Rotated Object Identification with and without

Rotated Object Identification with and without Orientation Cues PATRICIA A. MCMULLEN, JEFF HAMM Dalhousie University PIERRE JOLICOEUR University of Waterloo

Abstract The time to name two-dimensional line drawings of objects increases linearly for object rotations between 0° and 120° from the upright. Several theories attribute these effects of orientation to finding the top or the top-bottom axis of objects. By this account, prior knowledge of the location of the top or the top-bottom axis of objects should diminish effects of object orientation when they are named. When this hypothesis was tested by cuing the top or the top-bottom axis, no reduction in the effects of orientation on object naming was found. This result is inconsistent with effects of orientation on object naming being due to finding the top or the top-bottom axis. Instead, the top may be found prior to rotational normalization of the object image.

There is a linear increase in the time to name two-dimensional, line drawings of objects that are rotated between 0° and 120° from the upright (Jolicoeur, 1985; McMullen & Jolicoeur, 1990; 1992). It has been argued that the slope of the naming latency curve as a function of these orientations reflects the speed with which rotated object images are normalized through the shortest angular distance to align with canonically upright, object representations. Alternatively, a spatial reference frame (or coordinate system) used to define the top, bottom, left and right of the object memory, may be rotated to align with the disoriented object image (see Robertson, Palmer, & Gomez, 1987). During object naming, the spatial frame of reference that determines the upright is predominantly aligned with retinal as opposed to environmental coordinates (McMullen & Jolicoeur, 1990). Interestingly, objects rotated 180° are named faster than would be expected from extrapolation at other orientations. What characteristics of the image and long-term representation are matched during identification to produce this orientation sensitivity? Several characteristics have been proposed including the object's axis of elongation (Marr & Nishihara, 1978), axis of symmetry (Corballis & Roldan, 1975; Pashler, 1990), top-bottom axis (Marr & Nishihara, 1978; Tarr & Pinker, 1990; 1991), Canadian Journal of Experimental Psychology, 1995, 49:2, 133-149

134

McMullen, Hamm and Jolicoeur

top (Biederman, 1987; Rock, 1973), and/or the location of object features (see Koriat & Norman, 1989; McMullen & Jolicoeur, 1992; Ullman, 1989). The present investigation sought to test the hypothesis that part of the effects of orientation on object naming are due to finding the top or the top-bottom axis of objects. SUPPORT FOR THE EFFECTS OF ORIENTATION DUE TO FINDING THE TOP

Several theories of object recognition postulate effects of object orientation due to finding the top of objects. Rock (1973) emphasized the importance of correctly assigning the top during rotated object identification. He argued that this assignment occurs at the same time as the identity of the object is determined (Rock, 1973, p.40). Furthermore, he suggested that the assignment of the top direction is achieved via a normalization process similar to the mental rotation process used during left-right reflection discriminations (Shepard & Metzler, 1971; Shepard & Cooper, 1982; see Rock, 1973, p. 41). Jolicoeur (1985) supported this notion when he demonstrated similar slopes for the naming latency function and the latency function found when left-right reflections are determined for objects rotated between 0° and 120°. Similarly, Hock and Tromley (1978) have also proposed that the top of rotated object images are aligned with the top of long-term object representations. In their model, the top of the rotated object image is initially assigned to that part of the object image located closest to the environmental upright. Through trial and error, the object image is rotated until its true top matches the top of a long-term object representation. Hock and Tromley discovered that objects, in particular, letters, differed in the range of orientations perceived as upright. Finally, Biederman (1987; Biederman & Gerhardstein, 1993) postulated a theory of object recognition in which objects are parsed into universal, orientation-invariant, geometric components. In his view, the effect of orientation on recognition "arises not from the use of orientation-dependent features but from the perturbation of the 'top of relations among components" (Biederman, 1987, p. 140). In Biederman's model, a substantial component of the orientation effect on identification is expected to be associated with the time required to find the top of the object. Some empirical findings have been consistent with the notion that effects of orientation on object naming are due to finding the top. For instance, the time to find the top of objects is affected by object orientation in a manner similar to that found with object naming. When subjects judged whether a dot was located near the top or the bottom of rotated objects, linear increases in response time for rotations up to 120° from the upright were found with a slope that was not different from rotated object naming (McMullen & Jolicoeur, 1992). As well, response times to objects rotated 180° were faster

Orientation Cues and Rotated Object Naming

135

than would be expected from extrapolation from other orientations. These findings suggest that the speed of normalization, and indeed the orientation-sensitive processes involved, are similar for the two tasks and are consistent with effects of orientation on object naming due to finding the top of objects. SUPPORT FOR THE EFFECTS OF ORIENTATION DUE TO FINDING THE TOP-BOTTOM AXIS

