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.

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An objective behavioral profile that was previously shown to distinguish the effects of hallucinogens from those of other classes of drugs was used here to further study hallucinogenic behaviors. Saline, d-amphetamine sulfate and five doses of dimethyltryptamine (DMT) were administered to solitary adolescent rhesus monkeys in a totally dark environment and their behavior was observed via infrared monitors, videotaped, and scored in a number of categories. Scores in the following categories systematically increased with ascending doses of DMT: exploration, locomotion, stereotypy, spasm, tracking and duration of inappropriate behavior. In addition, some behaviors sensitive to hallucinogens occurred with greater frequency in the dark than in a previous study conducted in the light. Behaviors such as tracking and fear grimaces, usually associated with specific stimuli, emerged in the absence of such stimuli in the dark. These results suggested hallucinogen-induced changes in perceptual-motor systems, if not hallucinations per se.

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