The effects of aging and dorsal hippocampal lesions: performance on spatial and nonspatial comparable versions of the water maze

Aged intact and young hippocampal-lesioned rats show similar deficits on the spatial water maze. However, this does not necessitate that the source of these deficits in the aged animals is due to hippocampal damage. These water maze deficits may arise from other aging factors such as changes in thermoregulation, muscle fatigue, swim ability, and response to stress. Consequently, it is imperative to examine the performance of aged rats on a comparable nonhippocampal version of this task. Past attempts to develop a hippocampus-independent version of the water maze were confounded because these tasks were easier (i.e., the rats spent much less time swimming in the water) than the spatial versions of the task. The current study examined performance on a hippocampus-independent task comparable in difficulty to the spatial water one. Middle-aged (16-m) and old (25-m) male F344 rats were given sham or dorsal hippocampus lesions and tested on both a spatial and a nonspatial water maze. The middle-aged rats with hippocampal lesions were impaired on the spatial task but not on the nonspatial task. Conversely, aged animals showed a similar impairment on both types of water maze tasks. Additionally, hippocampal lesions exacerbated the age-related impairment on both tasks. These findings indicate that caution must be used when interpreting the results of water maze tasks for aged animals.     

EPISTEMIC ACTION,EXTENDED KNOWLEDGE,AND METACOGNITION

How should one attribute epistemic credit to an agent, and hence, knowledge, when cognitive processes include an extensive use of human or mechanical enhancers, informational tools, and devices which allow one to complement or modify one's own cognitive system? The concept of integration of a cognitive system has been used to address this question. For true belief to be creditable to a person's ability, it is claimed, the relevant informational processes must be or become part of the cognitive character of the agent, as a result of a process of enculturation. We argue that this view does not capture the role of sensitivity to epistemic norms in forming true beliefs. An analysis of epistemic actions, basic and extended, is proposed as offering an appropriate framework for crediting an agent with knowledge.     

Rehabilitation of reading in older individuals with macular degeneration: a review of effective training programs

Macular degeneration (MD) is the most common cause of visual impairment among older adults. It severely affects reading performance. People with MD have to rely on peripheral vision for reading. In this review, we considered several training programs that aim to improve peripheral reading, with a focus on eccentric viewing, oculomotor control, or perceptual learning. There was no strong support in favor of one particular training method for rehabilitation of reading in MD, but there is evidence that older individuals with MD can be trained to improve reading performance, even within limited time.     

How useful are landmarks when learning a route in a virtual environment? Evidence from typical development and Williams syndrome

The ability to learn a route through a virtual environment was assessed in 19 older children and adults with Williams syndrome (WS) and 40 typically developing (TD) children aged 6-9 years. In addition to comparing route-learning ability across groups, we were interested in whether participants show an adult-like differentiation between "useful" and "less useful" landmarks when learning a route and the relative salience of landmark position versus landmark identity. Each virtual environment consisted of a brick wall maze with six junctions. There were 16 landmarks in the maze, half of which were on the correct path and half on incorrect paths. Results showed that both groups could learn each route to criterion (two successful completions of a route without error). During the learning phase, the WS group produced more errors than the TD group and took longer to reach criterion. This was predominantly due to the large number of perseverative errors (i.e., errors that were made at the same choice point on consecutive learning trials) made by the WS group relative to the TD children. We suggest that this reflects a difficulty in inhibiting erroneous responses in WS. During the test phase, the TD group showed stronger recall of landmarks adjacent to junctions (more useful landmarks) than of landmarks along path sections (less useful landmarks) independent of each individual's level of nonverbal ability. This pattern was also evident in the WS group but was related to level of nonverbal maturation; the differentiation between recall of junction and path landmarks increased as nonverbal ability increased across WS participants. Overall, the results demonstrate that individuals with WS can learn a route but that the development of this ability is atypical.     

