The Role of Vision in the Corsi Block-Tapping Task: Evidence From Blind and Sighted People

Transcription

1 Neuropsychology 2010 American Psychological Association 2010, Vol. 24, No. 5, /10/$12.00 DOI: /a The Role of Vision in the Corsi Block-Tapping Task: Evidence From Blind and Sighted People Gennaro Ruggiero and Tina Iachini Second University of Naples, Italy Objective: This study aims at adapting the Corsi Block-Tapping task to measure serial-spatial memory in blind people and at clarifying the role of visual experience in the task. Method: Congenitally blind, adventitiously blind, and blindfolded sighted people were compared on a version of the Corsi board that allowed the haptic perception of block positions (Haptic-Corsi). Participants placed their fingers on the blocks that the experimenter moved upward according to sequences of increasing length. Afterward, participants reproduced the sequences in forward/backward order. Results: The results showed a significant interaction between groups and forward/backward span: F(2, 58) 5.74, MSE.39, p.01, In forward order the memory span was higher in adventitiously blind participants than blindfolded sighted ( p.05) but not congenitally blind participants. In backward order, there were no significant differences. Conclusions: The good performance of blind people, especially adventitiously ones, was interpreted as evidence that sequential haptic inputs were organized spatially. The possible cognitive processes underlying the performance were discussed. Keywords: Corsi task, blindness, serial-spatial memory span, forward/backward span, haptic perception One of the most popular experimental tools for the assessment of visuospatial working memory span in both clinical and research contexts is the Corsi Block-Tapping task (Corsi, 1972; Milner, 1971). Despite its wide use, the task has never been adopted to measure spatial memory span in blind people. The purpose of this study is twofold: (a) to adapt the Corsi task for blind presentation and (b) to clarify the role of visual experience in the task. The original Corsi consists of a set of nine white blocks (3 3 3 cm) arranged irregularly on a cm wooden flat board. On the experimenter s side of the board, the blocks are numbered from 1 to 9 on the vertical surface so as to allow the identification of the blocks that should be tapped by the experimenter. Participants have to reproduce the same sequences of increasing length in forward order and sometimes in backward order (see Berch, Krikorian, & Huha, 1998; Cornoldi & Mammarella, 2008). The maximum length above which the participant is unable to successfully reproduce the block-tapping sequence corresponds to the span capacity. Over the years, the task has been subjected to several methodological modifications (e.g., number and size of blocks, block placement, block-tapping rate, trials per level, recall orders, etc.) and used for different purposes (for review Berch et al., 1998). For example, it has been adopted to study the processing and planning of movement (Logie, 1995; Pickering, Gathercole, Hall, & Lloyd, 2001), the role played by the hierarchical organization in the representation of the blocks in the sequence (De Lillo, 2004), developmental changes and gender differences (e.g., Berch et al., Gennaro Ruggiero and Tina Iachini, Department of Psychology, Second University of Naples, Italy. We thank Lucia Abbamonte for language editing. Correspondence concerning this article should be addressed to Gennaro Ruggiero, Department of Psychology, Second University of Naples, Via Vivaldi 43, 81100, Caserta, Italy. gennaro.ruggiero@unina2.it 1998; Ruggiero, Sergi, & Iachini, 2008), children with disability in visuospatial learning (Mammarella & Cornoldi, 2005), and individuals with low and high spatial ability (Cornoldi & Mammarella, 2008). Within the working memory domain, the Corsi task has been particularly useful to clarify some theoretical assumptions (Baddeley, 1986). This task assesses serial-spatial memory as it involves the recall of both the positions in the sequence and the order in which they are shown. It is assumed that it relies on visuospatial and executive attentional resources (Rudkin, Pearson, & Logie, 2007). The level of executive involvement would be higher with the instruction to recall the sequence in backward order as a high degree of strategic control is necessary to reverse the original sequence input (Vandierendonck, Kemps, Fastame, & Szmalec, 2004). Moreover, the backward condition could imply various strategies to reduce the memory load, presumably based on nonsequential visuospatial processes (Mammarella & Cornoldi, 2005; Cornoldi & Mammarella, 2008) and on verbal processes (see Vandierendonck et al., 2004). The importance of visual and spatial processes in the Corsi task has long been debated (e.g., Logie, 1995; Rudkin et al., 2007). Some authors emphasized that the Corsi task would rely on a purely serial spatial component of visuospatial working memory, the inner scribe (Logie, 1995). The inner scribe would be responsible for the processing of spatial information and would also be implied in the processing and planning of movement sequences (Logie, 1995; Pickering et al., 2001). Consistently, the Corsi task is influenced by the simultaneous presentation of spatial but not visual tasks (Salway & Logie, 1995) and shows developmental fractionation with visual tasks (Logie & Pearson, 1997). Following this line, further insights into the nature of the processes underlying the Corsi performance could be provided by assessing serial spatial memory in the blind. In this research we address this issue by studying the effects of temporary (blindfolded 674

2 BRIEF REPORTS 675 sighted) and long-term (congenitally and adventitiously blind) visual deprivation on a version of the Corsi task adapted for haptic presentation. Overall, it is not clear the effect of blindness on spatial memory. Several studies have shown that blind participants can perform similarly, and sometimes even better, than controls in memory for positions and distances of haptically explored arrangements (for reviews Cornoldi & Vecchi, 2003; Heller & Ballesteros, 2006; Thinus-Blanc & Gaunet, 1997). Instead, other researchers have found specific difficulties in several spatial processes such as spatial inference and spatial memory, thereby supporting the idea of visual dominance in spatial cognition (for reviews, see Cornoldi & Vecchi, 2003; Thinus-Blanc & Gaunet, 1997). For example, Vecchi, Monticelli, and Cornoldi (1995), by using a wooden matrix, compared sighted and blind performances in a task that required either simple maintenance of information (passive task) or simultaneous maintenance and processing of information (active task) by following verbal statements of direction. The results showed that blind participants performed worse than controls in active but not passive spatial tasks. Subsequent research showed that the crucial factor underlying the blind s limitations was because of the requirement to simultaneously treat and maintain different spatial patterns (Vecchi, Tinti, & Cornoldi, 2004). Finally, data about onset of blindness at various times during development have shown that specific limitations are linked to early onset of blindness (Cattaneo et al., 2008). In short, the adoption of the Corsi task could help to clarify the factors underlying the serial-spatial memory in the blind and could give a hint about possible limitations. At the same time, it could help to clarify the role of visual experience in the task. The research presented here compares the memory span of persons with different kinds of visual experience: early onset of blindness (congenital), late onset of blindness (adventitious) and temporary deprivation (blindfolded sighted). To this end, an adaptation of the Corsi Block-Tapping task (called Haptic-Corsi) was devised that allowed haptic perception of block sequences. The term haptic was used to indicate that cutaneous, proprioceptive and kinesthetic inputs worked together to encode information (see Millar, 1999; Revesz, 1950). This version of the Corsi exploited the movement of the fingers to encode the position of block sequences. Spatial referencing was afforded by keeping the participant s fingers on the Corsi board, in alignment with the body midline (see Millar, 1999). We hypothesized that the absence of visual experience could affect negatively span capacity, especially in backward order. Sample Method A total of 62 right-handed participants took part in the experiment: 15 congenitally blind, 16 adventitiously blind, and 31 blindfolded sighted. Characteristics of blind participants are shown in Table 1. Blindfolded sighted participants were matched to blind persons in terms of gender, age, and educational level. Specific analyses of variance (ANOVAs) showed no difference between groups in age (F 1) and education, F(2, 59) 1.47, MSE 13.60, p.05. Mean age was: congenitally blind 40.2, SD 17.8; adventitiously blind 34.6, SD 13.2; blindfolded sighted 42.8, SD Mean education (years of schooling) was: congenitally blind 15.4, SD 2.3, adventitiously blind 13.8, SD 3.5 and blindfolded sighted 14.8, SD 4.6. Adventitiously and congenitally participants were totally blind and were recruited with the assistance of the UIC (Unione