G. William Farthing

Short-term memory and information processing in pigeons☆

Abstract Six pigeons were trained to asymptotic performance on a variable-delay matching-to-sample task in which the samples were sometimes line or color elements and sometimes line-color compounds. On compound-sample trials, the comparison stimuli were sometimes color elements and sometimes line-tilts. Sample type and delay (0, 1.5, and 4.5 sec) were varied within sessions, and sample duration (.4, 1.0, and 3.0 sec) was varied between sessions. Forgetting curves were steeper for line-tilt than for color. As sample duration increased, matching performance improved more for colors than for line-tilts, especially at delays greater than zero. Performance was better with element samples than with compound samples only on the line-tilt dimension at zero delay. Some predictions of a unitary trace growth and decay theory of pigeon short-term memory were not confirmed. A dual-code hypothesis was proposed to account for the data.

Involuntariness of response on the Harvard Group Scale of Hypnotic Susceptibility

Abstract Following a tape-recorded administration of the Harvard Group Scale of Hypnotic Susceptibility, Form A (HGSHS:A) of Shor and E. Orne (1962), some 272 Ss recorded their objective responses in the standard scoring booklet and then rated the voluntariness-involuntari-ness of their responses to each HGSHS:A item. The ratings indicated that in about 75% of the instances where HCSHS:A items were objectively passed, Ss experienced their response as completely or mostly involuntary, and this percentage did not differ between ideomotor items and the more difficult challenge items. For a subset of 35 Ss tested on the Stanford Hypnotic Susceptibility Scale, Form C (SHSS:C) of Weitz-enhoffer and Hilgard (1962), SHSS:C score was predicted reliably by HGSHS:A objective score. Thus, HGSHS:A is an adequate predictor of hypnotic susceptibility according to a criterion measure (SHSS:C), in spite of the fact that individual HGSHS:A items are not perfect measures of the classical suggestion effect according to the c...

Neither Daredevils Nor Wimps: Attitudes toward Physical Risk Takers as Mates

Farthing (2005) tested a prediction derived from costly-signaling theory, that women would prefer physical risk takers (brave, athletic, fit) over risk-avoiders as long-term mates. Using scenarios involving high-risk acts, the prediction was confirmed for heroic (brave, altruistic) but not for non-heroic (brave, non-altruistic) acts. Apparently, womens concerns over risks to their mates overrode any positive signal value of mens risk taking, when the acts were highly risky and had no redeeming practical value. The present studies revisited the costly-signaling hypothesis using both medium- and high-risk scenarios, and it was predicted that for non-heroic acts women would prefer risk takers over risk avoiders for medium-level risks but not for highly risky acts. The prediction was supported in two studies. In Study 1, risk takers were preferred for non-heroic medium-risk acts, but risk avoiders were preferred for high-risk acts. For heroic acts, risk takers were preferred for both high- and medium-risk acts. Study 2 crossed two act risk levels with two actor skill levels, with non-heroic risks. Risk takers were preferred for the least risky combination (medium-risk act, high-skill actor) and also for the two moderately risky combinations, but risk avoiders were preferred for the riskiest combination (high-risk act, medium-skill actor). In Study 1, participants compared high-level risk takers versus risk avoiders on several person adjectives. Both heroic and non-heroic risk takers were perceived as more brave, athletic, physically fit, impulsive, attention-seeking, and foolish, and less emotionally stable and self-controlled, compared to risk avoiders. But only heroic risk takers were perceived as more altruistic, agreeable, conscientious, and sexy than risk avoiders.

Effects of hypnotizability and mental imagery on signal detection sensitivity and response bias

Abstract It was hypothesized that the ability to selectively concentrate attention on mental images would be greater among high hypnotizable Ss than among low hypnotizable Ss, as indicated by a greater interference with visual signal detection by concurrent visual mental imagery in response to specified nouns. This hypothesis was not supported in the overall results, though the finding of a significant interference effect among the high hypnotizable female Ss, but not among other subgroups, indicates that further research with a more refined procedure might be worthwhile. On the control trials without images, the high hypnotizable Ss made more false alarms than lows, and had a significantly different bias index indicating that high hypnotizable Ss were more likely than lows to respond “yes” when uncertain about whether the signal was present; false alarms can be interpreted as a nonhypnotic measure of suggestibility. The high and low hypnotizable Ss did not differ in their times to generate images in resp...

