M. S. Weldon and K. D. Bellinger (1997) showed that people who collaborate on a recall test (collaborative group) perform much more poorly than the same number of people tested individually (nominal group). Four experiments tested the hypothesis that retrieval-strategy disruption underlies this collaborative inhibition when categorized lists are studied. Collaborative groups performed worse than nominal groups when categories were large (Experiment 1) and when category names were provided at recall (Experiment 2). However, collaborative- and nominal-group recall were equivalent when participants retrieved nonoverlapping parts of the list (Experiment 3) and when participants were forced to organize their recall by category (Experiment 4). Clearly, disorganized retrieval can account for collaborative inhibition with the materials and procedures used here.

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Articles you may be interested inStudy the effect of engagement force of ultrasound transducer on crack detectability in sonic IR imaging AIP Conf. Proc. 1511, 532 (2013); 10.1063/1.4789093Modeling turbine blade crack detection in sonic IR imaging with a method of creating flat crack surface in finite element analysis AIP Conf.Finite element modeling of the heating of cracks during sonic infrared imaging High-frequency pulsed sonic excitation is combined with an infrared camera to image surface and subsurface defects. Irreversible temperature increases on the surface of the object, resulting from localized heating in the vicinity of cracks, disbonds, or delaminations, are imaged as a function of time prior to, during, and following the application of a short pulse of sound. Pulse durations of 50 ms are sufficient to image such defects, and result in surface temperatures variations of ϳ2°C above the defect. As an example, sonic infrared images are presented for two fatigue cracks in Al and of interply delamination impact damage in a graphite-fiber-reinforced polymer composite. The shorter of the two fatigue cracks is ϳ0.7 mm in length, and is tightly closed. Thus, this new technique is sensitive, and capable of rapid imaging of defects under wide surface areas of an object.

Earlier we reported (Basden, Basden, Bryner, & Thomas, 1997) that, in comparison with nominal groups (three people tested individually), three-person collaborative groups recalled fewer presented words but intruded more nonpresented words. In the present research, Experiment 1 showed that when presented words were associatively related to critical nonpresented words, collaboration inhibited recall of presented words but did not influence recall of critical nonpresented words. Experiment 2 showed that with categorized lists, recall of high taxonomic frequency critical nonpresented words was greater for collaborative groups than for nominal groups. Collaboration did not inhibit recall of presented words, presumably because guessing supplemented recall in collaborative groups. Greater false recall in collaborative than in nominal groups appears to result from activation of superordinate-to-item associations rather than item-to-item associations. MEMORY DISTORTION IN GROUP RECALLIn reviewing previous research, our concern was with the effect of the collaborative efforts of several individuals on the overall accuracy of their recall. Perhaps the earliest research reporting that group remembering introduces memory distortions came in the form of Bartlett's (1932) classic descriptions of reconstructions in recall. Bartlett suggested that memory changes occurred in conjunction with the development of schemas, socially influenced representations of the gist of the passage. He used the Method of Serial Reproduction, in which one individual first reads a prose passage such as the North American folktale "The War of the Ghosts," and then relates it from memory to a second individual, who in turn relates it to a third individual, and so on. Bartlett did not compare distortions by individuals repeatedly recalling alone (The Method of Repeated Reproduction) with those by individuals who related the passage to others in a group (The Method of Serial Reproduction). However, he did report dramatic changes in content with both methods. Thus, Bartlett's studies, as well as Allport and Postman's (1945) studies of rumor transmission in groups, indicate that collective recall may reduce accuracy.Perlmutter (1953) extended Bartlett's (1932) research by testing the recall of collaborating two-and three-person groups twenty-four hours after they had recalled "War of the Ghosts" as individuals. Perlmutter reported that individuals tended to reproduce the same errors they had introduced earlier, and that these errors cumulated across the group to make the product of collaborative recall less accurate than that of individual recall. Similar findings were reported by Perlmutter and de Montmollin (1952). Stephenson, Brandstatter, & Wagner (1983) compared initial trial recall of "War of the Ghosts" by individuals and two-person groups. They concluded that twoperson groups showed more reconstructive errors and were more confident of those errors than individuals. In contrast, Yuker (1955) reported that group recall was more accurate than indiv...

The scanning photoacoustic microscope (SPAM) is used in both the conventional and phase-contrast modes to detect a well-characterized subsurface flaw in Al. The physical mechanism is that of thermal diffusion, with a subsurface probe depth and flaw resolution length of approximately one thermal-diffusion length. Comparison of the dependences of the photoacoustic signal upon chopping frequency from the different regions of the sample confirm that the differential signal from the flaw corresponds to a transition from thermally thick to thermally thin boundary conditions. Experimental results are in good agreement with calculations based upon a three-dimensional thermal-diffusion model.

We describe a quasichaotic mechanism for the generation of complex vibrations from the application of a 450 ms, 40 kHz excitation coupled nonlinearly to a sample under inspection by means of sonic infrared (SIR) imaging. Monitoring the sample vibration by means of a laser vibrometer, we find that the vibration switches from the fundamental and harmonics to several series of frequencies that are rational fractions of the fundamental driving frequency. The transition to this quasichaotic behavior is important in obtaining high-quality SIR images.

Finite-element modeling of acoustic chaos to sonic infrared imagingThe technique of sonic infrared imaging ͑SIR͒ consists of the excitation of an object with a short pulse of 15 to 40 kHz sound, in combination with IR imaging of the object's surface temperature as a function of time. Sonic infrared imaging is effective for detecting surface and subsurface cracks. The recent discovery of acoustic chaos has provided a means of greatly enhancing the effectiveness of SIR. We describe the properties of chaotic sound in the context of SIR crack detection, and show examples of the enhancement of the detectability of cracks through the use of chaotic sound.