RT patterns and chunks in SRT tasks: a reply to Jiménez (2008).

Previous research has shown that the formation of units or chunks contributes to sequence learning in serial reaction time (SRT) tasks (Koch & Hoffmann, Psychological Research 63:22-35, 2000). However, some of these results were assumed to be unrelated to sequence learning and to reflect preexistent response tendencies (Jiménez, Psychological Research 72:387-396, 2008). In the Experiment of this study, we aimed to evaluate this issue. One group of participants responded to a strongly structured sequence of digits by pressing one out of six response keys depending on digit identity. In a second experimental group, a weakly structured sequence was presented, which contained comparable transitions among the single items, but did not have series of ascending and descending triplets of successive digits. The results indicated that serial learning in general as well as response tendencies to certain fragments of the sequence were modulated by the manipulation of the strength of relational patterns. The data are consistent with the notion that relational patterns contribute to the formation of chunks as suggested in the original study.

Movements or targets: what makes an action in action-effect learning?

According to ideomotor theory, actions become linked to the sensory feedback they contingently produce, so that anticipating the feedback automatically evokes the action it typically results from. Numerous recent studies have provided evidence in favour of such action-effect learning but left an important issue unresolved. It remains unspecified to what extent action-effect learning is based on associating effect-representations to representations of the performed movements or to representations of the targets at which the behaviour aimed at. Two experiments were designed to clarify this issue. In an acquisition phase, participants learned the contingency between key presses and effect tones. In a following test phase, key-effect and movement-effect relations were orthogonally assessed by changing the hand-key mapping for one half of the participants. Experiment 1 showed precedence for target-effect over movement-effect learning in a forced-choice RT task. In Experiment 2, target-effect learning was also shown to influence the outcome of response selection in a free-choice task. Altogether, the data indicate that both movement-effect and target-effect associations contribute to the formation of action-effect linkages-provided that movements and targets are likewise contingently related to the effects.

Eye vergence is susceptible to the hollow-face illusion.

When an observer looks at a hollow mask of a face, a normal convex face is often perceived [the hollow-face illusion--Gregory 1973, in Illusion in Nature and Art (London: Duckworth) pp 49-96]. We show that in exploring an illusory face, the eyes converge at the illusory and not at the real distances of fixated targets like the tip of the nose. The 'vergence error' appears even though the resulting disparities of the two retinal images of the target provide feedback that would allow an immediate correction. It is presumably the success of recognising a familiar object (a face) which overrides the correction of convergence. This suggests that the brain strives for a congruency of eye vergence and distance perception.

Local contextual cuing in visual search.

Previous research has indicated that covariations between the global layout of search displays and target locations result in contextual cuing: the global context guides attention to probable target locations. The present experiments extend these findings by showing that local redundancies also facilitate visual search. Participants searched for randomly located targets in invariant homogenous displays, i.e., the global context provided information neither about the location nor about the identity of the target. The only redundancy referred to spatial relations between the targets and certain distractors: Two of the distractors were frequently presented next to the targets. In four of five experiments, targets with frequent flankers were detected faster than targets with rare flankers. The data suggest that this local contextual cuing does not depend on awareness of the redundant local topography but needs the redundantly related stimuli to be attended to.

The influence of response--effect compatibility in a serial reaction time task.

Participants performed a serial reaction time task, responding to either asterisks presented at varying screen locations or centrally presented letters. Stimulus presentation followed a fixed second-order conditional sequence. Each keypress in the experimental groups produced a contingent, key-specific tone effect. The critical variation concerned the mapping of tones to keys. In Experiment 1, keypresses in one control condition produced noncontingent tone effects, while in another control condition there were no tone effects. In Experiment 2, three different keytone mappings were compared to a control condition without tone effects. The results show that tone effects improve serial learning when they are mapped to the response keys contingently and in a highly compatible manner. The results are discussed with reference to an ideomotor mechanism of motor sequence acquisition.