from three additional training views A final recognition test showed that the study view and the training views were represented in memory, and that latency was a linear function of the angular distance to the nearest study or training view These results indicate that interobject spatial relations are encoded in a viewpoint-dependent manner, and that recognition of novel views requires normalization to the most similar representation in memory These findings parallel recent results in visual object recognition.

Multiple views of spatial memory

Recent evidence indicates that mental representations of large (i.e., navigable) spaces are viewpoint dependent when observers are restricted to a single view. The purpose of the present study was to determine whether two views of a space would produce a single viewpoint-independent representation or two viewpoint-dependent representations. Participants learned the locations of objects in a room from two viewpoints and then made judgments of relative direction from imagined headings either aligned or misaligned with the studied views. The results indicated that mental representations of large spaces were viewpoint dependent, and that two views of a spatial layout appeared to produce two viewpoint-dependent representations in memory. Imagined headings aligned with the study views were more accessible than were novel headings in terms of both speed and accuracy of pointing judgments.

Depth of spreading activation revisited: Semantic mediated priming occurs in lexical decisions ☆

Abstract Balota and Lorch 1986 Journal of Experimental Psychology: Learning, Memory, and Cognition , 12 , 336–345 have shown that semantic mediated priming (e.g., from “lion” to “stripes” via “tiger”) occurs in naming but not in lexical decisions (see also de Groot 1983, Journal of Verbal Learning and Verbal Behavior , 22 , 417–436). Several investigators have hypothesized that semantic mediated priming does not appear in lexical decisions because subjects attempt to expedite the binary lexical decision by engaging in postretrieval relatedness checking: Subjects are biased to respond “word” when a target is related to its prime and “nonword” when a target is unrelated to its prime. Because the relation between mediated pairs is usually quite subtle, subjects are biased to respond “nonword” for these items, which obscures facilitation that may be occurring from spreading activation. This account suggests that mediated priming will appear in lexical decisions if (a) directly related words (e.g., “lion-tiger”) are not included on test lists or (b) a task is used that discourages relatedness checking. Experiment 1 tested the first possibility and Experiment 2 tested the second. Both experiments demonstrated statistically reliable semantic mediated priming in lexical decisions. Two additional experiments showed that mediated priming was smaller than direct priming and that it generalized to new materials. These results support spreading-activation theories of retrieval but provide evidence against several “nonspreading-activation” theories.

Theories of priming. I : associative distance and lag

Automatic associative priming occurs in a large number or memory retrieval tasks, including semantic categorization, lexical decisions, item recognition, naming, and judgments or spatial location. Priming has been commonly attributed to one or the other of 2 alternative mechanisms: spreading activation or construction or compound retrieval cues. This article reports the results or 3 experiments that were designed to test spreading-activation and non-spreading-activation models or priming. The findings were consistent with the spreading-activation models, but inconsistent with the non-spreading-activation models. These results suggest that a rejection of spreading-activation mechanisms is premature

Orientation and perspective dependence in route and survey learning.

Three experiments investigated the role of egocentric orientation in subsequent memory for layouts learned via route (ground-level) and survey (aerial or overview) perspectives. Participants learned virtual environments from text descriptions (Experiment 1) or visual presentation (Experiments 1-3). In all experiments, scene recognition for route and survey images revealed a cost for switching perspective from study to test. In addition, recognition performance was facilitated when the test view matched the observers learned orientation but only for the same-perspective recognition test. Experiment 3 demonstrated orientation dependence in judgments of relative direction, with a strong emphasis on initial heading. Together, these results suggest that establishing a reference system for representing spatial information is dependent on specific characteristics of the learning situation.

Mental representations of large and small spatial layouts are orientation dependent

Previous research on spatial memory indicated that memories of small layouts were orientation dependent (orientation specific) but that memories of large layouts were orientation independent (orientation free). Two experiments investigated the relation between layout size and orientation dependency. Participants learned a small or a large 4-point path (Experiment 1) or a large display of objects (Experiment 2) and then made judgments of relative direction from imagined headings that were either the same as or different from the single studied orientation. Judgments were faster and more accurate when the imagined heading was the same as the studied orientation (i.e., aligned) than when the imagined heading differed from the studied orientation (i.e., misaligned). This alignment effect was present for both small and large layouts. These results indicate that location is encoded in an orientation-dependent manner regardless of layout size.

How are the locations of objects in the environment represented in memory

This chapter summarizes a new theory of spatial memory. According to the theory, when people learn the locations of objects in a new environment, they interpret the spatial structure of that environment in terms of a spatial reference system. Our current conjecture is that a reference system intrinsic to the collection of objects is used. Intrinsic axes or directions are selected using egocentric (e.g., viewing perspective) and environmental (e.g., walls of the surrounding room) cues. The dominant cue is egocentric experience. The reference system selected at the first view is typically not updated with additional views or observer movement. However, if the first view is misaligned but a subsequent view is aligned with natural and salient axes in the environment, a new reference system is selected and the layout is reinterpreted in terms of this new reference system. The chapter also reviews evidence on the orientation dependence of spatial memories and recent results indicating that two representations may be formed when people learn a new environment; one preserves inter-object spatial relations and the other comprises visual memories of experienced views.

Egocentric and geocentric frames of reference in memory of large-scale space

This experiment investigated the frames of reference used in memory to represent the spatial structure of a large-scale outdoor environment. Participants learned the locations of eight objects in an unfamiliar city park by walking through the park on one of two prescribed paths that encircled a large rectangular building. The aligned path was oriented with the building; the misaligned path was rotated by 45°. Later, participants pointed to target objects from imagined vantage points using their memories. Pointing accuracy was higher in the aligned than in the misaligned path group, and the patterns of results differed: In the aligned condition, accuracy was higher for imagined headings parallel to legs of the path and for an imagined heading oriented toward a nearby lake, a salient landmark. In the misaligned condition, pointing accuracy was highest for the imagined heading oriented toward the lake, and decreased monotonically with angular distance. These results indicated that locations of objects were mentally represented in terms of frames of reference defined by the environment but selected on the basis of egocentric experience.