Acquisition of locational information about reference points during blindfolded and sighted locomotion: Effects of a concurrent task and locomotion paths

Stand. J . Ps>~chol. 22, 101-108, 1981

Acquisition of locational information about reference points during blindfolded and sighted locomotion: Effects of a concurrent task and locomotion paths

ERIK LINDBERG TOMMY GARLING

University of Urneii, Sweden

Lindberg, E. & Garling, T.: Acquisition of locational information about reference points during blindfolded and sighted locomotion: Effects of a concurrent task and locomotion paths. Scandinavian Journal of Psychology, 1981,22, 101-108.

Acquisition of cognitive maps (locational information about reference points) was investigated by requiring subjects to walk repeatedly according to paths consisting of 2, 4 and 6 linear segments. The starting point of each path was designated as a reference point, to which direction and distance were estimated by the subjects at the end of the path. Acquisition was indicated by the finding that variable errors and latencies decreased across blocks of trials. Interfering with central processing of locational information during locomotion by means of a concurrent task, while impairing orientation performance, did not seem to prevent acquisition. As suggested by an increase in latencies with the number of path segments, the subjects performing the concurrent task may have been able to infer and store the location of the starting point after walking. Finally, orientation performance did not improve for blindfolded subjects, probably because they were unable to use stored information about locations. Tommy Garling, Department of Psychology, University of Umed S-90187 Umed, Sweden.

As noted by .Stokols (1978), people’s internal representations of the spatial properties of their everyday physical environment has become an im- portant research focus within the field of environmental psychology. The research carried out so far has been concerned mainly with descriptions of the internal representations (cognitive maps) that subjects have of the spatial layout of large-scale environments with which they are well acquainted (see e.g. Canter, 1977; Downs & Stea, 1973; Moore & Golledge, 1976; for reviews), whereas the prob- lem of how such cognitive maps are acquired and used has been largely neglected. However, acquisition of spatial information has been demonstrated by Allen, Siege1 & Rosinski (1978), Crane (1978) and Kozlowski & Bryant (1977), who found that maintenance of orientation relative to reference points in an initially unfamiliar environment im- proved with repeated exposure to the same locomotion pathlenvironment. The primary aim of the

present study was to investigate the circumstances under which such improvement takes place. A second aim was to investigate the nature of the improvement in greater detail than has been done previously. For instance, improvement of maintenance of orientation has been defined as decreased absolute errors, which may not differentiate between a correct representation used with some vari- ability and an incorrect one more consistently used. Therefore, other measures such as constant errors, variable errors, and latencies will be used here.

The ability to maintain orientation during locomotion has been investigated by means of a procedure in which the subjects, after being guided with vision occluded according to some locomotion path, are either required to return unguided to the starting point or to indicate the location of an initially seen reference point (Juurrnaa, 1966; Juurmaa & Suonio, 1975; Ross, Dickinson & Jupp, 1970; see also Howard & Templeton, 1966, for a review of

Srand. .I. Psyrhol. 22

102 E . Lindberg and T . Garling

A-F stops o outside view s swing door

L I I 0 1 0 50 meters

earlier studies). The main concern of these studies has been the role played by different sensory systems, but more recently Book & Garling (1980~7, 1980b) have shown that performance of the task may require central processing of information as well. As assumed by these authors, during locomotion orientation relative to a reference point is maintained by recurrent processing of information received through different sensory systems about locomotion distances and direction changes. Thus, the subject’s experience (or expectancy) of his/ her own position relative to the location of the reference point is recurrently updated during locomotion. However, these assumptions can not account for the fact that maintenance of orientation improves with repeated exposure to the same locomotion pathlenvironment.

Improvement of maintenance of orientation, as indicated by decreasing constant and variable errors and shorter latencies, may take place with repeated exposure to an unfamiliar environment because an increasing amount of information about the locations of reference points is stored in long-term memory. However, in line with Book & Garling (1980a, 1980b), a number of conditions must be fulfilled for this to occur. Firstly, the relevant fea- tures of the locomotion path (distances and direc- tions changes) must be attended to in order to be encoded in a short-term store. Secondly, this information must be further processed in order to yield the locations of reference points which cannot be directly perceived. Finally, the information about the locations must be permanently stored. Furthermore, it is assumed that all these stages of

Scand. J . Psychol. 22

Fig. I . Graph of paths walked by the subjects. (See text for further explanation.)

processing of locational information require central processing capacity. Thus, if central processing capacity is unavailable during the execution of any of these stages, mere repeated exposure to the same locomotion path should be insufficient for improvement of maintenance of orientation to take place. This hypothesis was presently subjected to empiri- cal test.

