The Persistent Interlocutor

A Persistent Interlocutor (PI) is someone who, in argumentative contexts, does not cease to question her opponent’s premises. The epistemic relevance of the PI has been debated throughout the history of philosophy. Pyrrhonians famously claim that our inability to dialectically vindicate our claims against a PI implies scepticism. Adam Leite disagrees (2005). Michael Resorla argues that the debate is based on a false premise (2009). In this paper, I argue that these views all fail to accurately account for the epistemic relevance of the PI. I then briefly present an account that aims to do better in this regard, based on the modal notion of safety. On the account proposed, the PI does not violate epistemic or dialectical norms. Rather, her behaviour tends to be epistemically perverse in the sense that it wastes cognitive resources. Perhaps surprisingly, this defect turns out not to be unique to the PI.

     

Search processes for detecting repeated items In a visual display

Evidence for successive serial exhaustive searches was found in a task requiring detection of repeated letters in visually presented lists of varying length. The time per comparison was 25 msec. Important differences in processing appeared between instances of adjacent repeated letters and instances of nonadjacent repeated letters.     

Extraretinal feedback and visual localization

The effect of saccades on visual localization was tested before, during, and after the eye movements. After saccades, localization errors were much less than the distance that the eyes had moved. It is argued that these results demonstrate that extraretinal feedback affects visual localization. The results also suggest that the feedback is related to acceleration rather than to position. Implications for inflow and outflow theories are discussed.     

A signal detection analysis of the effects of hearing on the visual recognition of two-digit numbers

A signal detection measure of visual recognition was used to assess the visual recognition of two-digit numbers in three different conditions: (1) voicing of the number as it was presented visually; (2) voicing of a different number than the one presented; and (3) no voicing. The three treatment means were significantly different, with matched voicing resulting in the best performance and no voicing, in the worst. There was no evidence that the treatments differentially affected response criteria.     

A conceptual category effect in visual search: O as letter or as digit

Evidence is presented for a processing mechanism in visual recognition that depends upon how the stimulus array is conceptually categorized rather than upon its physical characteristics. Ss had to detect a letter or digit target in a field of letters or digits. When target and field were of the same category, reaction time increased with display size. When target and field category differed, reaction times were independent of display size. This category effect held even for the ambiguous target character 0 that yielded reaction time functions appropriate to how it was specified prior to presentation: as “zero” or as “ō.”     

A method for the precise switching of speech

A simple procedure by which a speech signal may be switched on or off (or from one ear to the other) at a precise instant of time is described. The speech sample is first recorded on a magnetic tape loop. A reference pulse is then recorded preceding the speech signal. This reference pulse triggers an adjustable time delay which in tum operates an electronic switch at an appropriate time.     

A device for presenting targets and recording positioning responses in one dimension

Apparatus for recording manual target pointing localizations is described. The device, utilizing a position transducer and digital voltmeter, is capable of determining the position of either manual limb when localizing visual and/or auditory targets. The pointing localizations involve naturalistic limb movements made in a relatively unrestricted manner. The apparatus has the advantages of rapid accurate measurement, reliability, ease of reading, and the potential for automatic recording. When used for research involving adaptation to sensory rearrangement, there is the further advantage that the dependent measures are obtained in the same context as during exposure to the rearrangement.     

The psychological refractory period and vertex evoked potentials

The averaged sensory evoked potential (EP) was recorded from the scalp (vertex to mastoid) in a psychological refractory period experiment in which 12 young adults participated. Reaction times (RTs) were measured to either both or only the second of pairs of stimuli, in different trial blocks, with inter-stimulus intervals (ISIs) of 100, 200, 300 and 400 msec occurring in random sequence. EPs were recorded at each ISI. No latency changes could be found in the prominent non-specific components (P1-N1-P2) of the EP to stimulus 2 even at ISIs where the RT was substantially delayed. Thus the notions that the RT2 delay is due to occupation of a single channel central processor by S1 and that non-specific EP components reflect the time course of information processing in underlying neural tissue, do not lend each other mutual support. Furthermore, as profound amplitude refractoriness in components P1-N1 and N1-P2 persisted at ISIs where RT was as fast or faster than simple RT, there appears to be a dissociation between “psychological refractoriness” and “physiological refractoriness”. The implications of these results are discussed.     

A comparison of leverpress and head-poke discriminated Sidman avoidance

A discriminated Sidman avoidance procedure used by Forgione (1970) was replicated using a head-poke response instead of a leverpress as the avoidance operant. The resultant data were described in terms of the five dependent measures reported by Forgione. Head-poke avoidance was found to be more efficient than its leverpress counterpart and compared very favorably with the lever-disabling (or shock-timer-on) procedure used by Forgione to break up inefficient leverpress behavior patterns.