Italiana Ciechi), the main Association of Italian blind people in Caserta (Italy). They all were Braille readers. Visual handicap was never associated with neurological and/or psychiatric disorders. Congenital participants were blind from birth. Adventitious participants became blind later in life, mean age of onset 12.94, SD All participants gave their informed consent before taking part in the experiment. Materials The experiment took place in a sound-proofed comfortable room. Participants sat in front of a small table where the Haptic- Corsi was placed in alignment with their body midline. On the basis of several pilot studies, the classic Corsi board was modified by reducing the original size (23 28 cm) respectively by 39.13% and 28.57%. The new size corresponded to cm and allowed the best haptic perception of blocks (Figure 1). The blocks placement corresponded to the standard display (Corsi, 1972). The size of blocks was 3 cm per side. The blocks were numbered from 1 to 9 on the vertical surface by reproducing the original numbering of the blocks. Our device allowed the experimenter to put his or her hand under the board and to push upward with a finger the series of blocks. Each block was placed on a 3.5 cm long cylindrical basis that measured 2.5 cm per side, with a circular iron platform at its bottom. In this way the blocks could be easily raised upward of 1.5 cm through the board (2 cm) and went down as soon as the experimenter removed the finger. Procedure Blind and blindfolded sighted participants first explored freely the whole board with both hands. Then, the experimenter positioned the participants fingers on the blocks according to this order: inch, little finger, middle finger, ring-finger and forefinger of the left hand were respectively placed on the blocks numbered 1, 3, 5, 6, and 9; while inch, forefinger, middle finger, and ring finger or little finger (depending on the size of hands) of the right hand were respectively placed on the blocks numbered 2, 4, 8, and 7. During testing, fingers remained on blocks in such a way that the 9 positions were available, similarly to the visual presentation. Afterward, the experimenter said: tap the block immediately after I raise it. The experimenter raised all blocks sequentially for two times, at a rate of one each 1.5 s. If participants did not make any mistake, the testing phase started (Berch et al., 1998). After completing the training phase, the Haptic-Corsi task was administered in forward/backward orders. As regards the forward order, the instructions were: I will raise a series of blocks; as soon as I say Stop you have to reproduce the sequence by tapping with your corresponding fingers the same blocks. The starting level for the task began with two-block sequences. A random procedure was used to generate the block tapping sequences at the beginning of each trial. With regard to the backward order, the experimenter instructed participants to reproduce the sequence

3 676 BRIEF REPORTS Table 1 Characteristics of Blind Participants Age (years) Education (years) Etiology of deficit Onset of blindness (years) Congenitally blind CG Birth RF Birth CRP Birth CG Birth ONP Birth CG Birth ONP Birth RF Birth CRP Birth CG Birth CRP Birth RF Birth RF Birth CRP Birth CRP Birth Adventitiously blind G G G G RP RP RP DR DR DR G RP RP G RP RP 14.5 Note. CG congenital glaucoma; RF retrolental fibroplasia; CRp congenital retinitis pigmentosa; ONP optic nerve atrophy; G glaucoma; RP retinitis pigmentosa; DR detached retina. from the last block back to the first one. Participants had to successfully reproduce at least two trials out of three per each sequence length, otherwise the administration stopped and the span capacity was determined. Figure 1. An example of the administration of the Haptic-Corsi task is shown. The experimenter s hand (under) raises a block (n 9) of a series on which participant s fingers are placed. Results Analyses were based on a two-way ANOVA for mixed designs with terms for groups (three-level between factor) and forward/ backward span (two-level within factor). The span length represented the dependent variable. The Tukey s HSD test was used to analyze post hoc effects. Effect sizes were also calculated and expressed by the 2 index. The ANOVA revealed a main effect of Groups: F(2, 58) 3.56, MSE 1.46, p.05, The related means were: congenitally blind 4.1, SD 1.3; adventitiously blind 4.3, SD 1.04; and blindfolded sighted 3.7, SD.7. The post hoc analysis showed that the effect was because of adventitiously blind participants who overperformed blindfolded sighted controls ( p.05). Furthermore, the forward span (M 4.1, SD 1.0) was significantly higher than the backward span (M 3.7, SD.9): F(1, 58) 17.12, MSE 6.69, p.001, However, the most interesting result was a significant interaction between groups and forward/backward span: F(2, 58) 5.74, MSE.39, p.01, 2.16 (Figure 2). Means and SDs of groups are shown in Table 2. The post hoc test showed that in forward order adventitiously blind participants performed better than blindfolded sighted ( p.05) but not