Other theorists have suggested that determining the top-bottom axis underlies some of the effects of orientation on rotated object identification. For instance, Tarr and Pinker (1991) have proposed that two orientation-sensitive processes operate during rotated object naming: one which involves determining the location of the top-bottom axis and another slower process which involves normalizing the object image through the shortest angular distance to the upright. The slower normalization process depends on the axis information gleaned from the first process. This account predicts that prior knowledge of the location of the top-bottom axis should reduce but not abolish effects of orientation because prior orientation knowledge would by-pass only the first orientation-sensitive process. Tarr and Pinker (1991) believe that the "M" shaped naming latency function (reflected about 180°) is explained by the first orientation-sensitive process they have proposed: finding the top-bottom axis. They argue that when an object is upside-down, the top-bottom axis of the image is aligned with the top-bottom axis of an upright representation. The latency reduction in the response curve at 180° occurs because the top-bottom axis at this orientation is already aligned with the top-bottom axis of the representation, although the poles of the axis are reversed. At this orientation, none of the effects of orientation are due to axis finding. However, normalization of the object image to the upright is still necessary. Ullman (1989) proposed a computational model of object recognition in which a small set of "key" features (three are sufficient) can be used to bring the image of a rotated object into alignment with a stored representation of the object. Ullman suggests that properties of the object that are stable across various projections of the image, such as salient features, symmetry, axis of elongation, and the top-bottom axis could be used to define the features used in the alignment key. Contrary to Tarr and Pinker's view, recovery of object orientation based on key features occurs independently of orientation. Effects of orientation during identification are instead due solely to normalization of the image to align it with an upright representation (or normalization of the representation to align with the image), in a manner simiiar to the second orientation-sensitive process proposed by Tarr and Pinker. Since finding the top-bottom axis is an orientation-invariant process, this account predicts that prior knowledge of the location of the top-bottom axis of an object should

136

McMuIlen, Hamm and Jolicoeur

have no effect on naming latency. Empirical support for this account exists. The top-finding task previously described, in which a dot is located next to some part of a rotated object, was used to determine effects of orientation with rotated letters (Corballis & Cullen, 1986). Larger effects of orientation were found when the decision involved determining whether the dot was nearest the top or bottom pole than when the decision involved determining whether the dot was nearest the top-bottom or left-right axis. These results suggest that the location of the top-bottom axis may be available somewhat independently of orientation, whereas the location of the top is not. INFLUENCE OF PRIOR KNOWLEDGE OF ORIENTATION

The view that effects of orientation on object naming are due to finding the top predicts that prior knowledge of the location of the top should reduce effects of orientation on object processing. A previous test of the effects of prior knowledge of object orientation on naming met with equivocal results. Braine (1965) found no difference in the effects of orientation on object naming accuracy when subjects were told orally that an upcoming stimulus would be rotated in general relative to when subjects were told its precise orientation. However, there are at least four problems with Braine's study that make it difficult to interpret in the present context. First, a verbal-auditory cue may not influence early visual processes involved in identification. Second, Braine presented the same object stimuli repeatedly which has been shown to reduce effects of orientation found with a single presentation of each object (Jolicoeur, 1985). This factor could be important if the strongest effects of an orientation cue occur during the first presentation of an object. Third, Braine measured accuracy only. Effects of orientation on naming accuracy differ from those found on naming latency (Jolicoeur & Landau, 1984). Finally, Braine presented objects at 0°, 90°, 180° and 270°. Effects of rotation away from the upright were found, but they did not differ for 90°, 180° and 270°. Given that effects of orientation on naming are generally greatest for objects 120° from the upright, Braine may not have found effects of cue because the most sensitive object orientations were not tested. Cooper and Shepard's (1973) classic study of the effects of orientation cuing on left-right reflection discriminations of letters and digits demonstrated that providing an orientation cue facilitated overall response time by approximately 100 ms. However, effects of the cue did not interact with effects of orientation. A similar main effect of cue was found when object identity was precued. Based on these results, Cooper and Shepard (1973) postulated an order of processing in which an object is first identified, and then this identification provides orientation information to direct mental rotation of the image through the shortest angular distance to the upright.