Visual search for global/local stimulus features in humans and baboons

Fagot and Deruelle (1997) demonstrated that, when tested with identical visual stimuli, baboons exhibit an advantage in processing local features, whereas humans show the “global precedence” effect initially reported by Navon (1977). In the present experiments, we investigated the cause of this species difference. Humans and baboons performed a visual search task in which the target differed from the distractors at either the global or the local level. Humans responded more quickly to global than to local targets, whereas baboons did the opposite (Experiment 1). Human response times (RTs) were independent of display size, for both local and global processing. Baboon RTs increased linearly with display size, more so for global than for local processing. The search slope for baboons disappeared for continuous targets (Experiment 2). That effect was not due to variations in stimulus luminance (Experiment 3). Finally, variations in stimulus density affected global search slopes in baboons but not in humans (Experiment 4). Overall, results suggest that perceptual grouping operations involved during the processing of hierarchical stimuli are attention demanding for baboons, but not for humans.     

Book reviews

One Thousand Roads to Mecca. Michael Wolfe (Ed.), 1997. New York, Grove Press. 620 pp., hb. $32.50, ISBN 0 8021 1611 6

Early Mamluk Syrian Historiography: Al‐Yunini's Dhayl Mir'at al‐zaman. Li Guo, 1998. Leiden, E.J. Brill. 2 vols, 241 pp. and xv + 338 pp. Arabic, hb. n.p., ISBN 90 04 11028 3 and 90 04 11029 1

Defenders of Reason in Islam: Mu'tazilism from medieval school to modern symbol. Richard C. Martin & Mark R. Woodward with Dwi S. Atmaja, 1997. Oxford, Oneworld Publications. xv+ 251 pp., pb. £14.99/$22.95, ISBN 1 85168 147 7

Rethinking Tradition in Modern Islamic Thought. Daniel Brown, 1996. Cambridge Middle East Studies 5. Cambridge, Cambridge University Press. x+ 185 pp., hb. n.p., ISBN 0 521 57077 8

Ebu's su'ud, the Islamic Legal Tradition. Colin Imber, 1997. Edinburgh, Edinburgh University Press. 288 pp., hb. £40.00, ISBN 07486 0767 6

Islam and the West: the making of an Image. Norman Daniel, 1997 (1993). Oxford, Oneworld. 467 pp., pb. $25.95/£16.99, ISBN I 85168 129 8

Exegesis as Polemical Discourse: Ibn Hazm on Jewish and Christian Scriptures. Theodore Pulcini, 1998. Atlanta, GA, Scholars Press. 216 pp., hb. $44.95, ISBN 0 7885 0396 0; pb. $19.95, ISBN 0 7885 0395 2

Christians and Jews under Islam. Youssef Courbage & Philippe Fargues, trans. Judy Mabro, 1997. London and New York, I.B. Tauris. xii + 242 pp., hb. £39.50, ISBN 1 86064 013 3

The Construction of Nationhood: ethnicity, religion and nationhood. Adrian Hastings, 1997. Cambridge, Cambridge University Press. 235 pp., pb. £12.95, ISBN 0 521 62544 0

Muslim Identity and Balkan State. Hugh Poulton & Suha Taji‐Farouki (Eds), 1997. London, Hurst & Co.. 250 pp., hb. n.p., ISBN 1 85065 276 7; pb. n.p., ISBN 1 85065 348 8

Turkish and Other Muslim Minorities of Bulgaria. Ali Eminov, 1997. London, Hurst & Co.. 218 pp., hb. £25, ISBN 1 85065 319 4

Al‐yahūd fi misr min al‐fath al‐'uthmani hatta awa'il al‐qarn al‐tas’ ‘ashar. [History of the Jewish Community in Egypt from the Ottoman Invasion to the. Beginning of the Nineteenth Century] (Arabic). Mohsen Shouman, 1996. Cairo, privately printed (available from the author, Department of History, College of. Arts, University of Zaqaziq, Egypt). 492 pp., n.p., no ISBN

The Society of the Muslim Brothers in Egypt: the rise of an Islamic mass movement 1928–1942. Brynjar Lia, 1998. Reading, Ithaca. 272 pp., hb, £30.00, ISBN 0 86372 220 2