The procedure adopted was to expose subjects repeatedly to the same locomotion path, requiring them to learn the location of a designated reference point which was out of sight when the path had been traversed. In order to interfere with central information processing, half of the subjects were given an additional task of rapid backwards counting to be performed concurrently whilst walking. It was predicted that maintenance of orientation should improve across trials for subjects without the concurrent task, whereas subjects performing this task should show less improvement. Two additional manipulations were undertaken with the intention of further interfering with central processing of information. Firstly, the number of segments of the locomotion paths (and thus the number of direction changes) was increased, which should make central information processing more difficult (Lindberg & Garling, 1977a, 19776; Sadalla & Magel, 1980), thus leading to slower improvement of maintenance of orientation. Secondly, by requiring half of the subjects to walk blindfolded it was assumed that encoding should be made more difficult and therefore require more central processing of information. Furthermore, the task of blindfolded walking, being a novel of experience to

Acquisition of locational information 103

the subjects, may in itself have an interfering effect. Since the amount of central processing capacity available for maintenance of orientation thus should be reduced, it was expected that improvement across trials should be less rapid for blindfolded subjects.

The main prediction was thus that maintenance of orientation should improve with repeated exposure to the same locomotion path, unless a concurrent task which interferes with central information processing is performed during locomotion. Fur- ther, the interfering effects should be enhanced when the number of segmentsldirection changes of the locomotion path is increased and when subjects are required to walk the path with vision occluded.

METHOD

Locomotion paths and environment The experiment was carried out in the culverts beneath the University Hospital of Ume& In Fig. 1 the culverts are schematically depicted with the paths walked by the subjects and the places where they were to stop in order to estimate direction and distance marked out. Two different configurations of locomotion paths, ABC and DEF, respectively, were employed, each one for half of the subjects in each experimental condition. The stops belonging to each configuration were selected so as to be separated by two (AB and DE), four (BC and EF) and six AC and DF) linear path segments.

The artificially lighted culverts were about 3 m widex 2.5 m high, and, with the exception of the flow of people, generally featureless. The paths had with one exception 90 deg angles of turn and were approximately level throughout. As indicated in the figure, the subjects were with two exceptions prevented from outside views. Swing doors at the near end of the alleys prevented the subjects from seeing from one alley to another.

Design The design was 2 x 2 ~ 2 ~ 3 ~ 8 (sighted/blindfolded subjects x subjects with/without a concurrent task X path configuration x number of path segments x trials) factorial with repeated measures on the last two factors.

Procedure The subjects, who served individually, were met by the experimenter at the reception hall of the University Hos- pital and received their instructions, which thoroughly described the estimation tasks they were to perform. Two practice trials were given in alleys outside the culvert system used in the main session. Thereafter, the experimenter took the subject to the culverts at one of the stops and accompanied him/her along the path. In the blindfolded conditions the subjects were blindfolded on arrival at the culverts, then led by the experimenter by means of a short stick to one of the stops and further along the

path. Equal numbers of subjects in each condition started at each one of the stops.

On amval at the next stop along the path, the subject was told by the experimenter to stop and estimate direction and distance to the starting point without turning around. Direction estimates were to be given as the angle in degrees to the right or to the left between the direction of the last alley walked (i.e., 180 deg to the direction faced by the subject) and the direction to the starting point, distance estimates as the crowflight distance in meters to the starting point. The walk thereafter continued and at the following stops direction and distance to the last place where the subject had been stopped were estimated in the same way. The order of direction and distance estimates was counterbalanced for each subject and also between subjects in each condition. Latency of the estimate first given was on each trial measured to the nearest 10 msec by means of a manually triggered digital stopwatch. Although the subjects may have been aware of the time measurement, the instructions emphasized accuracy and nothing was mentioned about speed requirements. Each subject walked the same paths eight times, and the whole session lasted for about 2 hours including a 15-min pause in the middle of it.

In the conditions with a concurrent task the subjects were given an additional task to be performed concurrently whilst walking. This task consisted of counting aloud backwards in steps of three, four, six, or seven from a threedigit number read to them by the experimenter. The randomly chosen three-digit number and the size of the steps to be counted in were changed twice during each linear path segment in order to prevent the subjects from performing the concurrent task automatically. The counting was interrupted each time the subject arrived at a stop, then resumed immediately after the estimates had been given. The instructions emphasized maximal speed of counting.

