Biomedical subjects

Josh McDermott

Publications and source records attributed to Josh McDermott.

8 recordsLinked to original sources

PubMed2006

Nonhuman primates prefer slow tempos but dislike music overall.

Human adults generally find fast tempos more arousing than slow tempos, with tempo frequently manipulated in music to alter tension and emotion. We used a previously published method [McDermott, J., & Hauser, M. (2004). Are consonant intervals music to their ears? Spontaneous acoustic preferences in a nonhuman primate. Cognition, 94(2), B11-B21] to test cotton-top tamarins and common marmosets, two new-World primates, for their spontaneous responses to stimuli that varied systematically with respect to tempo. Across several experiments, we found that both tamarins and marmosets preferred slow tempos to fast. It is possible that the observed preferences were due to arousal, and that this effect is homologous to the human response to tempo. In other respects, however, these two monkey species showed striking differences compared to humans. Specifically, when presented with a choice between slow tempo musical stimuli, including lullabies, and silence, tamarins and marmosets preferred silence whereas humans, when similarly tested, preferred music. Thus despite the possibility of homologous mechanisms for tempo perception in human and nonhuman primates, there appear to be motivational ties to music that are uniquely human.

Animals↗

PubMed2005

Probing the evolutionary origins of music perception.

Empirical data have recently begun to inform debates on the evolutionary origins of music. In this paper we discuss some of our recent findings and related theoretical issues. We claim that theories of the origins of music will be usefully constrained if we can determine which aspects of music perception are innate, and, of those, which are uniquely human and specific to music. Comparative research in nonhuman animals, particularly nonhuman primates, is thus critical to the debate. In this paper we focus on the preferences that characterize most humans' experience of music, testing whether similar preferences exist in nonhuman primates. Our research suggests that many rudimentary acoustic preferences, such as those for consonant over dissonant intervals, may be unique to humans. If these preferences prove to be innate in humans, they may be candidates for music-specific adaptations. To establish whether such preferences are innate in humans, one important avenue for future research will be the collection of data from different cultures. This may be facilitated by studies conducted over the internet.

Animals↗

PubMed2004

The geometry of the occluding contour and its effect on motion interpretation.

Form information related to occlusion is needed to correctly interpret image motion. This work describes one of a series of investigations into the form constraints on motion perception. In the present study, we focus specifically on the geometry of the occluding contour, and in particular on whether its influence on motion can be accounted for merely by its effect on perceived occlusion. We used an occluded square moving in a circle, holding the T-junctions at points of occlusion constant while manipulating the occluding contour. We found evidence for two main influences of occluding contour geometry on motion interpretation and occlusion: the convexity of the occluding contour and additional static T-junctions that are formed elsewhere on the occluding contour. Our results suggest that convex occluding contours are more occlusive than concave ones, and that T-junctions along the contour increase or decrease the strength of occlusion depending on their orientation. Motion interpretation is influenced by both factors, but their effect on motion appears to be dominated by interactions occurring at an intermediate "semilocal" scale, which is larger than the scale at which junctions are defined, but smaller than the scale of the whole moving figure. We propose that these computations are related to occlusion but are not identical to the computations that mediate static occlusion judgments.

Form Perception↗

PubMed2004

Junctions and cost functions in motion interpretation.

Form, motion, occlusion, and perceptual organization are intimately related. We sought to assess the role of junctions in their interaction. We used stimuli based on a cross moving within an occluding aperture. The two bars of the cross appear to cohere or move separately depending on the context; in accord with prior literature, motion interpretation depends in part on whether the bar endpoints appear to be occluded. To test the importance of junctions in motion interpretation, we explored the effect of changing the junctions generated at the occlusion points in our stimuli, from T-junctions to L-junctions. In some cases, this change had a large effect on perceived motion; in others, it made little difference, suggesting junctions are not the critical variable. Further experiments suggested that what matters is not junctions per se, but whether illusory contours are introduced when the junction category is changed. Our results are consistent with an optimization-based computation that seeks to minimize the presence of illusory contours in the perceptual representation. Although it may be possible to explain our results with interactions between junctions, parsimony favors an explanation in terms of a cost-function operating on layered surface interpretations, with no explicit reference to junctions.

Form Perception↗

PubMed2004

Are consonant intervals music to their ears? Spontaneous acoustic preferences in a nonhuman primate.

