1. Repetition blindness for novel objects 作 者： Veronika Cotheart et al. 報告者：李正彥 日 期： 2006/3/30

2. Outline Introduction Experiment 1 Experiment 2 General discussion

3. Introduction Repetition blindness: when the presented rate is about 8~12 items/sec, observers have difficulty in detecting and reporting correctly for a repeated item. The purposes of 2 experiments: – To investigate the effects of repetition of novel objs. – Is it viewpoint dependent or object centred. Manipulated factor: – Experiment 1 － rate of presentation (105/166 ms) – Experiment 2- rotation in depth (10°/20°)

4. Sentences of 12 words can be accurately recalled after RSVP at rates of 10 words/sec (Potter, 1984). He suggested that such recall was mediated by a rapidly activated form of memory (Conceptual Short-term Memory). An inability to detect both occurrences of a repeated visual stimulus presented in a rapid visual sequence. It occurs when the rate of presentation is 100~180 ms/stimulus and when the lag between repetitions is no greater that about 3~4 items. (Kanwisher, 1987)

5. Researches of Repetition blindness: – Orthographically similar: reach/react (Kanwisher & Potter, 1990) – Phonologically identical (7/seven,one/won) or merely phonologically similar (freight/great). (Bavelier, 1999) – Recall advantage of semantically related pair-words. (Kanwisher et al., 1999) – Recall advantage of repeated nonwords and repeated pseudohomophones. (Coltheart & Langdon, 2003)

6. Theory of repetition blindness Token individuation theory (Kanwisher, 1987) – It supposes that rapidly presented words, letters, or numbers activate their type nodes in long-term memory, but that is insufficient to do recalling and distinguishing. – Episodic memory tokens must be established before an item’s occurrence can be reported. – Token individuation: the process that links an activated type node with a token node. Failure → RB

7. 2 stage theory (Chun & Potter, 1995) – Stage 1, type recognition: normal process which occurs without demanding allocation of conscious attentional mechanisms. – Stage 2, token individuation: require allocation of attention and the linking of activated type information activation. – The same type is activated → attache to the token →2 tokens collapse into a single token. Token creation need 2 process (Neill et al., 2002) – Instantiation: the recognition that an instance of a particular type has occurred. – Contextualization: the assignment of the instance to a specific temporal and spatial context.

8. General Model

9. Experiment 1 Does repetition blindness occur for simple 3-D novel objects? Method – Subjects: 36 undergraduate subjects. – Stimulus materials: 60 3D novel objects, each consisted of 2~4 different geons. – Masks were devised by randomly combining all of the geons. – Independent variables: presentation rate (105 / 166 ms) & repetition.

10. Procedure Repeated trial: 2 new / 2 old Control trial: 1 new / 3 old

11. Results and discussion – Repetition as a within-S factor, and presentation rate as a between-S factor. – There is a main effect of presentation rate. – The interaction is significant. (repetition & presentation rate) – The repetition blindness is significant at level 105 ms. – The values for intervening item did not differ significantly as a function of rate, nor of repetition. – In alternative performance measures, the result is the same.

13. Experiment 2 Whether repetition blindness involves viewer- dependent representations? Whether the magnitude of repetition blindness is affected by the degree of rotation in depth?

14. Method – Subjects: 42 new undergraduate students. – Stimulus material: Rotation angle as a between-S factor. (21/21) Repetition as a within-S factor. Repeat conditions (same view/different view) ; Control condition

15. Procedure – Trials 16 – same view repeated trials 16 – different view repeated trials 16 – control trials (C1≠C2) 8 – 2 item trials with mask inserted – Recognition arrays Presented in original unrotated view. The orientation is different on ½ the trials.

16. Result and discussion – The main effect of rotation is not significant. – The effect of view is not significant. – In different view condition, repeated pairs is significant worse than control pairs. – In A’ value, only the effect of repetition is significant. – Accuracy in detecting that a novel obj had occurred twice was not significantly affected by a change in view. It indicate that repetition blindness for novel obj is based on object- centred representations.

17. General Discussion Geons may be represented as units prior to object recognition. The findings can also be accommodated within the 2-stage token individuation hypothesis. The result implies that the episodic memory tokens formed at RSVP rates are based on object-centred representations constructed prior to object recognition. Token construction does not require activated entries in the visual object recognition system. The repetition blindness was reduced for visually dissimilar taxonomically related objects. The results suggest that the codes in episodic memory which are registered by verbal and pictorial stimuli are different.