Orientation Cues and Rotated Object Naming

137

Although these results suggest that knowledge of the location of the top of objects is available prior to normalization during left-right reflection discriminations, it is possible that normalization occurs prior to finding the top during object naming. There are at least three pieces of evidence to suggest that different normalization processes underlie object naming and left-right reflection discriminations. (Note, however, that there are alternatives to this view; see Jolicoeur, 1985; Rock, 1973). The latency functions differ at 180°, the spatial frames of reference differ (McMullen & Jolicoeur, 1990), and finally, the effects of orientation reduce with practice naming objects but not with practice making left-right reflection discriminations (Jolicoeur, 1985). If different normalization processes are used during these two tasks, it is quite plausible that different means of finding the top are employed as well. The aim of the current experiments was to determine if prior visual knowledge of the location of the top or the top-bottom axis reduces effects of orientation on the time to name objects presented once each, at incremental orientations of 60°. Such a demonstration would suggest that the effects of orientation on naming are partly or entirely due to finding the top or the top-bottom axis of object stimuli. Experiment 1 Rock (1973) and Biederman (1987) have proposed that the effects of orientation on rotated object naming are due to finding the top of objects. Consistent with this proposal, Corballis and Cullen (1986) reported that finding the top was more dependent on orientation than on finding the top-bottom axis. Cues to the location of the top of objects should then be the most likely pre-stimulus cue to reduce effects of orientation. The present study sought to maximize the likelihood that effects of orientation were reduced during rotated object naming by (1) employing a visual cue to the location of the top of upcoming objects, (2) using latency measures, (3) examining orientations that are known to exert the largest effects, and (4) by using a single presentation of each object. METHOD

Subjects Twenty-nine undergraduate students from the University of Waterloo with normal or corrected-to-normal vision participated in this experiment for pay. The data from twenty-four (twelve women and twelve men) of these subjects were included in the final analysis. Five subjects were excluded due to premature tripping of the voice key which produced an unacceptable number of spoiled trials. No remaining subject made more than 30% errors in each cell of the design of this experiment. All subjects reported English as their first language.

138

McMullen, Hamm and Jolicoeur

Stimuli and Apparatus One hundred and twenty two-dimensional line drawings of objects with a distinct top and bottom (horizontally asymmetric) were used (Snodgrass & Vanderwart, 1980; see Appendix A of McMullen & Jolicoeur, 1990). Al] stimuli were rotated, in the frontal plane, from the environmental vertical in 60° clockwise steps, ranging from 0° to 300°. The original stimuli were photographed using high-contrast film that was then cut and fit into 35 mm slide mounts. Twelve object slides not used during the experiment trials were used during practice trials. To construct slides for presenting cues, six pieces of black cardboard were cut to fit within a slide mount. A drill press was used to punch a small hole equidistant from the centre and located at one of the six angular orientations (0°, 60°, 120°, 180°, 240°, or 300°) in each of the six slides. One of these slides was used to mark the top of a rotated object on each cued trial. In addition to the six top-marker slides, a no-cue slide was prepared. This slide was identical to the others except that rather than a single hole at one of the six angular rotations, six holes were punched, one at each of the six angular locations. The experiment was programmed and conducted with a microcomputer that controlled two slide projectors fitted with electronic shutters. All 35 mm object and cue slides were rear-projected within a matt-black rectangular border. The screen, object stimuli, and top marker subtended approximate visual angles of 7.5°, 4.4° and 0.7°, respectively. Reaction time was measured from the opening of the shutter to the subject's response, and was recorded by the computer to the nearest ms. Procedure Twelve sets of 120 trials each were created. In each set, there were 120 objects, with 20 objects at each of the six orientations, half of which were cued for orientation and half of which were not cued. To control for the effects of item differences such as name frequency on the effects of orientation, equal numbers of objects known to produce slow and fast naming responses when averaged across all orientations, as determined by a pilot study, were included at each orientation for cued and uncued trials in a set. The objects in a set were ordered at random, subject to the constraints that no more than four consecutive trials have the same orientation or cue/no-cue designation, and that each set contain one instance of each object. Across six of the sets (sets 1-6), each object was in a different orientation, three orientations of which were cued and three of which were not. The other six sets (sets 7-12) were identical to these sets (1-6) except that the cued trials were replaced by uncued trials and vice versa. Each subject named one set of 120 objects in an individual testing session that lasted approximately twenty minutes. Instructions emphasizing speed,

Orientation Cues and Rotated Object Naming

139

accuracy, and clear articulation were given, followed by a practice session in which 12 rotated objects not shown during the experimental trials were presented. The experimenter pressed a key to initiate each trial. During cued trials, a bright disk of light appeared on the screen indicating the top of an upcoming object. During uncued trials, a ring of six bright disks appeared, one at each potential object orientation. The cue slide or the uninformative no-cue slide was presented for 1500 ms prior to the presentation of the object. The precuing slides remained on during the presentation of the object to-be-named which was shown for 4000 ms or until a response was made. Trial set and subject gender were counterbalanced. Reaction time was measured from the onset of the object presentation until a voice key tripped, at which time the shutter closed, ending the slide presentation. The experimenter coded each response on the computer keyboard as correct, incorrect, or spoiled. A trial was considered spoiled if the voice key tripped prematurely (e.g., the subject said "Ah..." or there was ambient noise), if the cue or object slide did not project properly, if the voice key failed to trip when the subject responded, or if the subject did not respond within 4000 ms. A trial was scored as incorrect if the response given was unacceptable (see McMullen & Jolicoeur, 1990, for acceptable responses). Across subjects, each of the twelve trial sets was run twice in the order one to twelve. RESULTS

