Jim Cheesman

Priming with and without awareness

In two experiments, no evidence for perception without awareness was found in a Stroop-priming task when the threshold for detecting color-word primes was measured reliably by a forced-choice procedure. Color words and color patches were either congruent or incongruent, and no priming occurred when the words were presented at the detection threshold. However, systematic increases in the level of detection for the primes led to correlated increases in the magnitude of priming. The results provide no support for recent claims that priming is a more sensitive indicator of perceptual processing than detection based upon verbal report. A resolution to the apparent discrepancy between the present results and previously reported findings is suggested.

Contingency learning without awareness : Evidence for implicit control

The results of four experiments provide evidence for controlled processing in the absence of awareness. Participants identified the colour of a neutral distracter word. Each of four words (e.g., MOVE) was presented in one of the four colours 75% of the time (Experiments 1 and 4) or 50% of the time (Experiments 2 and 3). Colour identification was faster when the words appeared in the colour they were most often presented in relative to when they appeared in another colour, even for participants who were subjectively unaware of any contingencies between the words and the colours. An analysis of sequence effects showed that participants who were unaware of the relation between distracter words and colours nonetheless controlled the impact of the word on performance depending on the nature of the previous trial. A block analysis of contingency-unaware participants revealed that contingencies were learned rapidly in the first block of trials. Experiment 3 showed that the contingency effect does not depend on the level of awareness, thus ruling out explicit strategy accounts. Finally, Experiment 4 showed that the contingency effect results from behavioural control and not from semantic association or stimulus familiarity. These results thus provide evidence for implicit control.

Rate and variability of finger tapping as measures of lateralized concurrent task effects

Using a sample of 48 normal right-handed adults, we assessed the effects of oral reading on concurrent unimanual finger tapping under all combinations of instructional set (speeded vs. consistent tapping), tapping movement (repetitive vs. alternating), task emphasis (reading emphasized vs. tapping emphasized), and tapping hand. Change in tapping rate and variability was measured relative to the corresponding single task control condition. Reading decreased the rate of speeded finger tapping but increased the rate of consistent tapping. In both instances, the right hand was affected more than the left hand. Asymmetries were comparable for repetitive and alternating tapping. When measured in terms of variability, however, effects were largely symmetric. The findings clarify the conditions under which lateralized concurrent task effects are most likely to occur and show that such effects are not statistical artifacts. It appears that subjects attempt to coordinate the timing of concurrent activities and that speech timing is more strongly linked to right-hand control than to left-hand control in right-handers.

PET Flasher: A machine language subroutine for timing visual displays and response latencies

PET Flasher presents a one-line stimulus display at any location on a PET/CBM (Commodore Business Machines) screen and measures reaction time from display onset. Display duration is accurately controlled in 16.7-msec steps, and reaction time measurement is accurate within ±1 msec. PET Flasher is easily incorporated within any PET/CBM BASIC program, since as a subroutine, it is called only when precise timing operations are required.

You can’t Stroop a lexical decision: is semantic processing fundamentally facilitative?

It is well documented that related prime words facilitate target processing in lexical decision (e.g., doctor facilitates nurse), but interfere with target processing in the Stroop task (e.g., the word blue slows the time to name the colour red). Five experiments explored several potential explanations for these differences. In Experiments 1 and 2, all stimuli were novel (as in a typical lexical decision design). Participants were faster both to make lexical decisions and to read colour words aloud that were primed by incongruent associates (e.g., banana) relative to a neutral prime (e.g., knot). Experiments 3 and 4 used a small set of repeatedly presented stimuli (as in a typical Stroop design). Incongruent colour words facilitated lexical decisions to target colour words, but interfered with identification (reading aloud). Experiment 5 further showed that interference is still observed in identification when the distractor set size is large but the target/response set size is small. These findings suggest that semantic connections are solely facilitative and that response competition only occurs when there is a small set of repeated responses and identification (rather than lexical decision) is required. The more general problem of research fragmentation is briefly discussed.

Female Advantage in Speeded Colour Naming: A Special Naming Factor or Superior Motor Sequencing?

Women name colours more quickly than men do, and our recent research suggests that the female advantage for colour naming extends to speeded naming of shapes. The female advantage could reflect a superiority in producing and executing the motor sequences underlying the required vocal response. Or, women could have faster access to or retrieval of colour labels. The present study tested these two possibilities by administering 3 speeded colour-naming tasks. In the first task, participants named a patch of colour as quickly as possible after it was presented. In she second task, participants made manual (instead of vocal) responses. In the third task, vocal responses were required but a randomly varying delay period was introduced between the presentation of the colour patch and the required response. Females responded more quickly on the first task but there was no such advantage in the manual or delayed conditions. Taken together, these results suggest that the female advantage for speeded naming tasks reflects an advantage for sequencing movements rather than a special naming ability.