4 BRIEF REPORTS 677 7,0 6,0 5,0 4,0 3,0 2,0 1,0 0,0 ADVENTITIOUS BLINDFOLDED SIGHTED congenitally blind ones. In backward order, no difference between groups emerged. Finally, the forward span was significantly higher than the backward span ( p.05) only in adventitiously blind participants. Discussion CONGENITAL FORWARD BACKWARD Figure 2. Memory span of adventitiously blind, blindfolded sighted, and congenitally blind participants in forward/backward orders. The results showed that overall adventitiously blind participants performed better than blindfolded sighted but not congenitally blind participants. Similarly to previous studies with the standard Corsi (Rudkin et al., 2007; Ruggiero et al., 2008; Vandierendonck et al., 2004), the memory span was higher in forward than backward order. Finally, in forward order the memory span was higher in adventitiously blind than blindfolded sighted participants but not congenitally blind ones. Instead, in backward order no difference between groups emerged. The span ranged from 4.8 in adventitiously blind participants in forward order, to 3.7 in blindfolded sighted participants in both orders. A comparison with previous literature about tactile short-term memory shows that the span for unnamable haptic items is smaller than here, that is, up to two or three items (e.g., Millar, 1999). Instead, the span for the visual Corsi is usually higher ( 5) in both orders (e.g., Iachini, Poderico, Ruggiero, & Iavarone, 2005; Rudkin et al., 2007; Ruggiero et al., 2008; Vandierendonck et al., 2004). Before discussing the possible theoretical relevance of these results, it is important to clarify to what extent the Haptic-Corsi is similar to the standard visual Corsi. To this end, a task analysis by following Berch s and colleagues (1998) task parameters is proposed and possible critical factors are discussed. As regards the display characteristics, our device resembled the original Corsi except for the reduction of the board size. The procedural criteria (e.g., block-tapping rate, trials per level and so forth) were in line with the studies reported in the literature. The most important variation regarded an aspect of the test administration: the pointing procedure. In the Haptic-Corsi the blocks were not pointed but raised upward by the experimenter, and participants responded by moving their fingers. In the standard procedure the type of movement is undoubtedly larger than here. Typically, participants respond by extending the arm and tapping block to block or by tapping a block, raising the forearm, tapping the next. The haptic version of the Corsi task might require forms of coding other than spatial, such as verbal, more than the visual Corsi. In principle it is possible to encode the sequence by verbalizing the order of the fingers (in terms of first right middle finger, second left forefinger and so forth ) or by associating each finger to numbers from 1 to 9 on the basis of the typical counting order. However, it takes time to code verbally all relevant information. In our task the interval between the to-be-counted positions and the study-test delay may actually have been short enough to prevent participants from verbally coding the perceived sequence. Although we do not have systematic observations, few participants at the ending of the session spontaneously reported that they tried to verbalize the sequence but it was too difficult. Furthermore, one could expect that here only haptic perception of movement limited to the fingertips occurs, and that this fine motor control area could not need spatial encoding of external space. However, depending on the task a variety of egocentric spatial representations anchored on different body parts can be activated (see Arbib, 1991). Finger locations can be coded spatially by referring to body-centered frames (Millar, 1999). In the Haptic-Corsi the hands were kept on the board, in alignment with the body midline, and this allowed for a hand-centered spatial representation of block positions. The fact that the mean span was higher than those usually reported in tactile spatial memory suggests that the spatial encoding of external positions according to egocentric reference frames played an important