Response Times Response times were subjected to two sets of analyses. One set of analyses was based on the correct response times, excluding outlier times of greater or less than 2.5 standard deviations from the mean for each cell for each subject. Response times were rejected recursively, on the basis of new cell means, until the data set satisfied this criterion. This criterion resulted in a rejection of 0.7% of the total number of trials. A further 0.9% of the total trials were spoiled and excluded from the analysis. Mean correct naming latencies were calculated over objects for each orientation, cue condition and subject. A repeated-measures Analysis of Variance was performed on these means with Orientation (0°, 60°, 120°, 180°, 240°, or 300°) and Cue Condition (cued or uncued) as within-subject variables. The mean naming latency for stimuli at each orientation and in each cue condition is shown in Figure 1. Orientation had a large overall effect, /•(5,115) = 8.9, MSe = 16776, p< .001. As has been demonstrated previously, response time increased linearly for rotations up to 120° from the upright. Responses to objects inverted 180° were faster than would be expected from linearly extrapolating from other orientations closer to the upright. These effects of orientation were not different for the cued and uncued conditions in the omnibus analysis,

140

McMullen, Hamm and Jolicoeur

1,340 1,320 CO

1,300

E

1,280

CD

1,260

E CD CO

1,240 1,220

c o 1,200 Q_

CO

CD

1,180

DC 1,160 C CD CD

1,140 1,120 1,100 1,080

0

60 120 180 240 300 360

Object Orientation (deg) Fig. 1 Mean response time to name objects for each stimulus orientation and cue condition in Experiment 1.

F(5,115) = 0.7, MSe = 14634. Nor was there a main effect of cue, ,F(1,23) = 0.4, MSe = 13776. Consistent with these findings, the slopes of the orientation functions for the two cue conditions were not different, using a linear contrast analysis, F(l,23) = 3.7, MSe = 6384, p < .07. This marginally significant interaction suggests that, if anything, the cue increased the effects of orientation relative to the no-cue condition. This trend is somewhat surprising. However, because it was not found in the median analysis of this experiment, nor in any analysis of the results of Experiment 2, we will not interpret it. The same pattern of effects found with analysis of the mean response times was found with an analysis of the median response times.

Orientation Cues and Rotated Object Naming

141

TABLE 1 Mean percentage error rates from the naming task for each stimulus orientation and cue condition in Experiment 1 Cue condition Orientation (") 0 60 120 180 240 300

Cue

No-Cue

5.4 7.2 7.6 5.4 5.5 7.1

4.3 6.7 8.1 7.6 9.2 5.0

Percentage Error All responses in which an incorrect name was given were considered errors. The average percentage error for each orientation and cue condition can be seen in Table 1. These data were submitted to the same analysis of variance as the response times. No reliable effects (all F < = 1) were found with the percentage error data, suggesting that none of the effects found in the latency analysis were due to speed-accuracy trade-offs. For the most part, in fact, error rates corresponded with response times. DISCUSSION

The most important finding was that cuing the location of the top of objects had no effect on the time to name the objects relative to trials in which the location of the top was not cued. These results were found despite measures designed to maximize the effects of orientation and of the cue. If recovering the location of the top was a significant time-consuming step in the production of the orientation effect on object naming, then we would expect that the cuing procedure used in this experiment should have reduced the size of the orientation effect. The fact that we did not observe any reduction in the size of the orientation effect is antithetical to models in which the effects of orientation on the time to name objects are thought to derive entirely or in part from finding the top of objects (Biederman, 1987; Hock & Tromley, 1978; Tarr & Pinker, 1991; Rock, 1973). Experiment 2 As outlined earlier, there were several reasons for postulating that the effects of orientation during object naming are due to finding the top of objects, a hypothesis tested by Experiment 1. Contrary to this hypothesis, knowing the location of the top of objects did not alter the effects of orientation on the time to name those objects. However, another suggestion has been that the effects of orientation lie at least partially in finding the top-bottom axis (Tarr & Pinker, 1991). Although