African Islam and Islam in Africa: encounters between Sufis and Islamists. David Westerlund & Eva Evers Rosander (Eds), 1997. London, Hurst & Co.. 347 pp., hb. £40, ISBN 85065 282 1; pb. £15.95, ISBN 1 85065 281 3

Transforming Female Identities: women's organizational forms in West Africa/Transformation des identités feminines: formes d'organisations feminines en Afrique de l'Ouest. Eva Evers Rosander (Ed.), 1997. Uppsala, Nordiska Afrikainstitutet 243 pp., pb. £18.95, ISBN 91 7106 403 6

The Pure and the Powerful. Nadia Abu‐Zahra, 1977. Reading, Ithaca, NY. xx+ 320 pp., hb. £35.00, ISBN 0 86372 179 6     

Associative learning in baboons (Papio papio) and humans (Homo sapiens): species differences in learned attention to visual features

We examined attention shifting in baboons and humans during the learning of visual categories. Within a conditional matching-to-sample task, participants of the two species sequentially learned two two-feature categories which shared a common feature. Results showed that humans encoded both features of the initially learned category, but predominantly only the distinctive feature of the subsequently learned category. Although baboons initially encoded both features of the first category, they ultimately retained only the distinctive features of each category. Empirical data from the two species were analyzed with the 1996 ADIT connectionist model of Kruschke. ADIT fits the baboon data when the attentional shift rate is zero, and the human data when the attentional shift rate is not zero. These empirical and modeling results suggest species differences in learned attention to visual features. Received: 30 May 1998 / Accepted after revision: 13 September 1998     

Individual differences in working memory strategies for reading expository text

This study investigated whether individual differences in working memory (WM) span are associated with different WM management strategies during the reading of expository text. In Experiment 1, probe questions were presented on line during reading to determine whether thematic information was maintained in WM throughout comprehension. The data indicated that readers across the range of WM span maintained thematic information in WM throughout the reading of a given passage. In Experiment 2, sentence reading times and accuracy for both topic and detail questions were measured in two conditions: when topic sentences were present and when topic sentences were absent. Subjects performed similarly across the range of WM span in the topic-present condition, but lower span subjects performed more poorly on detail questions in the topic-absent condition. In Experiment 3, the topic-present condition of the second experiment was replicated, except that subjects expected to receive questions about details only. Thematic processing and retention of topic and detail information all increased with span. Taken together, these results suggest that, for more difficult text processing tasks, high- and low-span subjects adopt different WM management strategies and these strategies influence what is learned from reading the text.     

Community violence, family conflict, and preschoolers' socioemotional functioning

This study examined the relations among family conflict, community violence, and young children's socioemotional functioning and explored how children's social cognition and mothers' psychological functioning may mediate the outcomes associated with this exposure. Mothers of 431 Head Start preschoolers completed questionnaires about their family demography, exposure to community violence, family conflict, and children's distress symptoms. Children were administered a social cognition assessment, and teachers rated their behavior. Results showed that mothers' reports of children's co-witnessing of community violence were positively associated with police department crime rates, children's distress symptoms, and teachers' ratings of aggression. A path analysis revealed that children's social awareness and mothers' depressive symptoms partially mediated the effects of community violence and family conflict on outcomes for children.     

Depth perception: cuttlefish (Sepia officinalis) respond to visual texture density gradients

Studies concerning the perceptual processes of animals are not only interesting, but are fundamental to the understanding of other developments in information processing among non-humans. Carefully used visual illusions have been proven to be an informative tool for understanding visual perception. In this behavioral study, we demonstrate that cuttlefish are responsive to visual cues involving texture gradients. Specifically, 12 out of 14 animals avoided swimming over a solid surface with a gradient picture that to humans resembles an illusionary crevasse, while only 5 out of 14 avoided a non-illusionary texture. Since texture gradients are well-known cues for depth perception in vertebrates, we suggest that these cephalopods were responding to the depth illusion created by the texture density gradient. Density gradients and relative densities are key features in distance perception in vertebrates. Our results suggest that they are fundamental features of vision in general, appearing also in cephalopods.