Humans find some sounds more pleasing than others; such preferences may underlie our enjoyment of music. To gain insight into the evolutionary origins of these preferences, we explored whether they are present in other animals. We designed a novel method to measure the spontaneous sound preferences of cotton-top tamarins, a species that has been extensively tested for other perceptual abilities. Animals were placed in a V-shaped maze, and their position within the maze controlled their auditory environment. One sound was played when they were in one branch of the maze, and a different sound for the opposite branch; no food was delivered during testing. We used the proportion of time spent in each branch as a measure of preference. The first two experiments were designed as tests of our method. In Experiment 1, we used loud and soft white noise as stimuli; all animals spent most of their time on the side with soft noise. In Experiment 2, tamarins spent more time on the side playing species-specific feeding chirps than on the side playing species-specific distress calls. Together, these two experiments suggest that the method is effective, providing a spontaneous measure of preference. In Experiment 3, however, subjects showed no preference for consonant over dissonant intervals. Finally, tamarins showed no preference in Experiment 4 for a screeching sound (comparable to fingernails on a blackboard) over amplitude-matched white noise. In contrast, humans showed clear preferences for the consonant intervals of Experiment 3 and the white noise of Experiment 4 using the same stimuli and a similar method. We conclude that tamarins' preferences differ qualitatively from those of humans. The preferences that support our capacity for music may, therefore, be unique among the primates, and could be music-specific adaptations.

Animals↗

PubMed2004

Psychophysics with junctions in real images.

Junctions, formed at the intersection of image contours, are thought to play an important and early role in vision. The interest in junctions can be attributed in part to the notion that they are local image features that are easy to detect but that nonetheless provide valuable information about important events in the world, such as occlusion and transparency. Here I test the notion that there are locally defined junctions in real images that might be detected with simple, early visual mechanisms. Human observers were used as a tool to measure the visual information available in local regions of real images. One set of observers was made to label all the points in a set of real images where one edge occluded another. A second set of observers was presented with variable-size circular subregions of these images, and was asked to judge whether the regions were centered on an occlusion point. This task is easy if junctions are visible, but I found performance to be poor for small regions, not approaching ceiling levels until observers were given fairly large (approximately 50 pixels in diameter) regions over which to make the judgment. Control experiments ruled out the possibility that the effects are just due to junctions at multiple scales. Experiments reported here suggest that, although some junctions in real images are locally defined and can be detected with simple mechanisms, a substantial fraction necessitate the use of more complex and global processes. This raises the possibility that junctions in such cases may not be detected prior to scene interpretation.

Contrast Sensitivity↗

PubMed2003

The evolution of the music faculty: a comparative perspective.

We propose a theoretical framework for exploring the evolution of the music faculty from a comparative perspective. This framework addresses questions of phylogeny, adaptive function, innate biases and perceptual mechanisms. We argue that comparative studies can make two unique contributions to investigations of the origins of music. First, musical exposure can be controlled and manipulated to an extent not possible in humans. Second, any features of music perception found in nonhuman animals must not be part of an adaptation for music, and must rather be side effects of more general features of perception or cognition. We review studies that use animal research to target specific aspects of music perception (such as octave generalization), as well as studies that investigate more general and shared systems of the mind/brain that may be relevant to music (such as rhythm perception and emotional encoding). Finally, we suggest several directions for future work, following the lead of comparative studies on the language faculty.

Animals↗

PubMed2002

Spatial frequency and orientation tuning dynamics in area V1.

Spatial frequency (SF) and orientation tuning are intrinsic properties of neurons in primary visual cortex (area V1). To investigate the neural mechanisms mediating selectivity in the awake animal, we measured the temporal dynamics of SF and orientation tuning. We adapted a high-speed reverse-correlation method previously used to characterize orientation tuning dynamics in anesthetized animals to estimate efficiently the complete spatiotemporal receptive fields in area V1 of behaving macaques. We found that SF and orientation tuning are largely separable over time in single neurons. However, spatiotemporal receptive fields also contain a small nonseparable component that reflects a significant difference in response latency for low and high SF stimuli. The observed relationship between stimulus SF and latency represents a dynamic shift in SF tuning, and suggests that single V1 neurons might receive convergent input from the magno- and parvocellular processing streams. Although previous studies with anesthetized animals suggested that orientation tuning could change dramatically over time, we find no substantial evidence of dynamic changes in orientation tuning.

Animals↗