142

McMullen, Hamm and Jolicoeur

the dot cue in Experiment 1 could have implicitly informed subjects of the location of the top-bottom axis, Experiment 2 made this information explicit and perhaps more salient with the presentation of an arrow cue. Minimally, this experiment should provide a replication of the null finding reported in Experiment 1. Data from this second experiment can also be combined with those from the first experiment to increase the power to detect a small interaction between orientation and cue condition. METHOD

Subjects Twenty-six Dalhousie psychology students (20 women, 6 men) participated in this experiment without payment or for course credit. Once again, all subjects whose data were used for analysis made fewer than 30% errors in each cell of the design. Two subjects failed to meet this criterion and their data were omitted. All subjects had normal or corrected-to-normal vision, were between the ages of 19 and 45, and spoke English as their first language. No subject had participated in Experiment 1. Stimuli and Apparatus The same apparatus and object stimuli used in Experiment 1 were used in this experiment. Unlike Experiment 1, preceding the presentation of objects, a single arrow pointed in the same direction as the object-to-be-named during cued trials. During uncued trials, six arrow heads pointing in all six possible orientations preceded the object. The arrows consisted of a triangular head with a short extension to indicate a shaft, totalling 1.1° of visual angle, plus a short tail section beginning 4.2° of visual angle further along the implied top-bottom axis, with the entire arrow subtending a total of 5.7° of visual angle. All object and cue slides were rear-projected onto a mylar projection screen framed by a circular paper matte. Procedure The procedure for running both the experimental and practice trials was the same as that reported for Experiment 1 with the following two exceptions; (1) Cues were presented for 900 ms and immediately replaced by an object, and (2) objects were projected in a location between those occupied by the arrow head and the tail segment in order to minimize masking effects of the cue. RESULTS

Response times The same design used for the analysis of the data from Experiment I was used to analyze the data from Experiment 2. The outlier criterion resulted in a rejection of less than 1% of the total trials. Spoiled trials represented a total

Orientation Cues and Rotated Object Naming

143

Arrow Cue No Cue

940

0

60 120 180 240 300 360

Object Orientation (deg) Fig. 2 Mean response time to name objects for each stimulus orientation and cue condition in Experiment 2. (Note: Although the range for this figure is different from that of Figure 1, the scale is the same).

of 6.4% of the total trials. The mean naming latency for each object orientation and cue condition is shown in Figure 2. Once again, orientation had a large overall effect, F(5,115) = 10.4, MSf = 9771, p < .001. These effects of orientation were not different for the cued and uncued conditions, with both the omnibus analysis, F ( 5 , 1 1 5 ) = 0.1, MSe = 11463, and a linear trend analysis of the effects of orientation for cued and uncued trials, F(l,23) = 0.03, MSe = 14155. As well, no main effect of orientation cue was found, F(l,23) = 1.3, MSe = 14499. In addition to an analysis of the mean response times, an analysis of the

144

McMullen, Hamm and Jolicoeur

TABLE 2 Mean percentage error rates from the naming task for each stimulus orientation and cue condition in Experiment 2 p

.

Cue condition

1

Orientation (") 0 60 120 180 240 300

Cue

No-Cue

3.1 2.6 4.2 2.5 3.5 4.9

2.6 4.9 5.7 5.1 4.0 3.5

median response times was conducted. The pattern of effects found with the median analysis was the same as that found with the mean analysis. Percentage Error The average percentage error rate at each orientation and in each cue condition can be seen in Table 2. No reliable effects (all F< = 1.0) were found with the percentage error rates, which fails to support speed-accuracy trade-offs. DISCUSSION

Consistent with the results of Experiment 1, simultaneously cuing the orientation of the top-bottom axis and the location of the top of rotated objects failed to diminish effects of orientation on naming. This finding provides a replication of our previous results. However, it is possible that neither experiment had sufficient power to detect an interaction between orientation and cue condition. To increase the power to find this effect, results of Experiment 1 and 2 were combined using Experiment as a between-subjects factor. Even with this increased power, the effects of orientation were not different for cued and uncued trials in both the omnibus, f(5,230) = 0.7, MSe - 9277, and linear contrast analyses, f(l,46) = 0.05, MSe = 5651. Orientation had a large effect on response time F(5,230) = 19.8, MSr = 12247, p < .001, and responses from the arrow cued group were faster than those from the dot cued group, F(l,46) = 11.6, MS, = 248373, p < .01. No other effects from this analysis reached significance. As a further precaution, a repeated-measures power analysis (GANOVA; Brecht, Woodward, & Bonett, 1989) was performed to calculate the power to detect an interaction between cue and orientation similar to that found by Cooper and Shepard (1973) when they cued with both orientation and identity. The analysis assumed a somewhat more conservative effect size in the range of known naming latencies and a flattened orientation effect between 120°,

