title: Size constancy in bat biosonar? Perceptual interaction of object aperture and distance.
abstract: Perception and encoding of object size is an important feature of sensory systems. In the visual system object size is encoded by the visual angle (visual aperture) on the retina, but the aperture depends on the distance of the object. As object distance is not unambiguously encoded in the visual system, higher computational mechanisms are needed. This phenomenon is termed "size constancy". It is assumed to reflect an automatic re-scaling of visual aperture with perceived object distance. Recently, it was found that in echolocating bats, the 'sonar aperture', i.e., the range of angles from which sound is reflected from an object back to the bat, is unambiguously perceived and neurally encoded. Moreover, it is well known that object distance is accurately perceived and explicitly encoded in bat sonar. Here, we addressed size constancy in bat biosonar, recruiting virtual-object techniques. Bats of the species Phyllostomus discolor learned to discriminate two simple virtual objects that only differed in sonar aperture. Upon successful discrimination, test trials were randomly interspersed using virtual objects that differed in both aperture and distance. It was tested whether the bats spontaneously assigned absolute width information to these objects by combining distance and aperture. The results showed that while the isolated perceptual cues encoding object width, aperture, and distance were all perceptually well resolved by the bats, the animals did not assign absolute width information to the test objects. This lack of sonar size constancy may result from the bats relying on different modalities to extract size information at different distances. Alternatively, it is conceivable that familiarity with a behaviorally relevant, conspicuous object is required for sonar size constancy, as it has been argued for visual size constancy. Based on the current data, it appears that size constancy is not necessarily an essential feature of sonar perception in bats.
authors: Department Biology II, Ludwig-Maximilians University Munich, Bavaria, Germany.
authors: Melina
authors: M
authors: Heinrich
authors: Lutz
authors: L
authors: Wiegrebe
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D002685:Chiroptera / Q000502:physiology*; D003463:Cues; D004215:Distance Perception; D004455:Echolocation; D008297:Male; D009949:Orientation; D013037:Spatial Behavior
references: J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2011 May;197(5):605-13
references: 20446089
references: Nature. 1945 Dec 8;156:692
references: 21007621
references: Behav Neurosci. 2003 Aug;117(4):833-9
references: 12931967
references: J Acoust Soc Am. 2000 May;107(5 Pt 1):2750-4
references: 10830397
references: Vision Res. 1992 Aug;32(8):1447-60
references: 1455718
references: Nat Neurosci. 2006 Mar;9(3):429-34
references: 16462737
references: J Exp Biol. 2006 Sep;209(Pt 17):3457-68
references: 16916981
references: Front Behav Neurosci. 2010 Aug 05;4:
references: 20740076
references: Vision Res. 2004 Jan;44(2):147-56
references: 14637364
references: PLoS Biol. 2006 Apr;4(4):e79
references: 16509770
references: Hear Res. 2007 Dec;234(1-2):1-9
references: 17630232
references: J Acoust Soc Am. 2010 Sep;128(3):1467-75
references: 20815481
references: J Comp Physiol A. 1990 Nov;167(5):589-616
references: 2074548
references: Behav Processes. 2012 Jan;89(1):61-7
references: 22085788
references: J Acoust Soc Am. 1973 Jul;54(1):157-73
references: 4738624
references: J Acoust Soc Am. 2006 Mar;119(3):1867-79
references: 16583925
references: J Exp Biol. 2011 Feb 1;214(Pt 3):394-401
references: 21228198
references: Vision Res. 1992 Aug;32(8):1433-45
references: 1455717
references: J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2008 Jan;194(1):61-7
references: 18034247
references: Neurosci Biobehav Rev. 2011 Nov;35(10):2073-83
references: 21238485
references: Proc Natl Acad Sci U S A. 2012 Jul 3;109(27):11019-24
references: 22699495
references: J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2011 May;197(5):595-603
references: 20473507
references: PLoS Biol. 2007 May;5(5):e100
references: 17425407
references: Science. 1971 Mar 5;171(3974):925-8
references: 5541661
references: Eur J Neurosci. 1991 Oct;3(11):1165-1181
references: 12106246
references: J Acoust Soc Am. 1982 Mar;71(3):585-90
references: 7085967
references: Percept Psychophys. 2001 Oct;63(7):1140-52
references: 11766940
references: J Neurophysiol. 2010 Jan;103(1):322-33
references: 19906883
references: J Comp Physiol A. 1996 Aug;179(2):245-54
references: 8765560
references: Science. 1966 May 20;152(3725):1102-4
references: 5931464
references: Biol Cybern. 2008 Jun;98(6):587-95
references: 18491168
references: J Neurophysiol. 1993 Nov;70(5):1988-2009
references: 8294966
references: J Neurosci. 2011 Oct 26;31(43):15618-27
references: 22031907