Subjects Forty-eight high-school students and undergraduates from Umei with a minimal familiarity with the culverts beneath the University Hospital participated as subjects, partly in order to fulfii a course requirement, partly in return for payment. Twelve subjects (6 men and 6 women) were randomly assigned to each one of four conditions (sighted/ blindfolded x with/without concurrent task), educational status being equally distributed in the different conditions.

RESULTS

Constant errors were calculated as the signed differences between the estimates and the correct values. Constant direction errors were given a positive sign if the direction estimates were to the right of the correct values, a negative sign if they were to the left; constant distance errors were counted as positive if distance was overestimated, negative if distance was underestimated.

Preliminary ANOVAs of the constant errors did not yield any significant main effects of trials, nor


104 E . Lindberg and T . Curling

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Fig. 2. Constant direction and distance errors (upper and lower panels respectively) for sighted and blindfolded subjects with and without a concurrent task as functions of number of path segments in each block.

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0 NO concurrent task, siqhted 0 - - " . blindfolded 4 Concurrent task, sighted A ' " , blindfolded

were there any significant main effects of blocks when trials were divided into four blocks of two trials. Therefore, trials were divided into two blocks of four trials in order to obtain the replicates neces- sary for calculating variable errors. Variable direction and distance errors were then obtained for each subject as standard deviations of constant errors within blocks and transformed according to log (SD2+ 1 .O) in order to achieve a better approxima- tion to the normal distribution (Scheffe, 1959).

Constant errors, variable errors and latencies of direction and distance estimates were separately subjected to ANOVAs (Seeing Condition x Concur- rent Task Condition x Number of Path Segments x Block) with repeated measures on the last two factors. Two additional factors were Order of Esti- mates (direction estimated before vs. after distance) and Path Configuration (ABC vs. DEF), included in the ANOVAs in order to reduce error variance. However, since these factors, besides having com-


paratively small or specific effects, were of minor interest in the present study, the results for them will not be reported. Further, since latencies were measured for first estimates only, the Order of Estimates factor did not enter the ANOVAs of this dependent variable.

Constant Errors As shown in Fig. 2, the constant errors did not uniformly decrease from the first to the second block, nor were the errors appreciably affected by the concurrent task in either block. However, for direction errors there was an interaction between block and seeing condition (F(1,40)=4.87, p<0.05, due to a tendency for the sighted subjects to im-' prove across blocks (p<O.lO as shown by tests of simple effects). The constant errors did not increase with the number of path segments, although the main effects of this factor were highly significant ( F ( 2 , 80)=9.56 and 36.20 for direction and


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distance errors respectively,p<O.OOl). For distance errors, finally, the effects of the number of path segments were larger in the conditions with the concurrent task than in the conditions without this task ( F (2, 80)=5.25, p<O.OI).

Variable Errors

The variable errors are displayed in Fig. 3. As can be seen, the errors decreased from the first to the second block (F (1, 40)=13.88,p<0.001, and 6.84, p<0.05, for direction and distance errors respectively). The concurrent task produced larger errors (F (1, 40)=7.47, p<O.Ol, and 4.23, p<0.05), but did not interact with block or any of the other factors. However, seeing condition interacted reliably with block ( F (1, 40)=4.93, p<0.05, and 9.93, p<O.Ol), due to the fact that the errors decreased only for sighted subjects (p<O.OOl). The variable errors were also larger in the blindfolded condition (F (1, 40)=10.51, p<O.Ol, and 4.32,p<0.05), but the difference was reliable only in the second block

4 6

Fig. 3 . Variable direction and distance errors (upper and lower panels respectively) for sighted and blindfolded subjects with and without a concurrent task as functions of number of path segments in each block.

(<0.001). Finally, the variable errors increased with the number of path segments ( F (2, 80)=24.03 and 25.5,p<0.001), but again there were no interactions with the remaining factors. As Newman-Keuls tests showed, the differences between two and four and between two and six path segments were reliable (P(O.01)

Latencies As shown in Fig. 4, there was an overall decrease in latencies from the first to the second block ( F (1, 40)=29.27, p<O.OOl, and 2.74, p<0.15, for latencies of direction and distance estimates respectively). but this decrease was largely unaffected by the remaining factors. Further, the latencies increased with the number of path segments ( F (2, 80)=6.65 and 8.18, p<O.OOl), an increase which tended to be modified by the concurrent task (F (2,80)=3.14,p<O.O5,and 1.16,n.s.)dueto thefact that the effect of the number of path segments was reliable only in the conditions with the concurrent

Scond. J . Psychol. 22


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task (p<O.OOl). In these conditions, all pairwise differences between different numbers of path segments were reliable except for the difference in distance latencies between four and six path segments (p<0.05 or less). Finally, the concurrent task raised the latencies (F (1, 40)=5.66, p<0.05, and 8.64, p<O.Ol), but reliably only for four and six path segments (p<O.OS or less).