Orientation Cues and Rotated Object Naming

145

180° and 240°. (Uncued condition: 975, 1050, 1220, 1220, 1220, 1050; Cued condition: 800, 850, 900, 900, 900, 850). A variance estimate was derived from our arrow cuing experiment (25,600) as was an average correlation of 0.7 amongst the 12 design cells. Using these parameters, only 9 subjects were needed to provide power of 0.8. The power to detect the effect, described above with 24 subjects, was 1.0. General Discussion In two naming experiments, conditions were designed to optimize the use of preview information about the location of the top pole and/or the orientation of the top-bottom axis of rotated objects. In both experiments the time to name objects was sharply affected by orientation, as was expected from several earlier studies (Jolicoeur, 1985; Maki, 1986; McMullen & Jolicoeur, 1990; 1992). However, both experiments failed to show reduced effects of orientation on object naming when orientation cues were available (see also Braine, 1965). DOES NORMALIZATION PRECEDE FINDING THE TOP?

Rock (1973, p. 40) suggested that image normalization is performed prior to and in order to find the top of objects. In his view, normalization proceeds via mental rotation in a trial-and-error manner during which a rotated image is periodically compared with a set of candidate representations until a match is found. At this point, both the identity and the orientation of an image is found. If we assume that Rock is correct, then knowing the location of the top before normalization should obviate the necessity for normalization. How might an orientation cue have been used to indicate the top of objects? It could have served to direct the rotation of an abstract frame of reference from its upright orientation to the orientation of the cue. An abstract frame of reference is a representational set of coordinates used to indicate the top, bottom, left, and right of an object of unspecified identity. If an abstract frame was rotated to the orientation of the cue, the top of the frame would be aligned with the top of the stimulus at the time of the object presentation, producing negligible effects of orientation on identification time. This explanation for the way in which the cue could have been used is plausible, provided that effects of orientation are due in some measure to finding the top of objects and that an abstract frame of reference can be rotated. CAN ABSTRACT FRAMES OF REFERENCE BE ROTATED?

Naming studies relevant to the rotation of abstract frames of reference have provided conflicting results. Jolicoeur (1990) found that when three letters were presented simultaneously, errors in naming each letter decreased when the orientation of a letter matched the orientation of one identified just before

146

McMullen, Hamm and Jolicoeur

it. This effect was independent of the identity of the letters and so supported the rotation of an abstract frame of reference. In contrast, Koriat, Norman, and Kimchi (1991) showed that the time to classify four rotated Hebrew letters varied as a function of the orientation of the immediately preceding letter only when the two letters had the same left-right reflection and identity. The authors concluded that in this condition, an image of the second letter was backward aligned with a template formed of the first letter. Since an effect of the orientation of the previous stimulus was dependent on its identity, these results failed to support the rotation of abstract frames of reference. Results from Jolicoeur (1990) and Koriat et al. (1991) may conflict for any of several reasons. Differences in experimental procedure, such as errors versus reaction time measures and explicit naming versus key-press classification provide two possibilities. At present, it is unclear which variable might exert the greatest influence on the ability to rotate an abstract frame of reference. Most of the work investigating the rotation of abstract frames has been done with left-right reflection discrimination tasks. Like identification tasks, these tasks have both supported (Hinton & Parsons, 1981; Robertson et al., 1987) and refuted (Cooper & Shepard, 1973; Koriat & Norman, 1988) the rotation of abstract frames. Given that some experiments support the rotation of abstract frames in identification and left-right reflection discrimination tasks and some do not, it is conceivable that more than one process underlies these effects. DOES FINDING THE TOP PRECEDE NORMALIZATION? Latency responses to disoriented objects suggest that object images are normalized through the shortest angular distance to the upright (e.g., Cooper & Shepard, 1973; Jolicoeur, 1985). This effect is consistent with knowledge of the location of the top of objects preceding normalization. If this is the case, then orientation cues should be redundant with whatever information informs the location of the top. A redundancy gain of this sort might be expected to reduce effects of orientation or minimally to facilitate responses overall. Neither effect was found in the current experiments. An overall facilitation of 100 ms was found when orientation cues were available in the classic left-right reflection discrimination study reported by Cooper and Shepard (1973). We did not find this effect with object naming. We hypothesized that our results were different from those of Cooper and Shepard because of a difference in our cuing procedure. In their no-cue condition, Cooper and Shepard presented a blank field. In our study, the no-cue condition consisted of a cue to all possible orientations. Our uninformative cue may have alerted subjects to the upcoming display. A blank field would not have this effect. This interpretation is bolstered by the fact