Behavioral contrast in pigeons learning an auditory discrimination

After an initial period of nondifferential training, 14 pigeons were trained on a go/no-go discrimination between different click frequencies. Keypeck responses during the positive stimulus were reinforced with food on a 1-min variable interval schedule, whereas responses during the negative stimulus were extinguished and prolonged the negative stimulus for 30 sec (correction procedure). Response rates in the positive stimulus increased during discrimination training in all subjects. A control group given extended nondifferential training had significantly lower response rates and contrast ratios. The results are inconsistent with a simple autoshaping theory of behavioral contrast.

Stimulus generalization and discrimination along the click-frequency (flutter) continuum in pigeons

Before tests for click-frequency generalization, pigeons had been reinforced for keypecks during one click frequency (S+). Some Ss received S+ training only, whereas other Ss also received unreinforced (S−) trials, during which the clicks were either absent (Experiments 1-3) or presented at some other frequency (faster or slower than S+: Experiment 4). When training included S+ trials only, birds responded approximately equally to all generalization test frequencies (0.0 to 53.5 pulses/sec, pps). Most Ss that had received both S+ and S− training trials responded fastest not during S+ but during click frequencies even further away from S− along the click-frequency dimension (peak shift). Complex bimodal gradients were obtained after training with S+ (1.6 pps) vs S− (0.0 pps); maximal responding generally occurred near S+ and at approximately 14.2 pps. Among other factors, the “nonorthogonality” of click absence (0.0 pps) to the click dimension seems crucially involved in producing these complex effects.

Overshadowing in the discrimination of successive compound stimuli

Pigeons were trained on a free-operant, go/no-go discrimination in which S+ (variable-interval reinforcement) was a line-color compound produced by rapidly alternating the separate line and color elements on the response key in a 0.8-sec cycle. For Group 1, S− (extinction) was a steady disk of light the same color as the S+ compound, whereas for Group 2 S− was a different color. Group 3 received nondifferential training with S+ only. Subsequently, line-tilt generalization gradients were significantly steeper in Group 1 than in either Group 2 or Group 3. Also, in the test, relative generalization from the line-color compound to the line element alone was significantly greater in Group 1 than in Group 3.

Effect of a signal previously paired with free food on operant response rate in pigeons

In Phase 1, food was presented independently of the birds’ behavior. In one group, the food was paired with an auditory CS; in the other group, CS and food occurred randomly. In Phase 2, the birds were trained to peck a key for variable-interval food reinforcement, with CS off. Then, following additional Phase 1 training, they were tested with CSs presented during operant extinction. For both key pecking and a photocell measure of activity near the speaker, the CS produced changes in behavior which, when measured independently of the direction of change, were significantly greater in the paired group than in the random group.

Stimulus control by dot position in pigeons

In Experiment I positive dot-position generalization gradients were obtained following training in which pecks at a white key with a black dot in a fixed position (at either the top, bottom, left, right, or center of the key) were sometimes reinforced (S+) and pecks at a blank white key were never reinforced (S−). Single-stimulus training was not sufficient to establish control by dot position. In Experiment II negative dot-position gradients were obtained following training on a discrimination between S+ blank vs. S− dot. Implications of these and other results for excitatory and inhibitory stimulus control were discussed.

Two Types of Correlation between Reinforcement and the Elements of a Compound Stimulus

Abstract2 types of correlation between reinforcement and the elements of a compound stimulus are described, as well as an experiment demonstrating their independent effects. Pigeons were trained to peck at compound line (0° vertical) and color (C1 or C2, red or green) stimuli. The Correlated (true discrimination) group was reinforced for responses to 0°C1 but not for responses to 0°C2; the Uncorrelated (pseudodiscrimination) group was reinforced for responses to both compounds; and the Control group was exposed only to 0°C1 with reinforcement. In a subsequent test the frequency of responding to the 0° element presented alone was greatest in the Uncorrelated group, intermediate in the Control group, and lowest in the Correlated group. However, the slopes of the relative line-tilt generalization gradients were not significantly different for the three groups.