DISCUSSION

The present results show that maintenance of orientation relative to a reference point improves with repeated exposure to the same locomotion path/ environment, since latencies and variable errors of the estimates of location decreased from the first to the second block. In contrast, improvement with regard to constant errors was almost negligible. While in agreement with the observation that some orientational errors can be rather persistent (see e.g.

Fig. 4. Latencies of direction and distance estimates (upper and lower panels respectively) for sighted and blindfolded subjects with and without a concurrent task as functions of number of path segments in each block.

Binet, 1894; Canter & Tagg, 1975), the latter finding may seem at odds with the results of Crane (1978) and Kozlowski & Bryant (1977) who observed increased accuracy of estimates of location across trials. However, since these authors only measured absolute errors which are a combination of constant and variable errors (see Attneave & Pierce, 1978; Schutz & Roy, 1973), there may not be any real contradiction between their findings and the results of the present study. Possibly, a decrease in constant errors should not be expected for the present degree of exposure to the environment unless ex- plicit feedback about the correct locations is given. Thus, under the present conditions the subjects seem to have acquired a spatial representation of the environment which, although incorrect, is used with increasing confidence and speed.

Contrary to prediction, interfering with central processing of locational information during locomotion by means of a concurrent task did not prevent



improvement of maintenance of orientation. This held true irrespective of the number of segments/ direction changes in the locomotion path. Thus, these manipulations of the amount of central processing capacity available for maintaining orientation during locomotion, while impairing orientation performance as shown by increased latencies and variable errors, seem to have had little effect on the acquisition of locational information. A possible explanation may be that the subjects performing the concurrent task were able to store information about the locomotion path whilst walking and then use that information to infer the location of the reference point at the time of performing the estimates (cf. Book & Garling, 1980~7, 1980b). This interpretation is supported by the finding that the latencies increased almost linearly with the number ofpath segments for these subjects, as should be expected if an approximately equal amount of time is needed for reading-out and coordination of information about each path segment. In contrast, the subjects without any concurrent task may have been able to keep track of the location of the reference point whilst walking, since their latencies were largely unaffected by the number of path segments.

Thus, the overall decrease in variable errors across blocks suggests that both keeping track of a location whilst walking and inferring it after walking leads to long-term storage of locational information. Possibly, the outcome of the methods employed by the subjects in maintaining orientation on each trial except the first one is compared to stored information about locations and the latter is adjusted accordingly. As the stored information is based on an increasing number of observations, these adjust- ments will become smaller, and, if the subjects’ responses are a function of the updated stored information, variable errors should decrease across trials. Also, this interpretation suggests that if given sufficient experience with the environment, the subjects may abandon their methods of maintaining orientation and instead directly access the stored information. However, as indicated by the latencies for subjects with a concurrent task, this did not occur in the present experiment. Consequently, the overall decrease in latencies across blocks may be ascribed to some information processing stage common to the two methods, such as retrieval of stored information, comparison of old and new information and/or response selection.

Finally, the variable errors did not decrease

across blocks for blindfolded subjects whether the concurrent task was performed or not and irrespective of the number of path segments. The fact that sighted and blindfolded subjects performed about equally well in the first block (cf. Garling et al., 1975) seems to preclude the possibility that the occlusion of vision interfered to any greater extent with keeping track of the location of a reference point (or with inferring its location after walking for subjects performing the concurrent task). Rather, the explanation may be that the blindfolded subjects were unable to benefit from information stored on previous trials because they could not recognize the places where the estimates were to be made in the absence of visual cues.

In summary, improvement of maintenance of orientation with repeated exposure to the same locomotion pathlenvironment was presently found and has been interpreted as ascribable to the acquisition of long-term stored locational information, i.e., a cognitive map. The results further suggested that interfering with central information processing during locomotion by means of a demanding concurrent task, while leading to a decrement in orientation performance, may not prevent acquisition, probably because the subjects are able to infer and store the location of a reference point (the starting point) after locomotion. Finally, the finding that blindfolded subjects did not improve from the first to the second block of trials was attributed to an inability to use stored information about locations in the absence of adequate retrieval cues.

The present study was financially supponed by grants from the Swedish Council for Building Research.

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Acquisition of locational information about reference points during blindfolded and sighted locomotion: Effects of a concurrent task and locomotion paths