role. Millar (1985) also showed that short-term tactile memory was enhanced by keeping exploring fingers over the stimuli. However, it is likely that enhanced tactile acuity in the blind may have facilitated the task. Nevertheless, what was crucial was the movement of the whole fingers to acquire and retrieve information about external spatial positions. The situation is quite different from a task requiring the recall of sequential information on the basis of vibro-tactile stimulation of fingertips: in this case not only the encoding is passive but all relevant information is hand-centered and there is no reference to external cues (e.g., Gallace & Spence, 2008). As in previous visual versions, then, the Haptic-Corsi seems to involve spatial, kinesthetic and temporal processes. All these aspects could be modulated by the different involvement of executive resources in forward and backward recall order (Rudkin et al., 2007). The crucial question is whether early, late or temporary visual deprivation has a differential influence on these processes. Temporal components are important not only because of the request to recall the order of presentation of positions, but also Table 2 Performance of Groups on Haptic-Corsi in Forward and Backward Orders Forward span Backward span M SD M SD Congenitally blind Adventitiously blind Blindfolded sighted

5 678 BRIEF REPORTS because the encoding of block positions is sequential. The present data do not clarify whether visual deprivation affects mainly the encoding and maintenance of spatial information (i.e., the spatial position of the blocks) or the order in which spatial information was presented. The literature suggests that while sighted people tend to code spatial information in the form of global, externally based representations, blind people tend to code spatial information in the form of route-like sequential representations (Noordzij, Zuidhoek, & Postma, 2007; Thinus-Blanc & Gaunet, 1997). This could be a consequence of their dominant perceptual modality that is inherently sequential, in contrast to sighted people who can capture at a glance a multiplicity of spatial relations. Thus, serial memory may be especially important for the blind. In accordance, Raz and colleagues (Raz, Striem, Pundak, Orlov, & Zohary, 2007) found that congenitally blind people overperformed sighted controls in verbal serial memory tasks. Furthermore, Röder, Rösler, and Spence (2004) showed superior temporal order judgments for tactile stimuli in the congenitally blind. If the Haptic-Corsi involved mainly temporal processes then the serial memory span should be higher in both blind groups than in blindfolded sighted participants. Therefore, we might infer that the temporal component is not the crucial factor and is not negatively affected by visual deprivation. Another important question is whether performance in the Haptic-Corsi depends more on spatial than kinesthetic processes. Likewise, kinesthetic processes play a more relevant role here than in the visual Corsi because of their involvement in both encoding and retrieval of sequences. Several findings support the idea that a low short-term tactile memory span (up to three items) can be explained by the paucity of reference cues for spatial encoding. Unorganized inputs coded in kinesthetic terms can survive in short-term memory but are less accurate and less stable than spatially organized stimuli (for review, see Millar, 1999). In summary, although temporal and kinesthetic components are important, we might speculate that what is crucial in the task is the spatial component and that visual deprivation influences mainly this component. Gallace and Spence (2008) suggested that the relevant difference between touch and vision might regard the facility of organizing single visual items into structured patterns, while this recoding process might be more difficult for tactile stimuli (e.g., Davis, Welch, Holmes, & Shepherd, 2001). Consistently, De Lillo (2004) found that in the visual Corsi the span is higher when the blocks configuration can support the emergence of holistic structured representations of the sequence. Moreover, the possibility of forming structured or not structured path configurations may influence the performance (Berch et al., 1998). Similarly to other memory domains, then, the possibility of forming chunks would improve the serial spatial span. We might speculate that there is a link between chunking processes, spatial processes and visual imagery processes. Chunking involves the processing of a set of spatial relations as a whole starting from an origin, which is a frame of reference. Visual imagery