Orientation Cues and Rotated Object Naming

147

that, in their study, an identity cue similarly facilitated responses by 100 ms relative to a blank field. This effect suggests that the content of the cue may have been inconsequential, and that facilitation with identity or orientation cues was simply due to an alerting effect of a cue relative to a blank field. We recently tested this hypothesis with an orientation cued, left-right reflection discrimination task similar to Cooper and Shepard's. Most importantly, in the no-cue condition, a cue to all possible orientations was presented. Similar to the results found by Cooper and Shepard, our results showed an overall facilitation in the cued condition, F ( 1 , 2 3 ) = 22.0, MSe = 39468, p < 001. As has been repeatedly shown, the cue failed to alter the effects of orientation, F(5,1 15) = 1.1, A/5, = 24310, p < 0.4. These results disconfirm our hypothesis that differences between our results and those of Cooper and Shepard are due to differences in the no-cue condition. Instead, they suggest that effects of orientation on naming versus left-right reflection discriminations may rely on different orientation mechanisms. If the top is found prior to normalization, it must be provided in a bottom-up manner from information present in the stimulus. A model of object recognition proposed by Hummel and Biederman (1992) supports this view. In their model, information about the location of the top of objects and other spatial relations between parts of an object are computed in a bottom-up neural network, within a retinotopic coordinate system. In such a network, prior presentation of a cue signalling the location of the top of an upcoming object would not facilitate processing that object because the spatial relations are only computed when the object is actually present in its entirety. However, the utility of this model is challenged by top-down effects on object processing. For instance, shape recognition accuracy increases when subjects know that the shapes may have been rotated to a different orientation from the learning to the test phase of a recognition memory experiment (Rock, 1973). In conclusion, finding the top may be an important process in naming rotated objects. However, our results and those from other orientation cuing experiments are consistent with determination of the top prior to normalization on the basis of bottom-up information. Effects of orientation are then primarily attributable to normalization of the object image to the upright and not to finding the top of objects. This research was supported by grants from the Natural Sciences and Engineering Research Council of Canada awarded to Patricia McMullen and Pierre Jolicoeur. We gratefully acknowledge the technical support of Margaret Ingleton. Correspondence should be addressed to: Patricia A. McMullen, Department of Psychology, Dalhousie University, Halifax, Nova Scotia B3H 4J1 (e-mail: [email protected]).

148

McMullen, Hamm and Jolicoeur

References Biederman, I. (1987). Recognition-by-components: A theory of human image understanding. Psychological Review, 94, 115-147. Biederman, I., & Gerhardstein, P.C. (1993). Recognizing depth-rotated objects: Evidence and conditions for three- dimensional viewpoint invariance. Journal of Experimental Psychology: Human Perception and Performance, 19, 1162-1182. Braine, L.G. (1965). Disorientation of forms: An examination of Rock's theory. Psychonomic Science, 3, 541-542. Brecht, M.L., Woodward, J.A., & Bonett, D.G. (1989). Analysis of linear models of experimental design: GANOVA. [Computer Program]. Harcourt, Brace, Jovanovich. Cooper, L.A., & Shepard, R.N. (1973). Chronometric studies of the rotation of mental images. In W.G. Chase (Ed.), Visual information processing (pp. 75-176). New York: Academic Press. Corballis, M.C., & Cullen, S. (1986). Decisions about the axes of disoriented shapes. Memory and Cognition, 14, 27-38. Corballis, M.C., & Roldan, C.E. (1975). Detection of symmetry as a function of angular orientation. Journal of Experimental Psychology: Human Perception and Performance, 1, 221-230. Hinton, G.E., & Parsons, L.M. (1981). Frames of reference and mental imagery. In A. Baddeley & J. Long (Eds.), Attention and Performance IX (pp. 261-277). Hillsdale, NJ: Erlbaum. Hock, H.S., & Tromley, C.L. (1978). Mental rotation and perceptual uprightness. Perception & Psychophysics, 24, 529-533. Hummel, J.E., & Biederman, I. (1992). Dynamic binding in a neural network for shape recognition. Psychological Review, 99, 480-517. Jolicoeur, P. (1985). The time to name disoriented natural objects. Memory and Cognition, 13, 289-303. Jolicoeur, P. (1990). Orientation congruency effects on the identification of disoriented shapes. Journal of Experimental Psychology: Human Perception and Performance, 16, 251-364. Jolicoeur, P., & Landau, M.J. (1984). Effects of orientation on the identification of simple visual patterns. Canadian Journal of Psychology, 38, 80-93. Koriat, A., & Norman, J. (1988). Frames and images: Sequential effects in mental rotation. Journal of Experimental Psychology: Learning, Memory and Cognition, 74,93-111. Koriat, A., & Norman, J. (1989). Why is word recognition impaired by disorientation while the identification of single letters is not? Journal of Experimental Psychology: Human Perception and Performance, 15, 153- 163. Koriat, A., Norman, J., & Kimchi, R. (1991). Recognition of rotated letters: Extracting invariance across successive and simultaneous stimuli. Journal of Experimental Psychology: Human Perception and Performance, 17, 444-457. Maki, R.H. (1986). Naming and locating the tops of rotated pictures. Canadian Journal of Psychology, 40, 368-387.

