Introspection,Anton's Syndrome,and Human Echolocation

Philosophers have recently argued that since there are people who are blind, but don't know it, and people who echolocate, but don't know it, conscious introspection is highly unreliable. I contend that a second look at Anton's syndrome, human echolocation, and ‘facial vision’ suggests otherwise. These examples do not support skepticism about the reliability of introspection.     

Human Echolocation as a Basic Form of Perception and Action

In this article we discuss known and possible uses of echolocation by humans. We argue that echolocation may be a basic perception-action ability of humans. We review studies which suggest that both blind and sighted humans are capable of substantial precision in the perception of properties of distal objects, such as distance, size, shape, substance, and relative motion. We analyze relations between acoustic pulse and echo that may provide information to support these percepts and others. Our analysis predicts echolocation-based sensitivity in humans and other animals to a number of properties of the animal-environment interaction. We also discuss echolocation-based acoustic specification of time-to-contact. We develop a new variable that provides this information and discuss acoustic Τs recently developed by Shaw, McGowan, and Turvey (1991) and by Lee, van der Weel, Hitchcock, Matejowsky, and Pettigrew (1992).Our analysis suggests that there may be important insights to be gained from an ecological study of echolocation in humans and other species. We end with suggestions for research derived from our analysis.     

Indirect interception actions by blind and visually impaired perceivers: Echolocation for interceptive actions

Vernat, J.-P. & Gordon, M. S. (2010). Indirect interception actions by blind and visually impaired perceivers: Echolocation for interceptive actions. Scandinavian Journal of Psychology, 51, 75–83.
This research examined the acoustic information used to support interceptive actions by the blind. Congenitally blind and severely visually impaired participants (all wearing an opaque, black eye-mask) were asked to listen to a target ball rolling down a track. In response, participants rolled their own ball along a perpendicular path to intercept the target. To better understand what information was used the echoic conditions and rolling dynamics of the target were varied across test sessions. In addition the rolling speed of the target and the distance of the participant from the target were varied across trials. Results demonstrated that participants tended to perform most accurately at moderate speeds and distances, overestimating the target's arrival at the fastest speed, and underestimating it at the slowest speed. However, changes to the target's dynamics, that is, the amount of deceleration it underwent on approach, did not strongly influence performance. Echoic conditions were found to affect performance, as participants were slightly more accurate in conditions with faster, higher-intensity echoes. Based on these results blind individuals in this research seemed to be using spatial and temporal cues to coordinate their interceptive actions.     

Reproduction of end-location and distance of movement in early and later blinded subjects

This study examined the ability of early and later blinded subjects to reproduce the end location and distance of preselected arm movements of two different amplitudes (approximately 30 degrees and approximately 60 degrees). Both groups were found to reproduce end location with greater accuracy and less variability than distance. The early blinded subjects were less accurate however, and more variable in their reproductions of both movement cues than the later blinded subjects. The complications of these findings for the role of visual representation in memory for movement are discussed.     

Discrete-trial alternation in the rat

The acquisition and maintenance by rats of single alternation, double alternation, and four other repeating patterns of reinforced and non-reinforced trials was studied in a discrete-trial lever-pressing situation. The rats learned all these patterns in a small number of experimental sessions. Single alternation was learned more rapidly than the more complex patterns. Rate of learning single and double alternation decreased moderately as inter-trial interval increased. Abrupt changes in the scheduling of trials, either by doubling the inter-trial interval or by shifting from fixed to variable trial spacing, temporarily disrupted the patterned performance. Two hypotheses concerned with the means by which the rats could have learned to conform to the pattern were examined: (1) “timing” of the interval between successive reinforcements; and (2) control of responding on a trial by the outcome of preceding trials, depending on the consistency with which these outcomes were associated with reinforced or non-reinforced trials in the pattern and on how many trials back these outcomes occurred. The second hypothesis accounted for the relative frequency of errors on trials at various locations in the sequences, and predicted most of the changes in error frequency observed in experiments in which “inter-trial stimuli” were added to the sequences.     

Light-aversion in the white rat

The Psychological Record -     

Parental recognition in the rat

Infant rats were tested in a 2-choice test for their preference for (a) their mother vs an alien mother, (b) their father vs an alien father and (c) their father, whom they had never experienced, vs an alien father. Pups were able to recognize their mother and showed a preference for her for the duration of the experiment. Pups could also recognize their father, even if they had never previously experienced him. However, they showed a reversal in preference for their father during the experiment, preferring their father at Days 10-14, but preferring an alien father at Days 18-22. It is concluded that fathers are recognized by general cues of kinship through “phenotype matching”, whereas mothers assume a positive reinforcing value and are recognized by individual cues.     

Habituation in the rat fetus

Rat fetuses exhibit motor and cardiac responses to chemosensory stimulation on Days 20 and 21 of gestation. The first experiment demonstrated that fetuses exhibit an increase in overall motor activity and decrease in heartrate in response to an initial intraoral infusion of a lemon solution. After a series of nine exposures, however, fetuses no longer exhibit motor or cardiac responses to lemon infusion, suggesting the existence of a habituation-like process. Responsiveness recovers spontaneously following a 3-to 9-min period without stimulation. In a second experiment, a dishabituation treatment was administered to distinguish habituation, which is a centrally mediated decrement in response, from effector fatigue, sensory adaptation, and other peripheral mechanisms that can result in reduced responsiveness. A single infusion of mint following a series of nine lemon exposures was effective in reinstating fetal motor responses to lemon on both Days 20 and 21, but reinstated cardiac responses only on Day 21. Rat fetuses habituate to repeated chemosensory stimulation, suggesting the utility of the habituation paradigm in measuring CNS development during the perinatal period.     

Prospective memory in the rat

The content of prospective memory is comprised of representations of an action to perform in the future. When people form prospective memories, they temporarily put the memory representation in an inactive state while engaging in other activities, and then activate the representation in the future. Ultimately, successful activation of the memory representation yields an action at an appropriate, but temporally distant, time. A hallmark of prospective memory is that activation of the memory representation has a deleterious effect on current ongoing activity. Recent evidence suggests that scrub jays and non-human primates, but not other species, are capable of future planning. We hypothesized that prospective memory produces a selective deficit in performance at the time when rats access a memory representation but not when the memory representation is inactive. Rats were trained in a temporal bisection task (90 min/day). Immediately after the bisection task, half of the rats received an 8-g meal (meal group) and the other rats received no additional food (no-meal group). Sensitivity to time in the bisection task was reduced as the 90-min interval elapsed for the meal group but not for the no-meal group. This time-based prospective-memory effect was not based on response competition, an attentional limit, anticipatory contrast, or fatigue. Our results suggest that rats form prospective memories, which produces a negative side effect on ongoing activity.