strategies may help recoding a sequence as a structured pattern and, consequently, chunking processes should be more difficult with blind people (Lederman & Klatzky, 1990). However, combinations of tactile stimuli that can be easily structured as a pattern should facilitate those processes (see Gallace & Spence, 2008; Heller & Ballesteros, 2006). The chunking strategy should be quite effortful but particularly efficacious with longer sequences (see also Berch et al., 1998). Because the backward condition is more demanding, there would not remain enough resources to manipulate a holistic spatial representation and to find out alternative strategies to reduce the impact of this difficulty. The degree of involvement of executive resources, then, could have an indirect influence on the blind s serial-spatial memory span by limiting the processing strategies available. One might argue that once a sequence is mentally represented like a configuration, recalling the locations along a path in backward order should not be more difficult than recalling the same locations in forward order. However, several studies have revealed that backward span is lower than forward span (Iachini et al., 2005; Rudkin et al., 2007; Vandierendonck et al., 2004) and shows a robust correlation with active spatial tasks such as mental rotation and spatial inference (Ruggiero et al., 2008). The combination of higher sequential ability in the blind and higher structural ability in the sighted might have modulated the pattern of results. Adventitiously blind participants showed a vantage over blindfolded sighted ones, especially in forward order. This might result from the integration of their prior visual ability (that helped to structure spatially the sequence) with their extensive haptic experience (that facilitated the sequential aspect). This finding is in line with previous research showing that in several spatial tasks adventitiously blind participants perform better than congenitally blind and blindfolded sighted participants and confirms that vision plays an important role in setting up spatial mechanisms during a critical period of development (for reviews see Cattaneo et al., 2008; Heller & Ballesteros, 2006; Thinus-Blanc & Gaunet, 1997). With regard to congenitally blind participants, their performance is in between the other two groups. We might argue that although they share with adventitiously blind participants the familiarity with the haptic modality and the facilitation in sequential processing, they are limited by the lack of any visual experience. Still Lederman and Klatzky (1990) suggested that people need to be able to use visual imagery strategies to interpret haptic patterns. As these strategies are lacking in the congenitally blind, they could meet difficulties in organizing holistically haptic stimuli (Lederman & Klatzky, 1990; see also Heller & Ballesteros, 2006). As regards the low performance of blindfolded sighted participants, a number of reasons may be invoked. First, they are relatively unfamiliar in using touch for spatial perception and have learned to use haptic exploration under visual control. Therefore their potential facilitation in organizing structured patterns is contrasted by the unnatural exploratory modality. Further, it is possible that when a task affords relevant spatial reference cues that are easily accessible through haptic discrimination, spatial performance is better in blindfolded sighted than blind people (see Thinus-Blanc & Gaunet, 1997). If this is not the case, blindfolded sighted people should rely more on kinesthetic encoding and therefore perform worse than blind people (see Cattaneo et al., 2008). However, we are aware that the present results offer some suggestions but open a number of issues. These should be clarified in future research by comparing, for example, the following aspects: spatial versus temporal components, regular versus irregular block placements, regular versus irregular paths generated by block sequences, facilitated versus disturbed egocentric cues.

