Apparent Movement and Real Movement Detection in the Pigeon: Stimulus Generalization

Abstract

Pigeons were trained to discriminate apparent movement Siegel (1970) suggested that pigeons can also detect lines in apparent movement (AM) over a wide range of directions. The mechanism of directional detection is unknown, although directional specific cells have been found in the pigeon retinae (Maturana and Frenk, 1963) and the optic tectum (Wylie, 1962). While it has been speculated that perception of real movement and apparent movement are derived from the same basic electrophysiological process (Aarons, 1964), thus far the two have been shown to be behaviorally equivalent only in the cat (Smith, 1937). The present study with pigeons was designed to assess stimulus generalization between real and apparent movement on the dimension of direction. Controls for the possibility that "flicker" provided the basis of the apparent movement discrimination (cf. Siegel, 1970) were included. METHOD SubjectsTwelve naive loft-reared homing pigeons were maintained at 70% of their free-feeding weights. Each was randomly assigned to one of three groups. ApparatusAll subjects were magazine trained. Key pecking was then conditioned in an operant discrimination unit equipped with two 2 by 2 in. (5 by 5 cm) Polacoat-projection surface response keys positioned above a central food magazine (Lehigh Valley Electronics, Fogelsville, Pennsylvania, special order). Only the response key to the right of the food magazine was used. A minimum force of 20 g (0.19 N) was required before a microswitch was operated and a response recorded. Scheduling and recording equipment was located in a separate room.For Groups 1 and 3 (AM problem), a 35-mm projector and special double-refracted slides rear-projected vertical lines on the response key. A polarized disc between the projector and the response key rotated at 120 rpm by means of a synchronous motor, and this produced four changes of polarization per second (4 cps) and apparent horizontal movement of the vertical lines at a velocity of 20 cm/sec. To produce "no motion" (NM), the polarized disc was maintained in a stationary position (0 cps). To produce the pulsating (P) effect, a polarized sheet was inserted between the projection lamp and the pattern so that the polarized axis was perpendicular to the slide display.

Perception of lateral movement by monocularly viewing pigeons

“…Note that this is apparent motion rather than real motion, since there is no actual motion within each 3-mm bar. Nevertheless, the motion is convincing to the human eye; moreover, Siegel (1971) has shown strong equivalence between real and apparent motion in pigeons, using apparent motion displays of considerably coarser "grain" than those of the present study.…”

“…In any case, for those birds which participated in both phases of the experiment, the discrimination phase actually preceded the nystagmus phase. It is, of course, conceivable that the discrimination procedure was somehow too insensitive to reveal subtle perceptual effects, or that apparent movement is perceived differently from real movement (despite Siegel's, 1971, evidence to the contrary), or that other parameters, such as distance, speed, or spatial frequency, crucially determine whether there is asymmetry or not. We think it more likely that the mechanisms underlying the asymmetry in the nystagmus response are simply quite separate from those involved in discrimination learning.…”

Ambiguity in Mind and Nature

“…Since we know that pigeons are able to see not only real movement, but also apparent movement, like the phi-phenomenon (Siegel, 1970(Siegel, , 1971Emmerton, 1990), we plan to use Stroboscopic Alternative Movement (SAM) as the reference pattern. If it is true that self-organization processes also occur in animal cognition, then there should also be multistability.…”

Stimulus Control of the Pigeon's Ability to Peck a Moving Target

“…Movement thresholds have been measured in humans (Brown, 1931), chimpanzees (Carpenter & Carpenter, 1958), cats (Kennedy & Smith, 1935), rats (Hawley & Munn, 1933), and pigeons (Hodos et al, 1976;Siegel, 1970Siegel, , 1971. Siegel (1970Siegel ( , 1971 demonstrated that pigeons can discriminate between stationary (nonmoving) stimuli and stimuli presented as real or apparent movement.…”

“…Siegel (1970Siegel ( , 1971 demonstrated that pigeons can discriminate between stationary (nonmoving) stimuli and stimuli presented as real or apparent movement. Hodos et al (1976) I wish to thank Coleman Paul for his contributions trained pigeons to discriminate between stationary and dynamic stimuli.…”