Orientation Cues and Rotated Object Naming

149

Marr, D., & Nishihara, H.K. (1978). Representation and recognition of the spatial organization of three-dimensional shapes. Proceedings of the Royal Society of London, 200, 269-294. McMullen, P.A., & Jolicoeur, P. (1990). The spatial frame of reference in object naming and discriminations of left-right reflections. Memory and Cognition, 18, 99-115. McMullen, P.A., & Jolicoeur, P. (1992). The reference frame and effects of orientation on finding the tops of rotated objects. Journal of Experimental Psychology: Human Perception and Performance, 18, 807-820. Pashler, H. (1990). Coordinate frame for symmetry detection and object recognition. Journal of Experimental Psychology: Human Perception and Performance, 16, 150-163. Robertson, L.C., Palmer, S.E., & Gomez, L.M. (1987). Reference frames in mental rotation. Journal of Experimental Psychology: Learning, Memory and Cognition, 13, 368-379. Rock, I. (1973). Orientation and form. New York." Academic Press. Shepard, R.N., & Cooper, L. (1982). Mental images and their transformations. Cambridge, MA: MIT Press. Shepard, R.N., & Metzter, J. (1971). Mental rotation of three-dimensional objects. Science, 171, 701-703. Snodgrass, J.G., & Vanderwart, M. (1980). A standardized set of 260 pictures: Norms for name agreement, image agreement, familiarity, and visual complexity. Journal of Experimental Psychology: Learning, Memory, & Cognition, 6, 174-215. Tarr, M.J., & Pinker, S. (1990). When does human object recognition use a viewer-centered reference frame? Psychological Science, 1, 253-256. Tarr, M.J., & Pinker, S. (1991). Orientation-dependent mechanisms in shape recognition: Further issues. Psychological Science, 1, 253-256. Ullman, S. (1989). Aligning pictorial descriptions: An approach to object recognition. Cognition, 32, 193-254. Date of acceptance: March 10, 1994

Sommaire L'identification d'illustrations au trait bidimensionnelles Le temps requis pour identifier des illustrations au trait bidimensionnelles d'objets usuels s'accroit de facon lineaire lorsqu'on fait pi voter, depuis une representation verticale, les objets de 0° a 120" sur le plan d'image. Plusieurs theories de reconnaissance des objets (voir Biederman, 1987; Rock, 1973; Tarr et Pinker, 1991) attribuent ces effets d'orientation a la determination spatiale de la partie superieure des objets ou de leur axe longitudinal. En vertu de cette hypothese, une connaissance prealable de l'emplacement de la partie superieure des objets, ou de leur axe longitudinal, devrait amenuiser les effets induits par l'orientation lorsqu'ils doivent etre identifies. On a mis cette theorie a l'essai dans le cadre de deux experiences. Dans un premiere, l'emplacement de la partie superieure etait signalee par un point avant la presentation des objets. Ce marquage de la partie superieure n'a eu aucun effet d'orientation sur la designation des objets. Les marquages de parties superieures n'ont pas plus contribue de maniere generale a faciliter les reponses. Allant a l'encontre de ce resultat, un indice sur l'orientation du mouvement de gauche a droite pendant le test de reconnaissance des objets que Ton faisait pivoter a semble faciliter generalement les reponses (Cooper et Shepard, 1973). Ces resultats suggerent que les effets d'orientation pour la designation et le discernement de gauche a droite pourraient temoigner de processus differents. Dans la deuxieme experience, l'axe longitudinal et la partie superieure des objets ont ete signales en presentant une fleche pointant dans la direction des objets a venir. Les resultats tires de cette experience ont ete semblables aux resultats de la premiere. L'incapacity a constater toute influence d'indice sur l'orientation ne pouvait etre imputable a 1'impossibility de deceler une telle interaction. Un nombre suffisant de sujets ont ete soumis aux deux experiences, seules ou combinees. Bref, ces constatations n'accreditent pas les theories de reconnaissance des objets qui tiennent pour acquis les effets d'orientation sur la capacite de nommer les objets en fonction du reperage de la partie superieure ou de I'axe longitudinal.

Revue canadienne de psychologie experimentale, 1995, 49:2, 150