6 BRIEF REPORTS 679 In conclusion, blind people are able to retrieve and maintain temporarily serial-spatial information acquired on the basis of the haptic Corsi board. Such coding depends on accessible reference frame cues, as does spatial coding in visual conditions. However, the lack of visual experience could limit the strategies available to process block sequences, particularly in the demanding backward order. The relative advantage of the adventitiously blind suggests that visual strategies could facilitate the encoding of a sequence of positions in clusters with a spatial organization. In line with De Lillo (2004), then, the results suggest that in the Corsi task spatial structural aspects are important, together with serial, kinesthetic and executive components. References Arbib, M. A. (1991). Interaction of multiple representations of space in the brain. In J. Paillard (Ed.), Brain and space (pp ). Oxford, United Kingdom: Oxford University Press. Baddeley, A. D. (1986). Working memory. Oxford, United Kingdom: Oxford University Press. Berch, D. B., Krikorian, R., & Huha, E. M. (1998). The Corsi blocktapping task: Methodological and theoretical considerations. Brain and Cognition, 38, Cattaneo, Z., Vecchi, T., Cornoldi, C., Mammarella, I., Bonino, D., Ricciardi, E., & Pietrini, P. (2008). Imagery and spatial processes in blindness and visual impairment. Neuroscience and Biobehavioral Review, 8, Cornoldi, C., & Mammarella, I. C. (2008). A comparison of backward and forward spatial spans. The Quarterly Journal of Experimental Psychology, 5, Cornoldi, C., & Vecchi, T. (2003). Visuo-spatial working memory and individual differences. Hove, United Kingdom: Psychology Press. Corsi, P. M. (1972). Human memory and the medial temporal region of the brain. Unpublished doctoral dissertation, Abstracts International, 34(02), 891B (University microfilms No. AA ). Davis, G., Welch, V. L., Holmes, A., & Shepherd, A. (2001). Can attention select only a fixed number of objects at a time? Perception, 30, De Lillo, C. (2004). Imposing structure on a Corsi-type task: Evidence for hierarchical organization based on spatial proximity in serial-spatial memory. Brain and Cognition, 55, Gallace, A., & Spence, C. (2008). The cognitive and neural correlates of tactile consciousness : A multisensory perspective. Consciousness and Cognition, 17, Heller, M. A., & Ballesteros, S. (2006). Touch and blindness. London: Erlbaum. Iachini, T., Poderico, C., Ruggiero, G., & Iavarone, A. (2005). Age differences in mental scanning of locomotor maps. Disability & Rehabilitation, 27, Lederman, S. J., & Klatzky, R. L. (1990). Haptic classification of common objects: Knowledge-driven exploration. Cognitive Psychology, 22, Logie, R. H. (1995). Visuo-spatial working memory. Hove, United Kingdom: Erlbaum. Logie, R. H., & Pearson, D. G. (1997). The inner eye and the inner scribe of visuo-spatial working memory: Evidence from developmental fractionation. European Journal of Cognitive Psychology, 9, Mammarella, I. C., & Cornoldi, C. (2005). Sequence and space: The critical role of a backward spatial span in the working memory deficit of visuo-spatial learning disabled children. Cognitive Neuropsychology, 22, Millar, S. (1985). The perception of complex patterns by touch. Perception, 14, Millar, S. (1999). Memory in touch. Psychotema, 11, Milner, B. (1971). Interhemispheric differences in the localisation of psychological processes in man. Cortex, 27, Noordzij, M. L., Zuidhoek, S., & Postma, A. (2007). The influence of visual experience on visual and spatial imagery. Perception, 36, Pickering, S. J., Gathercole, S. E., Hall, M., & Lloyd, S. A. (2001). Development of memory for pattern and path: Further evidence for the fractionation of visuo-spatial memory. The Quarterly Journal of Experimental Psychology A, 54, Raz, N., Striem, E., Pundak, G., Orlov, T., & Zohary, E. (2007). Superior serial memory in the blind: A case of cognitive compensatory adjustment. Current Biology, 17, Revesz, G. (1950). Psychology and art of the blind. London: Longmans. Röder, B., Rösler, F., & Spence, C. (2004). Early vision impairs tactile perception in the blind. Current Biology, 14, Rudkin, S. J., Pearson, D., & Logie, R. H. (2007). Executive processes in visual and spatial working memory tasks. The Quarterly Journal of Experimental Psychology, 60, Ruggiero, G., Sergi, I., & Iachini, T. (2008). Gender differences in remembering and inferring spatial distances. Memory, 16, Salway, A. F. S., & Logie, R. H. (1995). Visuospatial working memory, movement control and executive demands. British Journal of Psychology, 86, Thinus-Blanc, F., & Gaunet, C. (1997). Representation of space in blind persons: Vision as a spatial sense? Psychological Bulletin, 1, Vandierendonck, A., Kemps, E., Fastame, M. C., & Szmalec, A. (2004). Working memory components of the Corsi blocks task. British Journal of Psychology, 95, Vecchi, T., Monticelli, M. L., & Cornoldi, C. (1995). Visuo-spatial working memory: Structures and variables affecting a capacity measure. Neuropsychologia, 33, Vecchi, T., Tinti, C., & Cornoldi, C. (2004). Spatial memory in integration processes in congenital blindness. Neuroreport, 15, Received April 16, 2009 Revision received February 3, 2010 Accepted March 1, 2010